A native freshwater mussel inhabitant of Anzali wetland in Iran is Anodonta cygnea whose population is in danger due to pollution and habitat destruction by human manipulation. The objective of the present study was to survey some reproductive characteristics and gametogenesis of this bivalve in order to plan for future breeding programs. Reproductive traits of this species were evaluated for one year period using biometric and histological studies by standard method. The mean length, width, height, weight and age were 10.6 ± 0.1 cm, 6.04 ± 0.04 cm, 4 ± 0.04 cm, 132 ± 3 g, 6 ± 0.1 years old, respectively. In all shells, the two sexes were separated. There was no apparent sexual appearance. The frequency of female was 1.5 times that of male. The mean diameter of mature oocyte and sperm in fresh smears were 139.95 ± 8.1 and 4.5 ± 0.26 μm and in tissue slides were 59.6 ± 0.8 and 2.2 ± 0.03 μm, and the mean area of ??them by the fresh observation were 15255.58 ± 1834.4 and 9.1 ± 1.16 μm2 and by histological method were 3171.46 ± 79.4 and 3.9 ± 0.6 μm2, respectively. The mean fecundity was 107844.6 ± 20621.9. Both of male and female gonads were in developing phase in spring (May and June) and in summer (July and August). The spawning stage occurred in the fall and the post-spawning stage in the winter. Although, gametogenesis was active in all seasons, the peak of oogenesis was observed in July and September and the peak of spermatogenesis was in September. The development of glochidia was completed in January and the release of them from the gill has been occurred between January and March.
Keywords: anodonta, Anzali wetland, bivalve, gonad, maturation