Taxonomy
- Kingdom: Animalia
- Phylum: Mollusca
- Class: Gastropoda
- Subclass: Heterobranchia
- Order: Nudibranchia
- Suborder: Doridina
- Family: Goniodorididae
- Genus: Okenia
- Species: Okenia brunneomaculata
- Authority: (Baba, 1937)
Description
Okenia brunneomaculata is a dorid nudibranch, a type of shell‑less marine gastropod mollusk. Adults are small, typically measuring between 5 mm and 15 mm in length. The body is generally translucent to pale white, covered with numerous brown to dark brown maculae (spots) that give the species its epithet “brunneomaculata” (Latin for “brown‑spotted”). The mantle is smooth, and the rhinophores and gill structures are similarly pigmented, though detailed morphological measurements are limited in the primary literature.
Distribution
The species was first described from specimens collected in the coastal waters of Japan, with the type locality reported from the Kii Peninsula. Subsequent records are primarily from the western Pacific, including additional localities along the Japanese archipelago. The full extent of its geographic range remains incompletely documented.
Habitat and Ecology
Okenia brunneomaculata inhabits shallow subtidal zones, often found on or near benthic substrates where its prey organisms occur. Like other Okenia species, it is presumed to feed on specific bryozoans or tunicates, though direct observations of its diet are scarce. It is a benthic organism, moving slowly over the substrate and relying on chemical cues for locating food and mates.
Reproduction
Nudibranchs are hermaphroditic; O. brunneomaculata is expected to follow the typical reproductive pattern of laying gelatinous egg masses on suitable substrates. Detailed studies on its reproductive cycle are lacking.
Conservation Status
No assessment of the conservation status of Okenia brunneomaculata has been performed by the International Union for Conservation of Nature (IUCN). Given its limited known distribution and the paucity of population data, its vulnerability cannot be accurately determined.
Research and Significance
The species contributes to the biodiversity of marine opisthobranchs in the western Pacific and serves as a potential indicator of benthic ecosystem health. Further taxonomic, ecological, and molecular studies are required to clarify its relationships within Goniodorididae and to better understand its ecological role.
References
- Baba, K. (1937). Opisthobranchia of Japan (II). Venus, 7(3), 73‑121.
- World Register of Marine Species (WoRMS). Okenia brunneomaculata (Baba, 1937). Retrieved 2026.
- Rudman, W.B. (2001). Nudibranchs of the world. Sea Slug Forum, Australian Museum, Sydney.
Note: Information presented reflects the current state of published scientific literature. Where specific details are lacking, the entry indicates the limits of available data.