Seasonally dependent testicular apoptosis in the tropical Long-fingered bat (Miniopterus inflatus)

Abstract

Testicular morphology of long-fingered bats trapped in March and early April (a period of sexual dormancy) was studied using both light and electron microscopy. The interstitial tissue, generally smaller in proportion to the seminiferous tubules, was largely made up of compactly arranged interstitial (Leydig) cells. Physiological cell death (apoptosis) was characterized by the occurrence of dense cytoplasm obscuring most of the subcellular organelles, myelin-like whorls of residual bodies and lipid inclusions in the cytoplasm, and roughly spheroidal nuclei. Normal mitochondria were round in outline. Some of these apoptotic cells were phagocytosed by the interstitial tissue macrophages. In the seminiferous tubules this degenerative process was marked by spermatogonial karyolysis, apoptosis of spermatocytes and extensive accumulation of large lipid droplets in the Sertoli cell cytoplasm. The tubular walls and lumen were completely devoid of spermatids and spermatozoa. These observations suggest that the sexual dormancy in these bats is characterized by a marked apoptosis of testicular micro-structural components hitherto unreported.