EVIDENCE SUGGESTING THE EXISTENCE OF TWO SPECIES OF STRONGYLOCENTROTUS (ECHINOIDEA) IN THE NORTHWEST ATLANTIC

Abstract

What appear to be both Strongylocentrotus pallidus (G. O. Sars) 1871 and S. droebachiensis (O. F. Müller) 1776 are reported as occurring in the Gulf of St. Lawrence. A collection of each species from this region is compared with collections of each from widely scattered parts of the Northern Hemisphere, and no taxonomically significant differences within the species are noted. The collection of S. pallidus from the Gulf of St. Lawrence contains an unusually high percentage (7.4%) of individuals exhibiting situs inversus. S. echinoides A. Agassiz and H. L. Clark 1907 of the Pacific appears to be synonymous with S. pallidus.Small collections (some including both species) from the immediate vicinity of Station de Biologie marine, Grande-Rivière, Gaspé, Québec, but from different depths of water, are compared. The difficulties in distinguishing the species in mixed lots are discussed. Possible environmental preferences of the species and environmental effects on taxonomic characters within the species are considered. Facets of the problem needing further study are indicated.