Induction de l'èmission des gamètes et premiers stades du développement larvaire chez l'astérie fissipare Sclerasterias richardi

Sclerasterias richardi, a seastar living on the border (120 to 200 m) of the Mediterranean Continental Shelf, displays fissiparity concomitant with sexual reproduction. In order to describe the as yet unknown larva, artificial fecundation was induced in specimens collected in October, 1975. To obtain gametes, the seastars were treated with a 3x10^-6 M 1-methyladenine solution injected into the coelomic cavity. Histological study of the gonads revealed that the low proportion of the treated sample responding positively was due to the experiments being conducted at the end of the natural spawning period. The behaviour of males during sperm emission is described and discussed. Our observations suggest that S. richardi would exhibit epidemic sexuality under natural conditions. The development of fertilized ova, observed over a period of 42 days, produces planktotrophic larvae, the first photographs of which are presented.