Larval Development, Larval Nutrition and Growth for Two Boccardia Species (Polychaeta: Spionidae) from Victoria, Australia

Abstract

Larvae of Boccardia proboscidea and B. chilensis were reared in laboratory culture from egg capsules deposited by adults into tubes. B. proboscidea exhibits an unusual form of adelphophagia where 2 forms of larvae co-occur within the egg capsules: small forms incapable of feeding on nurse eggs and larger, more precocious larvae which feed on nurse eggs and smaller larval forms. The small larval forms are believed to be capable of a long pelagic life if they survive cannibalism by larger larvae; the large larvae have only a short pelagic life or none at all. This plasticity in mode of larval development should make it possible for B. proboscidea to disperse its larvae to distant localities, at the same time building up local populations. The larval development of B. chilensis is described from egg through large planktonic stages. Nurse eggs are lacking and larvae become planktonic at the 4-setiger stage. The apparently have a long pelagic life; metamorphosis was not induced in the laboratory. B. chilensis larvae are unusual among the species of Boccardia in lacking a dorsal medial row of chromatophores. There are minor differences between Australian B. chilensis larvae and published records of Chilean larvae. The biology of those spionid polychaete species exhibiting differences in reproductive patterns is reviewed and compared with B. proboscidea.