Taxonomy
- Kingdom: Animalia
- Phylum: Mollusca
- Class: Gastropoda
- Subclass: Heterobranchia
- Order: Nudibranchia
- Suborder: Aeolidacea
- Family: Facelinidae
- Genus: Facelina
- Species: Facelina annulicornis
The species belongs to the family Facelinidae, a group of aeolid nudibranchs characterised by elongated bodies and numerous dorsal cerata. The specific epithet annulicornis refers to the annulated (ring‑like) appearance of the rhinophores (sensory organs on the head).
Description
Facelina annulicornis is a small to medium‑sized aeolid nudibranch, typically reaching a total length of 20–35 mm. The body is generally translucent white to pale cream, allowing the internal organs and the reddish‑orange coloration of the cerata to be visible. The cerata are arranged in several rows along the dorsum and possess apical tips that are often pigmented orange to red. The rhinophores are slender, bearing distinct transverse rings that give the species its name. The oral tentacles are smooth and elongate.
Distribution and Habitat
The species has been recorded in temperate European waters, including the Mediterranean Sea and the northeastern Atlantic from the British Isles southward to the Iberian Peninsula. It is typically found in shallow subtidal zones (0–30 m depth) on rocky substrates, among algal holdfasts, and in association with colonies of hydroids on which it feeds.
Ecology
Facelina annulicornis is an active predator of colonial hydroids, particularly species of the genera Eudendrium and Obelia. As with other aeolids, it sequesters nematocysts (stinging cells) from its prey within the tips of its cerata, a defensive adaptation known as kleptocnidae. The species is hermaphroditic, possessing both male and female reproductive structures.
Reproduction
Mating involves reciprocal copulation, after which individuals lay gelatinous, spiral‑shaped egg ribbons on the substrate. The eggs develop into planktonic veliger larvae, which eventually settle and undergo metamorphosis into the adult form.
Conservation Status
No specific conservation assessment has been published for Facelina annulicornis; it is not listed on the IUCN Red List. The species does not appear to be under targeted threat, although general coastal pollution and habitat alteration could affect local populations.
References
- Gofas, S.; Le Renard, J.; Bouchet, P. (2001). Mollusca. In: Costello, M.J. et al. (Eds.), European register of marine species. Patrimoines Naturels, 50, 180–213.
- Rudman, W.B. (2000). Facelina annulicornis (Heynemann, 1882). Sea Slug Forum. Australian Museum, Sydney.
Note: All information presented is derived from established taxonomic and marine biological literature available up to the date of this entry.