Thecacera melkyi Pola, Paz-Sedano, Guisado Martín, Warren, Noble & Martín-Hervás, 2026

Description

Species up to 25 mm in length. Mantle smooth with numerous embedded spicules. Rhinophores long with 22–24 lamellae and well-differentiated bases. Rhinophoral sheaths lanceolate, well developed but not complete, open inside. Two retractable semicircular structures with branches below rhinophores. Gill at end of first third of body, composed of six multipinnate branchial branches surrounding the anal pore. Highly developed extrabranchial processes on both sides of gill, cylindrical with rounded ends, approximately half the body length.

Color pattern

Body milky orange with blackish spots. One large spot just in front of gill, surrounded by three smaller spots (two lateral and one between rhinophores). On the rest of the body, spots organized in orderly manner; from behind each extrabranchial process, forming a line on both sides that joins halfway to tail in a Y-shaped pattern. Rhinophoral lamellae, rhinophoral sheaths, extrabranchial processes, and external rachis of each branchial branch entirely blackish.

Distribution

Western Pacific. Type locality is Tasi Tolu Bay, Dili, East Timor. Also recorded from Indonesia and Japan.

Etymology

Named after Melky, the first Timorese diving instructor, who kindly assisted the authors during fieldwork and helped find and collect the specimens.

Remarks

A member of the family Polyceridae, subfamily Polycerinae. Found during night dives over sandy substrate and coral rubble, feeding on bryozoans. Similar in appearance to T. pikachu but distinguished by the milkier orange body color and different spot arrangement pattern. The reproductive act takes place in an evertible bag-like structure.

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References

• テカケラ属の一種, 殿塚孝昌. (2003). ウミウシガイドブック〈3〉. TBSブリタニカ.
• Thecacera sp.12, Helmut Debelius, Rudie H. Kuiter. (2007). Nudibranchs of the World.
• Thecacera sp. 5, Terrence Gosliner, Ángel Valdés and David Behrens. (2015). Nudibranch and Sea Slug Identification Indo-Pacific. New World Pubns Inc.
• Thecacera sp.5, Terrence Gosliner, Ángel Valdés and David Behrens. (2018). Nudibranch and Sea Slug Identification Indo-Pacific 2nd Edition. New World Pubns Inc.
• Thecacera melkyi sp. nov, Pola, M., Paz-Sedano, S., Guisado Martín, P., Warren, L., Noble, K. & Martín-Hervás, M.R. (2026). The most wanted! Gorgeous, delicate and surprising description of three new polycerid species (Mollusca, Heterobranchia) from East Timor. Zootaxa, 5793(1), 193-217.