THE CYTOLOGY OF SPERMATOGENESIS AND ULTRASTRUCTURE OF THE SEMINIFEROUS EPITHELIUM IN REPTILES

The annual cytological changes during spermatogenesis and the ultrastructure of the male germinal epithelium were investigated in European wall lizards, slider turtles, and American alligators. Wall lizards, alligators, and slider turtles all have the same type of temporal germ cell development. The majority of germ cells within a cross-sectional area of seminiferous tubule progress as a single population through the three phases of spermatogenesis. This temporal development leads to a single spermiation event at the end of germ cell development. Consistent spatial relationships (stages) between germ cells, which are found in mammals and birds, do not exist in these three reptiles. Wall lizards have a prenuptial pattern of spermatogenesis, where sperm development begins immediately prior to and continues through the months of breeding (April-following June). Alligators also have a prenuptial pattern of sperm development; however, the speed of their germ cell development occurs at an accelerated rate compared to the wall lizard and slider turtle. Spermatogenesis in the alligator begins in February and is completed by June, a five-month period. The slider turtle exhibits a postnuptial germ cell development that starts shortly after mating (May) and is completed by late fall (November). Their common temporal progression of germ cells through spermatogenesis within a tubular testis represents a transitional model that may be evolutionarily significant. Junctional complexes are observed in the slider turtle and wall lizard and include desmosome-like, gap-like, and tight junctions. All junctions in both species show ectoplasmic specializations, including subsurfaces densities, smooth endoplasmic reticulum (SER), and 7-9nm filaments. However, the SER is less organized and further away from the junctional complexes and the 7-9nm filaments are not as prominent as those seen in mammals. Tight junctions in both are also effective barriers to lanthanum penetration. Lanthanum surrounded spermatogonia and preleptotene cells, but it never penetrated to deeper meiotic or spermiogenic cells at any time during the year. In all samples observed in this study the barrier was never compromised, similar to mammals. The inconsistency and unorganized association of the SER and the 7-9nm filaments suggest that reptilian junctional complexes are more complicated than amphibians but simpler than mammals. Acknowledgments I express my sincerest appreciation for the guidance, encouragement, and patience provided by my advisor Dr. Daniel H. Gist. He was always there for me especially when I turned down the wrong road; he would always steer me back in the right direction. I would also like to thank Dr. Terri Roth, Dr. Lawrence Erway, and Dr. Edwin Griff for serving on my thesis committee and in the guidance given in organizing and editing my thesis. I would like to also thank Dr. Randall Morris for not only serving on my committee but for his time and patience in teaching me the techniques needed to complete the electron microscope portion of my research. Also I express my gratitude to Georgianne Ciraolo for her long hours of processing and sectioning of all of my samples for the electron microscopic portion of my research. Special thanks go to Dr. Ruth Elsey, Dr. Valentine Lance, and the staff at Rockefeller Wildlife Refuge, New Chenier, LA for their assistance and instruction in collecting alligators, which allowed me to complete the data needed for the light microscopy of spermatogenesis in that species Thanks also to Ken Yoshitomi, Matt Collier, Eric Waits, Mike Sanwald, Gina Segal, and many other graduate students for your friendship and camaraderie, which made graduate school bearable and at times very amusing. Last but not least, I would like to thank my wife from the bottom of my heart for all her patience and support. If it were not for you, I would never have made it through graduate school. You have always been there to support and help me in anyway possible and I dedicate this manuscript to you.