Raposo, Marcos A; da Silva, Helio Ricardo; Francisco, Barbara Cristina S; Vieira, Odilon; da Fonseca, Odirlei Vieira; de Assis, Claydson Pinto; Kirwan, Guy M; Capdevile, Tomás Gonçalves; Lourenço, Ana Carolina Calijorne; Sobral, Gisela; Bockmann, Flávio Alicino; Selvatti, Alexandre Pedro; Souza Dias, Pedro G B; Zacca, Thamara; Souza-Gudinho, Filipe; de Carvalho, Marcelo Rodrigues; Targino, Mariane; Frazão, Annelise
Birds, along with their dinosaurian precursors, possess a variety of bony cranial expansions. A deep understanding of the phenotypic complexity of these structures would be useful for addressing the development, evolution, and function of hard-tissue cranial ornamentation. Yet, the evolutionary significance and function of these structures have gone largely unaddressed because no unifying conceptual framework for interpreting bony cranial expansions currently exists. To provide such a framework, we examine osseous ornament variation in modern birds, using µ-CT imaging to examine the cranial casque components, structural composition, and developmental changes of two neognathous (Numida meleagris, Macrocephalon maleo) and one palaeognathous species (Casuarius casuarius) and survey the avian osteology literature of the 11 orders containing members with osseous cranial ornamentation. Our anatomical analyses suggest two broad configuration categories: (i) geminal, in which ornaments consist of paired elements only (i.e. within Neognathae) and (ii) disunited, in which ornaments consist of unpaired, midline elements along with paired bones (i.e. within Palaeognathae). Ornament bones contribute to casque elevation (proximal ornament support), elaboration (distal ornament shape), or both. Our results hold utility for unravelling the selection processes, particularly in difficult-to-decipher display roles, that shaped modern avian casques, as well as for the use of extant avians as comparative analogues of non-avian dinosaurs with ornamental head structures.
The distinctive caudal-fin skeleton of gadiforms has puzzled scientists for a long time, because of its many differences in comparison to other teleosts. Contradicting hypotheses interpreted this structure as (i) a highly derived teleostean caudal fin, (ii) a new formation with parts from the caudal, dorsal and anal fins, a so called pseudocaudal, or (iii) a complete evolutionary novelty, a so called neocaudal. To shed light on to this issue, the caudal-fin ontogeny of Lota lota was studied in detail. It differs from the development in non-gadiform teleostean taxa, e.g. by absence of a distinct and early notochord flexion. However, there are also many similarities with other teleosts, e.g. the caudal fin develops before the dorsal and anal fins. Furthermore, the morphology of adult caudal fins of all major gadiform families were studied and reviewed. Our results, in combination with the latest molecular phylogenies, allowed us to discuss the evolution of the gadiform caudal fin and resolve the origin of this highly debated character complex. Although their caudal-fin skeleton shows several derived apomorphies, the gadiform caudal fin is homologous to the caudal fins of other teleosts, without principal inclusion of dorsal- or anal-fin elements.
Seals (Pinnipedia) and otters (Lutrinae) are two major taxa of the mammalian order Carnivora that independently adapted to a semi-aquatic lifestyle. Their sensory capabilities, including hearing, are still not fully understood. Notably, the functional morphology of amphibious hearing presents an interesting example for studying convergent evolution. We therefore investigated the shape and dimensions of morphological traits of the inner ear and the surrounding structures involved in sound perception using Micro-Computer Tomography (µCT) data of 52 skulls belonging to 38 species of the carnivoran subgroup Caniformia. Principal component analysis (PCA) of cochlea shape variables revealed that 82% of shape variation is explained by PC1 and PC2. A number of traits (e.g. cochlea shape, reduction in cochlea turns, flattening of the cochlea, relative size of tympanum and round window) are significantly different from terrestrial Caniformia. We also found an external cochlea foramen in all Pinnipedia, which is likely related to coping with pressure compensation during diving. Finally, we demonstrate that hearing parameters, such as characteristic hearing frequency, correlate with changes in the morphological traits that separate seals and otters from other Caniformia. Our data suggest that large parts of the morphology of ear region of these semi-aquatic carnivorans have independently adapted to allow hearing in air and water.
Establishing relationships between soft tissues and bones in living species can inform our understanding of functional adaptations in their extinct kin in the absence of direct data on habitual behaviours. The koala and the wombats are the only surviving species of the vombatiform suborder, and represent the extant phylogenetic bracket for dozens of fossil marsupial species across nine families. Here we present the first quantitative architectural data on the forelimb myology of the koala and common wombat, alongside redescriptions based on physical and digital dissections. Despite obvious contrasts in how their forelimbs are used in arboreal (koala) and fossorial (wombat) functional contexts, overall they showed only minor differences in qualitative and quantitative measures of myology. When the architectural properties of antagonistic pairs of muscle groups crossing each joint were compared, the greatest contrasts were seen in muscles crossing the elbow, where the wombat exhibited greater relative emphasis on forceful elbow extension than the koala, indicative of adaptations for digging. Our findings reinforce the importance of the elbow as a useful system to explore when seeking discrimination between habitual patterns of forelimb use in extinct vombatiform species.
Skull shape analysis provides useful information on wildlife ecology and potential local adaptations. Common bottlenose dolphins (Tursiops truncatus) often differentiate between coastal and offshore populations worldwide, and skull shape analyses can be particularly useful in this context. Here we quantify skull shape variation between coastal populations from the Gulf of Guayaquil (Ecuador) and the Mediterranean Sea, compared to offshore specimens from multiple oceans. We analysed skull shape differences using 3D models from museum specimens through geometric morphometrics (3DGM). Two complementary landmark approaches included single-point semi-landmarks in homologous features, as well as pseudo-landmarks placed automatically. Results show skull shape distinction between both coastal populations and offshore specimens. Offshore specimens showed little differentiation between distinct locations. Skull shape patterns mostly diverged in the shape and length of rostrum, as well as the shape of the ascending processes of the maxilla, pterygoids, and occipital bones. However, both coastal populations differed in the patterns and direction of change of those features and were also morphologically distinct. Our results are consistent with local data on site fidelity and social structure in the coastal populations. Skull shape changes suggest divergent feeding and sound production patterns are potential drivers, probably specific to the local environment of each community.
The digestive tract of oligochaetes harbours a diverse ciliate community embracing plagiotomids, nyctotherids, astomes, and hysterocinetids. Although several hundred intestinal ciliate species are known, only two hysterocinetids have been reported from the intestine of Holarctic lumbricid earthworms hitherto. The present study is focused on the taxonomy, morphology, and molecular phylogeny of two lumbricid-dwelling taxa, the insufficiently known Protoptychostomum simplex and Hysterocineta bellerophon sp. nov., detected in Central Europe. Diagnoses of the genera Protoptychostomum and Hysterocineta were improved taking into account also features of the oral ciliature for the first time. In the past, the proper classification of hysterocinetids in the class Oligohymenophorea was hampered by the dramatic remodelling of the anterior body end into a thigmotactic sucker, as well as by the helicalization and transfer of the oral apparatus to the posterior body pole. The present phylogenetic analyses of nuclear and mitochondrial genes robustly reject the classification of hysterocinetids in subclass Scuticociliatia or as a distinct subclass, Hysterocinetia. However, hysterocinetids were consistently and robustly nested deep in subclass Hymenostomatia in a sister-position to the free-living Tetrahymena paravorax. The hymenostome affinity of hysterocinetids is also corroborated by the parakinetal stomatogenesis and the stichodyad paroral membrane accompanied by three regularly organized membranelles.
Adult Scolelepis are unique among spionids in having an elongated, pointed snout, used for digging in sediment. Earlier studies have suggested that the pointed part of the larval head was a peristomial extension. Despite this, modern authors characterize larvae and adults of Scolelepis as having an elongated, pointed prostomium. Based on new observations, as well as on literature data, I show that the pointed medioventral process of the head in larvae is formed by lateral peristomial lips, elongated and fused anteriorly, each supported internally by conspicuous fibres. During settlement and metamorphosis, the anterolateral parts of the prostomium extend ventrally and overgrow the basal part of the peristomial process in a tube-like manner, forming a typical adult snout. Thus, in adult Scolelepis, only the wide basal part of the snout is formed by the prostomium, while the anterior, pointed part of the snout (the rostrum) is of peristomial origin. The ventral peristomial lip does not develop in Scolelepis larvae, and the ventral part of the mouth in adults is formed by the anterior extensions of the first and second segments. The diverse composition of the mouth region of different spionids is illustrated, as well as other details of the morphology of Scolelepis.
Bláha, Martin; Patoka, Jiří; Policar, Tomáš; Śliwińska, Karolina; Alekhnovich, Anatoly; Berezina, Nadezhda; Petrescu, Ana-Maria; Mumladze, Levan; Weiperth, András; Jelic, Mišel; Kozák, Pavel; Maguire, Ivana
The narrow-clawed crayfish Pontastacus leptodactylus is a large native European astacid crayfish species distributed in the drainage area of the Azov, Black and Caspian Seas. The species shows immense morphological diversity across its range. Various species and subspecies have been described and, recently, eight species and two subspecies were confirmed in the updated classification of freshwater crayfishes. However, genetic diversity studies of the species are scarce, mostly from limited geographical areas. Therefore, we aimed to analyse the genetic diversity of this species using mtDNA and nuDNA from across their distributional range to verify the presence of described species. Analyses of individuals from 65 populations and 14 countries confirmed the existence of three divergent mtDNA phylogroups corresponding to the geographical area of Central and Southern Europe, Eastern Europe and Asia, and Turkey. Analysis of ancestral ranges revealed the Black Sea basin as the most likely area of origin. The nuDNA analysis showed low diversity partially corresponding to the mtDNA pattern. All analyses showed mitonuclear discordance indicating the existence of a single species. Therefore, we point out the possibility of taxonomic inaccuracy with the current number of valid species within the P. leptodactylus species complex.
Threadfins are primarily marine bony fishes that have part of the pectoral fin modified into specialized sensitive filaments. They compose the Polynemidae, a family with eight genera and 42 extant species. The internal relationships and phylogenetic position of Polynemidae within Percomorphacea are controversial, with highly conflicting hypotheses proposed by both molecular and phenotypic analyses. We performed a cladistic analysis of threadfins based on the most comprehensive sampling of morphological data ever done. The final dataset included 197 characters from external morphology, the laterosensory system, osteology, myology and neurology in representatives of all valid polynemid genera. More than half of the characters are reported here for the first time, notably the myological ones. A sensitivity analysis of 11 different weighting schemes (equal weighting and extended implied weighting parsimony) resulted in a fully resolved tree. Sciaenidae, not Pleuronectiformes, is recovered as sister to Polynemidae. All polynemid genera are resolved as monophyletic except Polydactylus, which is polyphyletic. Filimanus, Pentanemus and Polydactylus s.s. appear as successive sister taxa of all remaining threadfins. Leptomelanosoma, Parapolynemus and Polynemus form a monophyletic group. Eleutheronema and Galeoides appear intercalated with other species of Polydactylus in the apical portions of the polynemid tree.
The elucidation of mechanisms responsible for the reproductive isolation of species is a fundamental part of speciation research. South American poeciliid fishes in the genus Phalloceros represent a promising system in which to study the evolution of reproductive barriers between closely related species. Phalloceros are often found in sympatry with non-sister congeners, and most such species pairs have morphologically divergent female and male genitalia. In recent studies, it has been hypothesized that mismatched genitalia between co-occurring Phalloceros species might act as mechanical barriers to prevent hybridization and might help to explain the diversification of this group. However, this idea has not yet been evaluated empirically with genetic data. Here, we tested this hypothesis using morphological data in conjunction with mitochondrial and nuclear DNA sequence data. Our study focused on Phalloceros anisophallos and Phalloceros leptokeras, two non-sister species that have mismatched genitalia and that occur together in at least four rivers in south-eastern Brazil. Despite the prevalence of hybridization between closely related non-sister species of animals, especially fish, our phylogenetically-based results detected no evidence of mitonuclear discordance and (hence historical hybridization) between the two focal species. Our findings are therefore consistent with the hypothesis that mismatched genitalia prevent hybridization between sympatric species of Phalloceros fishes.
Merlionia zeeae, a new species belonging to a new genus, is described as a member of the cyclopoid family Anthessiidae (Copepoda), based on both sexes collected off the coast of Singapore. The new species was found in the gill cavities of the longnosed stargazer, Ichthyscopus lebeck (Actinopteri: Perciformes: Uranoscopidae), although almost all members of the family are associated with molluscan hosts. However, this copepod is not similar to other genera of the family Anthessiidae due to possessing the following characters: the curved hook-like antenna, which is similar to that of the family Chondracanthidae in both sexes; the distal portion of the maxilla covered with numerous spinules; and the lack of the maxilliped in the female. Both maximum likelihood and Bayesian inferences using partial SSU (18S) ribosomal RNA genes strongly supported a monophyletic clade formed by the new genus, and three anthessiid genera in this study. However, it was not supported that Anthessiidae and Chondracanthidae are closely related. Therefore, the new genus is considered to be a highly transformed member of the former, and the chondracanthid-form antenna might therefore be a product of convergent evolution attributable to the host-switching event from molluscs to fishes.
We assembled datasets of genetic (genomic ultraconserved elements [UCEs], mtDNA) and phenotypic (morphology, voice) characters to address species limits and taxonomy in the slaty-backed nightingale-thrush Catharus fuscater (Passeriformes: Turdidae), a polytypic complex of songbirds with a broad montane distribution in Central and South America. We identified 10 allopatric populations that have been evolving independently for multiple glacial cycles. Genetic structure is broadly correlated with divergence in phenotypic characters, including plumage colour, iris colour, maxilla (bill) colour, and the acoustic structure of vocalizations (calls and songs). We propose an integrative taxonomic revision that recognizes seven species in the complex, including a newly described species from eastern Panama, and four subspecies, of which two are newly described.
Hypotrichs are among the most complex and highly differentiated ciliate lineages, which are distributed in diverse habitats. Members of the family Deviatidae Foissner, 2016 are commonly found in freshwater or low-salinity habitats, as well as soils. During a study of freshwater wetland diversity in China, a novel deviatid ciliate Heterodeviata sinica gen. nov. et sp. nov. and a distinct population of Deviata multilineae Zhang et al., 2022 were investigated based on morphology, morphogenesis, and 18S rRNA gene sequences. The new genus Heterodeviata gen. nov. can be characterized by having two or more left and right marginal rows each, one frontoventral cirral row, the presence of caudal cirri, and two dorsal kineties, one of them being a dorsomarginal kinety. Phylogenetic analyses reveal that Heterodeviata is nested in a well-supported clade with Deviata Eigner, 1995, Perisincirra Jankowski, 1978 and Pseudosincirra Gao et al., 2021, which suggests that the family Deviatidae is monophyletic. The close relationship among the Deviatidae genera were supported after extensive morphological and morphogenetic investigations, as well as molecular phylogeny presented here.
Alonso, Felipe; Terán, Guillermo Enrique; Serra Alanís, Wilson Sebastián; Calviño, Pablo; Montes, Martin Miguel; García, Ignacio Daniel; Barneche, Jorge Adrián; Almirón, Adriana; Ciotek, Liliana; Giorgis, Pablo; Casciotta, Jorge
Killifishes (Cyprinodontiformes) are a group of fish that include a high proportion of small-bodied species living in seasonal aquatic habitats, with narrow geographical distributions and high human impact. They are among the most vulnerable vertebrates in the Neotropical region, with nearly half of the species in threat categories. Herein, we propose a new phylogenetic hypothesis of the Rivulidae genus Austrolebias, based on 10 genes (six nuclear and four mitochondrial) and 191 morphological characters, including 90% of the total valid species of this genus. An updated definition and diagnosis of the existing subgenera of Austrolebias is provided, and these are erected to genera. Also, four new genera are erected to accommodate the taxonomy of the group to the current phylogenetic hypothesis. Additionally, we describe Argolebias guarani sp. nov., from a seasonal pond in the Middle Paraná River basin, which is diagnosed by a unique colour pattern. This addition reinforces this area as a biodiversity hotspot of endemicity and highlights the importance of this region for conservation. Data on the ontogenetic changes in colour pattern, chorion ornamentation of the egg and ecology of this species are also provided.
The aptly named microcormorants (currently placed in the genus Microcarbo) form a morphologically diminutive and distinct clade sister to all other living cormorants and shags. However, the relationships within Microcarbo are largely speculative. Sequence data resolve these relationships unambiguously, with our phylogeny suggesting that the microcormorants separated from the other cormorants ~16 Mya and showing that the two African species [the reed (or long-tailed) cormorant, Microcarbo africanus, and the crowned cormorant, Microcarbo coronatus] are closely related sister taxa, forming a clade that diverged from the other microcormorants ~12 Mya. The deep split between the African microcormorants and the others is considerably older than many well-recognized generic splits within the cormorants (e.g. Leucocarbo and Phalacrocorax). Thus, we suggest that the African microcormorants warrant their own genus, and we erect Afrocarbo, with type species Pelecanus africanus. Within the reduced Microcarbo, we estimate that the little pied cormorant (Microcarbo melanoleucos of Australasia) separated from the sister pair of the Javanese and pygmy cormorants (respectively, Microcarbo niger from south/southeast Asia and Microcarbo pygmaeus from Europe) ~9 Mya and that the latter two species split ~2 Mya. Given the age of these splits, the microcormorants appear to represent another example of morphological conservatism in the Suliformes.