Runcina avellana

Runcina avellana Schmekel & Cappellato, 2001

Runcina avellana by Enric Madrenas

Taxonomy

	Superdomain	Biota
	Kingdom	Animalia
	Phylum	Mollusca
	Class	Gastropoda
	Subclass	Heterobranchia
	Infraclass	Euthyneura
	Subterclass	Tectipleura
	Order	Runcinida
	Superfamily	Runcinoidea
	Family	Runcinidae
	Genus	Pseudoilbia
	Species	Pseudoilbia avellana (Schmekel & Cappellato, 2001)

	Classification according to Bouchet et al. (2017) Taxonomic source: World Register of Marine Species (AphiaID: 744313).

Taxonomic note: In the description of the species by Schmekel & Capellato (2001), authors referred to a single anatomically studied specimen, 1.2 mm long when alive, as having a radular formula of 3 x 1.0.1, which is considered by the authors as the rudimentary radula of a juvenile. They found no internal shell nor could recover any gastric plates after treating the sample with NaOH. These features induced Ortea (2013) to propose the provisional inclusion of this species in the genus Pseudoilbia within the Ilbidae family, including species of the genus Ilbia Burn, 1963 and Pseudoilbia Miller & Rudman, 1968 with no gastric plates within their digestive tract and the second genus also without spinal tooth. Specimens studied by Araujo et al (2022) were characterized by features consistent with the original description of R. avellana (sensu Schmekel & Cappellato, 2001), like the shape of the body, presence of a round brownish mark on the centre of tail, general colour pattern, absence of gizzard plates and presence of gills, specimens collected at Roses (Spain) about 45 km from the type locality, and clustered in the phylogenetic analyses among species of the genus Runcina, questioning the assignment by Ortea (2013). Moreover, the lack of rachidian teeth in R. avellana reported by Schmekel & Cappellato (2001) might be an artefact since only one apparently juvenile specimen was studied by these authors. Unfortunately, Araujo et al (2022) were not successful on obtaining the radula for study so, in the meantime, at OPK we prefer to keep the species R.avellana within the genus Runcina until further studies of other specimens that may appear in future allow confirmation of the inclusion in one or another genus.

Synonyms

Pseudoilbia avellana Schmekel & Cappellato, 2001

Description
This species is about 2 mm long and has a clearly elongated body. The anterior notum is somewhat narrower than the foot and does not have any cephalic lobes while the rear end has an oval contour. The foot has the same width as the notum except in the front, where it protrudes slightly at the sides of the head region, and the rear, where it forms a short, rounded tail. The coloration is uniform chocolate brown except the anterior and lateral regions of the head, some areas of the edge of notum, foot and tail, which are semitransparent and lighter coloured. The eyes are clearly visible and are located near the side edges of the head region, on the lighter coloured area. The edge of the foot has small brown spots along its length and the tail has a larger spot of the same color, shaped like an inverted “Y”. Schmekel & Capellato (2001) state that the specimens had a single rounded branchial leaf.

Biology
This little-known species are known to live in Posidonia oceanica rhizomes, like other species of the same genus, and it has also appeared among masses of algae like Codium vermilara (personal communication of E. Madrenas).

Etymology

Runcina. The Latin word for carpenter’s plane, a tool used to smooth the surface of the wood.
Avellana. This is related to the city of Avellino (Campania, Italy) which was called “Abella” during the Roman domination, and was known for their hazel plantations, whose fruit was called “nux avellana”, Abella nut. The fruit of the hazel was also known in ancient Castilian as “avellina”. Refers to the chocolate brown colour of this opisthobranch’s body, similar to hazelnut.

Distribution
To date, R. avellana was only known from the town of Banyuls-sur-mer on the French coast of the western Mediterranean, thanks to the collection of 3 live specimens of 1, 1.2 and 1.5 mm in length. The record of a specimen collected from algae in the Medes Islands (Catalonia, Costa Brava) means the second global cite for this species, followed by a few more samples obtained by our group at Roses Bay (Spain) that were used in the study by Araujo et al (2022).

Known georeferenced records of the species: Runcina avellana
Sources:
: OBIS : GROC 2010-2011 : Enric Madrenas : João Pedro Silva : Bernard Picton : GBIF.ORG	: OPK : VIMAR : Manuel Ballesteros. : M@re Nostrum : Altres fonts : Marine Regions

Abundance

Western Mediterranean:	★☆☆☆☆
Eastern Mediterranean:	☆☆☆☆☆
Atlantic Ocean:	☆☆☆☆☆

Month

This chart displays the monthly observation probability for Runcina avellana based on our own records.

More pictures

Runcina avellana by Enric Madrenas

Runcina avellana @ Es Caials, Cadaqués, Spain by Enric Madrenas

Runcina avellana by Enric Madrenas

Runcina avellana @ Caleta (Palamós, Spain) by Enric Madrenas

Bibliography

Steve Long, 2006

Bibliography of Opisthobranchia 1554-2000

Gary McDonald, 2009

Bibliographia Nudibranchia

Further reading

Cite this article as:

Ballesteros, M., Madrenas, E. & Pontes, M. (2012-2025) "Runcina avellana" in OPK-Opistobranquis. Published: 19/09/2012. Accessed: 03/02/2025. Available at (https://opistobranquis.info/en/?p=2310)

Runcina avellana