Avaldesia albomacula (J. M. Chan & Gosliner, 2007)

Location: Naha Port, Okinawa Island (Chatan and Southern area), Okinawa, Japan
Date: 2012/04/19
Length: 20mm
Depth: 3.0m
Water temperature: 22.0℃

Description

Body oval-shaped with a low, irregular dorsal ridge pattern. Living specimens reach 28–42 mm in length (preserved specimens 6–25 mm), making it among the larger species of Avaldesia. Background colour ranges through light yellow, reddish-brown, dark brown, and mottled grey. The most diagnostic feature is the small to large white spot anterior to the gill pouch, consistently present in this species. Numerous filamentous tan papillae and occasional small white spots are scattered across the dorsum. Rhinophores are perfoliate with 12–17 lamellae; the lamellae are tan to brown with white apices. The gill is tripinnate with six branches. Foot anteriorly notched; oral tentacles digitiform. Living animals are often coated with sand and particulates.

Distribution

Type locality: Barrier Reef, 100 m north of Rasch Passage, north coast near Madang, Papua New Guinea, at 29 m depth. Widely distributed across the Indo-Pacific, with records from Madagascar, the Red Sea, Indonesia, the Philippines, Papua New Guinea, Australia, the Marshall Islands, Midway Atoll, and Hawaii. Found under coral rubble and on rocky reefs, sandy sediments, and algal fields in shallow water.

Etymology

From Latin albus (white) + macula (spot). The original description (Chan & Gosliner, 2007) explains that the name describes "the single white spot that occurs on the mantle immediately anterior to the gill of all specimens observed."

Remarks

Originally described as Thordisa albomacula Chan & Gosliner, 2007 and transferred to the new genus Avaldesia by a 2024 revision as the type species, based on phylogenetic and morphological evidence. The same paper also describes the new species Avaldesia tamatoa and transfers Avaldesia tahala from Thordisa to Avaldesia. The species is distinguished from Avaldesia tamatoa by the consistent presence of the white spot and the more numerous filamentous papillae.