Natural history, reproduction and regeneration of the sponge associate, Polydora colonia (Polychaeta: Spionidae) based on specimens from Long Island, New York

The polychaete Polydora colonia Moore, 1907 is a symbiont of sponges that is widely distributed in the western Atlantic Ocean and the Mediterranean Sea. P. colonia is redescribed based on newly collected specimens associated with the sponges Microciona prolifera and Halichondria bowerbanki from New York and aspects of its reproduction and feeding biology are described for the first time. The morphology of P. colonia was investigated using light and scanning electron microscopy. P. colonia possesses a rounded to slightly bidentate prostomium, a caruncle that extends to the middle of chaetiger 2 and the 5th chaetiger is enlarged with 3 to 4 modified spines with an incomplete sub-terminal collar. The morphology of P. colonia agrees with museum specimens and previous published reports of this species. P. colonia can produce more than 200 tubes per 100 cm2 of sponge. P. colonia produces eggs that are packed in the coelom from chaetigers 14-25. Eggs are deposited in capsules (14-19 eggs/capsule) and develop there until at least the 3rd chaetiger stage. Adelphophagy was observed with up to 25 nurse eggs consumed by a single larva. Six chaetiger larvae were found free swimming and contained a large amount of yolk, possibly due to nurse egg feeding. At the 13-chaetiger stage, juveniles were competent to settle on sponges. Gut content analysis of worms showed the presence of sponge material and spicules in 53% of the worms examined, the first evidence of sponge feeding in the Polydora complex. Two symbionts were found associated with P. colonia, one ciliate, Urceolaria sp. (prevalence = 25%) and one endoparasitic copepod Cymbasoma sp. (prevalence = 1%). P. colonia is a cryptogenic species found in marinas; its status as an introduced species is evaluated based on the current evidence.