New species and a new subgenus of Spirorbinae (Serpulidae: Polychaeta) from Kenya

Authors


Abstract

Four species were collected, all attached to marine angiosperms, Pileolaria daijonesi sp.n. being the most abundant. The other three have the collar folds fused dorsally, as is characteristic of Dexiospira (=Neodexiospira Pillai), which is here regarded as a subgenus of Janua. Janua (Dexiospira) formosa (Bush) and Janua (Dexiospira) steueri Sterzinger are distinguished clearly from one another for the first time and shown to be widely distributed in warm seas. Janua (Fauveldora) kayisubgen. et sp. n. is a very closely related sinistral form, which extends to the Persian Gulf and Ceylon.

Reviewing serpulids, it seems that the primitive position of the operculum in Serpulinae and Spirorbinae was sinistral. The most recent changes involving this character, however, have been situs inversus back-mutations, from stocks which are dextral and presumably more labile.

Summary:

Four species from Kenya were all opercular incubators and attached to marine angiosperms, Pileolaria daijonesisp.n. being much the most numerous. The other three all have the collar folds fused dorsally, but should be placed in the redefined genus Janua, two falling indisputably into the redefined subgenus Dexiospira (=Neodexiospira Pillai). These two, J. (D.) formosa Bush and J. (D.) steueri Sterzinger, are redescribed and distinguished clearly from one another for the first time, the easiest distinction being that the blades of the abdominal setae are broad in the former and narrow in the latter. Both are shown to be widely distributed in warm seas. The remaining species, Janua (Fauveldora) kayisubgen. et sp.n., which extends to the Persian Gulf and Ceylon, is closely related to Dexiospira, but its operculum and related coiling are sinistral. Reviewing these characters in serpulids generally, it seems clear that the primitive position of the operculum in Serpulinae and Spirorbinae was sinistral, that many Spirorbinae have become dextral and that the most recent evolutionary changes, involving this character, have been back-mutations from such dextral stocks.

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