Halgerda batangas Carlson & Hoff, 2000

Location: Cannibal Rock, Komodo, Indonesia
Date: 2015/07/21
Length: 40mm
Depth: 14.0m
Water temperature: 23.1℃

Description

Body translucent ivory white. The dorsum bears low irregular ridges, between which a delicate network of fine orange lines runs across the surface. Conical tubercles of varying sizes are scattered over the dorsum, each with an orange-red tip ringed at its base by a white band. A white band lacking the orange reticulation runs along the mantle edge. Rhinophores and branchial leaves are translucent white with scattered dark brown specks. Maximum length about 40 mm.

Distribution

Type locality is Mactan Island, Cebu, Philippines, with paratype material from Anilao, Batangas Province. Recorded broadly from the tropical western Pacific, including the Philippines, Indonesia, Malaysia, Papua New Guinea, the Solomon Islands, the Marshall Islands, New Caledonia, Fiji, and the Great Barrier Reef of Australia. A 2023 study added molecular records from Okinawa and the Federated States of Micronesia.

Etymology

The specific epithet batangas refers to Batangas Province in the Philippines, the locality of the paratype.

Remarks

A member of the Halgerda carlsoni species complex, long confused with Halgerda carlsoni Rudman, 1978. Molecular phylogeny by a 2023 study supports its status as a distinct species. H. batangas is distinguished from H. carlsoni by the continuous network of fine orange lines between the dorsal ridges (versus discrete orange specks in H. carlsoni) and by its smaller maximum size (about 40 mm in H. batangas versus up to 70 mm in H. carlsoni). It feeds on sponges and is typically encountered on shallow reefs between 2 and 20 m.