''Aeolidiella alderi'' is a

species In biology, a species is the basic unit of 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 the appropriate s ...

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 t ...

, an aeolid nudibranch in the family

Aeolidiidae Aeolidiidae, a family of aeolid nudibranchs, are a family of sea slugs, shell-less marine gastropod molluscs.Bouchet, P. (2014)''Aeolidiidae'' Gray, 1827.Accessed through: World Register of Marine Species on 2014-10-24 Most, or perhaps all, mem ...

.Gofas, S. (2015)
''Aeolidiella alderi'' (Cocks, 1852).
In: MolluscaBase (2015). Accessed through: World Register of Marine Species on 2015-11-12 It is native to northwestern Europe where it occurs in the

intertidal zone The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various species o ...

. It is a

predator 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 ...

and feeds on

sea anemone Sea anemones are a group of predation, predatory marine invertebrates of the order (biology), order Actiniaria. Because of their colourful appearance, they are named after the ''Anemone'', a terrestrial flowering plant. Sea anemones are classifi ...

Description

This is a small nudibranch that can reach a length of . The body shape is flattened and broad, but not as wide as ''

Aeolidia papillosa ''Aeolidia papillosa'', known as the common grey sea slug, is a species of nudibranch in the family Aeolidiidae.Gofas, S''Aeolidia papillosa''.In: MolluscaBase (2017). Accessed through: World Register of Marine Species (WoRMS), 26 July 2017. Dis ...

'' and '' Aeolidia filomenae''. The pair of oral

tentacle In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work main ...

s on the head are longer than the rhinophores. The dorsal surface of the body has up to 16 oblique rows of cerata on either side. These are outgrowths of the body wall that increase the area available for respiration, and contain extensions of the gut, so vary in colour according to the animal's diet. The first row of cerata have reduced digestive gland extensions and are white, forming a collar. The cerata are tipped with

cnidosac A cnidosac is an anatomical feature that is found in the group of sea slugs known as aeolid nudibranchs, a clade of marine opisthobranch gastropod molluscs. A cnidosac contains cnidocytes, stinging cells that are also known as cnidoblasts or nemato ...

s containing stinging cells, derived from the

s that the nudibranch has eaten and which pass unmetabolized through its body.

Distribution

The species was described from England. It was also recorded from the North Atlantic Ocean, off

Ireland Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic Ocean, in Northwestern Europe, north-western Europe. It is separated from Great Britain to its east by the North Channel (Grea ...

, the

North Sea The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...

and 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 ea ...

. It is a shallow water species and occurs in the

, under boulders and in rock pools.

Ecology

A carnivore, ''A. alderi'' feeds on

s. It seems to have a preference for '' Cereus pedunculatus'', '' Diadumene cincta'' and species of ''

Sagartia ''Sagartia'' is a genus of sea anemones in the family Sagartiidae. The genus was first described by Philip Henry Gosse in 1855 and the image is his painting of several species found in British waters included in his book, ''A history of the Brit ...

'' such as ''

Sagartia elegans ''Sagartia elegans'', the elegant anemone, is a species of sea anemone in the family Sagartiidae. It is found in coastal areas of northwest Europe at depths down to 50 metres. Description The base of ''S. elegans'' is wider than the column and m ...

'' and ''

Sagartia troglodytes ''Sagartia troglodytes'' is a species of sea anemone in the family Sagartiidae, also known as the mud sagartia or the cave-dwelling anemone. Description The base is anchored in holes in the rock and is a little wider than the column. This is ...

''. It also feeds on '' Metridium dianthus'', '' Sagartiogeton laceratus'', '' Paractinia striata'', '' Actinothoe sphyrodeta'' ''

Aiptasia mutabilis ''Aiptasia mutabilis'', also known as the trumpet anemone, rock anemone, and glass anemone, is a species of anemone typically found attached to substrates in cold waters of the Atlantic Ocean. Its unique trumpet shape gives it its common name and ...

'', '' Anemonia viridis'' and ''

Aulactinia verrucosa ''Aulactinia verrucosa'', the gem anemone, is a species of sea anemone in the family Actiniidae. It is found on rocky coasts in the northeastern Atlantic Ocean, North Sea and Mediterranean Sea. Description ''Aulactinia verrucosa'' has a cylindr ...

''. The rhinophores are sensory structures and are able to analyse the chemicals dissolved in the water around the sea slug, enabling it to detect its prey. Sea anemones are avoided by many predators because of their defensive stinging cells. The sea slug approaches a sea anemone with the greatest caution, gradually inching towards it, and extending the cerata that form the collar to two or three times their normal length. When close enough (fractions of a millimetre), the cnidosacs in the collar cerata are discharged into the column of the anemone, poisoning the tissues and causing necrosis. The sea slug can then feed. Reproduction is hermaphroditic. The eggs are large and are laid in a spiral string of

mucous Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It is ...

on the substrate. Development is direct, without any larval stage, the young crawling away after hatching. The juveniles have no cerata at first, and these develop as the animal grows. Reproduction seems to take place all year round, and the young reach maturity after several months of growth.

Etymology

The name honours

Joshua Alder Joshua Alder (7 April 1792 – 21 January 1867) was a British cheese, cheesemonger and amateur zoologist and malacologist. As such, he specialized in the Tunicata, and in gastropods. He was a member of the Hancock Museum, Natural History Societ ...

References

* Gofas, S.; Le Renard, J.; Bouchet, P. (2001). Mollusca. in: Costello, M.J. et al. (Ed.) (2001). ''European register of marine species: a check-list of the marine species in Europe and a bibliography of guides to their identification.'' Collection Patrimoines Naturels. 50: pp. 180–213. {{Taxonbar, from=Q5052513 Aeolidiidae Molluscs of the Atlantic Ocean Molluscs of the Mediterranean Sea Gastropods described in 1852