''Echinaster luzonicus'', the Luzon sea star, 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 ...

starfish Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea (). Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or basket stars. Starfish ...

in the family

Echinasteridae The Echinasteridae are a family of starfish in the monotypic order Spinulosida. The family includes eight genera and about 133 species found on the seabed in various habitats around the world. Taxonomy Echinasteridae contains eight genera and ...

, found in shallow parts of the western Indo-Pacific region. It sometimes lives

symbiotically Symbiosis (from Ancient Greek, Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different Organism, biological organisms, be it Mutualism (biolog ...

with a

copepod Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...

or a

comb jelly Ctenophora (; ctenophore ; ) comprise a phylum of marine invertebrates, commonly known as comb jellies, that inhabit sea waters worldwide. They are notable for the groups of cilia they use for swimming (commonly referred to as "combs"), a ...

, and is prone to shed its arms, which then regenerate into new individuals.

Description

''Echinaster luzonicus'' is normally a six-armed starfish but is often rather asymmetrical in appearance because of its habit of shedding arms. It is somewhat variable in colouring, ranging from red to dark brown. Both these colour morphs were collected off Heron Island in the

Great Barrier Reef The Great Barrier Reef is the world's largest coral reef system composed of over 2,900 individual reefs and 900 islands stretching for over over an area of approximately . The reef is located in the Coral Sea, off the coast of Queensland, ...

, and individuals seemed able to change their colour from red to brown and back again, possibly as a response to the amount of ambient light they received.

Distribution and habitat

''Echinaster luzonicus'' is found in the tropical and sub-tropical western Indo-Pacific region. Its range extending from Madagascar and the east coast of Africa to Northern Australia, Indonesia and the Philippines. A common species, it is found on both reef crests and in the intertidal zone.

Ecology

''Echinaster luzonicus'' feeds on bacterial and algal films that it extracts from the sediment. This species is unique in its genus in that it

reproduces asexually Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the fu ...

by autotomizing its arms; the shed arm then regenerates, growing a new disc and further arms. This species has not been recorded breeding in any other way. A species of

, lives

on the oral (under) surface of ''Echinaster luzonicus''; it is so cryptically coloured as to be almost indistinguishable from its

host A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places * Host, Pennsylvania, a village in Berks County People *Jim Host (born 1937), American businessman * Michel Host ...

. Another associate of this starfish is the

, ''

Coeloplana astericola ''Coeloplana astericola'', the creeping comb jelly, is a species of benthic comb jelly from the tropical western Indo-Pacific region that lives as an episymbiont on starfish such as '' Echinaster luzonicus''. Description Platyctenids are unlik ...

'', which grows in abundance on its aboral (upper) surface. Three symbionts recorded on ''E''. ''luzonicus'' was the ectoparasitic snail ''Melanella martinii'' (A. Adams in Sowerby, 1854), followed by the pontoniine shrimp ''Zenopontonia soror'' (Nobili, 1904) and the polychaete scaleworm ''Asterophilia carlae'' Hanley, 1989 in the waters of a volcanic island.

Research

A novel cyclic steroid

glycoside In chemistry, a glycoside is a molecule in which a sugar is bound to another functional group via a glycosidic bond. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. ...

has been isolated from the tissues of ''Echinaster luzonicus'' and has been named luzonicoside A. Four further cyclic glycosides containing

carbohydrate In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may or ma ...

fragments have since been named luzonicosides B to E; luzonicoside F, another glycoside, is an open carbohydrate chain steroid. These metabolites exhibit varying degrees of lysosomal activity.

References

External links

* {{Taxonbar, from=Q2148773 Echinaster Fauna of the Indian Ocean Fauna of the Pacific Ocean Starfish described in 1840 Taxa named by John Edward Gray