FIRST CASE OF ADELPHOPHAGIA STUDIED IN NE REIDAE (ANNELIDA, POLYCHAETA) - ECOLOGICAL SIGNIFICANCE OF THIS BEHAVIOR DEVELOPED BY NEREIS-DIVERSICOLOR (MULLER,O.F.)

Nereis diversicolor (O.F. Muller) is one of the rare nereid species to reproduce when atokous, with the female incubating its offspring for several weeks inside its gallery. During the incubation, postlarvae co mmonly become adelphophagous as they reach the three-setigerous-segmen t stage; the absence of oocytes in our rearings during the second week caused a near 50% decrease in the number of individuals, a pause of m ore than 14 days in their development, and an increase in the variabil ity of growth patterns between individuals. Results are discussed in t erms of the possible effects of this deficiency on the morphophysiolog y of young worms and in terms of the ecological consequences of the ad elphophagous behaviour on the reproductive and incubating behaviours o f the female.