About Hypselodoris bullockii (Collingwood, 1881)
Hypselodoris bullockii (Collingwood, 1881) is a species of colourful sea slug, a dorid nudibranch, and a marine gastropod mollusc in the family Chromodorididae. This nudibranch is typically a pale purple colour. It has frequently been mistaken for multiple other species, including the closely related Hypselodoris variobranchia and Hypselodoris violacea, as well as the unrelated species Hypselodoris iba. Hypselodoris apolegma, a visually similar species distinguished by a reticulate pattern that gradually blends into pinkish purple, was previously thought to possibly be a different colour form of H. bullockii. However, molecular phylogenetic data confirms that all these species are distinct. This species was first described from a 70 mm (2.8 in) long specimen dredged from 110 m (360 ft) depth at Recruit Island, Senkaku Islands, 150 miles northeast of Taiwan, at coordinates 25.922745°N 124.558247°E. Currently, the name H. bullockii is associated with a species that is widespread in shallow water of the central Indo-Pacific region. Many existing records of this species are incorrect, as research has confirmed that at least eight different species were previously misidentified and grouped under the H. bullockii name. The H. bullockii clade includes seven species, with H. iba acting as a mimic of H. bullockii. Six of these species can be found in the Philippines. Hypselodoris apolegma occurs throughout the western Pacific, ranging from Okinawa, Japan to the Philippines, Indonesia, and Sabah, Malaysia. Hypselodoris brycei is found only in Western Australia, from the Houtman Abrolhos Islands to the Exmouth Region and the Dampier Archipelago. Hypselodoris bullockii itself is considered widespread across the western and central Pacific, found in Japan, Taiwan, Hong Kong, the Philippines, Indonesia, Malaysia, eastern Australia, the Marshall Islands and New Caledonia. By contrast, Hypselodoris melanesica is known only from Papua New Guinea and the Solomon Islands, areas where H. bullockii is not present. Hypselodoris rositoi appears to be restricted to the northern Philippines, and Hypselodoris violacea appears restricted to Sabah, Malaysia and Palawan Island, Philippines. Hypselodoris variobranchia appears restricted to Okinawa, Japan, Taiwan, the Philippines, Malaysia, Indonesia, and Queensland, Australia.
