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

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

Can Assisted Reproductive Technologies Help Conserve 300 Million Years of Evolution? A First Attempt at Developing These Technologies for Male Reptiles

Biodiversity loss is the most critical environmental problem threatening ecosystem, animal, and human health today. Increases in extinction rates have been observed over the past 50 years, with reptile losses occurring twelve times faster than traditional extinction rates. This demonstrated biodiversity loss is secondary to climate change, habitat destruction, infectious disease, invasive species, poaching, and unsustainable trade. Approximately 20% of all reptiles are threatened with extinction and population declines are approaching rates similar to the current amphibian extinction crisis. Preventing the extinction of reptiles will require humans to acknowledge these losses and develop plans to preserve these evolutionary sentinel species. Assisted reproductive technologies (ART) are well developed in a handful of species, and these technologies have become integral parts of conservation programs for threatened and endangered species. The creation of functional and sustainable reproductive assistance programs for reptiles using ART will strengthen our conservation capacity. Combining ART with an understanding of reproductive physiology will enable scientists to capture genetic material from different animals housed at different institutions, overcoming reproductive barriers. Subsequent gamete transport will reduce the need to transport animals from stressful or dangerous environments for breeding. Additionally, these gametes could be stored indefinitely to preserve genetic diversity. The goal of this research was to systematically apply ART to male reptiles. Semen was safely and successfully collected from veiled (Chamaeleo calyptratus) and panther chameleons (Furcifer pardalis) using electroejaculation. The annual reproductive cycles of these two chameleons were characterized under captive conditions, and both species follow season breeding cycles. Human chorionic gonadotropin can be used to increase circulating plasma testosterone concentrations in veiled chameleons. Short-term cooled semen storage can be done in red-eared sliders (Trachemys scripta elegans) and diamondback water snakes (Nerodia fasciata) using Ham’s F10, INRA 96, and sperm washing buffer; green anole (Anolis carolinensis) semen could not be stored using these same extenders. Red-eared slider turtle spermatozoa motility was lost following cryopreservation, but plasma membrane integrity remained. Reptile survival is dependent on how we plan today. ART will help us develop programs to preserve the genetics of these sentinel animals

Aspidoscelis costatus costatus (Squamata, Teiidae): high elevation clutch production for a population of whiptail lizards

Artículo del tamaño de nidada en la lagartija Aspidoscelis costatus costatus.Clutch size and number of clutches per reproductive cycle are important life history traits that can be influenced by anatomical, physiological, evolutionary, and ecological factors. This report on the clutch size and number of clutches of an endemic Mexican whiptail lizard, Aspidoscelis costatus costatus (Cope, 1878), is based on a study of population at an unsually high elevation for a member of this genus. The study site is located in Ixtapan de la Sal, southeastern Estado de México, Central Mexico, at 2090 m a.s.l. Lizards were sampled in June 2006, and from May to July 2007, where females of Aspidoscelis costatus costatus were collected by hand along a drift fence. Female reproductive condition was evaluated based on abdominal palpation for presence of developing eggs; clutch size was determined by actual counts of either vitellogenic follicles or oviductal eggs. The smallest reproductive female was 77 mm snout vent length; females produced a minimum of two clutches during the breeding season, the mean clutch size of 6.5 eggs (n = 33) was one of the largest reported for the genus. However, both length and width of its eggs, and the relative clutch mass have not been diminished by development of a large clutch. Additionally, comparisons of clutch size were undertaken within the polytypic A. costatus complex, within the genus Aspidoscelis, and between certain genera of whiptail lizards. This apparently represents the first study of whiptail lizards (genus Aspidoscelis), assessing the aforementioned reproductive characteristics, in a population above 2000 m

Determinación sexual de Basiliscus vittatus (Squamata: Corytophanidae)

Tesis doctoralLa determinación sexual es un proceso que influye en muchos aspectos biológicos en la historia de vida de los organismos, como el establecimiento del sexo; así como de gran importancia en el desarrollo de los individuos y la proporción sexual dentro las poblaciones. El tamaño de la nidada, masa relativa de la nidada, estadio embrionario en la oviposición, diferenciación sexual, son características importantes que se relacionan con factores bióticos y abióticos que interactúan con los reptiles. En el presente estudio, se dan a conocer rasgos de la historia de vida de Basiliscus vittatus sobre las limitantes de la respuesta reproductora debida a la morfología de las hembras. Además, por primera vez, se detalla la descripción del estadio embrionario a la oviposición de un integrante de la familia Corytophanidae y el mecanismo de determinación sexual de B. vittatus. El estadio embrionario se asoció con el largo máximo del huevo, el cual parece estar relacionado con factores fisiológicos y morfológicos de las hembras, así como por su estrategia de forrajeo. El mecanismo de determinación sexual de B. vittatus es genético con presencia de un sistema de novo de micro- cromosomas sexuales de tipo XY, diferente al que comparten los demás miembros que integran el clado Pleurodonta. Las condiciones térmicas de incubación influyen en el número de días que son necesarios para que un embrión pase de un estadio de desarrollo embrionario a otro: una mayor temperatura resulta en menores tiempos de incubación. Sin embargo, se observó que la temperatura de incubación no tiene un efecto en la diferenciación gonadal del embrión, siendo en el estadio 35 cuando se acentúan diferencias entre ambos sexos a nivel histológico. Además, la temperatura no tiene un efecto en 3 la determinación sexual de los basiliscos, dado que el genotipo (XX vs. XY), determinado a través de la presencia del gen CAMSAP1 ligado al cromosoma Y, coincidió con el fenotipo (ovarios vs. testículos) proveniente de la histología de las gónadas. La presencia de órganos copuladores ocurre desde el estadio 34 en ambos sexos y es posible que embriones de B. vittatus presenten una forma de pseudohermafroditismo temporal en la cual ovarios y hemipenes están presentes al mismo tiempo durante múltiples estadios de desarrollo. Será necesario realizar más estudios donde se integre la biología térmica y la biología molecular para entender cómo las temperaturas de incubación pueden influir en el mecanismo de determinación sexual y en las características de la historia de vida de los reptiles