''Ophidiaster granifer'', the grained seastar, 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 Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Ophidiasteridae. It is found in the Red Sea and the Indo-Pacific and is the only known species of starfish to reproduce by

parthenogenesis Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and development ...

Description

''Ophidiaster granifer'' is a small five armed starfish with a cryptic mottled brown colouration. It has a rough, granular appearance and grows to a diameter of about . The disc is quite small and the medium-length, fairly broad arms have rounded tips.

Biology

No male ''Ophidiaster granifer'' has ever been identified and all known adults are female. As far as is known, ''Ophidiaster granifer'' is the only member of the

phylum In biology, a phylum (; plural: phyla) is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature f ...

Echinodermata An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the sea li ...

to reproduce exclusively by

. In this species,

eggs Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...

are liberated into the sea in a synchronous spawning event but no fertilisation takes place. The eggs are large, with a diameter of and the mother attaches some of them to the underside of boulders. Here they develop until they undergo

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some inse ...

into juvenile starfish. Other eggs are

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

ic and drift with the currents. In either case, the larvae are lecithotrophic and feed off the yolks of their eggs. This reproductive strategy may be linked to the starfish's low fecundity rate and its low population density.

Distribution and habitat

''Ophidiaster granifer'' is found on

coral reef A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups. Co ...

s in shallow waters in the Red Sea and Indo-Pacific Ocean. It is known from the South China Sea, Japan, Tonga, Fiji, Samoa, northern and western Australia, 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, ...

, New Guinea, Indonesia, the East Indies and the Philippines. It usually hides under boulders and is found on outer reef flats and patch reefs in lagoons, among broken coral rubble and among the dead bases of tangled coral thickets.

References

External links

* {{Taxonbar, from=Q2028193 Ophidiasteridae Animals described in 1871