Reproductive seasonality and annual fecundity in Arcidens confragosus (Unionidae: Unioninae: Anodontini) from Tennessee River, Alabama, USA

Specimens of Arcidens confragosus (Say 1829) were collected monthly from the Tennessee River, Pickwick Reservoir, Alabama, USA, between 21 March 2000 and 26 February 2001. A total of 143 individuals were examined. Microscopic and gross examinations of gonadal and marsupial tissue were used to determine temporal patterns of gamete production, spawning, brooding, and glochidia discharge. In addition, 14 females were collected between October and January to obtain estimates of annual fecundity and three gravid females were used to study internal morphology of gill tissue. The male-to-female sex ratio was equal in the population and individuals reproduced once during their annual cycle. Gametogenesis began in May, peaked in July and August, and spawning occurred between August and September. Embryos were found in September and mature glochidia were brooded between September and February. Fecundity estimates ranged from 75,833–897,500 (  =  408, 452). Secondary water tubes were found within the marsupial gills...