''Asterina pancerii'', commonly known as the seagrass asterina, 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 ...

of starfish in the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Asterinidae The Asterinidae are a large family of sea stars in the order Valvatida. Description and characteristics These are generally small sea stars, flattened dorsally and bearing very short arms, often giving a pentagonal shape in the body ;example: ...

. It is native to shallow parts of 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 ...

where it is usually found in

seagrass meadows A seagrass meadow or seagrass bed is an underwater ecosystem formed by seagrasses. Seagrasses are marine (saltwater) plants found in shallow coastal waters and in the brackish waters of estuaries. Seagrasses are flowering plants with stems and ...

Description

''Asterina pancerii'' is a very small starfish, seldom exceeding in diameter. It is pentagonal with five short, broad arms scarcely differentiated from the disc. The somewhat inflated aboral (upper) surface is covered by a mosaic of tiled plates each bearing a small tuft of three to eight regularly spaced crystalline spines. The marginal plates are fine, some bearing

pedicellaria A pedicellaria (plural: pedicellariae) is a small wrench- or claw-shaped appendage with movable jaws, called valves, commonly found on echinoderms (phylum Echinodermata), particularly in sea stars (class Asteroidea) and sea urchins (class Echi ...

e, and the tips of the arms have long, slender sensory

tube feet Tube feet (technically podia) are small active tubular projections on the oral face of an echinoderm, whether the arms of a starfish, or the undersides of sea urchins, sand dollars and sea cucumbers; they are more discreet though present on br ...

and inconspicuous eyespots. The aboral surface is a radially symmetric star-shape of red, pink, purple and white plates; the oral (under) surface is a plain colour matching the main colour of the aboral surface.

Distribution and habitat

''Asterina pancerii'' is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

to the Mediterranean Sea. It is most common on the Mediterranean coasts of Spain, France and Italy, but has also been reported from the coasts of Tunisia, Libya, Malta, Greece, Crete and Turkey. Some of these populations in the eastern Mediterranean may turn out to be a new species when genetic testing is done. ''Asterina pancerii'' appears to be a rare species, but this may be because it is seldom noticed because of its small size and unobtrusive behaviour. It usually occurs in seagrass meadows, particularly ''

Posidonia oceanica ''Posidonia oceanica'', commonly known as Neptune grass or Mediterranean tapeweed, is a seagrass species that is endemic to the Mediterranean Sea. It forms large underwater meadows that are an important part of the ecosystem. The fruit is free f ...

''. Although most frequently seen at depths between , it sometimes occurs in deeper meadows at down to .

Ecology

''Asterina pancerii'' is probably a predator, feeding on micro-organisms on the surface of the seagrass blades. It is a

sequential hermaphrodite Sequential hermaphroditism (called dichogamy in botany) is a type of hermaphroditism that occurs in many fish, gastropods, and plants. Sequential hermaphroditism occurs when the individual changes its sex at some point in its life. In particular, ...

, starting life as a female and later becoming a male. The eggs are deposited on the substrate where, after being fertilised, they are brooded by the female. They undergo

direct development Marine larval ecology is the study of the factors influencing dispersing larvae, which many marine invertebrates and fishes have. Marine animals with a larva typically release many larvae into the water column, where the larvae develop before met ...

, with no

plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...

ic larval phase, and crawl away from the female when sufficiently large.

References

{{Taxonbar, from=Q2671856 pancerii Fauna of the Mediterranean Sea Animals described in 1876