Justin L. Rheubert

The Testicular Sperm Ducts and Genital Kidney of Male Ambystoma maculatum (Amphibia, Urodela, Ambystomatidae)

The ducts associated with sperm transport from the testicular lobules to the Wolffian ducts in Ambystoma maculatum were examined with transmission electron microscopy. Based on the ultrastructure and historical precedence, new terminology for this network of ducts is proposed that better represents primary hypotheses of homology. Furthermore, the terminology proposed better characterizes the distinct regions of the sperm transport ducts in salamanders based on anatomy and should, therefore, lead to more accurate comparisons in the future. While developing the above ontology, we also tested the hypothesis that nephrons from the genital kidney are modified from those of the pelvic kidney due to the fact that the former nephrons function in sperm transport. Our ultrastructural analysis of the genital kidney supports this hypothesis, as the basal plasma membrane of distinct functional regions of the nephron (proximal convoluted tubule, distal convoluted tubule, and collecting tubule) appear less folded (indicating decreased surface area and reduced reabsorption efficiency) and the proximal convoluted tubule possesses ciliated epithelial cells along its entire length. Furthermore, visible luminal filtrate is absent from the nephrons of the genital kidney throughout their entire length. Thus, it appears that the nephrons of the genital kidney have reduced reabsorptive capacity and ciliated cells of the proximal convoluted tubule may increase the movement of immature sperm through the sperm transport ducts or aid in the mixing of seminal fluids within the ducts.

Reproductive Biology of Sceloporus consobrinus (Phrynosomatidae): Male Germ Cell Development and Reproductive Cycle Comparisons within Spiny Lizards

Abstract Reproductive cycles of lizards have long been studied in both field and laboratory scenarios. However, comparisons of spermatogenic cycles and germ cell development strategies in different populations across a large geographic range have yet to be explored. The purpose of this study is to A) describe the spermatogenic cycle and germ cell development strategy of a population of Sceloporus consobrinus in southeast Louisiana, B) compare this cycle to a more northern population of this species, and C) compare the reproductive cycles of species within Sceloporus (N = 21). In S. consobrinus from Louisiana, recrudescence begins in the fall (October and November), and the peak of spermatogenesis is reached the following spring/summer (May, June, July). This spermatogenic cycle is similar to that of a more northern population of S. consobrinus from Missouri. Within the genus Sceloporus, there are two seasonal patterns of spermatogenesis: initiation of spermatogenesis in the summer/fall and initiation of spermatogenesis in the spring. In both summer/fall and spring spermatogenic patterns, spermiogenesis occurs in the spring and may continue into the summer. The seasonal timing of recrudescence is an extremely plastic trait that has evolved multiple times throughout the Sceloporus clade. However, there appears to be an association of summer/fall and spring recrudescence with latitude. Tropical populations have a higher frequency of spring recrudescence and temperate populations have a higher frequency of summer/fall recrudescence.

Ontogenic development of spermatids during spermiogenesis in the high altitude bunchgrass lizard (Sceloporus bicanthalis)

The body of ultrastructural data on spermatid characters during spermiogenesis continues to grow in reptiles, but is still relatively limited within the squamates. This study focuses on the ontogenic events of spermiogenesis within a viviparous and continually spermatogenic lizard, from high altitude in Mexico. Between the months of June and August, testicular tissues were collected from eight spermatogenically active bunchgrass lizards (Sceloporus bicanthalis) from Nevado de Toluca, México. The testicular tissues were processed for transmission electron microscopy and analyzed to access the ultrastructural differences between spermatid generations during spermiogenesis. Interestingly, few differences exist between S. bicanthalis spermiogenesis when compared with what has been described for other saurian squamates. Degrading and coiling membrane structures similar to myelin figures were visible within the developing acrosome that are likely remnants from Golgi body vesicles. During spermiogenesis, an electron lucent area between the subacrosomal space and the acrosomal medulla was observed, which has been observed in other squamates but not accurately described. Thus, we elect to term this region the acrosomal lucent ridge. This study furthers the existing knowledge of spermatid development in squamates, which could be useful in future work on the reproductive systems in high altitude viviparous lizard species.

The ultrastructure of spermatid development during spermiogenesis within the rosebelly lizard, Sceloporus variabilis (Reptilia, Squamata, Phrynosomatidae).

Several recent studies have mapped out the characters of spermiogenesis within several species of squamates. Many of these data have shown both conserved and possibly apomorphic morphological traits that could be important in future phylogenetic analysis within Reptilia. There, however, has not been a recent study that compares spermiogenesis and its similarities or differences between two species of reptile that reside in the same genus. Thus, the present analysis details the changes to spermiogenesis in Sceloporus variabilis and then compares spermatid morphologies to that of Sceloporus bicanthalis. Many of the morphological changes that the spermatids undergo in these two species are similar or conserved, which is similar to what has been reported in other squamates. There are six main character differences that can be observed during the development of the spermatids between these two sceloporid lizards. They include the presence (S. variabilis) or absence (S. bicanthalis) of a mitochondrial/endoplasmic reticulum complex near the Golgi apparatus during acrosome development, a shallow (S. variabilis) or deep (S. bicanthalis) nuclear indentation that accommodates the acrosomal vesicle, filamentous (S. variabilis) or granular (S. bicanthalis) chromatin condensation, no spiraling (S. variabilis) or spiraling (S. bicanthalis) of chromatin during condensation, absence (S. variabilis) or presence (S. bicanthalis) of the longitudinal manchette microtubules, and the lack of (S. variabilis) or presence (S. bicanthalis) of nuclear lacunae. This is the first study that compares spermiogenic ultrastructural characters between species within the same genus. The significance of the six character differences between two distantly related species within Sceloporus is still unknown, but these data do suggest that spermiogenesis might be a good model to study the hypothesis that spermatid ontogeny is species specific. J. Morphol. 275:258–268, 2014.

Observations on Variation in the Ultrastructure of the Proximal Testicular Ducts of the Ground Skink, Scincella lateralis (Reptilia: Squamata)

The North American Ground Skink, Scincella lateralis, is a member of the most speciose family of lizards, the Scincidae. The only descriptions of the testicular ducts of skinks concern the light microscopy of 13 species in eight other genera. We combine histological observations with results from transmission electron microscopy on a sample of skinks collected throughout the active season. The single rete testis has squamous epithelium with a large, indented nucleus and no junctional complexes between cells or conspicuous organelles. Nuclei of sperm in the rete testis area are associated with cytoplasmic bodies that are lost in the ductuli efferentes. The ductuli efferentes have both ciliated and nonciliated cells and show little seasonal variation except for the narrowing of intercellular canaliculi when sperm are absent. When the ductus epididymis contains sperm, the anterior one‐third lacks copious secretory material around luminal sperm, whereas in the posterior two‐thirds sperm are embedded in a dense matrix of secretory material. Light and dark principal cells exist and both contain saccular, often distended rough endoplasmic reticula, and widened intercellular canaliculi that bridge intracellular spaces. Junctional complexes are lacking between principal cells except for apical tight junctions. Electron‐dense secretory granules coalesce at the luminal border for apocrine release. The cranial end of the ductus deferens is similar in cytology to the posterior ductus epididymis. Each of the nine squamates in which the proximal testicular ducts have been studied with electron microscopy has some unique characters, but no synapomorphies for squamates as a group are recognized. J. Morphol., 2013.

Observations on the Sexual Segment of the Kidney of Snakes with Emphasis on Ultrastructure in the Yellow‐Bellied Sea Snake, Pelamis platurus

The sexual segment of the kidney (SSK) is an accessory sex structure in male lizards and snakes (Squamata). We describe histology of the SSK in 12 species of snakes, including one from the basal Scolecophidia, Leptotyphlops dulcis, and from the more advanced Alethinophidia, species from the Acrochordidae (Acrochordus granulatus), Homalopsidae (Cerberus rynchops), Uropeltidae (Teretrurus sanguineus), and eight species from the Elapidae, including six species of sea snakes. We also describe the ultrastructure of the SSK of the sea snake, Pelamis platurus. The SSK of L. dulcis does not include the ureter but does include distal convoluted tubules (DCTs) and collecting ducts. In all other snakes examined, the SSK is limited to the DCTs and does not differ in histology by any consistent character. We found apparently mature individuals of several species with inactive SSKs. Hypertrophied SSKs give positive reactions for protein secretions but variable reactions for carbohydrates. Ultrastructure of the SSK of P. platurus reveals nuclei situated medially in the epithelium and mature electron dense secretory vacuoles in other areas of the cytoplasm. Product release is apocrine. Junctional complexes only occur at the luminal border, and intercellular canaliculi become widened and are open basally. No cytologically unique characters occur in the SSK of P. platurus. The ancestral condition of the SSK in squamates is the presence of simple columnar epithelium specialized for secretion of a protein + carbohydrate product that matures and is released seasonally. Anat Rec, 2012.

Spermiogenesis in the imbricate alligator lizard, Barisia imbricata (Reptilia, Squamata, Anguidae)

Although the events of spermiogenesis are commonly studied in amniotes, the amount of research available for Squamata is lacking. Many studies have described the morphological characteristics of mature spermatozoa in squamates, but few detail the ultrastructural changes that occur during spermiogenesis. This studys purpose is to gain a better understanding of the subcellular events of spermatid development within the Imbricate Alligator Lizard, Barisia imbricata. The morphological data presented here represent the first complete ultrastructural study of spermiogenesis within the family Anguidae. Samples of testes from four specimens collected on the northwest side of the Nevado de Toluca, México, were prepared using standard techniques for transmission electron microscopy. Many of the ultrastructural changes occurring during spermiogenesis within B. imbricata are similar to that of other squamates (i.e., early acrosome formation, chromatin condensation, flagella formation, annulus present, and a prominent manchette). However, there are a few unique characteristics within B. imbricata spermatids that to date have not been described during spermiogenesis in other squamates. For example, penetration of the acrosomal granule into the subacrosomal space to form the basal plate of the perforatorium during round spermatid development, the clover‐shaped morphology of the developing nuclear fossa of the flagellum, and the bulbous shape to the perforatorium are all unique to the Imbricate Alligator Lizard. These anatomical character differences may be valuable nontraditional data that along with more traditional matrices (such as DNA sequences and gross morphological data) may help elucidate phylogenetic relationships, which are historically considered controversial within Squamata. J. Morphol., 2013.

Conspecific pheromone trailing and pheromone trail longevity in the African Colubrid Boaedon fuliginosus

Abstract In snakes, pheromone trailing is a strategy used for long-distance location of conspecifics. The two existing hypotheses for this behaviour are: a) to locate individuals for reproductive purposes; and b) to form aggregations during the winter/dry season. Pheromone trailing for reproductive purposes has been observed in over 20 snake species representing four different families. The ability of adult male African brown house snakes (Boaedon fuliginosus) to track a sexually attractive female (assumed to be producing pheromones), as well as a conspecific male, was tested using a standard Y-maze. The length of time a females pheromone remained distinguishable to a male was also tested using the same methodology. Male B. fuliginosus showed a strong ability to trail females both immediately after the trail was left by a female (100%; n=14) and seven days after a female left a trail (100%; n=14). After 14 days, however, only 71.4% (n=14) of males chose the same arm as the female, demonstrating that the pheromone trail degraded over time. Males also trailed other males in 77.8% (n=18) of trials, which suggests that males may use other male trails to locate females, or navigate through unfamiliar territories.

Novel Cloacal Glands in Snakes: The Phylogenetic Distribution of Ventral Urodaeal Glands in Thamnophiini

Abstract:u2003 Novel ventrally positioned extra-cloacal glands were discovered through examination of cloacal histology of female thamnophiine snakes. The glands discovered, termed ventral urodeal glands, are paired and empty into the caudal extremity of the urodeum, lateral to the opening of the urodeal sphincter, through primary ducts that resemble folds of the urodeal wall. In concordance with historical literature, these glands are the first cloacal glands described in snakes that definitively empty into the urodeum from a ventral position. Ventral urodeal glands are complex, with multiple branching ducts that empty the terminal alveolar glands. The epithelial linings of the branching duct networks are stratified (primary and secondary ducts), pseudostratified (tertiary ducts), or simple (quaternary ducts and terminal alveoli). The epithelia of the terminal alveoli stain weakly with hematoxylin, and an eosinophilic secretory material is common in the lumina of alveoli. The secretion produced in the alveoli stains positive with the periodic acid-Schiffs procedure, negative with brilliant blue, and positive with fast green, indicating that the majority of the secretion is composed of a neutral carbohydrate moiety with a minor protein component. Ventral urodeal glands were observed in all taxa of Nerodia examined, except N. cyclopion, and were not observed in any other taxa of Thamnophiini. Through optimization to Thamnophiini topologies, ventral urodeal glands either evolved once on the branch leading to Nerodia and were subsequently lost on the branch leading to N. cyclopion, or they evolved independently on the branches leading to N. floridana and all other species of Nerodia. Like many of the cloacal glands in squamates, the function of ventral urodeal glands is unknown, and further investigation is needed to elucidate the function of the secretions of these glands.

Histology of the Urogenital System in the American Bullfrog (Rana catesbeiana), with Emphasis on Male Reproductive Morphology

Previous studies have revealed variations in the urogenital system morphology of amphibians. Recently, the urogenital system of salamanders was reviewed and terminology was synonymized across taxa. Discrepancies exist in the terminology describing the urogenital system of anurans, which prompted our group to develop a complete, detailed description of the urogenital system in an anuran species and provide nomenclature that is synonymous with those of other amphibian taxa. In Rana catesbeiana, sperm mature within spermatocysts of the seminiferous tubule epithelia and are transported to a series of intratesticular ducts that exit the testes and merge to form vasa efferentia. Vasa efferentia converge into single longitudinal ducts (Bidders ducts) on the lateral aspects of the kidneys. Branches from the longitudinal ducts merge with genital kidney renal tubules through renal corpuscles. The nephrons travel caudally and empty into the Wöffian ducts. Similar to salamanders, the caudal portion of the kidneys (termed the pelvic kidneys in salamanders) only possesses nephrons involved in urine formation, not sperm transport. Data from the present study provide a detailed description and synonymous nomenclature that can be used to make future comparative analyses between taxa more efficient.