Journal of Morphology

doi: 10.1002/jmor.1052090301pmid: N/A

Munshi, J. S. D.; Hughes, G. M.

doi: 10.1002/jmor.1052090302pmid: 29865547

The epithelial and sub‐epithelial organization of the accessory respiratory organs of Anabas testudineus has been compared with that of gills by using light and transmission electron microscopy. The details of vascular supply of respiratory islets (RI) and gill filaments and the presence of venous sinusoids in the two systems suggest that the RI have been derived from gill filaments and lamellae. The biserial arrangement of transverse capillaries (TC) in the respiratory islets (RI) is evident under the scanning electron microscope and their homology with the gill filaments and their secondary lamellae has been established. The two sets of transverse capillaries of respiratory islets have been derived either from embryonic transverse or marginal channels of two sets of lamellae of a gill filament. These capillaries with their endothelial septate valves and tongue‐like processes offer resistance to blood flow.

Miyazaki, Katsumi; Makioka, Toshiki

doi: 10.1002/jmor.1052090303pmid: 29865548

As in other pycnogonids, the adult female reproductive system of Endeis nodosa is limited to the trunk and walking legs of the cephalothorax. The U‐shaped trunk ovary extends eight blind branches separately into the corresponding walking legs up to each femoral segment. In both the trunk and pedal region, the ovary lies dorsally above the gut, sandwiched between the dorsal and the ventral layer of the horizontal septum. Oogonia and very young oocytes occur throughout the ovary. They fill the trunk ovary and, in the tubular pedal ovary, are aggregated into several cord‐shaped longitudinally arranged germ zones. More advanced oocytes occur only in the pedal ovary. None lie in the germ zones. but instead they protrude individually from the wall of the pedal ovary into the hemocoel on cellular stalks. Vitellogenesis occurs in the larger stalked oocytes. An oval genital pore with a cuticular lid lies on the ventral surface of the second coxa of each walking leg. The pedal ovarian lumen is directly connected to the genital pore by a short oviduct in the second coxa. The ovarian structure and oogenetic modes in this pycnogonid species show some common characteristics with those of most chelicerates.

Grove, Bryon D.; Wourms, John P.

doi: 10.1002/jmor.1052090304pmid: 29865557

Embryos of the poeciliid Heterandria formosa develop to term in the ovarian follicle in which they establish a placental association with the follicle wall (follicular placenta) and undergo a 3,900% increase in embryonic dry weight. This study does not confirm the belief that the embryonic component of the follicular placenta is formed only by the surfaces of the pericardial and yolk sacs; early in development the entire embryonic surface functions in absorption. The pericardial sac expands to form a hood‐like structure that covers the head of the embryo and together with the yolk sac is extensively vascularized by a portal plexus derived from the vitelline circulation. The hood‐like pericardial sac is considered to be a pericardial amnion‐serosa. Scanning and transmission electron microscopy reveal that during the early and middle phases of development (Tavolga's stages 10–18 for Xiphophorus maculatus) the entire embryo is covered by a bilaminar epithelium whose apical surface is characterized by numerous, elongate microvilli and coated pits and vesicles. Electron‐lucent vesicles in the apical cytoplasm appear to be endosomes while a heterogeneous group of dense‐staining vesicles display many features characteristic of lysosomes. As in the larvae of other teleosts, cells resembling chloride cells are also present in the surface epithelium. Endothelial cells of the portal plexus lie directly beneath the surface epithelium of the pericardial and yolk sacs and possess numerous transcytotic vesicles. The microvillous surface epithelium becomes restricted to the pericardial and yolk sacs late in development when elsewhere on the embryo the non‐absorptive epidermis differentiates. We postulate that before the definitive epidermis differentiates, the entire embryonic surface constitutes the embryonic component of the follicular placenta. The absorptive surface epithelium appears to be the principle embryonic adaptation for maternal‐embryonic nutrient uptake in H. formosa, suggesting that a change in the normal differentiation of the surface epithelium was of primary importance to the acquisition of matrotrophy in this species. In other species of viviparous poeciliid fishes in which there is little or no transfer of maternal nutrients, the embryonic surface epithelium is of the non‐absorptive type.

Selman, Kelly; Wallace, Robin A.; Player, Denifield

doi: 10.1002/jmor.1052090305pmid: 29865550

The ovary of the seahorse, Hippocampus erectus, is a cylindrical tube bounded by an outer layer consisting of a mesothelium and muscular wall and by an inner luminal epithelium, with a single row of developing follicles sandwiched between the two layers. Follicles are produced by a germinal ridge, which contains oogonia, early oocytes, and prefollicle cells, and which runs along the length of the ovary. The germinal ridge is an outpocketing of the luminal epithelium, as indicated by a continuous underlying basal lamina. Prefollicle cells invest diplotene oocytes and the complex eventually pinches off the germinal ridge as a primordial follicle surrounded by a basal lamina derived from the germinal ridge. Subsequent investment of the primordial follicle by elements of the theca complete the process of folliculogenesis. H. erectus has two ovaries and each ovary has two dorsally located germinal ridges. Thus, in each ovary the derived follicular lamina is bilaterally symmetrical: two temporally and spatially arranged sequences of developing follicles are produced, with the largest follicles found along the ventral midline of the ovary. The advantages of developmental, kinetic, and systemic analyses of these unusual ovaries are indicated.

Blouin, Michael S.

doi: 10.1002/jmor.1052090306pmid: 29865537

Hyla cinerea and H. gratiosa are closely related treefrogs that differ at metamorphosis in the length of the hind limb relative to snout vent length. A developmental series of larvae of the two species raised under uniform laboratory conditions reveals that H. cinerea have proportionately longer legs at metamorphosis than H. gratiosa for the following reasons: 1) Hyla cinerea initiate limb growth at a smaller body size than H. gratiosa, 2) H. cinerea have a faster rate of limb growth, and 3) body growth rates in H. cinerea and H. gratiosa are nearly identical until just before metamorphosis.

de Sá, Rafael O.; Trueb, Linda

doi: 10.1002/jmor.1052090307pmid: 29865541

Hamptophryne boliviana is a medium‐sized microhylid frog inhabiting the forest‐floor leaf litter of South American rainforests. Larvae of this species typically are found near the bottom of small ponds and water‐filled depressions in the forest. On the basis of cleared‐and‐stained specimens, the larval chondrocranium is described, as well as the development of the skeleton and its condition in adults. Contrary to previous reports, adult Hamptophryne boliviana possess neopalatine (= palatine) bones. The vomer is divided into anterior and posterior parts; the degree of development of the posterior vomers varies among individuals and bilaterally within individuals. In its osteological development, Hamptophryne differs from most other anurans studied in that the vomer, and bones of the suspensorium and mandible, appear postmetamorphically. Similarly, the ischium, pubis, carpals, and tarsals do not appear until metamorphosis is completed. The chondrocranium possesses paired suprarostral cartilages—elements that have been reported to be absent in microhylid larvae. Furthermore, the chondrocranium differs from those described for other microhylid taxa by the possession of 1) a subpalatoquadrate bar that is described herein and 2) a greatly expanded, fenestrate sheet of cartilage associated with the larval otic process and otic capsule.

Falen, Steven W.; Szeverenyi, Nikolaus M.; Packard, David S.; Ruocco, Martin J.

doi: 10.1002/jmor.1052090308pmid: 1942074

Magnetic resonance imaging (MRI) techniques were used to study the morphology of the latebra and concentric rings seen in the yolk of White Leghorn eggs during development of the avian embryo. Previous studies of the macroscopic structure of avian yolk have revealed the latebra, a vaseshaped structure beneath the blastoderm composed of white yolk. The bulbous portion in the center of the yolk is termed the body of the latebra. The thinner portion extending toward the blastoderm is referred to as the neck of the latebra. As the neck of the latebra approaches the blastoderm, it flares out to become the nucleus of Pander. The remainder of the yolk often features alternating concentric layers of white and yellow yolk. These layers, which appear as rings in sections, are thought to represent the daily accumulation of yolk during oogenesis. In this study eggs were imaged with a single slice spin echo sequence using MRI parameters that maximized the visualization of the latebra and concentric rings in the egg yolk. Some experiments were conducted for 2 to 3 day periods with eggs kept in the bore of the magnet using a small incubator that was constructed using a temperature‐controlled water pump. The concentric rings of the yolk and the body of the latebra flatten and become more elliptical during development. The neck of the latebra becomes shorter and disappears around the 7th day of incubation. The body of the latebra starts to become incorporated into the embryo at about the 7th day of incubation and usually disappears by the 13th day. The concentric rings are no longer visible as distinct entities at this time. Histochemical procedures carried out as a result of MRI findings indicate that the latebra is an iron‐rich structure.

Dallai, R.; Afzelius, B. A.; Lanzavecchia, S.; Bellon, P. L.

doi: 10.1002/jmor.1052090309pmid: 29865540

The flagellum of the thysanopteran spermatozoon has been examined by electron microscopy and computer‐aided image analysis. The flagellum consists of 27 microtubular elements that probably are formed as outgrowths from three separate basal bodies. Nine of the elements are normal microtubular doublets that carry dynein arms and nine are doublets without dynein arms. The remaining nine elements are microtubular singlets that apparently bear dynein arms and have the same appearance as A‐subtubules of microtubular doublets. The 27 elements are arranged in a fixed pattern that consists of nine groups, each of which begins with a microtubular singlet and ends with an arm‐less microtubular doublet. Computer‐aided image analysis has shown that the A‐subtubules of the doublets and the microtubular singlets have lumens with very similar patterns. The sperm tail is known to have some motility; it generates fast waves running along its length. The amalgamated axonemes hence act as a functional flagellum. The thysanopteran sperm tail is the only type of flagellum known to us that consists of microtubules in a highly asymmetric array.