Reproductive biology of a brooding Diopatra species: Diopatra marocensis

The reproductive cycle of Diopatra marocensis Paxton et al., 1995 has been studied in a population from Ria de Aveiro, Western Portugal with monthly samples, during a two-year period. This species presents a direct development with brooding in the parental tube and specimens with gametes inside the coelom and female tubes with eggs and/or larvae were observed in every sampling month. This suggested that the species reproduces during the whole year, with the main reproductive period from April to September. The male:female sex ratio ranged from 1:2 to 1:4, with females always dominating the population. A comparison with other Diopatra Audouin and Milne Edwards, 1833 (Onuphidae) showed that D. marocensis is the largest species with direct development and with the highest number of eggs and larvae inside the parental tube. With the exception of the colour, due to the presence of the gametes in the coelom cavity, no morphological differences between males and females were observed.