Reproductive Cycle of the Penshell Atrina Seminuda (Mollusca: Bivalvia) in Northern Waters of Venezuela

We examined reproduction of the pinnid bivalve Atrina seminuda (Lamarck, 1819) in tropical waters off northeastern Venezuela and compare it with reproduction of the same species in temperate waters of Argentina, as reported elsewhere (Soria et al., 2002). In Venezuela, a proportion of individuals was reproducing throughout the year, although there was increased spawning activity in certain periods (May-July 2004, September-November 2004, and February 2005). Stepwise multi-regression analyses correlating the frequency of the different gametogenic stages with various environmental factors suggested that reproduction was likely controlled primarily by temperature and secondarily by food abundance (as measured by chlorophyll a). During the first part of the year gamete production appeared to be supported by food resources obtained from the environment (indicating an opportunistic reproductive strategy), whereas gamete production during a period of relatively low phytoplanktonic food availability (June-September) suggested that it was supported by tissue reserves (a conservative reproductive strategy). The above reproductive pattern contrasts with A. seminuda in Argentina where gametogenesis is highly synchronized among individuals and follows an annual cycle. Also, A. seminuda in Argentina displays only the conservative reproductive strategy, with gamete production occurring during the period of food scarcity in the autumn and probably supported by reserves from the adductor muscle (Soria et al., 2002). Together, these data provide the first comparison of reproduction of the same species in both tropical and temperate waters (separated by 50° in latitude).