''Astroides'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of stony cup corals 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 ...

Dendrophylliidae Dendrophylliidae is a family of stony corals. Most (but not all) members are azooxanthellate and thus have to capture food with their tentacles instead of relying on photosynthesis to produce their food. The World Register of Marine Species incl ...

. It is

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

and the only

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 ...

is ''Astroides calycularis'', which 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 elsew ...

to the western Mediterranean Sea. The species was first described in 1766 by the German naturalist

Peter Simon Pallas Peter Simon Pallas Fellow of the Royal Society, FRS FRSE (22 September 1741 – 8 September 1811) was a Prussian zoologist and botanist who worked in Russia between 1767 and 1810. Life and work Peter Simon Pallas was born in Berlin, the son ...

Description

''Astroides calycularis'' is a

colonial Colonial or The Colonial may refer to: * Colonial, of, relating to, or characteristic of a colony or colony (biology) Architecture * American colonial architecture * French Colonial * Spanish Colonial architecture Automobiles * Colonial (1920 au ...

coral, consisting of a group of polyps, each of which sits in a stony cup known as a calyx. The colonies are in diameter and high and each polyp is about in diameter. The polyps are yellow or orange, each with a fringe of about thirty very short

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 surrounding a slit-shaped mouth. The colony grows by

asexual reproduction 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 ...

, new polyps budding off existing polyps and secreting their own calices. Deep-water colonies are bush-shaped, the calices are circular and budding occurs at various heights on the calyx walls. Shallow-water colonies tend to be ellipsoid in shape, the calyces are polygonal and budding occurs in the centre of the colony as well as round the edges.

Distribution and habitat

During the

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

, ''Astroides calycularis'' had a wider distribution than it does now, and was present in the whole of the western Mediterranean. Since then it has disappeared from the northern part of that range as a result of the lower sea temperatures that resulted from glaciation. Nowadays it is native to the part of the western

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 ...

that is south of

Sardinia Sardinia ( ; it, Sardegna, label=Italian, Corsican and Tabarchino ; sc, Sardigna , sdc, Sardhigna; french: Sardaigne; sdn, Saldigna; ca, Sardenya, label=Algherese and Catalan) is the second-largest island in the Mediterranean Sea, after ...

and is also present in the Atlantic Ocean near the

Strait of Gibraltar The Strait of Gibraltar ( ar, مضيق جبل طارق, Maḍīq Jabal Ṭāriq; es, Estrecho de Gibraltar, Archaic: Pillars of Hercules), also known as the Straits of Gibraltar, is a narrow strait that connects the Atlantic Ocean to the Medi ...

. Before 1989 it was restricted to the area west of

Sicily (man) it, Siciliana (woman) , population_note = , population_blank1_title = , population_blank1 = , demographics_type1 = Ethnicity , demographics1_footnotes = , demographi ...

, but in that year it appeared in the

Adriatic Sea The Adriatic Sea () is a body of water separating the Italian Peninsula from the Balkan Peninsula. The Adriatic is the northernmost arm of the Mediterranean Sea, extending from the Strait of Otranto (where it connects to the Ionian Sea) to t ...

for the first time. This coincided with a sudden change of circulation in the eastern Mediterranean which may have allowed the short-lived pelagic larvae to survive long enough to settle on the seabed of the Croatian coast. ''A. calycularis'' is found on rocks and walls, under overhangs and in submarine caves at depths down to about . In suitable locations, colonies can cover 90% of the available substrate. In a cave in Italy, it was more common in better lit parts than was the solitary sunset cup coral (''

Leptopsammia pruvoti ''Leptopsammia pruvoti'', the sunset cup coral, is a solitary stony coral in the family Dendrophylliidae. It is an azooxanthellate species, meaning its tissues do not contain the symbiotic unicellular algae (zooxanthellae) of the genus ''Symbiodi ...

''), and was more abundant near where sulphurous spring water flowed into the cave.

Biology

''Astroides calycularis'' is nocturnal, the polyps remaining retracted back into their calices during the day. When expanded at night, they feed on

zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...

, small fish and perhaps bacteria. This coral is azooxanthellate, meaning it does not contain

symbiotic Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...

dinoflagellate The dinoflagellates (Greek δῖνος ''dinos'' "whirling" and Latin ''flagellum'' "whip, scourge") are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered algae. Dinoflagellates are ...

s in its tissues as do many species of coral. ''A. calycularis'' colonies are

gonochoristic In biology, gonochorism is a sexual system where there are only two sexes and each individual organism is either male or female. The term gonochorism is usually applied in animal species, the vast majority of which are gonochoric. Gonochorism c ...

with all the polyps in a colony being of the same sex. Males liberate sperm into the sea and fertilisation takes place in the coelenteron (gastric cavity) of the female. The eggs have yolks, and the embryos are brooded in the coelenteron until they are liberated into the water column as

planula A planula is the free-swimming, flattened, ciliated, bilaterally symmetric larval form of various cnidarian species and also in some species of Ctenophores. Some groups of Nemerteans also produce larvae that are very similar to the planula, which ...

larvae.

References

{{Taxonbar, from1=Q626731, from2=Q2868573 Scleractinia genera Monotypic cnidarian genera Dendrophylliidae Biota of the Mediterranean Sea