''Berthella ocellata'' is a

species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

sea slug Sea slug is a common name for some marine invertebrates with varying levels of resemblance to terrestrial slugs. Most creatures known as sea slugs are gastropods, i.e. they are sea snails (marine gastropod mollusks) that over evolutionary ...

, a marine gastropod mollusc in the family Pleurobranchidae. It is native to the eastern Atlantic Ocean and the Mediterranean Sea where it inhabits the shallow

sublittoral zone The neritic zone (or sublittoral zone) is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately in depth. From the point of view of marine biology it forms a relatively stable and well-illuminated ...

Description

The adult length of ''Berthella ocellata'' is about . It has an oval shape when extended and moving around, and circular when stationary. The head bears a pair of small black eyes and the mouth is underneath, with the buccal veil protruding on either side. The

rhinophore A rhinophore is one of a pair of chemosensory club-shaped, rod-shaped or ear-like structures which are the most prominent part of the external head anatomy in sea slugs, marine gastropod opisthobranch mollusks such as the nudibranchs, sea ...

s are just in front of the eyes, and are tubular, with a split on the under surface; they project from the front edge of the mantle. When moving, the foot trails behind the slug; the underside of the foot is whitish or pale brown. There are two distinct colour forms of this sea slug, either brown, or whitish; in both cases the body is covered with white or pink, translucent, slightly-domed tubercles, each surrounded by a white rim. The

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they ar ...

is yellow and

bipinnate The following is a list of terms which are used to describe leaf morphology in the description and taxonomy of plants. Leaves may be simple (a single leaf blade or lamina) or compound (with several leaflets). The edge of the leaf may be regular ...

and is located between the mantle and the foot, on the right-hand side at the back. Under the mantle dorsally, there is a small, rudimentary, whitish internal shell.

Distribution and habitat

This species occurs in the

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ...

, the eastern

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth#Surface, Earth's surface and about 29% of its water surface area. It is known to separate the "Old World" of Afr ...

, including the

Canary Islands The Canary Islands (; es, Canarias, ), also known informally as the Canaries, are a Spanish autonomous community and archipelago in the Atlantic Ocean, in Macaronesia. At their closest point to the African mainland, they are west of Mo ...

. It is found on rocks in the shallow

, mostly at depths less than but sometimes as deep as .

Ecology

Being

nocturnal Nocturnality is an ethology, animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnality, diurnal meaning the opposite. Nocturnal creatures generally have ...

, ''B. ocellata'' spends the day under stones, in crevices or in caves; it feeds on sponges such as '' Plakina trilopha'', '' Plakinastrella copiosa'' and '' Corticium candelabrum'', using its muscular

radula The radula (, ; plural radulae or radulas) is an anatomical structure used by molluscs for feeding, sometimes compared to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food ...

to rasp off fragments. Its foot produces acidic secretions which are distasteful to

predators Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

. These slugs are

hermaphrodite In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many taxonomic groups of animals (mostly invertebrates) do not have ...

s. The genital pores are on the right-hand side in front of the gill, and two individual slugs will position themselves in a head-to tail position, and each pass sperm to the other. Fertilisation is internal, and the eggs are probably laid in a gelatinous spiral, as is the case with other members of the genus.

References

* Ortea J. & Moro L. (2017). ''Redescripcion de ''Staurodoris atypica'' Eliot, 1906 y nuevas citas de "lesmas do mar" (Mollusca: Heterobranchia) para las islas de Cabo Verde.'' Avicennia. 20: 15–20.

External links

Delle Chiaje S. (1823-1831). Memorie sulla storia e notomia degli animali senza vertebre del regno di Napoli. Napoli: Fratelli Fernandes (vol. 1), and Società Tipografica (vol. 2-4). Vol. 1, pp. i-xii, 1-84 [1823
pp. 1-184 [1824]; vol. 2, pp. [1-4] + 185-224 [1825], pp. 225-444 [1826]; vol. 3, pp. i-xx, pp. 1-232 [1828]; vol. 4, pp. i-vii [1831], 1-116 [1830], pp. 117-214 [1831]; pl. 1–4; pl. 1-69 [date?], pl. 70-109 [1830) ] {{Taxonbar, from=Q13438945 Pleurobranchidae Molluscs of the Atlantic Ocean Molluscs of the Mediterranean Sea Gastropods described in 1830 Taxa named by Stefano delle Chiaje