Journal of the Marine Biological Association of the United Kingdom

Research Article

A Comparative Study of the Setae of Pogonophora and Polychaetous Annelida

J. David Georgea1 and Eve C. Southwarda1

a1 British Museum (Natural History), Cromwell Road, London, and The Laboratory, Citadel Hill, Plymouth, PL1 2PB

Pogonophora are long thin tube-dwelling invertebrates similar in size to polychaetous annelids, but lacking both mouth and gut, and found mainly in the deep sea. Current discussion of their systematic position had revealed a need for more information about particular aspects of their morphology and embryology (Southward, 1971a). The earlier attribution of Pogonophora to the echinoderm-chordate group, Deuterostomia, based mainly on their apparently tricoelomate structure, has been questioned recently, following the discovery of the previously unknown posterior end (Webb, 1964a; Ivanov, 1965). This posterior end is a small and delicate structure composed of several coelomate segments separated by septa and provided with short bristles. It has such a strong resemblance to the posterior end of an annelid, though of course it does not contain a gut, that there has been much speculation about the possibility of a relationship between Pogonophora and Annelida and some reconsideration of the features thought to indicate affinity to the Deuterostomia (Livanov & Pornrieva, 1967; Webb, 1969b; Ivanov, 1970; Norrevang, 1970a, b; Southward, 1971a).