Abstract

Moxostoma lacerum was the first member of the North American ichthyofauna to be documented as extinct. The unique oral morphology of the species has been of interest, as has its unusual diet of small snails. Because of the rarity of specimens, and the disarticulated condition of available skeletons, we take this opportunity to describe the oral skeletal morphology, using the HRXCT technology to reconstruct the skeleton digitally. We find that the premaxillary bones lie posteromedial to the maxillae and that maxilla shape is asymmetrical; it is likely that the animal sucked snails from their shells while holding the shells with a keratinized mandibular shelf.

Abstract

The endocranial space, nerve pattern, and inner ear of a specimen of Uropeltis woodmasoni are described from digital endocasts rendered from high-resolution X-ray computed tomography scans. The cast of the endocranial space reveals short, stout olfactory bulbs as well as general shortening of the brain along the longitudinal axis. The pattern of innervation agrees with descriptions reported for other uropeltid snakes, although this individual exhibits skull asymmetry in the pathway of the glossopharyngeal nerve and the bifurcation of the jugular canal. There are no internal connections between the perilymphatic canal leading to the foramen pseudorotundum, the recessus scala tympani, and the jugular canal, a situation that differs from those of other alethinophidian snakes. The inner ear is compactly packaged with smoothly curved semicircular canals located in close proximity to the vestibule. Semicircular canal size is comparable to those of larger snakes, and the small size of the skull (9.4 mm) coupled with relative enlargement of the sensory regions of the brain and otic capsule is consistent with the morphological pattern of miniaturized vertebrates, although compounding factors, including phylogeny, ontogeny, and variation, are currently not well understood.

Abstract

Secretory activity of serous (poison) cutaneous glands was studied with light and transmission electron microscopy over the ontogenetic cycle of the Black-legged Dart Frog Phyllobates bicolor. Serous gland activity includes two steps: biosynthesis and maturation. Biosynthesis is performed by the rough endoplasmic reticulum, smooth endoplasmic reticulum, and Golgi apparatus, and follows the usual pathways of exocrine secretory processes. Maturation is typical of anuran serous glands, which accumulate their products in syncytial secretory units. Maturation involves merging processes between secretory deposits (vesicles and/or granules) distally from the Golgi stacks, as well as an increase in the surface area between the syncytial cytoplasm and the secretory vesicles/granules. In P. bicolor, this interface area increases through the formation of peculiar cytoplasmic outgrowths. These outgrowths allow transport processes involved in maturational changes of secretory product. During maturational storage, the secretory products of P. bicolor acquire a repeating substructure of spherical to short tubular subunits. This recurrent pattern is seen in cutaneous poisons of several anuran species, regardless of their phylogenetic relationships. Among anurans, condensing serous cutaneous products into repeating aggregations of subunits appears to be a successful strategy, which allows intracytoplasmic accumulation of pharmacologically active and/or toxic molecules through various post-Golgian processes. The present findings provide evidence of a novel repertory of cytological activities that stress the large diversity of the maturational pathways leading to the peculiar repeating arrangement of secretory subunits.

Copeia, the journal of the American Society of Ichthyologists and Herpetologists (ASIH), invites submissions of original work dealing with the biology of fishes, amphibians, or reptiles or using those organisms as models for testing hypotheses of broad significance. Appropriate topics include such areas as ecology, conservation, life history, evolution, systematics, taxonomy, biogeography, phylogeography, and physiology. Principal criteria for acceptance of articles are quality and significance of research, breadth of interest, and clarity and conciseness of expression. The journal does not publish range extensions, listings of species inhabiting geographic areas, teratological notes, or unsolicited review articles. Final acceptance of a

Taxonomic Review of the Western Indian Ocean Species of the Genus Acanthopagrus Peters, 1855 (Perciformes: Sparidae), with Description of a New Species from Oman