Reproduction and larval development ofManayunkia aestuarina (Bourne, 1883) (Polychaeta,Sabellidae) in a coastal region of the southern Baltic

The reproduction and larval development ofManayunkia aestuarina, a polychaete typical of brackish lenitic waters, was studied in a tideless shallow region on the south Baltic coast in 1990. Reaching abundances of up to 50 000 ind./m², it is an important element of the benthic community in this area. Reproduction started in late March/early April, when the females deposited their eggs in the tubes. On the average, 4 (maximum: 16) developing embryos were found in a maternal tube during the reproduction period. The females probably produced a mean of about 12 eggs. Development in the maternal tube lasted about 8 weeks. The first juveniles were found outside the tubes in mid-May. The survival rate during the first few weeks was estimated to be 15–20%. After reproducing, the adult animals survived until October. The changes involved in the development from eggs to juvenile animals are illustrated by drawings.