Glaucillus marginata Bergh, 1868
This is a bluish-brown nudibranch with a bluish underside. It resembles most nudibranchs in shape. The elongated, flattened body is up to 1.2 cm long. The papillae (up to 139 in number) are placed in four pairs of clusters (Glaucillus marginata). It lives in the pleuston of all oceans.
The naked body is elongate and flat. The body is brown ventrally (= upperside in living animals) the dorsal side is silver-blue. The head is small, blunt, it has a pair of small oral tentacles near the mouth and a pair of extremely small rhinophores on the dorsal side. There are always four pairs of clusters of papillae (or cerata) placed on peduncles on the lateral side of the body. The papillae are placed in more than one row (multiseriate), in total their may be 139 (or more). The genital pore is on the ventral side, at the right; the renal pore is close above the anus between the second and third cluster of papillae; the anus is situated at the right dorso-laterally between the second and third pair of papillae. The penis is not armed. The foot is flat and slender and found on the ventral side, the metapodium is short.
Body length up to 18 mm.
A special description is not available.
This species is hermaphroditic. The eggs are 58-67 µm wide and 74-82 µm long. Eggs are delivered in straight strings up to 6.4 mm long.
This species is carnivorous and lives in the pleuston where it feeds on Velella, Porpita and Physalia. Cannibalism is common.
This species occurs in the warm waters of the Pacific Ocean, see the Glaucillus marginata map.