A hermaphroditic Sphaerosyllis (Polychaeta: Syllidae) with epitokous genital chaetae from intertidal sands of the Island of Phuket (Thailand)

Abstract

The small interstitial Sphaerosyllis hermaphrodita n.sp. from sand beaches of Phuket (Thailand) is unique within the genus in being a simultaneous hermaphrodite. Chaetigers 8, 9, and 10 are male and the following three segments contain oocytes. Investigation of about 90 specimens of various sizes revealed that during maturation chaetiger 9 alters its shape and loses most of its normal chaetae. They are replaced by a strong chaeta with sawlike subdistal teeth, which is assumed to be a genital structure used during the process of sperm transfer.