First Record of Epitokous Metamorphosis and Swimming Behaviour of Glycera nicobarica (Polychaeta: Glyceridae), in the Seto Inland Sea, Western Japan

Abstract

Epitokous metamorphosis and swimming behaviour of the glycerid polychaete Glycera nicobarica Grube, 1866 are re- corded for the first time, as the first such observation for any Asian glycerid. A total of 88 mature adults (epitokes) swim- ming in the surface water were collected from six sites in the Seto Inland Sea, Japan, at various phases of the moon, mostly within two hours aſter sunset in July to November in 2009 to 2011. By a morphological comparison with 36 immature ben- thic individuals (atokes) of comparable body size, we confirmed characteristic features of epitokous metamorphosis, includ- ing flattening of the body, reduction of the proboscis, enlargement of the parapodia, elongation and increase in number of the chaetae, and addition of simple capillaries in the neuropodia. The epitokous metamorphosis of G. nicobarica is basically similar to those previously described in eight other species of Glycera.