Reproduction of Donax venustus Poli 1795, Donax semistriatus Poli 1795 and Intermediate Morphotypes (Bivalvia: Donacidae) in the Littoral of Málaga (Southern Spain)

The reproduction and sexual cycles of Donax venustus Poli 0684\ Donax semistriatus Poli 0684\ and individuals with intermediate shell morphotypes were studied in the littoral of Ma laga "Southern Spain# from February 0889 to January 0880\ using histology and analysing the changes in ~esh dry weight( The littoral of Ma laga has mild seawater temperatures and several upwellings with high levels of chlorophyll a( Due to these environmental conditions\ the reproductive periods of these bivalve species are very extensive\ from February to November( The his! tological study shows asynchronous sexual cycles\ with continuous but partial individual spawnings from April to November in about 49) of the D( semistriatus population\ and percentages higher than 39) of the sample in most months for D( venustus( An important decrease in the ratio ~esh dry weight:length 2 was noted from June to August in the three populations^ this is apparently related with peaks of spawning( Based on the macroscopic observation of the gonads\ on the ~esh dry weight study and on histological data\ the sexual cycle of the intermediate morphotypes is simultaneous and similar throughout the year with those of D( venustus and D( semistriatus(