 Back
Research Article
ScienceAsia 26 (2000) : 069-080 |doi: 10.2306/scienceasia1513-1874.2000.26.069
Structure and Development of the Testis of Bullfrog, Rana catesbeiana, and Their Changes
during Seasonal Variation
Jittipan Chavadeja,*, Aungkura Jerareungrattanab, Prapee Sretarugsaa and Prasert Sobhona
ABSTRACT: The testes of fully mature bullfrogs, Rana catesbeiana, were studied by light microscope. The
germ cells in the developing testis can be classified into 12 stages based on nuclear characteristics.
Primary (type A) and secondary (type B) spermatogonia are the earliest germ cells, with the former
showing large and completely euchromatic nuclei with prominent nucleoli and the latter with small
blocks of heterochromatin distributed along the nuclear envelope. Spermatocytes consist of five stages;
namely, leptotene, zygotene, pachytene, diplotene and diakinesis metaphase spermatocytes. Succeeding
stages show increasing condensation of chromatin : from the coarse fibers, that are evenly distributed
throughout the nucleus in leptotene stage to the highly condensed blocks of heterochromatin in pachytene
and diplotene stages. Nucleoli are not detected in any stages. Secondary spermatocytes have blocks of
completely condensed heterochromatin attaching to the nuclear envelopes. There are three stages of
spermatids: the early stage shows coarse chromatin granules occurs evenly over the nucleus, the middle
stage has increased chromatin condensation over the entire oval nuleus while the nuclear size decreases.
The late stage exhibits completely condensed chromatin in an elongated nucleus, and its cytoplasm
becomes highly vacuolized and starts to degenerate. In fully mature spermatozoa, the nucleus becomes
highly elongated and chromatin completely condensed. During development of the testis, sex cords in
putative testis appear in two-month-old frogs. Seminiferous tubules containing primary spermatogonia
appear in the definitive testis of four-month-old frogs while spermatocytes are present in five-monthold
frogs. Spermiogenesis and full production of spermatozoa could be detected from the seventh month
onwards. The frogs become fully mature about sixteen months when their testes undergo cyclical change. During breeding period (April-September), there are abundant spermatozoa, round spermatids in
seminiferous tubules, while during non-breeding period (October-March), such cells are much fewer in
number and most remaining cells are spermatogonia and primary spermatocytes.
Download PDF
a Department of Anatomy, Faculty of Science, Mahidol University, Bangkok 10400, Thailand.
b Department of Clinical Microscopy, Faculty of Medical Technology, Mahidol University, Bangkok 10700, Thailand.
* Corresponding author.
Received 9 Nov 1999, Accepted 8 Mar 2000
|
