title: Seasonal spermatogenesis in the Mexican endemic oviparous lizard,Sceloporus aeneus(Squamata: Phrynosomatidae).
abstract: Oviparous species ofSceloporusexhibit either seasonal or continuous spermatogenesis and populations from high-elevation show a seasonal pattern known as spring reproductive activity. We studied the spermatogenic cycle of a high-elevation (2700 m) population of endemic oviparous lizard,Sceloporus aeneus, that resided south of México, D.F. Histological analyses were performed on the testes and reproductive ducts from individual lizards collected monthly. This population ofS. aeneusshowed a seasonal pattern of spermatogenesis, with 4 successive phases common in other lizards. These include: 1) Quiescence in August, which contained solely spermatogonia and Sertoli cells; 2) Testicular recrudescence (September-January) when testes became active with mitotic spermatogonia, spermatocytes beginning meiosis, and the early stages of spermiogenesis with spermatids; 3) Maximum testicular activity occurred from March to May and is when the largest spermiation events ensued within the germinal epithelia, which were also dominated by spermatids and spermiogenic cells; 4) Testicular regression in June was marked with the number of all germs cells decreasing rapidly and spermatogonia dominated the seminiferous epithelium. February was a transitional month between recrudescence and maximum activity. The highest sperm abundance in the lumina of epididymides was during maximum testicular activity (March-May). Thus, before and after these months fewer spermatozoa were detected within the excurrent ducts as the testis transitions from recrudescence to maximum activity in February and from maximum activity to quiescence in June. Maximum spermatogenic activity corresponds with warmest temperatures at this study site. This pattern known as spring reproductive activity with a fall recrudescence was similar to other oviparous species of genusSceloporus.
authors.affiliation: Facultad de Ciencias; Universidad Autónoma del Estado de México ; Toluca, Estado de México, México ; Departamento de Zoología; Instituto de Biología; Universidad Nacional Autónoma de México ; Distrito Federal, México.
authors.forename: Oswaldo
authors.initials: O
authors.lastname: Hernández-Gallegos
authors.affiliation: Departamento de Zoología; Instituto de Biología; Universidad Nacional Autónoma de México ; Distrito Federal, México.
authors.forename: Fausto Roberto
authors.initials: FR
authors.lastname: Méndez-de la Cruz
authors.affiliation: Laboratorio de Biología Tisular y Reproductora; Departamento de Biología Comparada; Facultad de Ciencias ; Universidad Nacional Autónoma de México ; Distrito Federal, México.
authors.forename: Maricela
authors.initials: M
authors.lastname: Villagrán-SantaCruz
authors.affiliation: College of Sciences; The University of Findlay ; Findlay, OH USA.
authors.forename: Justin L
authors.initials: JL
authors.lastname: Rheubert
authors.affiliation: Facultad de Ciencias; Universidad Autónoma del Estado de México ; Toluca, Estado de México, México.
authors.forename: Gisela
authors.initials: G
authors.lastname: Granados-González
authors.affiliation: Biology Department; University of Indianapolis ; Indianapolis, IN USA.
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Gribbins
keywords: endemic; histological analyses; oviparous lizard; spermatogenic cycle; spring reproductive activity