Berthella perforata

Berthella perforata (Philippi, 1844)

• Pleurobranchus (Bouvieria) perforatus Philippi, 1844
• Pleurobranchus perforatus Philippi, 1844

Taxonomic note: Formerly known in the Mediterranean as Berthella plumula, following the study by Ghanimi et al. (2020) it turned out that Berthella plumula (Montagu, 1803) is actually a complex of two differentiated species; the name B. plumula is retained for specimens from the Atlantic, while the name Berthella perforata (Philippi, 1844) is proposed for specimens from the Mediterranean.

Description
This species can grow up to 35 mm. The overall body color is whitish or pale, but orange animals are not rare. Light brown viscera can be seen, by transparency, in the center of the dorsum. The mantle is quite flat and is characterized by having a lattice pattern consisting of differently shaped small depressions, that provide the dorsum a porous appearance. The visual identification of specimens of B. perforata is problematic due to the color variation in this species. Some of the specimens display a pattern of stellate markings similar to that of specimens of B. stellata, while others are yellowish or whitish, with no stellate markings, resembling the Atlantic species B. plumula. With a binocular microscope, numerous star like spicules can be seen under the mantle epidermis. The inner shell can also be observed in the central area of the mantle. The head veil, the rhinophores, the branquia and foot are whitish or yellowish. The gill is free for about 1/3 of its total length and has about 20 lamellae on either side of the central shaft.

Biology
It is an sporadical finding, usually under stones or associated to shallow Posidonia oceanica rhizomes. The foot of this species has glands that produce acidic defensive secretions. Little is known about the biology of this species, which could feed on sponges and colonial tunicates.

Etymology

• Berthella. 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.
• Plumula. Latin origin, the aftershaft of a feather. The first bud, or gemmule, of a young plant; the bud, or growing point, of the embryo, above the cotyledons.

 Distribution
This species inhabits all European coasts, both Atlantic and Mediterranean, and in the Iberian Peninsula it has been collected all along its coastline. In the Catalan coast is a rare species.

Known georeferenced records of the species: Berthella perforata
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:	☆☆☆☆☆