Reproductive cycle of quadrula metanevra (Bivalvia: Unionidae) in the Pickwick Dam tailwater of the Tennessee River

摘要

Quadrula metanevra were collected monthly from Pickwick Dam tailwater (Tennessee River mile 201.3), Tennessee, between July 1988 and June 1990. A total of 227 specimens were examined. The population consisted primarily of dioecious individuals (98%) and had an unequal sex ratio (1.5 female: 1 male). Histological examinations showed that typical spermatogenesis began in autumn (September), increased in spring (March-April), and continued until midsummer (July). Atypical spermatogenesis predominated during July and August, and may have increased the number of sperm produced in autumn and winter. Oogenesis followed a pattern similar to that of typical spermatogenesis, with smallest average oocyte size observed in August. Gamete release occurred between late winter-early spring (March) and midsummer (July). Brooding females were found between late March and July.