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Description and monthly variation in reproductive stages of the clam Arca zebra (Swainson, 1833) in the Chacopata bank, Araya peninsula, Sucre state, Venezuela

Abstract:

Monthly variation (12 months) in reproductive stages and histology in adult specimens of Arca zebra harvested from natural bed of Chacopata, Sucre state, Venezuela were studiedied. The histological characteristics of gonadal tissue were described according to their reproductive stages: resting (0), onset of maturity (I), total maturity (II), partial spawning (III), total spawning and degeneration (IV). There were no significant differences in the total proportion of sexes, although there was significant differences in the 1M:1F relation in some months. The species presents asynchrony in the maturation of the follicles, however, quantitative analysis shows that while stages II and III were present throughout the sampling period. Males were observed in stages 0 and IV, but in females. Changes in the frequency of the stages were associated with significant variations presented the monthly mean diameter of follicles and the lumen in both sexes, were always higher in females. The average diameter of mature eggs was 5,88 ± 0,11 μm, showing its highest proportion in stage II. The increase in stage II observed from July to September 2002 was correlated with increases in temperature, while the increase of stage III coincides with the observed temperature decreases from October 2002 to January 2003. Salinity showed little variation, and the chlorophyll remained constant during the study, indicating that there is a limiting factor, so it is suggested that temperature is the main factor associated with reproductive changes in A. zebra.