الفهرس 
Materials and methods
Study areaOnly 14 pages are availabe for public view
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Abstract
The present study deals with some biological aspects of the clams Donax trunculus and Donax semistriatus inhabiting the Mediterranean Sea water at the western area of Gamasa city and the eastern area of Port Said city respectively. It was found that individuals of D. trunculus and D. semistriatus are wedge-shaped clams reaching about 4.00 cm long and 1.30 cm wide (in D. trunculus) and about 3.40 cm long and 1.15 cm wide (in D. semistriatus). The shells differ greatly in colours. The age of D. trunculus ranged between one to four years (for individuals that are more than 14 mm) while the age of D. semistriatus ranged between one to three years (for individuals that are more than 11 mm). In the two species, the animal attained its first sexual maturity at the age of one year. All allometric relationships are directly proportional. Analysis of length-frequency distribution indicated that the population of D. trunculus has two periods of recruitment. There is one annual reproductive cycle, the sexes are separate, no sexual dimorphism and the sex ratio is close to equality with a slight preponderance of males in the two studied species. The reproductive cycle includes five stages of gonadal development: ripe, partially spent, spent, early active and late active. There are four types of auxiliary cell-oocyte relationship during oogenesis of the bivalve D. trunculus. Seasonal variations in the biochemical composition (proteins, lipids and glycogen) and other biochemical indices as well as the concentrations of some heavy metals were studied in the soft tissues of two marine bivalves, D. trunculus and D. semistriatus collected from two water sites with different levels of heavy metals pollution. A comparison between the two studied Donax species for all measured biochemical parameters and the level of heavy metals bioaccumulation was also carried out.