REVISION OF THE SPECIES OF RIDGEIA FROM NORTHEAST PACIFIC HYDROTHERMAL VENTS, WITH A REDESCRIPTION OF RIDGEIA-PISCESAE JONES (POGONOPHORA, OBTURATA EQUALS VESTIMENTIFERA)

Examination of vestimentiferan worms attributed to the genus Ridgeia f rom more than 50 vent sites in the northeast Pacific indicates that on ly one species is present. We amalgamate Ridgeia piscesae Jones and R. phaeophiale Jones under the name R. piscesae and include other forms previously suspected to be different species. Allozyme evidence suppor ts the hypothesis that the populations belong to a highly plastic phen otype. The distance data indicate no substantial genetic differences a mong populations along Juan de Fuca Ridge and across a transform fault to the northern Gorda Ridge. Morphological data indicate that the ori ginal distinction of two species on the basis of obturacular saucer nu mber and tube colour was based on the extremes of a continuum of chara cteristics that relate to animal size, levels of predation, and probab ly vent fluid conditions. The intriguing effect of habitat on phenotyp e in this abundant vent animal requires further investigation now that the taxonomy is better understood.