Abstract
Background: Pollution of the aquatic environment by inorganic and organic chemicals is a major factor posing serious threat to the survival of aquatic organisms including fish. Lake Manzala (LM) is one of the Egypt’s northern Delta Lakes situated on the Mediterranean Coast of the Delta. It is affected by drainage water polluted by different heavy metals that their concentrations exceed the maximum world permissible levels. Aim: This study aims to study the testicular histopathological alterations of Oreochromis niloticus using light microscope and the mature sperm using TEM during spawning season in LM. Materials and methods: Samples of water and 48 specimen of Nile tilapia, Oreochromis niloticus about 14-20 cm in length were collected from two areas; Demitta branch of river (RN) at Mansoura city as a control site and LM as a polluted area during the spawning season from March- June. The gonado-somatic index (GSI) was then calculated for each fish samples. Pieces of testes were then taken and prepared for light and electron microscopic studies. Cd and Pb were estimated in water samples during the spawning season from March to June. Results: Examined Sections revealed that the testes of specimens of LM had degenerative germinal epithelium of the seminiferous tubules, vacuolization in proliferating germ cells; decline in spermatogenic cell and sperm density than those collected from RN. Ultrastructure study of mature sperm of LM revealed nuclear degeneration, vacuolization and shortage of bilateral fins of the flagellum comparing to mature sperm of RN. Conclusion: This study giving an alarm that environmental hazard like increasing the levels of different heavy metals as Cd and Pb could alter the sperms structure and their ability to produce new offspring, and further studies may be needed to confirm these findings.
Highlights
The importance of Nile tilapia, Oreochromis niloticus in aqua cultures is due to its spreading in most countries of the world [1]
This study giving an alarm that environmental hazard like increasing the levels of different heavy metals as Cd and Pb could alter the sperms structure and their ability to produce new offspring, and further studies may be needed to confirm these findings
Samples of water and 48 specimen of Nile tilapia, Oreochromis niloticus about 14-20 cm in length and 120-200 g in weight were collected from two areas; Demitta branch of RN at Mansoura city as a control site and Lake Manzala (LM) as a polluted area during the spawning season from March- June and transported to the laboratory in tanks provided with oxygen pump
Summary
The importance of Nile tilapia, Oreochromis niloticus in aqua cultures is due to its spreading in most countries of the world [1]. The mean values of some heavy metals (Cd, Pb, Fe, Cr and Mn) recorded in LM were higher than the world permissible levels [5] and according to the Egyptian laws [6]. Such heavy metals are not lethal to fish, but concentrated in their flesh and create a hazard to the consumer [7,8]. Lake Manzala (LM) is one of the Egypt’s northern Delta Lakes situated on the Mediterranean Coast of the Delta It is affected by drainage water polluted by different heavy metals that their concentrations exceed the maximum world permissible levels
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