The present study aimed to investigate the morphological changes in the testis of brown-banded bamboo shark using routine histological and PCNA immunohistochemical techniques in order to describe the role of cell division versus cell death in germ cells and Sertoli cells during summer and winter seasons. Four mature brown-banded bamboo male sharks testes were used in this study; the first two were collected during winter season and the other was collected during summer season. Testicular specimens were used for histological and PCNA immunohistochemistry. The obtained results revealed that the testis of brown-banded bamboo shark showed a diametric pattern of development in which the testis was divided into several zones including germinal, spermatogonial, primary spermatocyte, secondary spermatocyte, spermatid, spermatozoal and degenerative zones. Noteworthy, PCNA expression was restricted to nucleus of spermatogonia, spermatocytes and Sertoli cells in both mitotic and pre-meiotic zones only while it was absent in the post-meiotic zone. Moreover, the intensity of expression was different among the various zones as its expression was prominent in the nucleus of spermatogonia in the germinal zone compared with spermatogonial zone. The intensity of PCNA expression in the testis of shark was different either during summer or winter season. In conclusion, the testis of brown-banded bamboo Shark have a diametric pattern of development starting from the dorsal part of the testis wherein, the germinal zone toward the epigonal organ ventrally wherein, the spermatozoal and degenerative zone. This diametric pattern of development is the best model to track the cascade of the process of spermatogenesis where each zone represent only one type of cells in addition to Sertoli cells which is not found in the mammalian testes. The season has non-significant effect on the PCNA expression on the testis of brown-banded bamboo Shark.
Key words: Shark, testes, Morphology, PCNA immunohistochemistry
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