A New Species of Saccocirrus (Archiannelida) from the West Coast of North America

Abstract

A new species of archiannelid, Saccocirrus eroticus, from shell gravel from Orcas Island, Washington, U.S.A., is described. The species is characterized by being 1 to 2.2 cm long when adult and comprising up to 125 body segments. It has unilateral gonads which begin in segment 13 and run to an achaetous region at the pygidial end; thus it has over 100 segments bearing reproductive organs. The achaetous region is composed of 4 to 11 segments. There are two tail lappets bearing 7 to 22 papillate ridges. The internal anatomy is described in detail and compared with other known species of Saccocirrus. Eggs released from females showed normal spiral cleavage and trocophores developed after 24 hours. The relationship of the saccocirrids to the protodrilid archiannelids and orbiniid polychaetes is discussed in relation to feeding and locomotory structure and function.