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Gonad variation and development of freshwater mussel Chambardia rubens Lamarck, 1819 (Bivalvia: Mutelidae) from the River Nile in Egypt

1Zoology and Entomology Department, Faculty of Science, Helwan University, Egypt. 2Zoology Department, Faculty of Science, Cairo University, Egypt. *Corresponding author, E-mail: myame_mostafa@yahoo.com DOI: 10.21608/jbaar.2018.154710 Abstract: The gametogenesis, reproductive cycle, and larval morphology of Chambardia rubens (Bivalvia: Mutelidae) are studied for the first time in Egypt. A total of 46 mussels were collected seasonally from winter to autumn 2017 from Benha (Qaluobiya Governorate) along the River Nile in Egypt. Histological examinations demonstrate that C. rubens is a dioecious species and 22 were females with a prevalence rate of 47.8% and 24 were males with a prevalence rate of 52.2 %. The gonads of both male and female specimens were found to be paired and symmetrical organs, situated between the digestive gland and intestine. Oogenesis was divided into four stages; oogonia, previtellogenic oocytes, vitellogenic oocytes, and postvitellogenic oocytes while spermatogenesis passed through spermatogonia, spermatocytes, spermatids, and spermatozoa. Sperm morulae were also detected. The reproductive cycle was intense in winter including the four developmental stages of gonads; developing, ripe (mature), spawning, and spent stages, respectively. The eggs and larval stages (lasidia) were incubated for a short period within the inner demibranchs so C. rubens can be considered as endobranchous and tachytictic brooders. Light microscopy revealed that the eggs with vitelline membrane and the larvae contain internal threads with an anterior outgrowth. Scanning electron microscopy examinations revealed that the eggs are with smooth membrane without any folds with the presence of anterior outgrowth in the larvae. Keywords, Bivalvia, Mutelidae, Chambardia rubens, gametogenesis, reproductive cycle, larval morphology.