ScienceAsia 23 (1997): 075-086 |doi: 10.2306/scienceasia1513-1874.1997.23.075

STRUCTURE OF THE TESTIS OF RANA TIGERINA AND ITS CHANGES DURING DEVELOPMENT AND SEASONAL VARIATION

PRAPEE SRETARUGSA^a, VIMONWAN NAKIEM^b, PRASERT SOBHON^a, JITTIPAN CHAVADEJ^a, MALEEYA KRUATRACHUE^c AND E. SUCHART UPATHAM^c

ABSTRACT:Testes of one- to fourteen - month - old Rana tigerina, a native rice-field frogs of Thailand, were studied by light microscopy. Based on the nuclear characteristics, 12 stages of male germ cells could be identified in the seminiferous tubules. Primary and secondary spermatogonia are the earliest germ cells that show large euchromatic nuclei with prominent nucleoli. Primary spermatocytes consist of five stages, namely, leptotene, zygotene, pachytene, diplotene and metaphase 1 spermatocytes. Secondary spermatocytes have blocks of highly condensed heterochromatin attached to the nuclear envelopes resembling a "clock-face" pattern. There are three stages of spermatids : the early, the middle and the late stages. The cytoplasm of the late stage spermatid becomes highly vacuolated and starts to degenerate. In a fully mature spermatozoon, the nucleus becomes highly elongated, and chromatin completely condensed. Spermatozoa are embedded in the cytoplasm of Sertoli cells. At each stage of division and differentiation, a clone of cells derived from a single spermatogonium is surrounded by processes of folliculo-Sertoli cells. Leydig cells are found between seminiferous tubules. During development/ testis with hollow sex cords appears during the second month. Definite seminiferous tubules are formed during the third month. Spermatogonia are present in the epithelium of seminiferous tubules during the early part of the fourth month. Active spermatogenesis begins during the fifth month, and full production of spermatozoa could be detected from the sixth month onwards. In adult male frogs, there are abundant spermatozoa and round spermatids in semini(erous tubules during the breeding period (from March to SeptemberJi while during the non-breeding period (from October to February), such cells are much fewer in number. Moreover, the late stages of germ cells are also detached from seminiferous epithelium.

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a Department of Anatomy, Faculty of Science, Mahidol University, Bangkok 10400, Thailand.
b Department of Anatomy, Faculty of Public Health, Burapha University, Chonburi, Thailand.
c Department of Biology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand.

Received April 3, 1997