LARVAL DEVELOPMENT, METAMORPHOSIS AND EARLY GROWTH OF THE GUMBOOT CHITON CRYPTOCHITON STELLERI (MIDDENDORFF, 1847) (POLYPLACOPHORA: MOPALIIDAE) ON THE OREGON COAST

Cryptochiton stelleri is the largest herbivore in the intertidal and subtidal zone throughout its North Pacific range, but its larval development and metamorphosis have not been well documented. A description of larval development for specimens in Hokkaido, Japan, has been used in multiple textbooks yet shows many features atypical of chiton development. In the present study in Oregon, C. stelleri larvae were raised in culture and displayed developmental stages similar to other chitons, very different from the previous description. Plate development began 3 days after hatching. Larvae were competent beginning 3 days posthatching and metamorphosed in response to extract from encrusting coralline algae. Larvae survived for over a month without metamorphosing and did not metamorphose in response to increased temperature, presence of adults or the addition of algal foods of adults or juveniles. Juvenile C. stelleri were discovered in the field and grew c. 4 mm per month in captivity. Juveniles had exposed shell plates and fed on the red alga Cryptopleura.