Reproduction and larval development of Perinereis rullieri Pilato in the Mediterranean Sea (Polychaeta : Nereididae)

The reproductive biology and larval development of a brackish water population of the nereidid polychaete Perinereis rullieri Pilato was investigated. About 100 specimens were collected monthly over the course of a year from the Venice Lagoon. Observation on gametogenesis indicates that oogenesis takes about 12 months while spermatogenesis is faster and takes about 6 months. The study showed that reproduction occurs once a year with a good synchronization between individuals and that spawning occurs without epitokal metamorphosis. Larval development was studied under laboratory conditions; the stages of trochophora and metatrochophora developed within the periovular jelly matrix and the first free living stage was the 3-setigers nectochaeta. In this species many life history traits can be interpreted as an adaptation to the brackish environments. In particular the adaptive significance of the variable age at maturity and the enclosing of the fertilized eggs in a jelly matrix are discussed.