Distal Urogenital Anatomy of Male Southern Coal Skinks, Plestiodon anthracinus pluvialis (Reptilia: Scincidae)

I investigated the morphology and histology of the distal urogenital anatomy of male southern coal skinks (Plestiodon anthracinus pluvialis) from reproductively active individuals collected in Arkansas in order to provide comparative information with recent studies on squamate urogenital anatomy. Specifically, I focused on the basic anatomy and positioning of posterior ducts in this skink, which included portions of the ductus deferens, the ampulla ductus deferentis, the sexual segment of the kidney, the ureter and collecting ducts, as well as aspects of the urodaeal chamber and urogenital papillae. I found a much reduced ampulla ductus deferentis comprising only 0.7 mm in length in the caudal region of the ductus deferens. The sexual segment of the kidney was well developed, being located in collecting ducts of the kidney proper, in walls of collecting ducts leading away from the kidney as well as within anterior portions of the ureter. The anterior dorsal recess of the urodaeum possessed epithelial crypts within a highly folded epithelium. Finally, a ductal triad (ductus deferens, ureter, and a single collecting duct) terminates at each orifice of the paired urogenital papillae. The distal urogenital anatomy of this scincid lizard revealed anatomical features similar to other species within the genus Plestiodon

Hyla versicolor-chrysoscelis Species Complex of Gray Treefrogs in Arkansas: Histological and Ultrastructural evidence

We investigated the Hyla versicolor-chrysoscelis species complex (tetraploid and diploid species, respectively) of cryptic gray treefrogs from Arkansas using light and scanning electron microscopy. From previous studies of this treefrog complex in other states, H. versicolor has been shown to exhibit larger nuclear diameters and larger toe pad epithelial cells than H. chrysoscelis. Based upon average nuclear diameters of eyelid epithelial cells, we found two or possibly three groups of frogs. The presumed H. versicolor exhibited greatly enlarged toe pad epithelial cells using scanning electron microscopy and were found in four counties, three of which are in the Ozark Mountains. Hyla chrysoscelis occurs throughout the stat

Bilateral Diaphyseal Chondrodysplasia and Polymorphic Osteodysplasia of the Tibiofibulas in a Southern Leopard Frog, Lithobates sphenocephalus (Amphibia: Anura: Ranidae)

Much attention has been focused on limb malformations in anurans following the startling discovery of major limb deformities in Northern Leopard Frogs (Rana pipiens) in Minnesota in 1995. The numerous causes for these malformations can be attributed to a number of natural phenomena, or they can be considered as being manmade. In the present study, we report on a previously undescribed type of limb abnormality in a single individual of the Southern Leopard Frog (Lithobates sphenocephalus) from Arkansas. Histological examination of left tibiofibula revealed a complete disruption of the normal diaphyseal bone structure in this adult frog. The tibiofibula was separated into two poorly ossified and mostly fragmented bony shaft regions on opposite sides of the bone lesion. These peripheral segments of compact bone were surrounded by hypertrophic regions of hyaline cartilage intermingled with complexes of dysplastic bone. We observed three major polymorphic bone aggregates. The overall design of these osteogenic regions can best be described as an arachnoid-like patchwork of numerous pockets, channels, spaces, and nodules separated by trabeculae containing a matrix embedded with subperiosteal bone cells. At present, we are unaware of any environmental conditions that could account for the osteochondrous dysplasia in our specimen. Moreover, the remarkable bilateral placement of the 2 lesions in our specimen suggests the possibly of a genetic factor leading to a pairing of hindlimb developmental anomalies during embryonic bone growth in our specimen

Age Estimation using Phalangeal Skeletochronology in Northern Crawfish Frogs, Lithobates areolatus circulosus (Amphibia: Anura: Ranidae), from Arkansas

As an obligate crayfish burrow dweller, crawfish frogs have historically occupied a relatively narrow ecological niche throughout their distribution in the tall grass prairies and grasslands of the central and south-central United States. In Arkansas, the Northern Crawfish Frog, Lithobates areolatus circulosus, occurs in only 19 of its 75 counties. Because of their secretive nature, late winter-early spring breeding season, and current protected status by the Arkansas Game and Fish Commission, this species remains a rarity in most museum collections in the state. Moreover, only anecdotal information exits regarding any aspect of their natural history in Arkansas. In the present study, we chose to conduct a phalangeal skeletochronological investigation using museum specimens (n = 9) deposited in the herpetological collection housed in the Arkansas Center for Biodiversity Collections located at Arkansas State University. Our results were mostly similar to the age-body length distributions from southern Illinois. Our oldest males exhibited 4 lines of arrested growth (LAGs), and this estimated age matched well with the body sizes of 4-year-old males found in Illinois. Two of our 3-year-old males had slightly larger body sizes compared to the Illinois sample. Our oldest female was 5 years old. Her body size was comparable to values found for 5-year-old females in Illinois. Also, 5 years was the maximum age recorded for this species in our study as well as for the frog in Illinois. Nine years has been reported as the maximum lifespan for this species

Mandibular Dentition in Six Species of Salamanders, genus Plethodon (Caudata: Plethontidae), from Arkansas Using Scanning Electron Microscopy

The mandibular (dentary) dentition of six species of Plethodon (P. caddoensis, P. dorsalis, P. fourchensis, P. glutinosus, P. ouachitae, and P. serratus) from Arkansas was studied using scanning electron microscopy. In all species, the mandibular teeth were bicuspid, and each tooth possessed a prominent labial cusp and a well-developed, inward-curving lingual cusp. All species showed similar tooth crown features, except P. caddoensis which exhibited a reduced tooth height and a reduced lingual cusp (only slightly larger than the labial cusp). We compared our data with other studies on premaxillary, maxillary, and palatal teeth in Plethodon and found overall similarities in tooth types. Tooth morphology does not appear to be an effective tool for taxonomic purposes in our Plethodon species because of the range of morphological variation in tooth structure

Toe Tip Morphology in Six Species of Salamanders, genus Ambystoma (Caudata: Ambystomatidae) from Arkansas Using Scanning Electron Microscopy

The toe tip friction surface in six species of Ambystoma (A. annulatum, A.maculatum, A.opacum, A. talpoideum, A. texanum, and A. tigrinum) from Arkansas was examined using scanning electron microscopy. We found no sexual dimorphism in cell surface ultrastructure. Variation within and between species was considerable. The most active burrower, A. tigrinum, possessed the most disorganized cell surface, whereas the least active burrowers (A.annulatum, A.maculatum, and A. opacum) had morphologically similar and relatively smooth toe tips. In A. talpoideum and A. texanum, cell surfaces exhibited microprojections. Only these two species possessed mucous pores in close proximity to the friction surface. The microstructure of cell surfaces transcended species groups in Ambystoma and would not represent a reliable taxonomic tool

Cnemidophorus sexlineatus

Number of Pages: 12Integrative BiologyGeological Science

Germinal Epithelium Cytology during Spermatogenesis in the Alligator Snapping Turtle, Macrochelys temminckii (Reptilia: Chelydridae)

We investigated the cytology of the seminiferous epithelia of the Alligator Snapping Turtle (Macrochelys temminckii). Spermatogenic and regressed testes were assessed from 2 adult individuals collected in Arkansas in May and September of 1993. Specifically, we focused on the cellular phases of germ cell development and maturation. The germ cell morphology and developmental strategy within the germinal epithelium of M. temminckii appear similar to that of other genera of turtles previously studied. Interestingly, mitotic, meiotic, and spermiogeneic cells are nearly identical to that of other turtles studied based on light microscopy. There are also 6 recognizable steps to spermiogenesis, which is slightly different than the 7 steps of most turtles (step 7 absent). Though this study only uses 2 individuals (because of its endangered status), M. temminckii appears to start spermatogenesis in the spring, and the climax of spermiogenesis occurs in the fall similar to that of other temperate turtles studied to date based on light microscopy. Peculiar to both turtles in this study were the regular appearance of very large germ cells in the basal compartment of the germinal epithelium. Based on previous research and our histological analysis these enlarged spermatogonia exhibit hypertrophic characteristics typical of cells undergoing apoptosis