FEEDING AND GROWTH OF THE AEOLID NUDIBRANCH CUTHONA-NANA (ALDER AND HANCOCK, 1842)

Feeding and growth of the aeolid nudibranch Cuthona nana was documented. Cuthona nana feeds specifically on the colonial hydroid Hydractinia echinata. Nudibranchs were observed on hermit crab shells in Gosport Harbor at the Isles of Shoals, Maine and on old bridge pilings near Gerrish Island, Maine. Grazing rates of nudibranchs (3-25 mm) were quantified over 24 hour periods in the laboratory. Larger nudibranchs consumed more hydroid tissue feeding mostly on polyps, whereas smaller individuals consumed less and fed on mat tissue. Grazing intensity in the field at Gosport Harbor was determined by estimating the area of grazed patches of hydroid colonies attached to hermit crab shells. The average patch size was 5.75% of the total colony area. Growth rates for nudibranchs were determined in the laboratory. Growth rates were greatest prior to maturation and oviposition. Animals from Gerrish Island and Gosport Harbor decreased in size after oviposition due to senescence. Nudibranchs from Gerrish Island reached a maximum size of 12 mm, compared to 23 mm for animals at Gosport Harbor.