Halgerda profunda Donohoo & Gosliner, 2023

Description

The preserved holotype measures about 60 mm. The body is oval, rigid, and gelatinous. The dorsum is translucent white with small black spots along the mantle edge, and bears irregular black ridges topped by large, conical tubercles with light yellow tips. A thin white band runs along the mantle margin. The gill, encircling the anus, consists of four bipinnate leaves that are translucent white with thin black stripes and small black spots; the anal papilla is black-tipped. The rhinophores are tapered and perfoliate, with about 24 cream-colored lamellae and a black stripe along the posterior stalk. The foot is translucent white with scattered dark spots and blotches.

Distribution

Type locality: off Lubang Island, Occidental Mindoro, Philippines, at about 91 m depth. Known from the Philippines, where it inhabits dimly lit mesophotic reefs at roughly 60-90 m - below normal scuba-diving depths.

Etymology

The specific epithet "profunda" is Latin for "deep", referring to the lower mesophotic depths where the species occurs.

Remarks

Molecular data (COI, 16S, H3) place this species in a mesophotic clade together with the Philippine deep-water species Halgerda mesophotica and Halgerda takipsilim, from which it differs by more than 5.8% in the COI gene. Externally it is distinguished by its black dorsal ridging, yellow-tipped conical tubercles, and the black stripe on the posterior rhinophore stalk. In the similar H. takipsilim the ridging is brown and the lamellae are light yellow, whereas H. mesophotica lacks ridging and each tubercle bears brown lines radiating from its tip.

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References

• Halgerda sp. 5 (Gosliner et al. 2015), Terrence Gosliner, Ángel Valdés and David Behrens. (2015). Nudibranch and Sea Slug Identification Indo-Pacific. New World Pubns Inc.
• Halgerda sp. 12 (Gosliner et al. 2018), Terrence Gosliner, Ángel Valdés and David Behrens. (2018). Nudibranch and Sea Slug Identification Indo-Pacific 2nd Edition. New World Pubns Inc.
• Halgerda profunda sp. nov., Donohoo S.A., Villalobos S.G., Hallas J.M. & Gosliner T.M. (2023). Hyperdiversity of the genus Halgerda Bergh, 1880 (Nudibranchia: Discodorididae) with descriptions of fourteen new species. Marine Biodiversity. 53(3): 42. https://doi.org/10.1007/s12526-022-01334-9