Fried Egg Sea Slug

Colpodaspis thompsoni is a species of sea slug, or headshield slug, a marine opisthobranch gastropod mollusk in the family Colpodaspididae.

Description

It is a snail-like headshield sea slug. It is small, only growing to a maximum of 5 mm in length. The globose body is black or dark brown with large patches of vivid white that contain one or more raised yellow circular pustules giving that classic fried egg appearance. It possesses a fragile bubble-shaped shell that is wholly internal being completely covered by the mantle. The black head tentacles are joined at their bases forming a vee shape. They are greyish on the outer edges and rolled into tubes each connecting with a deep groove laterally. There is a distinctive exhalent siphon on the right side and the tail is long tapering and unadorned-black in colour. The sole of the foot is a semitranslucent dirty white to grey colour and has a deep midline longitudinal groove for the posterior half that is fed mucus from a large gland positioned at the halfway point of the sole. It is postulated that the sticky mucus it produces helps provide attachment to the substrate in current and surge.

Distribution

In the Indo-Pacific from the Red Sea and the African east coast right across to Hawaii, up to Japan and down to the central east coast of New South Wales, Australia.

Habitat and Biology

It is a moderately rare species found in rocky habitats at moderately protected to exposed sites. It occurs from depths of 1 m to at least 29 m. They are hermaphrodites but due to the locations of the openings to the male and female sexual organs they cannot inseminate simultaneously like most of the nudibranchs, but rather adopt a head to tail position, the specimen acting as the male being behind. The penis is located on the right side of the head right along side the mouth. It is quite long having been observed entering the partner’s exhalent siphon to access the female pore inside the enclosed mantle cavity. The spawn of Colpodaspis thompsoni consists of quite large capsules in a mass of jelly-like mucus without any particular shape.