Ecotypes often occupy an environmental gradient, which can lead to divergence in physiological traits between ecotypes. We tested the hypothesis that alligators from inland and coastal environments have physiologically and genetically diverged from one another by exposing coastal and inland alligators to hypo-osmotic (0 PSU), iso-osmotic (10 PSU), and hyper-osmotic (20 PSU) salinities. For each alligator, we measured natremia before and after exposure, 1 behavioural trait, 10 histological traits, and gene expression levels in the liver and kidney. We found little evidence supporting population genetic differentiation between coastal and inland alligators, yet found significant physiological divergence between the 2 ecotypes. Coastal alligators exhibited slightly elevated natremia across salinity treatments both pre- and post-trial and there were large structural differences between the ecotypes in both the kidney and liver tissues. Broadly, the metabolic features of the liver were decreased and the osmoregulatory abilities of the kidney were increased to a greater extent in the coastal alligators than in the inland alligators, especially at high salinities. This was also reflected in the gene expression data, where most differentially expressed genes were involved in metabolic pathways. Together, these findings suggest that coastal alligators maintain sodium balance through a combination of increased renal processing capacity and a slightly elevated natremia set point. Overall, we found that the salinity gradient used in our study elicited contrasting physiological responses between alligators from coastal and inland environments.

The demography of the northern watersnake, Nerodia sipedon sipedon (Linnaeus, 1758), was systematically studied over a 17-year period in a complex of artificial ponds on protected property in the northern Allegheny Mountains of southwestern Pennsylvania. Sexual maturity was reached by the age of three years in males and four years in females. Asymptotic body size was reached at 55 cm in five years in males and at 85 cm in seven years in females. Population size was estimated to be about 43 snakes per year, with most adult males ranging 50-59 cm in body size and adult females ranging 70-79 cm in body size. Annual survivorship, recapture probability, and population size all increased in the years after wetland renovation. Among first captures, male:female sex ratio was 0.29:1.00, and juveniles comprised 26.4% of the population. Most adults were approximately five years old, and recapture intervals indicated minimum maximum ages of eight years for both males (n = 1) and females (n = 2), with skeletochronology estimating maximum ages ranging 16-18 years among the oldest and largest females. Clutch sizes averaged 19 young. Two of the six swabbed females tested positive for Ophidiomyces but with low fungal loads. Many of the life history traits examined in our study population conformed to those of other northern watersnake populations at northern latitudes. However, our results were indicative of a large population subjected to strong selection against small individuals and conflicting rewards for increasing body size.

Currently, there is limited histological data for spermatid morphologies within the testes of squamates. There are only 10 species of lizard that have complete ultrastructural data across the entire process of spermiogenesis, including several species of Sceloporus. These studies have shown that differences can be seen between spermatids of saurians within the same family or genus. Thus, the present study continues to test the hypothesis that differences exist in spermatid morphology between species within the same family. We collected five Phrynosoma cornutum males from Arizona. Their testes were extracted and processed with standard TEM techniques. Many of the characteristics of spermiogenesis within P. cornutum are conserved and similar in morphology to other phrynosomatid lizards. These similarities include the development of the acrosome, perforatorium, subacrosomal cone, nuclear rostrum, and epinuclear lucent zone. However, there were also differences observed in P. cornutum spermatids that are distinct compared to other phyrnosomatids. For example, P. cornutum spermatids include a wider and more robust perforatorium and less spiraling of the chromatin during condensation than that of other phrynosomatid lizards. The present results corroborate previous studies and indicate that even with morphological conservation within saurian spermatids, character differences between species can be recognized. Further studies on spermiogenesis are required to judge the relevance of these ontogenetic changes in terms of using them in amniotic or squamate spermatid/spermatozoa phylogenic analysis.

In some species of vertebrates egg brooding is a costly form of parental care. Therefore, misdirection of parental care can significantly lower a female’s fitness. Because of the maternal investment and increased survivorship to offspring from egg guarding, a brooding female should home to her nest site after being displaced a short distance and discriminate between her own eggs and eggs from other females. In this study, we experimentally tested, in the field, alternative hypotheses concerning homing ability and egg discrimination in a population of nesting western slimy salamanders ( Plethodon albagula ). Fourteen brooding females were displaced 1 m to the left or right of their nest sites (determined randomly) for the homing experiment. Furthermore, brooding females (n = 13) were presented with their own clutches, which were displaced 50 cm to the left or right (determined randomly), and unfamiliar egg clutches at their original nest sites. The females were released at an equal distance from both egg clutches. After 24 hours, 12 displaced females (86%) had returned to their own nest sites and were brooding their egg clutches. Also, after 24 hours, nine test females had returned to their own nest sites and were brooding the unfamiliar egg clutches. No control or test females were present at the other new nest site locations. Therefore, we suggest that brooding female P. albagula do home to their nest sites and exhibit indirect egg discrimination.

I investigated the microanatomy of the distal urogenital system of the male Wood Frog (Lithobates sylvaticus) from a small sample (n = 6) collected in northern Arkansas in February 2020. Specifically, my primary objectives were as follows: 1) to focus on the histology of the paired Wolffian (urogenital) ducts caudally from the kidneys to their merging with the urodeum of the cloaca, 2) to reveal the structure of the paired seminal vesicles (sperm storage structures), and 3) to compare epithelial morphologies between the distal urogenital tract and its neighboring distal alimentary tract. This information will promote a clearer understanding of this anatomical region for a North American ranid species and allow for comparisons to be made with other ranid frogs worldwide.

The flat-headed snake, Tantilla gracilis Baird and Girard is a small reptile belonging to the family Colubridae. Feces from a single T. gracilis from McCurtain County, Oklahoma, USA, was collected and examined for coccidia; it was found to be passing a new species of Caryospora. Oöcysts of Caryospora sargentae n. sp. are spheroidal to typically subspheroidal with a moderately-pitted bi-layered wall, measure (L × W) 20.7 × 19.2 µm, and have a length/width (L/W) ratio of 1.1; a micropyle and oöcyst residuum were absent but one to several small, irregular to spheroidal masses of non-refractile debris within the oocyst was present as well as a polar granule attached to the inner oöcyst wall. Sporocysts are ovoidal and measure 15.0 × 11.0 µm, L/W 1.4; a nipple-like Stieda body is present as well as a distinct rounded sub-Stieda body. The sporocyst residuum is composed of a large, dense, irregular mass of various sized granules located between and often obscuring the sporozoites. This is the third coccidian described from the flat-headed snake. In addition, we include some data on the endogenous development of the coccidian.

During October and November 2021, 33 creek chubs, Semotilus atromaculatus, were collected from 3 sites in Polk County, Arkansas (Ouachita River drainage), and their gills, gallbladder, fins, integument, musculature, and other major organs were examined for myxozoans. The gills of 9 (27%) were infected with a new myxozoan, Myxobolus fountainae n. sp. Qualitative and quantitative morphological data were from fresh and formalin-fixed preserved spores, while molecular data consisted of a 1918 base pair sequence of the partial small subunit ribosomal RNA gene. Phylogenetic analysis grouped M. fountainae n. sp. with the other leuciscid-infecting myxobolids from North America and within a larger clade of European myxozoans. In addition, histological information is provided on the infection. A previous record of Myxobolus muelleriBütschli, 1882, from the gills and ureters of S. atromaculatus is considered invalid and represents an unknown species. Myxobolus fountainae n. sp. is the only named myxozoan known to infect the gill filaments of S. atromaculatus, whereas Myxobolus pendula (Guilford, 1967) infects the gill arches.

I investigated the seasonal testicular histology and acystic lobular spermatogenesis in the Western Lesser Siren, Siren intermedia nettingi, from periodic sampling of this salamander over a span of 21 yr (1994-2015) in northeastern Arkansas. My results include the following general findings: 1) the largest testicular lobules occurred primarily in January-February during spermiogenesis and spermatozoa maturation; 2) lobular regression and spermatogenic cell recrudescence were underway by late March; 3) proliferation of secondary spermatogonia in lobules was prominent in May; 4) transformation of secondary spermatogonia into primary spermatocytes occurred by mid-July, and these cells became larger in diameter through increased nuclear size and by being heavy laden with lipid droplets, 5) lobular diameters gradually increased through the expansion of lobular luminal open space in July-August, and 6) lobular size continued to increase in October-December with lumina containing numerous secondary spermatocytes. Specifically, my primary objective in this part of a long-term study was to present histologically, for the first time, the annual testicular cycle in this species along with an explanation of the unique cellular complexities of acystic lobular spermatogenesis, a process which this sirenid species shares with another genus (Pseudobranchus) within the salamander family Sirenidae. No other vertebrates of any kind possess this type of spermatogenesis.

Between November 2018 and December 2021, 35 juvenile and adult Western Creek Chubsuckers, Erimyzon claviformis, were collected from 5 sites in western and southern Arkansas (Ouachita and Red River drainages), and their gills, gallbladders, fins, integument, other major organs, and musculature were examined for myxozoans. The fins of 12 (34%) individuals were infected with a novel species, Myxobolus stuartae n. sp. Qualitative and quantitative morphological data were obtained from formalin-fixed preserved myxospores. Molecular data from ethanol-preserved specimens consisted of a 2,028 base pair sequence of small subunit (SSU) ribosomal DNA (rDNA) from a specimen collected in Nevada County. Three other specimens from Polk County yielded partial SSU rDNA sequences that were identical to the first sequence. Phylogenetic analyses placed M. stuartae n. sp. as sister to Myxobolus bibullatus (Kudo, 1934), both clustering with other catostomid-infecting myxobolids. This is the first fin-infecting myxozoan reported from E. claviformis.

Nothing is known of the coccidian parasites of the Carolina wren, Thryothorus ludovicianus ludovicianus (Latham, 1790). Here, we report a new species of Isospora from T. l. ludovicianus from Oklahoma, USA. Faecal samples were collected between September and December 2021 from five adult T. l. ludovicianus taken with a mist net from McCurtain County, Oklahoma, USA, and examined for coccidian parasites. Samples were placed in individual vials containing aqueous potassium dichromate. They were examined for coccidia after flotation in Sheather’s sugar solution, measured, and photographed. Tissue samples from the intestine of a single positive bird were removed and placed in 10% neutral-buffered formalin for examination of coccidian endogenous stages. A single Carolina wren (20%) was found to be passing a new species of Isospora. Oocysts of Isospora edwardwilsoni n. sp. were subspheroidal to ovoidal with a smooth bi-layered wall, measured (L × W) 23.8 × 20.3 µm, and had a length/width (L/W) ratio of 1.2; a micropyle and oocyst residuum was absent but typically one to up to four polar granule(s) was present. Sporocysts are ovoidal to ellipsoidal and measured 15.3 × 9.7 µm, L/W 1.6; a knob-like Stieda body was present as well as a distinct rounded sub-Stieda body. The sporocyst residuum was composed of various-sized granules in a compact irregular mass or dispersed between and across the sporozoite, or a combination of both within the same sporocyst. Information is also presented on the endogenous development of this coccidian. This is the first coccidian reported from T. l. ludovicianus and, more importantly, the first known from the members of the family Troglodytidae in North America.

Between November 2018 and December 2021, 35 juvenile and adult Western Creek Chubsuckers, Erimyzon claviformis, were collected from 5 sites in western and southern Arkansas (Ouachita and Red River drainages), and their gills, gallbladders, fins, integument, other major organs, and musculature were examined for myxozoans. The fins of 12 (34%) individuals were infected with a novel species, Myxobolus stuartae n. sp. Qualitative and quantitative morphological data were obtained from formalin-fixed preserved myxospores. Molecular data from ethanol-preserved specimens consisted of a 2,028 base pair sequence of small subunit (SSU) ribosomal DNA (rDNA) from a specimen collected in Nevada County. Three other specimens from Polk County yielded partial SSU rDNA sequences that were identical to the first sequence. Phylogenetic analyses placed M. stuartae n. sp. as sister to Myxobolus bibullatus (Kudo, 1934), both clustering with other catostomid-infecting myxobolids. This is the first fin-infecting myxozoan reported from E. claviformis.

I examined the morphology of Rathke’s glands (RG) in the Alligator Snapping Turtle, Macrochelys temminckii, using light microscopy and scanning electron microscopy. This species possesses 4 pairs of RG (i.e., an axillary and three inframarginals) that are embedded beneath marginal bones and are named primarily according to the anatomical location of their orifices. These holocrine-type, exocrine, integumentary glands are anatomically and ultrastructurally similar to one another. Each gland contains a single and highly vascularized secretory lobule, which is bounded by a thick tunic of asymmetrically-arranged striated muscle bundles. Two types of secretory vacuoles were identified within the holocrine cells of the glandular epithelium. The results of this study generally support my previous findings on RG in Chelydra serpentina, the Snapping Turtle; however, some lack of cellular and structural conformity was evident compared to glands in this close relative as well as to RG in other turtle species. For example, epithelial cell layer depth and configuration and glandular lumen composition were inconsistent with prior observations. Moreover, the dearth of secretory cells and their products within the lumen of glands suggests that storage or temporary retention of glandular materials differs markedly from the conditions found in RG of other cryptodiran turtles. The functional role of RG secretions in all turtles remains speculative.

Previous studies demonstrated that nasolacrimal ducts were present in the ancestral plethodontid lineage. Two lineages within Plethodontidae contain individuals that do not possess nasolacrimal ducts: Desmognathus and Eurycea. Earlier works examined only two species of Desmognathus, D. fuscus and D. monticola. We obtained every Desmognathini (Phaeognathus + Desmognathus) species possible from novel collections and museum collections and assessed presence or absence of nasolacrimal ducts using contrast-enhanced computed tomography and routine histological procedures. The goal was to test the hypothesis that nasolacrimal ducts were lost on the evolutionary branch leading to Desmognathus. We rejected our hypothesis by finding that nasolacrimal ducts were absent in all Desmognathus that we examined and Phaeognathus hubrichti; thus, we recovered the absence of nasolacrimal ducts on the evolutionary branch leading to Desmognathini.

Ozark hellbenders (Cryptobranchus alleganiensis bishopi) have undergone marked population declines across their entire distribution. A variety of ecological life history research has been conducted to determine the cause(s) of the declines. Historically, hellbender diet studies used stomach content examination methods; however, alternative approaches such as less intrusive stable isotope analyses are now options for researchers. The goals of our study were to conduct stable isotope analysis on live and formalin-preserved museum specimen Ozark hellbender tissues to identify diet composition in the Eleven Point and Spring rivers, Arkansas. Also, we used stable isotope analysis to investigate if Spring River hellbender diets have changed over time. We sampled fish, live hellbenders (non-destructively), and formalin-preserved hellbender tissues from museum collections for stable isotope analysis. We sampled crayfish for assemblage composition and stable isotope analysis. The results of our stable isotope study revealed three main findings: (1) there were no statistically significant differences between hellbender δ13C and δ15N values among sites and hellbender stable C and N isotopes were correlated with body length; (2) traditional δ13C versus δ15N bi-plots and trophic discrimination values did not provide complete discernment in hellbender diets; however, Bayesian MixSIAR models revealed hellbenders to be generalists, and (3) the use of δ13C and δ15N values adjusted historic formalin-fixed and ethanol preserved hellbenders matched well with current crayfish and fish stable isotope values based on Bayesian MixSIAR models. These findings provide important diet information and a possible tool to examine dietary patterns from preserved specimens that may be used for hellbender conservation and management.

We examined the distal excurrent ductal morphology and penile anatomy of the urogenital system in the Mississippi Mud Turtle, Kinosternon subrubrum hippocrepis, from a small sample of individuals collected in Arkansas in order to provide additional information regarding turtle urogenital anatomy.Specifically, we focused on the basic anatomy and histology of distal excurrent ducts (ductus deferens and ureter), associated structures (urogenital papillae), and penile histology in this kinosternid turtle.In addition, we provide an overview of the gross urogenital anatomy in this turtle, given that little detailed information exists on this topic in the chelonian literature.

During July 2019, 21 Golden Topminnows (Fundulus chrysotus) were collected from an oxbow lake in McGehee, Desha County, Arkansas, and examined for parasites. Found were 4 taxa of endoparasites, including 3 digeneans (Clinostomum marginatum, Homalometron sp., and Posthodiplostomum minimum) and a nematode (Spiroxys contortus). We document a new host record for S. contortus and the first report of parasites in F. chrysotus from the lower Mississippi River Drainage.

I examined histologically the distal urogenital anatomy in male Prairie Racerunners (Aspidoscelis sexlineatus viridis) from a small seasonal sample of individuals collected in Arkansas in order to provide additional information regarding squamate urogenital anatomy.Specifically, I focused on the basic anatomy and positioning of posterior ducts and associated structures in this teiid lizard.The anatomical structures included the ductus deferens, ampulla ductus deferens, ampulla urogenital papilla (Aup), ureter, inner core tissue mass, urodaeum, and the urogenital papilla.The two Aup, which are small complimentary blind pouches representing the terminal repositories for products released by urogenital ducts, are striking anatomical features of the distal urogenital anatomy in this lizard.Interestingly, the Aup, which are characteristic anatomical structures present in very few additional lizard species (e.g., in some members of families Gerrhosauridae, Gymnophthalmidae, and Varanidae) are also present in colubrid snakes and not in crotalid snakes.

The urogenital system of male squamates consists of the testis, testicular ducts, and sexual segment of the kidney. These structures undergo seasonal variation, and their morphology is variable across taxa. Despite multiple studies examining the morphology of the various components of the reproductive system, few studies have examined squamates in sympatry. The purpose of this study was to investigate the morphology and seasonal variation of the reproductive system in two taxa that are sympatric with one another, Anolis carolinensis and Sceloporus undulatus, from southeastern Louisiana. Specimens were collected monthly for an entire year and processed for histological and ultrastructural analysis. Both species have a single rete testis leading from the testis to the ductuli efferentes, which leads into the proximal portion of the epididymis. The rete testis consists of a simple squamous epithelium with irregularly shaped nuclei, the ductuli efferentes consists of a ciliated simple cuboidal epithelium, and the epididymis a pseudostratified columnar epithelium. No differences were observed in the morphology of the urogenital systems between taxa but phenological variation was observed in terms of the tissue development for reproduction. Anolis carolinensis has an extended active period and two separated periods of maximal activity evidenced by two peaks in the ductuli efferentes epithelial height and tubular diameter (March and July) whereas Sceloporus undulatus only had a single peak occurring in June. These results suggest that reproductive morphology may be conserved at taxonomic levels above family level, and reproductive activity may be constrained phylogenetically and is not solely dependent on environmental factors, at least in terms of geographic range, though it is acknowledged that microhabitats may play a major role in cyclicity of reproductive events. Future studies examining species at various taxonomic levels, as well as species in sympatry, will provide additional insight into hypotheses concerning abiotic factors and reproductive biology.

Vast differences in available resources between habitats can have profound influences on aspects of an organism's life history, such as reproductive investment. Our study investigated how differences in nutrient availability affect sperm size in Diamond-backed Watersnakes (Nerodia rhombifer). We compared body size and sperm morphometrics between two populations with differing nutrient availability: a naturally occurring lake and a commercial fish farm. We hypothesized that prey availability affects sperm morphometrics. Our null hypothesis was that there would be no significant difference in sperm morphometrics between populations, whereas our alternative hypothesis was that the snakes from the fish farm would have significantly longer sperm. We measured total sperm length, sperm head length, sperm tail length, and snout–vent length (SVL). We then used two-tailed t-tests and AIC model selection to test our hypotheses. SVL was not correlated with sperm size. Furthermore, none of the sperm morphometrics were significantly different between the two populations. Finally, a nearly 1:1 correlation between sperm tail length and total sperm length was found. AIC model selection corroborated these results by choosing only sperm head length and sperm tail length as significant predictors of total sperm length. This is the first published study to explicitly compare sperm morphometrics between two populations of the same snake species. Additional studies of this nature are required to corroborate whether lack of significant differences in sperm morphometrics among snake populations are common.

I examined histologically the distal urogenital anatomy in male Prairie Racerunners ( Aspidoscelis sexlineatus viridis ) from a small seasonal sample of individuals collected in Arkansas in order to provide additional information regarding squamate urogenital anatomy. Specifically, I focused on the basic anatomy and positioning of posterior ducts and associated structures in this teiid lizard. The anatomical structures included the ductus deferens, ampulla ductus deferens, ampulla urogenital papilla (Aup), ureter, inner core tissue mass, urodaeum, and the urogenital papilla. The two Aup, which are small complimentary blind pouches representing the terminal repositories for products released by urogenital ducts, are striking anatomical features of the distal urogenital anatomy in this lizard. Interestingly, the Aup, which are characteristic anatomical structures present in very few additional lizard species (e.g., in some members of families