Environmental Contaminant-Induced Spermatozoa Anomalies in Fish Inhabiting Lake Mariut, Alexandria, Egypt

This investigation was designed to evaluate reproductive impairment of tilapia (as a bioindicator organism), inhabiting three sites in Lake Mariut which varied in nature and degree of physicochemical and organic criteria. It is concerned with monitoring bioaccumulation of metal in sperms of Oreochromis niloticus using SEM-X-ray microanalysis and illustrating concomitant ultrastructure sperm abnormalities. Fish caught from polluted sites exhibited a higher proportion of heavy metals, in particular Cu, Zn and Hg, than in reference site. Morphologically, sperms of O. niloticus were anacrosomal aquasperm which is typical of species with external fertilization. It appears that each spermatozoon possesses a short round head, few mitochondria and underdeveloped middle piece. However, sperms of fish caught from the polluted sites showed variable deformations including: changes in head morphology, incomplete chromatin condensation, malformed middle piece, altered axonemal structure, wavy and sometimes ruptured plasma membrane, head-to-head and head-to-tail sperm agglutinations. It is believed that the observed alterations in sperms may result from metal accumulation leading to reproductive impairment. It seems also that the ability of metal exposed fish to produce viable offspring is seriously reduced. Therefore, new recruitment, which is very important to the stability of fish population, will be sharply influenced. Also, alterations in spermatozoa should be included as a model for predicting environmental hazards.