Guide to Opisthobranchs Pleurobranchida Berthellina edwardsii

Berthellina edwardsii

Berthellina edwardsii (Vayssière, 1896)

Berthellina edwardsii by Enric Madrenas

Taxonomic note: This species has been traditionally confused with Berthella aurantiaca because its external morphology is very similar, so much so that it is virtually impossible to distinguish them “de visu”. To differentiate these species is mandatory an study of the mandibular structure and the radular teeth. The radula of B. edwardsii has numerous denticulate teeth (more than 150) in each semi-row and an elongated jaws and with smooth mandibular parts while the teeth of the radula of B. aurantiaca are much less numerous (from 50 to 80 per semi-row) ) the mandibles are shorter and with the mandibular parts with denticles on the sides. Adult specimens can also be differentiated by the size of the inner shell, which in B.edwardsii never exceeds 5.5mm (in specimens up to 60mm) since it stops growing when the animals reach circa 15mm in length (Jakov Prkić, com.pers.), whereas in Berthella aurantiaca the shell is proportionally larger (Vayssière reported a 15mm shell in a 30mm specimen), as it protects the entire visceral mass.

Synonyms

Berthella edwardsii Vayssière, 1896

Description
This species can reach a size up to 60 mm in length, although specimens usually seen in the upper infralittoral usually measure between 20 and 30 mm in length. The body is characteristically highly domed and their color is very striking: orange or uniform yellowish orange. The mantle covers the entire animal but the rhinophores, the cephalic veil and back of the foot, that protrudes slightly. The mantle, apparently smooth, when viewed under binocular microscope shows tiny round bumps that form and dissolve in the living animal, and also numerous and very tight rounded structures corresponding to the output of the ducts of the acidic glandular formations that characterize the majority of the Pleurobrancomorphs species. The internal shell cannot be seen by transparency through the mantle tissue, as in other species of Berthella. The shell is flat and auriculate and is covered by a thin membranous periostracum. The cephalic veil is frustoconical shaped with a wider anterior area; ventrally, the cephalic veil is crossed laterally. Auriculate rhinophores can be seen over the cephalic veil, they emerge together from the base and are directed somewhat obliquely in the form of “V”. Rhinophores are of the same color as the body and can be retracted below the anterior mantle. When they are fully extended some slight folds transverse along their surface. The eyes can be seen right behind of the external side of the rhinophores base. The gill is located on the right of the body, between the mantle and the foot, it is bipinnate and has about a dozen lamellas to each side of the central axis. Under the binocular microscope shows that each lamella is also finely pinnulated. The anal orifice is located just above the gill. The foot is broad and oval shaped even in the tail, which is rounded. The color is of lighter yellow than the body and in the center you can see a brown spot due to the viscera below. All along the edge of the foot there is a groove that completely surrounds it.

Biology
Studying the anatomy of the specimens that have been found in the north of the Costa Brava, under stones, down to 15-20 meters deep, we have concluded that they all belong to B. edwardsii. Because there has been confusion with B. aurantiaca, few biological data can be secured to B. edwardsii. It could feed on encrusting sponges such as Corticium sp., Tethya aurantium, Aaptos aaptos and Hemimycale sp., all being species that live on the underside of stones where the opistobranch could be found. The spawn consists of a flat light colored ribbon wound in spiral and attached to the substrate by one of its sides, forming characteristic undulations.

Etymology

Berthellina. Probably dedicated to Sabin Berthelot (1794-1880), a French naturalyst who enrolled the Navy and participated in the Napoleonic wars. He lived part of his life at the Canary islands, in his post as French consul in Tenerife. The abbreviation “Berth” is used to indicate Sabin Berthelot as an authority in the scientific botanical description and classification. He wrote the “Historia Natural de Canarias” and directed the Botanical Garden of Puerto de la Cruz.
Edwardsii. Dedicate to Henry Milne-Edwards (1800-1885), a French zoologyst supporting the study of animals in their natural environment and not from stuffed specimens.

Distribution
Because of confusion with B. aurantiaca, reports of B. edwardsii should be confirmed. Cervera et al. (2004) conclude, however, that this species is found throughout the Iberian coast, the Balearic Islands, Madeira, Azores and Cape Verde. It is cited as Berthella plumula, B. engeli and B. citrina also on the coasts of France, Italy and other Mediterranean areas. In the Catalan coast B. edwardsii is a common species along the northern coast of the Costa Brava, in places like Cala Sant Antoni, Es Caials and the Medes Islands. VIMAR group has studied the anatomy and morphology of specimens aurantiaca / edwardsii found in the Costa Brava (N.E. Spain), under stones, from the lower tide area down to 15-20 m deep and, so far, they are all B. edwardsii .

Known georeferenced records of the species: Berthellina edwardsii
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 Berthellina edwardsii based on our own records.

Videos

More pictures

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. (2023) "Berthellina edwardsii" in OPK-Opistobranquis. Published: 15/05/2012. Accessed: 07/06/2023. Available at (https://opistobranquis.info/en/GXUXd)

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Berthellina edwardsii