Reproductive biology of the cockle Cerastoderma glaucum (Bivalvia:Cardiidae) from Lake Qarun, Egypt

The cockle Cerastoderma glaucum is an important component of the benthic community in Lake Qarun, Egypt. Reproduction and gonad development in this species were investigated during the period from February 2008 to May 2009. Reproductive maturity was estimated by assessment of length–weight relationship, gonad index and microscopic examination of gonadal smears and sections. Results indicate lack of periodicity in the sexual cycle. An annual pattern of four spawnings was recorded. The depletion of ripe gametes during spawning was rapidly compensated by the onset of gametogenesis. Monthly changes in flesh and gonad weight reflect reproductive cycle with weight loss during spawning. C. glaucum is a gonochoric species without any hermaphrodites or sex reversals. The overall samples presented a male biased sex ratio (F:M=1:1.29). The size at which 50% of the population reached maturity was 9.6 and 8.5mm of shell length for females and males, respectively.