A New Volvatella (Mollusca: Ascoglossa) from Bermuda, with Comments on the Genus

A new species of Volvatella, V. bermudae, is described from eastern Bermuda. Major diagnostic features of the species include a flattened head and displaced, rotated and inverted buccal mass, a siphonal canal with a length of about one-third the total shell length, a thick rigid shell, and apparent symbiotic retention of intact algal chloroplasts. The new species lives epifaunally upon its food alga, Caulerpa racemosa (Forsskål) Agardh.

Using conchological characteristics, only five other species of Volvatella can be reliably separated at present: V. fragilis Pease, 1860; V. vigourouxi (Montrouzier, 1861); V. candida Pease, 1868; V. viridis Hamatani, 1976; and V. elioti (Evans, 1950). The genus Volvatella exhibits digestive gland anatomy intermediate between that of Ascobulla and the Elysiidae, supporting the concept of Volvatella as the basal stock for adaptive radiation in the Ascoglossa. The appearance of functional symbiotic chloroplasts in the Ascoglossa apparently correlates with the transition from burrowing to epifaunal forms, as exhibited by various members of the genus Volvatella (burrowing forms are generally white, epifaunal forms green).