''Aeolidia papillosa'', known as the common grey sea slug, 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 ...

nudibranch Nudibranchs () are a group of soft-bodied marine gastropod molluscs which shed their shells after their larval stage. They are noted for their often extraordinary colours and striking forms, and they have been given colourful nicknames to match, ...

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
''Aeolidia papillosa''.
In: MolluscaBase (2017). Accessed through: World Register of Marine Species (WoRMS), 26 July 2017.

Distribution

This nudibranch species thrives in cold-temperate waters in the Northern Hemisphere on the

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

coast of The British Isles and Northern Europe, the Atlantic coast of North America, and the north

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contine ...

Coast of North America. This species has recently been shown to have a more restricted distribution than previously thought, with animals from California, France and Chile being three other species.

Description

''Aeolidia papillosa'' can be easily identified by its large number of cylindrical cerata covering its body except for a triangular area that extends from 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 ha ...

s to the mid dorsum. The color is variable, usually with speckled darker markings in the head and back regions. To distinguish from different Aeolidia, A. papillosa has a distinct "V"- shaped pattern on the head of the animal that extends from one oral tentacle to its opposing pair tentacle. Adult A. papillosa reach up to 120 mm in length.

Anatomy

In the order of Nudibranchia, these 'sea slugs' are not considered marine worms but instead mollusks who lack a shell which is a main characteristic in classification.

Nudibranch Nudibranchs () are a group of soft-bodied marine gastropod molluscs which shed their shells after their larval stage. They are noted for their often extraordinary colours and striking forms, and they have been given colourful nicknames to match, ...

ia exhibit bilateral symmetry in overall body structure as well as in

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 are ...

feature.

Orientation and outer body plan

Since they lack an outer shell, Nudibranchia exhibit a specialized epithelium that protects them from predation and attacks from prey. Located in the epithelium are several vacuoles that aid them in secretions. The outside of the body is also covered with several

cerata :''The tortrix moth genus ''Cerata'' is considered a junior synonym of ''Cydia. Cerata, singular ceras, are anatomical structures found externally in nudibranch sea slugs, especially in aeolid nudibranchs, marine opisthobranch gastropod mollusks ...

, singular ceras, that have numerous functions. This feature, from the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

word "κέρας" means "horn", is often associated with the suborde
aeolid
nudibranch. These protrusions are filled with blood and cover the animal laterally and dorsally. Inside each ceras, there is a duct that connects to the digestive system as well as a sac called

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 n ...

that holds defensive stinging nematocysts it acquires from eating its prey cnidaria. The

pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compou ...

s of cerata are dependent on the color of the digestive gland which can change by diet in

translucent In the field of optics, transparency (also called pellucidity or diaphaneity) is the physical property of allowing light to pass through the material without appreciable scattering of light. On a macroscopic scale (one in which the dimensions ...

species.

Internal organs and processes

Unlike other Aeolidida, the family Aeolidiidae possesses radular teeth which aid in feeding on their prey (See Fig. 2). The radula is a feature in majority of mollusks located in the mouth, like a tongue, containing thousands of teeth that help cut up food for digestion by scraping against rocks or even FMIB_48639_Two_teeth_from_the_radula_of_Aeolis_papillosa_L

FMIB_48639_Two_teeth_from_the_radula_of_Aeolis_papillosa_L

drilling holes in prey in some species. This order is also classified by solid or circular columns of sensory tissues in the form of tentacles called rhinophores. In several groups of

ia, eyes can be located toward the bottom of these

s which can entail possible homology of related ancestors. In internal organs, developing from the stomach is the intestine composing of a thick fold of tissue termed

typhlosole {{Unreferenced, date=December 2009 A typhlosole is an internal fold of the intestine or intestine inner wall. Typhlosoles occur in bivalve mollusks, lampreys and some annelids and echinoderms. In earthworms, it is a dorsal flap of the intestine ...

which is plesiomorphic to Nudibranchia. In the superfamily

Aeolidioidea Aeolidioidea is a superfamily of sea slugs, the aeolid nudibranchs. They are marine gastropod molluscs in the suborder Cladobranchia. Taxonomy As of 2019, the superfamily Aeolidioidea consisted of the following families: * Aeolidiidae Gray, ...

, the typhlosole is present. The function of the typhlosole has not been determined, in some clades, it is possible that it aids in a secretion to help excretion of wastes or provides support in digestion of hard structures like sponge spicules.

Behavior and adaptations

Food sources

The family Aeolidiidae, as well as other Nudibranchia families, are often studied for their adaptable defense from the stinging nematocyst discharge of

Cnidaria Cnidaria () is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the latter. Their distinguishing feature is cnidocytes, specialized cells that ...

n sea anemones in particular

Actinia ''Actinia'' is a genus of sea anemones in the family Actiniidae. Actinia display a rare form of heteromorphosis in which a cut inflicted on a specimen can develop into a second mouth. Species The following species are listed in the World Regis ...

, Anemonia, Metridium, Sagartia and Urticina. Other food sources compose of

zooxanthellae Zooxanthellae is a colloquial term for single-celled dinoflagellates that are able to live in symbiosis with diverse marine invertebrates including demosponges, corals, jellyfish, and nudibranchs. Most known zooxanthellae are in the genus ''S ...

dinoflagellates which live in mutualistic relationship within the Nudibranch that provide nutrition in the tissues through

photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...

. A. papillosa participate in "ingestive conditioning" in which they consume the nematocyst from their prey in response for predators in the same environment.

Nematocyst utilization

Nematocysts are found in the epidermal

mucus 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 ...

coat of several nudibranch families. The amount of inhibition ranges based on the different species of sea anemones preyed upon. By consuming distinct species, the outer mucous layer inhibition alters but if two separate prey species are constantly eaten, the mucous layer will inhibit for both species. Anemones are also covered with a protective mucous layer that i
compositionally
unique from the mucous layer that is produced by nudibranch species. The thickness of the mucous layer ranges by the different families of Nudibranchia but members of Aeolidiidae express relatively thin layers which limit the amount microvilli-like activity possible by volume.

Reproduction

In the order of Nudibranchia, all experience a

hermaphroditic 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 ...

nature with complete male and female reproductive organs. For A. papillosa, self-fertilization is rare and predominantly reproduces by means of

copulation Sexual intercourse (or coitus or copulation) is a sexual activity typically involving the insertion and thrusting of the penis into the vagina for sexual pleasure or reproduction.Sexual intercourse most commonly means penile–vaginal penetra ...

Organ arrangement

These sexual organs are in the form of openings located on the right side of the body. Successful impregnation occurs when the penis of one releases sperm in packets around the mates vaginal opening which is in the shape of a cone. If sperm is not properly administered around the cone it will remain in the outside wall layer where it was penetrated for several days without correct

fertilization Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development. Proce ...

Spawning and eggs

Spawning times range between January through August usually on harder substrate like rocks. This species of nudibranch shed their eggs in masses around 20 million offspring or more. Egg shape is arranged in a spiral pattern in its own capsule and color ranges from white to pink (See Fig. 1). Egg composition arranges in two equivalent layers which can be detected by electron micrographs.

References

External links

Grey sea slug (''Aeolidia papillosa'').
The Marine Life Information Network (MarLIN), Marine Biological Association of the UK. {{Taxonbar, from=Q174694 Aeolidiidae Gastropods described in 1761 Taxa named by Carl Linnaeus Molluscs of the Atlantic Ocean Molluscs of the Pacific Ocean