TY - JOUR
AU - Griffiths, Charles L
AB - Abstract Surveys of species diversity in sublittoral waters along the coasts of the Cape Peninsula on the Atlantic coast of South Africa yielded three species of Mysidopsis G.O. Sars, 1864. A new species, M. abbreviata n. sp., is described, a supplementary description is given for M. similis (Zimmer, 1912), and the female of M. zsilaveczi Wittmann & Griffiths, 2014 is described for the first time. The new species is characterized, among other characters, by a transversely shortened rostrum. Field observations of M. zsilaveczi and M. abbreviata n. sp. showed the greatest intraspecific diversity of colour patterns ever documented for mysids. Stomach contents, together with differences in the armature of perioral mouthparts and in the foregut, suggest that all three species are specialized predators, mainly of crustaceans. An updated key to the species of Mysidopsis in southern Africa is given. INTRODUCTION A long-term cooperation between academic institutions and citizen scientists has resulted in the discovery of four new species of mysid crustaceans from littoral and sublittoral waters along the coasts of the Cape Peninsula, South Africa (Wittmann & Griffiths, 2014, 2017). This study underlines the outstanding biodiversity at this location by additional descriptions of new or little-known mysids and by depicting aspects of morphological and ecological diversity. These surveys yielded the greatest diversity of colour patterns ever documented for mysids, in the present case among diurnal epibenthic species of Mysidopsis G.O. Sars, 1864. Based on detailed microscopical examination, efforts were made to uncover potential species-specific patterns within the large set of colour variants versus patterns possibly resulting from colour adaptation to the substrate. Among the anatomical profiles extracted, that of M. similis (Zimmer, 1912) needed to be verified by crosschecking with the type material, that of M. zsilaveczi Wittmann & Griffiths, 2014, could be complemented by first description of the female, and a third form is described as M. abbreviata n. sp. The different colour patterns provided a first indication of a partitioning of ecological niches by the three sympatric species. This was confirmed by the study of stomach contents and by species-specific differences in the feeding apparatus. The new species is added to 49 extant species and one non-nominotypical subspecies of Mysidopsis, occurring globally, as listed by Mees (2017). An updated key to the ten species known from southern Africa (Namibia and South Africa) is also provided. MATERIALS AND METHODS Specimens were collected from hard bottoms in 4–6 m depth at four stations along a 14 km section (34°12’S 18°28’E to 34°20’S 18°28’E) of the western coastline of False Bay, on the Atlantic coast of South Africa. The mysids were either photographed in situ and then collected manually by SCUBA divers, or were collected and transported alive to a nearby laboratory at the University of Cape Town, where they were photographed alive or recently dead in a small seawater tank. The individuals depicted in 13 out of the total of 16 photographs (Figs. 1, 4, 6) were verified by examining the actual specimens, those in Figures 4E and 6F were verified by photographs and material of closely similar specimens, whereas only Figure 4F is not supported by a matching specimen. Figure 1. View largeDownload slide Mysidopsis similis (Zimmer, 1912): laboratory images of adult male (A, B), females (C, D) sampled from marine hard substrates in sublittoral habitats off the Cape Peninsula, South Africa; live specimen, body length 9 mm (A); live (B, C) and recently dead (D) specimens, 8 mm. Photographs by Charles L. Griffith. Figures not to scale. Figure 1. View largeDownload slide Mysidopsis similis (Zimmer, 1912): laboratory images of adult male (A, B), females (C, D) sampled from marine hard substrates in sublittoral habitats off the Cape Peninsula, South Africa; live specimen, body length 9 mm (A); live (B, C) and recently dead (D) specimens, 8 mm. Photographs by Charles L. Griffith. Figures not to scale. Terminology of larval stages follows Wittmann (1981). Abbreviations used for the substages of the nauplioid stage are N1 for larvae freshly hatched from the egg membrane, to N4 for those shortly before the molt that leads to the postnauplioid stage. Terminology of gross structures of the foregut follows Kobusch (1998). Depending on availability, contents of 4–10 full stomachs per species were withdrawn and smeared on slides for microscopical examination. Remaining methodology, terminology, and the textual schemes of species diagnosis and descriptions follow Wittmann & Griffiths (2014). Body length was measured from the tip of rostrum to the terminal margin of the telson without spines; carapace, antennular trunk, and its articles were measured along the dorsal midline. The easily confounded, large interarticular joint between the basis and the flagellum of thoracic exopods is not included in counts of articles. Type materials were deposited at the Iziko South African Museum, Cape Town (SAM), Zoological Museum Berlin (ZMB), and the Natural History Museum of Vienna (NHMW). SYSTEMATICS Family Mysidae Haworth, 1825 Subfamily Leptomysinae Czerniavsky, 1882 Tribe Mysidopsini Wittmann, Ariani & Lagardère, 2014 Genus Mysidopsis G.O. Sars, 1864, Mysidopsis similis (Zimmer, 1912) (Figs. 1–3; 11A, D; 12A, B) Paramysidopsis similis Zimmer, 1912: 6, pl. 2, figs. 36–38 [type locality: Radford Bay, Namibia]. Leptomysis tattersalli O.S. Tattersall, 1952: 177, fig. 9 [type locality: Langebaan Lagoon, Cape Peninsula west coast, South Africa]. Mysidopsis similis - Illig, 1930: 586 [in key]. — O.S. Tattersall, 1955: 157, fig. 38; 1958: 378; 1969: 65. — Wooldridge, 1983: Table 4; 1988: 100 [in key]. — Wooldridge & Mees, 2000: 67. — Wittmann & Griffiths, 2014: 1427 [in key]. Type material: The two type specimens of Paramysidopsis similis Zimmer, 1912, were separated herein into a lectotype, adult female with 10.2 mm body length (ZMB 16993) and a paralectotype, subadult male 7.9 mm (ZMB 30655), Namibia, Port of Lüderitz, Radford Bay (about 26°39’40”S, 15°09’04”E), 1903, leg. L. Schultze. Additional material examined: All samples from South Africa, Cape Peninsula, False Bay, coast near Simonstown: adult male 8.8 mm (ZMB 30656), between Rooikrans and Buffels Baai (34°19’53”S, 18°28’07”E), 6 m, 10 Dec. 2015, leg. Jessica Micklem; adult female 8.2 mm, subadult female 8.3 mm, adult male 11.2 mm, subadult male 6.5 mm, 2 immatures, 12 juveniles (SAM MB-A067543), ‘A-Frame’ dive site at Oatlands Point (34°12’30”S, 18°27’47”E), 6 m, 25 Sep. 2016, leg. Jessica Micklem; 3 adult males 8.2–9.5 mm (SAM MB-A067544), subadult male 6.6 mm, adult female 8.2 mm, subadult female 7.6 mm (NHMW-25931), 2 immature females 6.0, 6.5 mm (ZMB 30657), sublittoral waters at Miller’s Point (34°13’46”S, 18°28’28”E), 4–6 m, 25 Oct. 2016, leg. Craig Foster; subadult male 8.2 mm, 4 immature females 6.7–7.7 mm (SAM MB-A067545), 4–5 m, 6 June 2017, same sampling data. Type locality: South Eastern Atlantic Ocean, Radford Bay, Namibia. Diagnosis: Intermediate to robust body form. Rostrum well developed, triangular, terminally forming 40–70° angle, tip rounded; at most slightly bent ventrally, extending almost to inner anterior angle of eyestalks or beyond. Carapace with well-marked cervical sulcus; without mid-dorsal protuberance; posterior margin of carapace excavated, leaving last 1 or 2 thoracic somites dorsally exposed. Eyes, eyestalks well developed, with large bulbous cornea; no eyestalk papillae present. Antennules with short, stout, 3-articulated trunk. Appendix masculina robust, comparatively large. Antennal scale length 3.3–3.8× maximum width, scale extending 32–66% of length beyond antennular trunk; scale without spines, setose almost along all margins, with short, but distinct apical article. Mandibles without molar part; palp normal, 3-articulated. Sympods of maxillula, maxilla without setiferous expansion. Second article of maxilla with 3 setiferous endites. Exopod of maxilla slender, ending in normal-size, plumose seta, in continuous series with setae on outer margin of exopod. Maxillary palp comparatively large, 2-articulated; terminally evenly rounded. First thoracic epipod large, linguiform with narrow tip, subbasally with single seta. First thoracic endopod with ischium plus merus fused as single element, as typical in genus. Remaining endopods with separate ischium, merus. Both maxillipeds (thoracic endopods 1, 2) comparatively stout, with separate carpus, propodus, each not subdivided. Carpopropodites of endopods 3–8, each 3-articulated, middle article always much shorter than remaining 2 articles. Endopods 1–8 terminally strongly setose, strong claw throughout. Marsupium normal, thoracopod 6 with small but distinct, linguiform oostegite. Penes well developed, tubular, large, wide, each penis with 2 lobes flanking ejaculatory opening. Female pleopods reduced, setose; pleopod 1 minute, bilobate; pleopods 2–5 short, rod-like, with indistinct to absent endopodal lobe. All male pleopods biramous, densely setose, with large, subquadrangular to subrectangular sympod. Endopods 1–5 with 2, 7, 7, 7, 7 articles, respectively; basal article caudally with large, linguiform exite. Second article of endopod 1 modified as linguiform blade; article 0.6–1.1× length of exite. Exopods of all pleopods with 7 articles. Terminal article of exopod 4 terminally with large, straight, modified seta. Seta subterminally with series of short, acute barbs on inner margin, only few barbs on outer margin. Both sexes with proximal 48–62% of uropod endopods with 19–31 spines, ventrally arranged in dense linear series along inner margin; spines continuously increasing in length distally. Endopod extends 0–31% of telson length beyond telson, exopod 41–55%. Telson subtriangular, terminally pointed, with weakly sigmoid lateral margins, 65–80 spines along all margins; 2 large spines at tip plus 30–41 shorter spines along each lateral margin. Series of lateral spines not interrupted by unarmed section. Revised description: Average body proportions (Fig. 1): body length of adults 8.3–11.2 mm in males, 8.2–10.2 mm in females. Carapace 27–33% body length, cephalothorax 29–41%, pleon without telson 44–53%, telson 11–13% body length. Thoracic sternites normal, not reinforced by crossbeams. Pleomeres 1–6 contribute 17–19%, 16–19%, 16–17%, 14–15%, 13–15%, 18–21%, respectively, of total pleon length. Abdominal somites 1–5 are 0.9–1.0, 0.8–1.0, 0.8–0.9, 0.7–0.8, 0.7–0.8× length of sixth somite. Terminal margin of sixth pleonite with subtriangular, terminally rounded, lateral shields covering basis of uropods. Eyes (Figs. 1, 2A): Cornea large, bulbous, diameter in dorsal view 38–49% antennal scale length or 5.6–7.8% body length. Eyestalks, including cornea, 51–66% antennal scale length or 8.0–11.0% body length. Surface of eyestalks covered by minute scales along subbasal to basal margins. Carapace (Fig. 2A–D): 3 mid-dorsal groups of pores: field of 19–25 pores 2–10% carapace length behind cervical sulcus (Fig. 2A, B); transverse series of 17–31 pores (Fig. 2A, C) above the cardial sulcus, 14–24% carapace length in front of posterior margin; additional small group of 10–11 pores (Fig. 2A, D) 8–11% in front of posterior margin. Figure 2. View largeDownload slide Mysidopsis similis (Zimmer, 1912), male, body length 9.5 mm (A–D), female 8.2 mm (E–J); anterior body region of male (A); details from A showing dorsal view of series of pore groups on carapace (B–D); right antennula of female, dorsal (E); thoracopod 6 of female, rostral (F); details from F showing modified setae from carpopropodus (G, H); dactylus with claw of thoracic endopod 6, rostral (J). B–D, pore diameters not to scale. Figure 2. View largeDownload slide Mysidopsis similis (Zimmer, 1912), male, body length 9.5 mm (A–D), female 8.2 mm (E–J); anterior body region of male (A); details from A showing dorsal view of series of pore groups on carapace (B–D); right antennula of female, dorsal (E); thoracopod 6 of female, rostral (F); details from F showing modified setae from carpopropodus (G, H); dactylus with claw of thoracic endopod 6, rostral (J). B–D, pore diameters not to scale. Antennules in both sexes (Fig. 2A, E): Terminal article of trunk dorsally with 3 or 4 medium-sized, spine-like setae at inner distal corner, 3 minute, smooth setae more ventrally. Dorsal face of terminal article near distal margin with medio-terminal lobe with a digitus plus 3 or 4 barbed setae, and more proximally small lobe with large, smooth seta plus short, barbed seta. Antero-lateral corner of basal article with lobe-like extension with 3 large, plumose, plus 1 or 2 smaller, barbed setae. Part of setose lobes on median and basal articles bilaterally inversely located between sexes (Fig. 2A versus Fig. 2E). Antennular trunk of females (Fig. 2E): Basal article 1.5–1.7× as long as broad, 53–55% trunk length. Middle article 13–18%, terminal article 33–36% trunk length. Flabellum formed by plumose setae in ventral position, closely behind anterior margin of terminal article. Two plumose setae ventro-medially in nearly central position of inner margin. Distal margin of median article dorsally, with short lobe near inner face, lateral portion of lobe with 1 or 2 plumose setae, medial portion with 4 smooth setae. Distal margin of basal article dorsally with lobe with 5 barbed setae on lateral portion, 2 long, smooth setae accompanied by minute smooth seta on inner portion. Antennular trunk of males (Fig. 2A): Basal article 1.2–1.3× as long as broad, contributing 42–44% trunk length, middle article 17–23%, terminal article 36–40% trunk length. Terminal article ventrally with large, strongly-setose appendix masculina, longer than combined 2 distal articles of trunk (basal portions of appendix below drawing plane in Fig. 2A). Distal margin of median article dorsally with short lobe near outer face, outer portion with 2 plumose setae, medial portion with 2 long, smooth setae. Medially beneath lobe, 3 additional shorter, smooth setae on anterior margin of median article. Basal article with 2 long, smooth setae, latero-dorsally close to anterior margin. Antennae (Fig. 2A): Antennal sympod with large spiniform process on outer distal corner. Antennal scale setose almost along all margins, except for smooth margins at basal 9–14% of length, outer margin weakly, but inner margin strongly, convex. Short apical article marked by inconspicuous, oblique suture 4% of total scale length from tip. Apical article with 5 large, plumose setae. Antennal flagellum backward curved, reaching pleonite 1 or up to pleonite 3 when stretched backwards. Both sexes with flagellum showing 3-articulated peduncle, clearly shorter than antennal scale. Basal article 27–31% peduncle length, second 39–40%, third 31–33% peduncle length. Mandibles (see Fig. 11D): Processus incisivus of left mandible with 3 or 4 strong, plus 3–5 small, teeth; lacinia mobilis strong, with 4–6 serrated teeth; pars centralis with 8–10 densely set, serrated teeth, decreasing in size proximally, with proximal brush of stiff bristles. Processus incisivus of right mandible with 4 or 5 strong teeth; lacinia mobilis with 4 or 5 small, serrated teeth; pars centralis with 6–8 subequal, serrated teeth plus bristles. Mandibular palp with small basal article smooth along all margins; both remaining articles densely setose; median article with smooth setae only; terminal article mostly with smooth setae, but distal half with moderately long, modified seta (central portions bilaterally with acute barbs), accompanied by 6–9 shorter setae with such barbs only on distal 50–70% seta length; no setae with soft barbs. Maxillula (see Fig. 11A): Terminal article moderately slender, apex with 7–10 moderately strong spines, serrated (with small teeth) on central third portion. Endite large, with 1 or 2 smooth setae plus seta with bilateral series of minute, acute barbs along distal 60–70% of its margin; additional smooth seta half-way along outer face. Maxilla: Palp with large distal article, broad, almost evenly-rounded tip. Large setae on distal margin and on terminal 70% of inner margin of apical article; setae bilaterally barbed along slightly less than proximal half, but smooth, thinner in distal portions. Basal article small, mostly smooth along all margins. Narrow exopod with plumose setae on apex, most of outer margin; no setae on proximal 90% of inner margin. Dense coverage by small hairs only along non-setose portions of margins of exopod and on distal article of palp. Three endites of sympod with numerous smooth, some spine-like, setae along inner margins. Only most proximal endite with 2 additional, long, plumose setae. Thoracopods (Fig. 2F–J): Coxae of sympods 2–7 with 2 linguiform lobes (Fig. 2F). Bases 3–8 with soft lobe ending in finger-like process on rostral face near insertion of endopod. Flagellae of exopods 1, 8 all 8-articulated; flagellae 2–7 all 9-articulated. Endopods 1, 2 normal. Claw of endopod 2 strong, but shorter than in remaining endopods. Carpopropodus of endopods 3–8 terminally with 1 or 2 large paradactylary setae (Fig. 2H) flanking dactylus on each side (total of 2–4 setae). At distal half, setae of carpopropodus bear dense, one-sided comb of conspicuously thin setules, whereas thicker proximal part remains smooth. Similar setae also present on first, second articles of carpopropodus. One to three of these setae unilaterally with series of secondary spinules in submedian to subbasal portions (Fig. 2G). Caudal face of dactylus (Fig. 2J) with claw plus 3 or 4 smooth setae, with outermost seta terminally bent or curled to various degrees. Minute, well-sclerotized evagination on inner margin of dactylus. Penes: Length 60–70% of merus length of last thoracic endopod. Terminally with 2 subequal lobes. Anterior lobe close to terminal margin with obliquely transversal row of 5 or 6 large, smooth, posteriorly-bent setae. Posterior lobe with 3 such setae in terminal position. Penis with small, barbed seta near outer distal corner plus 7 or 8 short, soft setae, barbed along distal half, in roughly linear series along outer face. Pleopods (Fig. 3A–D): Length of reduced female pleopods (Fig. 3D) increases in sequence of pleopods 1–5. Pleopod 1 sparsely setose, pleopods 2–5 with flabella of plumose setae (Fig. 3D). Male pleopods (Fig. 3A–C): first exopod 3 or 4× length of endopod, whereas exopods 2–5 only slightly surpass endopods. Linguiform, outwardly directed lobes from basal articles of endopods 1–5, each terminally with 4 or 5 small, barbed setae. Each article of endopods 2–5 with 2 large, plumose setae on distal margin; basal article with an additional smaller seta in about median position on inner margin. Second article of endopod 1 subterminally with small, smooth seta. All endopods with basal article showing 2 or 3 smooth setae on rostral face (Fig. 3A). Article also with 2–6 small, barbed setae. Second to penultimate articles of endopods 2–5 each with 1 or 2 small, smooth setae on mid-anterior face (more often on outer anterior face); no such setae on terminal article. Almost every article of exopods 1–5 with 2 large, plumose setae on distal margin, except terminal article of exopod 4, which bears large modified seta on tip plus small, smooth seta in subterminal position on outer face (Fig. 3C). All except exopod 4 show minute seta in subterminal position on rostral face of penultimate article. Figure 3. View largeDownload slide Mysidopsis similis (Zimmer, 1912), male, body length 9.5 mm (A–C), female 8.2 mm (D–F); male pleopod 1, rostral (A); male pleopod 4, caudal (B); detail of B showing the large terminal seta of the exopod (C); female pleopod 5, rostral (D); uropods, ventral (E); telson, dorsal (F); nauplioid larva at early substage N2, length 1.3 mm, lateral (G). Figure 3. View largeDownload slide Mysidopsis similis (Zimmer, 1912), male, body length 9.5 mm (A–C), female 8.2 mm (D–F); male pleopod 1, rostral (A); male pleopod 4, caudal (B); detail of B showing the large terminal seta of the exopod (C); female pleopod 5, rostral (D); uropods, ventral (E); telson, dorsal (F); nauplioid larva at early substage N2, length 1.3 mm, lateral (G). Uropods (Fig. 3E): Sympod 0.1–0.2× telson length, endopod 1.0–1.1, exopod 1.5–1.6; exopod 1.3–1.6× endopod. Exopod oblong, leaf-like, with straight outer, markedly convex inner margins, setose along all margins. Length 4.5–5.1× maximum width. Statolith composed of fluorite, diameter 0.10–0.15 mm; habitus discoidal, with prominent tegmen, concave fundus; statolith formula 2 + 2 + (0–1) + (8–9) + (0–5) = 12–19. Telson (Fig. 3F): Length 1.9–2.0× maximum width, 1.2–1.5× length of last pleomere. Lateral margins with roughly evenly-spaced (sub)equal spines in continuous series along margins; density of spines lower on median portions of lateral margins. Foregut (see Fig. 12A, B): Lateralia, dorso-lateral infolding, superomedianum of cardiac chamber with stout, serrated spines. Lateralia in addition with long, slender, apically coronate spines. Setae, but no spines, close to inlet (end) of oesophagus. Primary cardiac filter formed ventrally by dense combs of stiff setae behind inlet. Lateralia, infoldings, superomedianum with weak, but distinct setation in addition to armature of spines. Food: Four full foreguts from field samples contained macerated, unidentifiable material and fragments of copepods. Content of midgut and hindgut finely particulate to fully digested, unidentifiable material. Colour (Fig. 1): Live specimens in laboratory showed a relatively uniform, yellow, brown to golden tinge. Cornea golden to brown. Large brown to black chromatophores: two dorsally on telson (Figs. 1, 3A), one ventrally on each of pleomeres 1–5, and one dorsally on thoracomere 8. Apart from these chromatophores, pleon of females (Fig. 1C, D) appeared almost transparent. Habitat: Previously reported from shallow seaweed stands, from night plankton above sandy bottoms at 5–7 m, from plankton above rocky reefs at 18–20 m, also epibenthic down to 35 m (Zimmer, 1912; O.S. Tattersall, 1955; Wooldridge, 1983; Wooldridge & Mees, 2000). According to O.S. Tattersall (1969) the species occurs in swarms, living on the bottom by day in shallow water among seaweeds, but about 2 m above the bottom by night. Samples collected during this study with a hand net swept above rocky reefs at 4–6 m during daytime. Eggs and larvae (Fig. 3G): Two females (8.2 mm in body length) carried four or five eggs each (0.43–0.50 mm diameter) (N = 4). Another female (10.2 mm) carried 12 nauplioid larvae at substage N2 (length 1.2–1.5 mm) (N = 10). Besides the features typical of their state of development, nauplioids showed small setae on antennules, antennae, and along a short stretch ventrally behind mandibular rudiment. A pair of cercopods flanked the end of the abdomen. Each cercopod had 11–16 acute laminae (spines) apically increasing in size (N = 10). Mysidopsis zsilaveczi Wittmann & Griffiths, 2014 (Figs. 4, 5; 11C, F; 12E–G) Mysidopsis zsilaveczi Wittmann & Griffiths, 2014: 1414, figs. 1–4. — Mees, 2017 [in list]. Figure 4. View largeDownload slide Mysidopsis zsilaveczi Wittmann & Griffiths, 2014: diversity of colour patterns in adult female (A), immature (B) or adult males (C–F) from marine hard substrates in part overgrown by sponges and encrusting organisms, in sublittoral habitats off Cape Peninsula, South Africa; laboratory (A) and in situ photographs (C–F) of live specimens 10–12 mm body lengths; laboratory image of recently dead specimen, 6 mm (B). Photographs by Charles L. Griffiths (A, B) and Guido Zsilavecz (C–F). Figures not to scale. Figure 4. View largeDownload slide Mysidopsis zsilaveczi Wittmann & Griffiths, 2014: diversity of colour patterns in adult female (A), immature (B) or adult males (C–F) from marine hard substrates in part overgrown by sponges and encrusting organisms, in sublittoral habitats off Cape Peninsula, South Africa; laboratory (A) and in situ photographs (C–F) of live specimens 10–12 mm body lengths; laboratory image of recently dead specimen, 6 mm (B). Photographs by Charles L. Griffiths (A, B) and Guido Zsilavecz (C–F). Figures not to scale. Figure 5. View largeDownload slide Mysidopsis zsilaveczi Wittmann & Griffiths, 2014, adult female, body length 10.4 mm; anterior body region (A); carapace, lateral (B); left antennula, ventral (C); thoracopod 6, rostral (D); details from D, showing dactylus (F) and modified setae from carpopropodus (E, G); pleopods 1, 4, 5, rostral (H–K); uropods, ventral (L); telson, dorsal (M). Figure 5. View largeDownload slide Mysidopsis zsilaveczi Wittmann & Griffiths, 2014, adult female, body length 10.4 mm; anterior body region (A); carapace, lateral (B); left antennula, ventral (C); thoracopod 6, rostral (D); details from D, showing dactylus (F) and modified setae from carpopropodus (E, G); pleopods 1, 4, 5, rostral (H–K); uropods, ventral (L); telson, dorsal (M). Type material: Slides from two dissected paratypes reexamined: adult male with 10.8 mm body length (NHMW 25607) from the type locality, the east coast of Cape Peninsula; adult male 13.0 mm (NHMW 25603), Oudekraal Bay, west coast of Cape Peninsula (see Wittmann & Griffiths, 2014). Additional material examined: All samples from South Africa, Cape Peninsula, False Bay, coast near Simonstown: adult female 10.4 mm (NHMW 25932), between Rooikrans and Buffels Baai, (34°19’53”S, 18°28’07”E), 6 m depth, 10 Dec. 2015, leg. Jessica Micklem; immature female 5.6 mm, immature male 6.0 mm (SAM MB-A067546), Miller’s Point (34°13’46”S, 18°28’28”E), 4 m, 25 Oct. 2016, leg. Craig Foster; 4 immature females 6.8–10.8 mm (SAM MB-A067547, ZMB 30659), Miller’s Point, 4–5 m, 6 June 2017, leg. Craig Foster; 4 adult males 11.7–12.2 mm (NHMW 25933, ZMB 30658), dive site ‘A-Frame’ at Oatlands Point (34°12’29”S, 18°27’40”E), 6–7 m, 7–24 Sep. 2013, leg. Guido Zsilavecz. Type locality: Atlantic coast of South Africa, sublittoral waters at Oatlands Point, off Simonstown, False Bay, Cape Peninsula. Diagnosis: Modified and updated from Wittmann & Griffiths (2014) to include the newly discovered female. Intermediate to robust body form. Rostrum well developed, subtriangular, terminally forming 60–115° angle, tip rounded; rostrum at most slightly bent ventrally, extending at most to inner anterior angle of eyestalks. Carapace with marked cervical sulcus; single mid-dorsal protuberance (variable in size) at some distance behind cervical sulcus; posterior margin of carapace strongly excavated, leaving last 1.5–2.5 thoracic somites dorsally exposed. Eyes, eyestalks well developed, with large bulbous cornea; eyestalk papillae absent. Antennules with short, stout, 3-articulated trunk. Appendix masculina robust, relatively large. Antennal scale length 2.2–2.7× maximum width, scale extending 28–58% of length beyond antennular trunk; scale without spines, setose almost along all margins, with short but distinct, apical article. Mandibles without molar part; palp normal, 3-articulated. Sympods of maxillula and maxilla without setiferous expansion. Second article of maxilla with 3 setiferous endites. Exopod of maxilla slender, ending in relatively long, plumose seta with size not in continuous series with setae on outer margin of exopod. Maxillary palp conspicuously large, 2-articulated; terminally unevenly rounded. First thoracic epipod large, linguiform with narrow tip, subbasally with large seta. First thoracic endopod with ischium plus merus fused to single element, as typical in genus. Remaining endopods with separate ischium and merus. Both maxillipeds (thoracic endopods 1, 2) noticeably stout, with separate carpus and propodus, both unsubdivided. Carpopropodites of endopods 3–8 3-articulated, middle article always much shorter than remaining 2 articles. Endopods 1–8 terminally strongly setose, with strong claw throughout. Marsupium normal, thoracopod 6 with small, but distinct, linguiform oostegite. Penes well developed, tubular, large, wide, each penis with 2 lobes flanking ejaculatory opening. Female pleopods reduced, weakly setose; pleopod 1 minute, bilobate; pleopods 2–5 short, rod-like, with indistinct to absent endopodal lobe. All male pleopods biramous, densely setose, with large, roughly subquadrangular sympod. Endopods 1–5 with 2, 7, 7, 7, and 7 or 8 articles, respectively; basal article caudally always with large, expanded, plate-like exite. Second article of endopod 1 modified as large, linguiform blade, 1.4–2.0× length of exite. Exopods of pleopods 1–5 with 7, 7, 7, 7–8, 7 articles, respectively. Terminal article of exopod 4 terminally with large, straight, modified seta. Seta bears short, acute barbs in 2 parallel longitudinal series, subterminally along part of distal half. Both sexes with proximal 35–45% of uropod endopods having 10–18 spines along inner margin; spines crowded near basis, in linear, almost continuous series more distally; spines increasing in length distally. Endopod extends 12–31%, exopod 40–55% of telson length beyond telson. Telson linguiform, 33–46 spines along all margins; 1–3 (usually 2) large spines at tip, 14–23 shorter spines on each lateral margin. Series of lateral spines not interrupted by an unarmed section. Description (additions to description by Wittmann & Griffiths, 2014). Body length of adults 10.8–13.7 mm in males, 10.4 mm in only adult female (Fig. 4A) available. Carapace 27–31% body length, cephalothorax 33–36%, pleon without telson 50–54%, and telson 13–16% body length. Pleomeres 1–6 contribute 17–20%, 17–19%, 14–16%, 13–17%, 13–16%, 16–20% pleon length, respectively. Abdominal somites 1–5 are 0.9–1.1, 0.9–1.2, 0.8–0.9, 0.7–0.9, and 0.7–0.8× length of sixth somite, respectively. Terminal margin of sixth pleonite with sinusoidal lateral shields covering basis of uropods. Eyes (Fig. 5A): Cornea large, bulbous, diameter in dorsal view 49–62% antennal-scale length or 6–8% body length. Eyestalks, including cornea, 59–72% antennal scale length or 7–9% body length. Antennules (Fig. 5A, C): Antennular trunk with basal article 1.5–1.6× as long as broad in female, 1.0–1.1 in males. Basal article subrectangular, in female 51–52% length of antennular trunk, middle article subtriangular with 11–16%, and terminal article subquadrangular with 32–39% length of antennular trunk, equivalent to 40–44%, 17–21%, or 39–40%, respectively, in stouter antennules of males. Female antennular trunk with terminal article dorsally, with 4 or 5 spine-like setae on inner distal corner. Anterior margin ventrally, with flabellum formed by 11 or 12 plumose setae; length of setae decreases in continuous series on both sides of longest, submedian seta. Dorsal face of terminal article near distal margin with medio-terminal lobe bearing 1 or 2 digits plus 3 or 4 small, barbed setae; small, more proximal lobe with large spine-like seta, plus short, barbed seta. Large plumose seta near inner margin, medially from small lobe. Dorsally, behind anterior margin of median article, in submedial position, a small lobe with 2 barbed, 2 smooth setae. Medially, beneath basis of lobe, a spine-like seta, together with 0–1 barbed seta. Distal margin of basal article dorsally with spine-like seta, laterally together with anteriorly directed lobe with 4 shorter, barbed setae. Antero-lateral corner of basal article with lobe-like extension with 4 barbed to plumose setae at tip. Antennae (Fig. 5A): Both sexes with flagellum with 3-articulated peduncle, clearly shorter than antennal scale. Basal article 25–34%, second 38–43%, third 32–37% length of peduncle. Mandibles (see Fig. 11F): Masticatory surface only with smooth teeth, bristles. Left mandible: processus incisivus with 5–7 strong teeth; lacinia mobilis with 5 or 6 strong teeth; pars centralis with 11–12 spine-like, densely set teeth, weakly decreasing in size proximally, with proximal brush of stiff bristles. Right mandible: processus incisivus with 4 or 5 strong teeth; lacinia mobilis with 5–7 teeth; pars centralis with 6 or 7 teeth plus bristles. Maxillula (see Fig. 11C): Terminal article moderately slender, apex with 9 or 10 strong, smooth spines. Thoracopods (Fig. 5D–G): Coxae of sympods 2–7 each with 2 proximal linguiform lobes (Fig. 5D). Flagellae of exopods 1–8 with 8, 9, 9, 9–10, 9, 9, 9, 8–9 articles, respectively. Caudal face of dactylus (Fig. 5F) of endopods 3–8 with terminally-coiled seta. Pleopods (Fig. 5H–K): Length of reduced female pleopods increases successively from pleopod 1–5. Pleopod 1 sparsely setose (Fig. 5H), pleopods 2–5 with flabella of plumose setae (Fig. 5J, K). Uropods (Fig. 5L): Sympod 0.2× telson length, endopod 0.9–1.2, exopod 1.1–1.5× length; exopod 1.1–1.5× endopod. Exopod oblong, leaf-like, with straight to slightly concave outer, distinctly convex inner margins, setose along all margins; length 3.5–4.0× maximum width. Telson (Fig. 5M): Length 1.8–2.2× maximum width, 1.3–1.9× length of last pleomere. Lateral margins with roughly evenly spaced (sub)equal spines throughout in continuous series; lower density of spines in median portions of lateral margins. Foregut (see Fig. 12E–G): Lateralia and superomedianum of cardiac chamber with stout, serrated spines. Lateralia with long, slender, apically coronate spines, and more caudally with apically hooked spines. The coronate spines with or without few teeth on proximal half. The hooked spines with series of minute secondary spinules along terminal third to half of inner margin, also partially along median portions. Dorso-lateral infolding not visible. Setation patterns of the foregut as in M. similis. Food: Seven full foreguts from field samples contained macerated, unidentifiable material and remains of crustaceans. Main identifiable crustacean remains were fragments of copepods, followed by amphipods and a total of six ostracods. Contents of midgut and hindgut finely particulate to fully digested, unidentifiable. Colour (Fig. 4): Live specimens of both sexes in laboratory (N = 4; Fig. 4A, B) with pink, red, brown or rusty cephalothorax, including eyes and proximal portions of thoracic legs. Antennae and pleon mostly transparent. Each pleonite ventrally with a large chromatophore, telson with two chromatophores subbasally on dorsal face. Field males (N = 8; Fig. 4C–F) with a great variety of colour patterns, in part reflecting the main colour and colour patterns of the substrate. All specimens, however, with horizontally banded cornea and with semi-ocellate spots bilaterally on thorax. Both structures show variable colour, strongly to only weakly contrasting from colour of surroundings. Banded eyes best visible in Figure 4D–F, semi-ocellate spots in Figure 4A, B, D. Colour and colour patterns disappeared in ethanol-fixed material. Habitat: Solitary during daytime, settled on rocky reef walls mainly overgrown by sponges in 6–10 m depths (Wittmann & Griffiths, 2014). Present samples taken with sweep net at 4–7 m depth on rocky reefs overgrown with benthic invertebrates and algae. Mysidopsis abbreviata n. sp. (Figs. 6–10; 11B, E; 12C, D) Figure 6. View largeDownload slide Mysidopsis abbreviata n. sp.: diversity of colour patterns in adult females (A, B), adult males (C–F) from marine hard substrates in part overgrown by algae and encrusting organisms, in sublittoral habitats off the Cape Peninsula, South Africa; laboratory images of live (A) and recently dead (B) adult females, each 7 mm body length; in situ photographs of adult males, 9 mm (C–F). Photographs by Charles L. Griffiths (A, B), Guido Zsilavecz (C–E), and Jessica Dawson (F). Figures not to scale. Figure 6. View largeDownload slide Mysidopsis abbreviata n. sp.: diversity of colour patterns in adult females (A, B), adult males (C–F) from marine hard substrates in part overgrown by algae and encrusting organisms, in sublittoral habitats off the Cape Peninsula, South Africa; laboratory images of live (A) and recently dead (B) adult females, each 7 mm body length; in situ photographs of adult males, 9 mm (C–F). Photographs by Charles L. Griffiths (A, B), Guido Zsilavecz (C–E), and Jessica Dawson (F). Figures not to scale. Figure 7. View largeDownload slide Mysidopsis abbreviata n. sp., paratypes, male, body length 8.7 mm (A–D, H, K, L), female 7.3 mm (E–G, J); anterior body region of male (A); details from A, showing series of pore groups on carapace, dorsal (B–D); anterior margin of carapace expanded on slide, dorsal (E); right antennula of female, ventral (F); tip of left antennular trunk in female, dorsal (G); tip of right antennular trunk in male, dorsal (H); right antenna, proximally with antennal gland and end sac, ventral (J); labrum, ventral (K); mandibles, caudal (L). B–D, pore diameters not to scale. Figure 7. View largeDownload slide Mysidopsis abbreviata n. sp., paratypes, male, body length 8.7 mm (A–D, H, K, L), female 7.3 mm (E–G, J); anterior body region of male (A); details from A, showing series of pore groups on carapace, dorsal (B–D); anterior margin of carapace expanded on slide, dorsal (E); right antennula of female, ventral (F); tip of left antennular trunk in female, dorsal (G); tip of right antennular trunk in male, dorsal (H); right antenna, proximally with antennal gland and end sac, ventral (J); labrum, ventral (K); mandibles, caudal (L). B–D, pore diameters not to scale. Figure 8. View largeDownload slide Mysidopsis abbreviata n. sp., paratypes, female, body length 7.3 mm (A, C, E), male 9.5 mm (B, D, F–J); labium with part of sternite, ventral (A); maxillula, caudal (B); maxilla, frontal (C); thoracic sternites 1–8 in male (D); first thoracopod (caudal) with sternites 1–4 (ventral) in female (E); right thoracopod 3, rostral (F); details of F, showing modified setae from carpopropodus (G, H); detail of F showing dactylus (J). Figure 8. View largeDownload slide Mysidopsis abbreviata n. sp., paratypes, female, body length 7.3 mm (A, C, E), male 9.5 mm (B, D, F–J); labium with part of sternite, ventral (A); maxillula, caudal (B); maxilla, frontal (C); thoracic sternites 1–8 in male (D); first thoracopod (caudal) with sternites 1–4 (ventral) in female (E); right thoracopod 3, rostral (F); details of F, showing modified setae from carpopropodus (G, H); detail of F showing dactylus (J). Figure 9. View largeDownload slide Mysidopsis abbreviata n. sp., paratypes, female, body length 7.3 mm (A–F, L–N), male 9.5 mm (G–K); left thoracopod 2, rostral (A); details from A, showing modified setae from propodus (B, C); right thoracopod 6, rostral (D); details from D, showing modified setae from carpopropodus (E, F); right thoracopod 8 with penis and part of sternite, rostral (G); details from G, showing modified setae from carpopropodus (H, J); dactylus of left endopod 8, caudal (K); left pleopods 1, 4, 5, in female, rostral (L–N). Figure 9. View largeDownload slide Mysidopsis abbreviata n. sp., paratypes, female, body length 7.3 mm (A–F, L–N), male 9.5 mm (G–K); left thoracopod 2, rostral (A); details from A, showing modified setae from propodus (B, C); right thoracopod 6, rostral (D); details from D, showing modified setae from carpopropodus (E, F); right thoracopod 8 with penis and part of sternite, rostral (G); details from G, showing modified setae from carpopropodus (H, J); dactylus of left endopod 8, caudal (K); left pleopods 1, 4, 5, in female, rostral (L–N). Figure 10. View largeDownload slide Mysidopsis abbreviata n. sp., paratypes, males, body length 9.5 mm (A–D), 8.7 mm (H), 7.5 mm (F), female 7.3 mm (E, G); left pleopod 1 in male, rostral (A); right pleopod 4 in male, caudal (B); detail of B, showing the large terminal seta of the exopod (C); right pleopod 5 in male, caudal (D); last somite with tail fan (E); uropods, ventral (F); spine series along inner margin of endopod of uropod, ventral (G); telson, dorsal (H); nauplioid larva at late substage N2, length 1.4 mm, lateral (J). Figure 10. View largeDownload slide Mysidopsis abbreviata n. sp., paratypes, males, body length 9.5 mm (A–D), 8.7 mm (H), 7.5 mm (F), female 7.3 mm (E, G); left pleopod 1 in male, rostral (A); right pleopod 4 in male, caudal (B); detail of B, showing the large terminal seta of the exopod (C); right pleopod 5 in male, caudal (D); last somite with tail fan (E); uropods, ventral (F); spine series along inner margin of endopod of uropod, ventral (G); telson, dorsal (H); nauplioid larva at late substage N2, length 1.4 mm, lateral (J). Figure 11. View largeDownload slide Caudal aspects of the masticatory portions of the maxillulae (A–C) and left mandibles (D–F) in Mysidopsis similis (A, D), M. abbreviata (B, E), and M. zsilaveczi (C, F). From dissections of females, body lengths of 8.2 mm (A), 10.4 mm (C, F), 7.3 mm (E), and males 8.7 mm (B), 9.5 mm (D). Figure 11. View largeDownload slide Caudal aspects of the masticatory portions of the maxillulae (A–C) and left mandibles (D–F) in Mysidopsis similis (A, D), M. abbreviata (B, E), and M. zsilaveczi (C, F). From dissections of females, body lengths of 8.2 mm (A), 10.4 mm (C, F), 7.3 mm (E), and males 8.7 mm (B), 9.5 mm (D). Figure 12. View largeDownload slide Cardiac portion of the foregut in Mysidopsis similis (A), M. abbreviata (C), and M. zsilaveczi (E) in dorsal view, dorsal wall omitted; details of A, C, E, showing modified spines from the respective, right lateralium (B, D, F); tip of left lateralium in large male of M. zsilaveczi (G). Material dissected from females, body lengths of 8.2 mm (A, B), 10.4 mm (E, F), and males 9.5 mm (C, D), 13.0 mm (G). Figure 12. View largeDownload slide Cardiac portion of the foregut in Mysidopsis similis (A), M. abbreviata (C), and M. zsilaveczi (E) in dorsal view, dorsal wall omitted; details of A, C, E, showing modified spines from the respective, right lateralium (B, D, F); tip of left lateralium in large male of M. zsilaveczi (G). Material dissected from females, body lengths of 8.2 mm (A, B), 10.4 mm (E, F), and males 9.5 mm (C, D), 13.0 mm (G). Type material: South Africa, Cape Peninsula, False Bay, coast near Simonstown: holotype adult male with 9.3 mm body length (NHMW 25934), paratype adult male 9.5 mm (NHMW 25935), sublittoral waters at A-Frame dive site at Oatlands Point (34°12’29”S, 18°27’40”E), 7 Sep. 2013, leg. Guido Zsilavecz; paratypes 2 adult males 8.7, 8.8 mm (SAM MB-A067548), dive site as above, 14 Sep. 2013, leg. Guido Zsilavecz; paratypes adult female 7.3 mm, subadult male 7.3 mm (NHMW 25936), False Bay, between Rooikrans and Buffels Baai (34°19’53”S, 18°28’07”E), 6 m depth, 10 Dec. 2015, leg. Jessica Micklem; paratypes subadult female 6.0 mm, immature female 5.7 mm, 3 subadult males 6.3–7.5 mm (SAM MB-A067554, MB-A067555), False Bay (34°13’46”S, 18°28’28”E), 4 m, 25 Oct. 2016, leg. Craig Foster; paratypes 2 adult males 7.5, 9.7 mm, 3 adult females 6.8–7.3 mm, subadult female 6.3 mm (SAM MB-A067549, ZMB 30660), False Bay, 4–5 m, 6 June 2017, leg. Craig Foster. Type locality: Atlantic coast of South Africa: sublittoral marine coastal waters off Simonstown, False Bay, Cape Peninsula, close to the type locality of Mysidopsis zsilaveczi Wittmann & Griffiths, 2014. Etymology: The species name is a Latin adjective with female gender, referring to the transversely shortened rostrum. Diagnosis: Intermediate to robust body form. Rostrum truncate with rounded latero-terminal edges, less frequently broadly sinusoidal; rostrum slightly bent ventrally. Carapace with well-marked cervical sulcus; without dorsal protuberance; posterior margin of carapace excavated, leaving last 1 or 2 thoracic somites dorsally exposed. Eyes, eyestalks well developed, with large bulbous cornea; no eyestalk papillae present. Antennules with short, stout, 3-articulated trunk. Appendix masculina robust, relatively large. Antennal scale length 2.4–2.8× maximum width, scale extending 15–43% of length beyond antennular trunk; scale without spines, setose almost along all margins, with short, poorly distinguished, apical article. Mandibles without molar part; palp normal, 3-articulated. Sympods of maxillula, maxilla without setiferous expansion. Second article of maxilla with 3 setiferous endites. Exopod of maxilla slender, ending in long, plumose seta in continuous series with setae on outer margin of exopod. Maxillary palp relatively large, 2-articulated; terminally about evenly rounded. First thoracic epipod large, linguiform with narrow tip, no setae present. First thoracic endopod with ischium and merus fused as single element, as typical in genus. Remaining endopods with separate ischium, merus. Both maxillipeds (thoracic endopods 1, 2) conspicuously stout, with carpus, propodus separate, each not subdivided. Carpopropodites of endopods 3–8 each 3-articulated, middle article much shorter than remaining 2 articles. Endopods 1–8 terminally setose, with strong claw throughout. Marsupium normal, thoracopod 6 with small but distinct, linguiform oostegite. Penes well developed, tubular, large, wide, each penis with 2 lobes flanking ejaculatory opening. Female pleopods reduced; pleopod 1 small, stout, weakly setose; pleopods 2–5 short, rod like, well setose; pleopods 1–5 with indistinct to absent endopodal lobe. All male pleopods biramous, densely setose, with large, subrectangular sympod. Endopods 1–5 with 2, 7, 7, 7, 7 articles, respectively; basal article caudally with plate-like exite, linguiform in endopod 1, whereas large, expanded in pleopods 2–5. Second article of endopod 1 is 1.2–1.7× length of exite. Exopods of pleopods with 7 articles throughout. Terminal article of exopod 4 terminally with large, straight, modified seta. Seta subterminally with series of short, acute barbs on inner margin, only few barbs on outer margin. Both sexes with proximal 32–38% of endopods of uropods, with 5–7 spines below statocyst in almost continuous series along inner margin, only basal-most, small spine can be out of line; spines increasing in length distally. Endopod extends 8–37%, exopod 44–60% of telson length beyond telson. Telson subtriangular with rounded apex; slightly sigmoid lateral margins, along all margins with 30–44 spines; 2 large spines at tip, plus 14–21 shorter spines along each lateral margin. The series of lateral spines not interrupted by unarmed section, density of spines slightly lower in central portions of lateral margins. Description: Body length of adults 6.8–7.3 mm in females, 7.5–9.7 mm in males. Carapace 27–34% body length, cephalothorax 33–38%, pleon without telson 48–64%, and telson 11–14% body length. Thoracic sternites reinforced by weakly sclerotized crossbeams (see Fig. 8D, E). Sternites 1, 2 with not always visible, inconspicuous, median humps. Pleomeres 1–6 contribute 18–23%, 15–18%, 14–18%, 14–18%, 12–14%, 17–19%, respectively, to total pleon length. Abdominal somites 1–5 are 1.0–1.3, 0.8–1.1, 0.7–1.0, 0.7–1.1, and 0.6–0.8× length of sixth somite, respectively. Terminal margin of sixth pleonite with sinusoidal lateral shields covering basis of uropods. Eyes (Fig. 7A): Cornea large, bulbous, diameter in dorsal view 40–66% antennal scale length or 6.8–7.7% body length. Eyestalks, including cornea, 44–79% antennal scale length or 8.4–9.2% body length. Surface of eyestalks covered by minute scales in subbasal to basal portions of anterior and posterior margins. Carapace (Fig. 7A–E) with 3 mid-dorsal groups of pores: roughly V-shaped group of 36–51 pores 2–6% carapace length behind cervical sulcus (Fig. 7A, B); additional V-shaped group of 25–38 pores (Fig. 7A, C) 24–28% in front of posterior margin; transversal series of 21–26 pores (Fig. 7A, D) above the (not always visible) cardial sulcus 7–11% in front of posterior margin. Antennules (Fig. 7A, F–H): Basal article subrectangular, middle article subtriangular, terminal article subquadrangular, contributing 31–50%, 13–21%, 32–48% length of trunk, respectively. Trunk stouter in males, with basal article 1.1× as long as broad, compared to 1.3–1.4 in females. Terminal article distally with short, obliquely forward-pointing inner flagellum, and long, mostly sideward-curved outer flagellum, inner distal corner dorsally with 2 or 3 spine-like setae. Males ventrally with large appendix masculina, females with flabellum formed by plumose setae. Appendix masculina strongly setose, longer than combined 2 distal articles of trunk (basal portions of appendix not visible in Fig. 7A). Dorsal face of terminal article near distal margin with medio-terminal lobe with digitus, 4 barbed setae, plus more proximally small lobe with large, spine-like seta, shorter plumose or barbed seta, all in both sexes. Only females with large plumose seta near inner margin, inserted ventro-medially from small lobe on terminal article. Distal margin of median article in both sexes dorsally with small lobe; spine-like seta plus 3 or 4 barbed setae near inner face of lobe. Large plumose seta together with large, spine-like seta subterminally on inner face (only in females). Distal margin of basal article in both sexes dorsally with long, spine-like seta plus, more laterally, anteriorly directed lobe with 3 or 4 shorter, barbed setae. Antero-lateral corner of basal article with lobe-like extension with 3–5 plumose setae at tip. Antennae (Fig. 7A, J): Antennal sympod with spiniform process on outer distal corner. Antennal scale setose almost along all margins, except for smooth margins at basal 9–14% of length; outer margin weakly, inner margin strongly, convex. Short apical article with inconspicuous, oblique suture 4% of total scale length from tip. Apical article with 5 or 6 large, plumose setae. Antennal flagellum backward-curved, reaching to pleonites 1, or up to 3 when stretched backwards. Peduncle 3-articulated, shorter than scale. Basal article 28–32% peduncle length, second 33–37%, third 34–40%. Labrum (Fig. 7K) weakly asymmetrical, with subtriangular, almost smooth ventral face; posterior face with setose ventral portions; strongly cuticularized masticatory surface in postero-dorsal portions. Labium (Fig. 8A) roughly symmetrical, basis and inner face of the 2 lobes densely setose. Mandibles (Figs. 7L, 11E): Masticatory surface with smooth teeth and bristles only. Left mandible: processus incisivus with 3 or 4 large, 3–5 small teeth; lacinia mobilis with 3 or 4 strong teeth; pars centralis with 9–11 spine-like teeth decreasing in size proximally, with brushes of stiff bristles. Right mandible: processus incisivus with 4 or 5 strong teeth; lacinia mobilis with 4–6 teeth; pars centralis smaller than in left mandible, with only 4 large plus 0–1 small teeth plus bristles. Mandibular palp with small basal article smooth along all margins; both remaining articles densely setose; median article with smooth setae only; terminal article mostly with smooth setae as well, but distal half with one moderately long, modified seta (central portions bilaterally with acute barbs), accompanied by 6–12 shorter setae with such barbs only on distal 70%; terminal article with mid-longitudinal series of 4–8 soft, all-around barbed setae on distal 40–60% of rostral face (below drawing plane in Fig. 7L). Maxillula (Figs. 8B, 11B): Terminal article with 8 or 9 strong, smooth spines at transversely truncate apex. Endite (inner lobe) large, with only few smooth setae, 3 setae near apex plus single small seta halfway along outer face. Maxilla (Fig. 8C): Palp with relatively large, terminal article with broad, evenly-rounded tip. Basal article small, mostly smooth along all margins or medio-caudally with plumose seta (not figured) near outer margin. Large setae on distal margin and along most of inner margin of apical article; setae bilaterally barbed along slightly less than proximal half; setae smooth, more slender in their distal portions. Narrow exopod with plumose setae along distal, most of outer margin, plus 2–5 plumose setae, together with small hairs, on distal 15–20% of inner margin. Dense coverage of small hairs along non-setose portions of margins of exopod, as well as of distal article of palp. Three endites of sympod with numerous, smooth, partly spine-like, setae along inner margins. Only most proximal endite with additional long, plumose seta. Thoracopods 1–8 (Figs. 8E, F; 9A, D, G): Coxae of sympods 2–7 with 1–2 (mostly 2) linguiform lobes. Large, densely-barbed seta close to insertion of all exopods on sympod, in most cases accompanied by smaller seta, each associated with large interarticular joints. Sizes increase from exopod 1 to 4–6, decreasing from 6 to 8 in both sexes. Basis of all exopods plate like, with rounded lateral expansion. Basal plate 1.2–1.5× as long as broad in both sexes. Plates show the same relative sizes as the series of exopods, but more discontinuously. Flagellae of first, eighth exopods 8-articulated (Figs. 8E, 9G); flagellae 2–7 all 9-articulated (Fig. 8F). Endopod lengths increasing from endopods 1 to 4, decreasing from 4 to 8 in both sexes. Distinct dactylus (Figs. 8J, 9K) with claw in all thoracic endopods. Sizes of dactyli increasing from endopod 1 to 2, decreasing in discontinuous series from 2 to 8. Maximum rectilinear extension of curved claws increasing in sequence of endopods 2, 1, 3, about equal for 3, 4, decreasing from 4 to 8. Thoracopod 1 (Fig. 8E): Epipod leaf-like, smooth, without seta or hairs (2 setae in Fig. 8E pertain to sympod). Sympod: coxa with medially projecting endite with single large plumose seta at tip; coxa without additional setae, not counting those close to insertion of exopod. Endopod: merischium about 2× carpus length, slightly longer than combined propodus plus dactylus; carpus basally on inner margin with 2–4 smooth setae, latero-distally with smooth seta. Propodus inwardly inclined; propodus with diverse groups of smooth setae on distal half, inner distal corner with longer, smooth seta. Dactylus without spines, densely setose by smooth setae, close to inwardly bent claw by shorter setae. Thoracic endopod 2 (Fig. 9A-C): Smaller than endopods 3–8, with shorter claw compared to 1, 3–7; comparatively large, swollen propodus. Carpus about same length as combined ischium plus merus, but distinctly shorter than propodus. Terminal half of carpus with only 2 smooth setae. Propodus with relatively long, plus several shorter, smooth setae at inner distal corner. Dense set of smooth setae plus modified setae along distal half of outer, rostral face (Fig. 9B). Most setae of the dactylus alike. Rostral face of dactylus only about half its length, with transverse row of 5–8 modified setae (Fig. 9C). Thoracopods 3–8 (Figs. 8F–J, 9D–K): Comparatively short, stout, normal as in species of Mysidopsis. Basis with soft lobe ending in finger-like process, on rostral face near outer distal corner in both sexes. Fifth endopod extends to eyes when stretched. Merus conforms with total length of endopods in that size increases between endopods 3, 4, then continuously decreases to endopod 8. Unlike length of merus, length of ischium and tarsus, decreases from endopod 3 to 8. For this series, relative size of ischium is 99–106%, 80–87%, 68–76%, 65–70%, 60–68%, 57–67% merus length, respectively. Distal half of all endopods with dense set of smooth setae, maximum setation in endopod 3 (Fig. 8F). Carpopropodus 3–8 terminally with 1 or 2 large, paradactylary setae (Figs. 8H, 9F, J) flanking dactylus on each side (total of 2–4 setae). Distal half of setae with dense, one-sided comb of relatively thin setules, thicker proximal part of setae smooth. Similar setae also present on first and second articles of carpopropodus. Setae on endopods 3–7 unilaterally with comb of thin barbs in submedian to subbasal portions (Figs. 8G, 9E). Endopod 8 with corresponding setae (Fig. 9H) without comb in both sexes. Dactylus (Figs. 8J, 9K) of endopods 3–8 with claw, 4 or 5 smooth setae, with outermost one terminally curled. Minute, well-sclerotized evagination on inner margin of dactylus. Penes (Fig. 9G): Length 60–92% of merus length of last thoracic endopod. Anterior terminal lobe slightly shorter than posterior lobe, both lobes with smooth terminal margins. Anterior lobe close to terminal margin, with transverse row of 10–14 large, smooth, posteriorly bent setae. Penis with 3 or 4 plumose setae near outer distal corner; additional 7–10 shorter, soft setae, barbed at distal half, in roughly linear series along outer face. Pleopods (Figs. 9L–N, 10A–D): Total length of female pleopods (Fig. 9L–N) increasing from pleopod 1 to 2, about equal from 2 to 4, increasing from 4 to 5. Total length less variable in male pleopods (Fig. 10A, B, D). Maximum length of male sympods increasing by 16–26% from pleopods 1 to 3, decreasing by 12–24% from 3 to 5, sympods 1, 5 thus showing almost the same length. First exopod 2 or 3× the length of endopod, exopods 2–5 only slightly surpassing endopods. Plate-like exites from basal articles of endopods 1–5 each bearing 4 or 5 small barbed setae on outermost margin; endopods 2–5 with 1 or 2 additional setae on mid-lateral margin. Each article of endopods 2–5 with 2 large, plumose setae on distal margins; basal article with additional smaller seta in subbasal to subterminal position on inner margin. Second article of endopod 1 with convex inner, nearly straight outer lateral margins; (sub)terminally with small, smooth seta. All endopods with basal article with 2–4 smooth setae on rostral face (Fig. 10A). Basal article with 2 or 3 minute, barbed setae. Second to penultimate articles of endopods 2–5 each with 0–2 (mostly 1) smooth seta on mid anterior, more often on outer anterior, face; setae absent on terminal article. Almost every article of exopods 1–5 with 2 large plumose setae on distal margin, except terminal article of exopod 4. Terminal article with large modified seta on tip and 1 or 2 additional, small smooth setae in subterminal position on outer face (Fig. 10C). All except exopod 4 with minute seta in subterminal position on rostral face of penultimate article. Uropods (Fig. 10E–G): Sympod 0.2× telson length, endopod 1.0–1.1× telson, exopod 1.3–1.5× telson, exopod 1.2–1.4× endopod. Endopod subbasally with large statocyst; statolith composed of fluorite; statolith diameter 0.11–0.19 mm. Habitus of statolith discoidal, with prominent tegmen plus concave fundus; statolith formula 2 + 2 + (0–2) + (7–9) + (5–11) + (3–6) = 22–29. Exopod oblong, leaf-like, with straight to slightly convex outer and distinctly convex inner margins, setose along all margins. Length 3.4–4.3× maximum width. Telson (Fig. 10E, H): Length 1.6–1.8× maximum width, 1.2–1.5× length of last pleomere. Lateral margins with roughly evenly-spaced (sub)equal spines. Perioral armature (Fig. 11B, E) and foregut (Fig. 12C, D): Mandibles, maxillulae plus foregut together forming powerful tool with strong spines, teeth. Cardiac chamber of foregut with powerful, weakly bent, smooth spines on lateralia, dorso-lateral infoldings and latero-distal portions of the superomedianum. Ventral portions of superomedianum with weaker, serrated spines (Fig. 12B). Anterior part of the lateralia also with long, slender, apically hooked spines (Fig. 12D). Setation patterns of the foregut as in M. similis. Food: Ten full foreguts from field samples contained macerated, unidentifiable material, detritus, and remains of crustaceans and polychaetes. Main identifiable crustacean remains were ostracod shells (N = 32), followed by fragments of copepods, small mysids, amphipods, cladocerans, and decapod larvae. An adult male (body length 8.7 mm) had a swollen prestomach, filled with 11 entire ostracod shells (length 0.48–0.55 mm, height 0.17–0.29 mm), that included four entire ostracods, three with soft parts partly macerated, and four empty shells. Midgut and hindgut with unidentifiable, finely particulate to fully digested material. Colour (Fig. 6): Live specimens of both sexes examined in the laboratory (N = 9; Fig. 6A, B) with red to pink cephalothorax, including eyes and proximal portions of thoracic legs; antennae and pleon mostly transparent. Laboratory specimens often showed a semi-transparent to transparent pleon, in part with a traverse band (Fig. 6A, B) over terminal portions of pleonite 6 and proximal portions of uropods and telson. Living specimens (Fig. 6A, C–F) of both sexes from laboratory and field shared 1 or 2 blue spots on eyestalks and a pair of varyingly coloured dorsal stripes on thorax; however, these structures were poorly visible in some specimens (Fig. 6A, C; not visible in the recently-died female in Fig. 6B). A broader spectrum of colours was visible in males photographed in situ (N = 6; Fig. 6C–F). As indicated by the distribution of colours on body, eyes, and appendages, there was an important, but limited, effect of the substrate colour patterns. Blue spots on the eyestalks and red-blue stripes on the thorax nonetheless persisted independently of substrate. Colour and colour patterns disappeared in ethanol-fixed material. Larvae (Fig. 10J): A female (6.8 mm body length) carried six nauplioid larvae at substage N1 (length 0.9–1.0 mm); female (7.3 mm) with six N2 (1.1–1.2 mm); female (7.3 mm) with 12 late N2 (1.3–1.5 mm). Besides features typical of the respective development stage, a pair of cercopods flanked the end of the larval abdomen. Each cercopod showed 10–18 acute laminae (spines) with apically-increasing size (N = 15). Apart from the cercopods, the body and naupliar appendages appeared smooth. Habitat: Collected at daytime at 4–6 m on rocky reefs among benthic invertebrates and algae. Nomenclatural statement: A life science identifier (LSID) number was obtained for the new species: zoobank.org/25F1C924-7CBB-4EB5-B74C-20B7298C2E2E. DISCUSSION Morphological comparison The newly sampled material identified as M. similis (Zimmer, 1912) corresponds well to the types, and mostly to the description and drawings of Zimmer (1912). Zimmer (1912) attributed M. similis to Paramysidopsis Zimmer, 1912, which was characterized by ‘branchiae’ on the sympods of thoracopods 3–8. Zimmer (1918) withdrew Paramysidopsis in favour of Mysidopsis G.O. Sars, 1864, but did not revoke the interpretation of the structures as branchiae. According to Nouvel (1964) and Wittmann & Griffiths (2014), such structures are merely lobes ending in a finger-like process (Figs. 2F; 5D; 8F; 9D, G), as found in a number of species of Mysidopsis and Metamysidopsis W.M. Tattersall, 1951, and in at least one of the two known species of Cubanomysis Băcescu, 1968. For Paramysidopsis, Zimmer (1912) mentioned only an undivided endopod of the first male pleopod. The only male in the type material of M. similis is, however, a subadult with a body length of 7.9 mm. The two subadult males in the new material, 6.5 mm and 8.2 mm long, also show an undivided endopod. The subadult status was judged from the short, poorly modified seta at the tip of exopod of pleopod 4, and from the short (as in Zimmer, 1912: figs. 35, 36 versus Fig. 2A), though setose appendix masculina of the antennula. In contrast, all four adult males (8.3–11.2 mm), based on the first pleopods of the new material, have a two-articulated endopod (Fig. 3A). The dissected specimens showed small lobes on the coxae of thoracic sympods 2–7 (Fig. 2F), which were not mentioned or figured by Zimmer (1912). Such lobes were found in all the three species of Mysidopsis examined, the first documentation of these lobes in members of Leptomysinae. Details of the proximal margin of sympods were rarely documented by previous authors, so it is premature to judge the taxonomic importance of this character. There is a close morphological similarity between the three Mysidopsis species from the Cape Peninsula, all sharing most non-chromatic details of the eyes, antennules, antennae, thoracopods, and pleopods. The three species are, however, clearly distinguished by the numbers of spines on endopods of uropods: 5–7 in M. abbreviata n. sp., 10–18 in M. zsilaveczi, and 19–31 in M. similis. The species are also unambiguously distinguished by species-specific sets of modified spines in the foregut (Fig. 12). The interspecific differences among mysid foreguts documented here are paralleled by a great diversity of setae and spines on the foregut lateralia in ten species of Antarctic amphipods (Coleman, 1991). Mysidopsis abbreviata shows a terminally shortened, mostly truncate rostrum having rounded edges, whereas M. zsilaveczi is the only species with a mid-dorsal protuberance on the carapace, a maxillary palp having a terminal article with an unevenly rounded tip, and with a non-linear, crowded arrangement of the basal spines on the endopods of the uropods. Mysidopsis similis also differs from its two congeners by having more strongly modified setae on the carpus of thoracic endopods 3–8, by a smaller and more linguiform exite on the basal article of the endopod of the male pleopods, by a larger number of spines, more densely set on uropods and telson, and by a longer series of spines extending more distally on the endopods of the uropods. Wittmann & Griffiths (2014) discussed in detail the diagnostic characters that separate the 49 previously known extant species (plus one subspecies) of Mysidopsis, simplifying the comparison between M. abbreviata n. sp. and its congeners. The new species appears unique by its shortened, mostly transversely truncate rostrum. As far as known, it shares the comparatively large, two-articulated endopod of the male pleopod 1 only with the South African M. buffaloensis Wooldridge, 1988 (the basal lobe-like structure in Wooldridge, 1988: fig. 3D, interpreted as basal article), M. similis, and M. zsilaveczi, or with the Indian M. indica W.M. Tattersall, 1922. The endopod 1 of the new species is shorter than in M. zsilaveczi, about equal to M. indica, and longer than in at least 32 of the species where the males are known. Moreover, it differs from at least 37 species by a strong, plane, outwards expansion of the exite of the endopod in male pleopods 2–5. Feeding apparatus and food The stomach contents and structure of the feeding apparatus in the three species studied support the finding of Mauchline (1980) that the species Mysidopsis are predominantly carnivorous. Metillo (1995) considered the foregut of two predatory Mysidopsini, M. gibbosa G.O. Sars, 1864, and Americamysis bigelowi (W.M. Tattersall, 1926) (as M. bigelowi) as an extreme case of specialisation because certain spines, found on the lateralia of most mysid species examined, are transformed into tooth-like structures. By analogy, the foreguts of the three Mysidopsis species studied differ from each other by different sets of spines, with the spines showing different structure and size (Fig. 12). Analogous differences are evident for the teeth and spines of mandibles and maxillulae (Fig. 11). According to the review of Mauchline (1980), ostracods are rarely found among stomach contents of mysids. Our data on M. abbreviata n. sp. (and to a lesser degree on M. zsilaveczi) are the first describing ostracods as a main food source of a mysid species. Large amounts of externally uninjured ostracod shells containing tissues at various stages of maceration, were found in the foreguts of M. abbreviata, indicating that the mysids did not bite small pieces from the ostracods, but rather ingested whole these large-sized prey. Maceration to empty shells appears to occur only in the cardiac portion of the foregut. The externally uninjured shells were obviously too large to pass through the narrow foregut funnel into the midgut; accordingly, no traces of shells were found behind the cardiac portion of the foregut. These findings, together with the presence of large, smooth spines (Fig. 12D) rather than serrated spines (Fig. 12F) on the lateralia, suggest that M. abbreviata crushes ostracod prey in the foregut and egests the non-digestible empty shells. The toothed spines of the maxillula (Fig. 11A) and the serrated teeth of the lacinia mobilis (Fig. 11D) in M. similis appear capable of cutting the prey into pieces. The analogous tools in M. abbreviata (Fig. 11B, E) and M. zsilaveczi (Fig. 11C, F) are smooth but more powerful and may thus have a stronger capability of smashing food. The strong, toothed spines on the lateralia of M. similis (Fig. 12A, B) and M. zsilaveczi (Fig. 12E–G) are closely similar to those described by Metillo (1995: fig. 9.5A–E) for M. gibbosa and Americamysis bigelowi, considered to be capable of cutting and masticating chitinous and bulky food. This appears compatible with the predominance of cut and masticated components found in the foreguts of M. similis and M. zsilaveczi. Colour diversity Photographs and materials submitted by divers point to a great colour diversity of the local species of Mysidopsis, particularly M. zsilaveczi (Fig. 4) and M. abbreviata n. sp. (Fig. 6). This includes adaption to the colour patterns of the substrate (Figs. 4C, D; 6F). The phenotypic colour adaptation of crustaceans is mostly related to camouflage and mimicry as defence against visual predators (Tan & Richer de Forges, 1993; Noël & Chassard-Bouchaud, 2004; Guinot & Wicksten, 2015). Despite the obvious diversity, there are also common colour patterns within each of the studied species. Mysidopsis similis is relatively uniform in colour, with a yellow, brown to golden tinge (Fig. 1). Zimmer (1912) had noted a brown body tinge in his description of the species. Mysidopsis zsilaveczi shows banded corneas (Fig. 4D–F) together with semi-ocellate spots (Fig. 4A, B, D) dorso-laterally on the thorax. Detailed examination showed that both structures are always present, but are not clearly visible (bands on the cornea in Fig. 4A, B; semi-ocellate spots in Fig. 4C, F) in some specimens. Most specimens of M. abbreviata show one or two blue spots dorsally on the eyestalks, together with a pair of variously coloured dorsal stripes on the thorax (Fig. 6F). Banded eyes and semi-ocellate spots are found in a great variety of animals, including diverse groups of crustaceans, and are discussed as anti-predator devices and in the context of intraspecific communication signals (Wickler, 1971; Bedini et al., 2002; Blut et al., 2012). Key to the species of mysidopsis from southern africa (modified from wooldridge, 1988, and wittmann & griffiths, 2014) 1 Carapace without distinct mid-dorsal protuberance…………………………………………………………………………… 4 – Carapace with one or two mid-dorsal protuberances behind cervical sulcus ……………………………………………………………………………2 2 Carapace with two mid-dorsal protuberances, followed by a longitudinal saddle. Median article of mandibular palp with large triangular, lateral expansion armed with two spines. Apex of telson truncate with rounded latero-terminal angles Mysidopsis camelina O.S. Tattersall, 1955 (only female known, Atlantic coast of South Africa: False Bay; 10–29 m). – Carapace with only one mid-dorsal protuberance. Apex of telson well rounded ……………………………………………………………………………3 3 Endopod of uropod subequal in length to telson and bears nine spines of approximately equal length near statocyst Mysidopsis eremita O.S. Tattersall, 1962 (only female known, Atlantic coast of South Africa: Lambert’s Bay; coastal). – Endopod of uropod extends strongly beyond telson and bears 10–18 spines increasing in length distally Mysidopsis zsilaveczi Wittmann & Griffiths, 2014 (Atlantic coast of South Africa: False Bay, Cape Peninsula; shallow sublittoral hard bottoms, 4–10 m). 4 Lateral margins of telson without spines ……………………………………………………………………………6 – Lateral margins of telson with spines ……………………………………………………………………………5 5 Lateral margins of telson fringed all along with spines ……………………………………………………………………………7 – Lateral margins of telson with series of spines, sub-basally interrupted by a large smooth (spine-free) section. Rostrum triangular, acutely pointed; rostrum long, reaching base of terminal article of antennular trunk ………… …………………………………… ……Mysidopsis buffaloensis Wooldridge, 1988 (Indian Ocean coast of South Africa: Orient Beach to Buffalo River harbour, East London). 6 Telson subtriangular, its narrow terminal margin with incipient emargination flanked by only one pair of long spines ……………………………………………………………………………………………………… Mysidopsis bispinosa O.S. Tattersall, 1969 (Atlantic and Indian Ocean coasts of South Africa: Table Bay to Algoa Bay; shallow water, sandy beaches, 5–7 m). – Telson trapezoid, with three pairs of spines at traverse, somewhat rounded, terminal margin; median pair longest flanking an incipient cleft, submedian pair by one third shorter, outermost pair minute …………………………………………………… Mysidopsis suedafrikana O.S. Tattersall, 1969 (Atlantic coast of South Africa: Langebaan Lagoon, False Bay; shallow water, 7–9 m, sandy bottom). 7 Telson linguiform to trapezoid ……………………………………………………………………………9 – Telson subtriangular ……………………………………………………………………………8 8 Rostrum long, triangular, with rounded tip. Endopod of uropods ventrally with dense, linear series of 19–31 spines along subbasal to subterminal portions of inner margin ……………………………………………… Mysidopsis similis (Zimmer, 1912) (Atlantic and Indian Ocean coasts of southern Africa: Namibia, Radford Bay; South Africa, Langebaan Lagoon to Algoa Bay; sublittoral hard bottoms, sandy beaches, 4–35 m). – Rostrum short, truncate with rounded latero-terminal edges, less frequently broadly sinusoidal. Endopod of uropods with 5–7 spines in continuous series, spines not densely set, only on proximal half near statocyst Mysidopsis abbreviata n. sp. (Atlantic coast of South Africa: False Bay, Cape Peninsula; shallow sublittoral hard bottoms, 4–6 m). 9 Telson slightly tapering posteriorly. Endopod of uropods ventrally with dense series of spines all along inner margin between statocyst and tip …………………………………………… Mysidopsis schultzei (Zimmer, 1912) (Atlantic and Indian Ocean coasts of southern Africa: Namibia, Radford Bay; South Africa, Lambert’s Bay, False Bay, Algoa Bay; sandy beaches, seaweeds, 5–7 m, closer to surface at night). – Telson terminally broadly rounded. Endopod of uropods ventrally with dense series of spines along subbasal to subterminal portions of inner margin, although without spines on distal 15–30% ……………………………… Mysidopsis major (Zimmer, 1912) (Atlantic and Indian Ocean coasts of southern Africa: Namibia, Lüderitz Bay; South Africa, Great Berg estuary, False Bay, Algoa Bay; benthic, sandy beaches, seaweeds, 0–12 m, more pelagic at night). 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TI - A new species of Mysidopsis G.O. Sars, 1864 from the Atlantic coast of South Africa, with supplementary descriptions of two additional species and notes on colour and feeding apparatus (Mysida: Mysidae)
JF - The Journal of Crustacean Biology
DO - 10.1093/jcbiol/rux118
DA - 2018-03-01
UR - https://www.deepdyve.com/lp/oxford-university-press/a-new-species-of-mysidopsis-g-o-sars-1864-from-the-atlantic-coast-of-Z2Q88RkX9e
SP - 215
EP - 234
VL - 38
IS - 2
DP - DeepDyve
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