Systematics and Ecology of Shell-Boring Polychaetes from New England

In a survey of shell-boring polychaeles of New England, representatives of five families were found: Spionidae, Cirratulidae, Capitellidae, Terebellidae, and Sabellidae. The five spionid species were studied extensively. These include Polydora commensalis Andrews, found only in shells occupied by hermit crabs, P. concharum Verrill, P. socialis (Schmarda) , P. websleri Hartman, and Boccardia hamata (Webster), found in various types of shell. Breeding periods were defined and the larval development described for each species. Polydora concharum deposits egg capsules inwinter months, while the oilier polydorids spawn in spring or summer. Morphology of planktonic larvae is distinct in each species, although P. websteri larvae may be confused with non-boring species such as P. ligni Webster. Polydora socialis adults are found in both shells and sediment and have a unique grinding apparatus, a gizzard, between the esophagus and intestine. The cirratulid, Dodecaceria sp., follows an asexual mode of reproduction. The syslematics of Dodecaceria is complex owing to multiple modes of reproduction. No sexually mature individuals were observed during the course of this study. Asexual budswere found in the Fall. A sabellid, Pseudopolamilla reniformis (Miiller), is commonly found in the shells of Placopeclen magellanicits (Gmelin) in Maine waters. Its reproduction is unknown.