''Astrangia solitaria'', the dwarf cup coral or southern cup coral, 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
stony coral
Scleractinia, also called stony corals or hard corals, are marine animals in the phylum Cnidaria that build themselves a hard skeleton. The individual animals are known as polyps and have a cylindrical body crowned by an oral disc in which a ...
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 ...
Rhizangiidae
Rhizangiidae is a family of stony corals in the order Scleractinia. This family is closely related to Oculinidae. Members of this family are non-reef building corals and reproduce from stolons. The corallites are small and the septa are simple.
...
. It is native to shallow water in the western Atlantic Ocean and the Caribbean Sea.
Description
A
colony
In modern parlance, a colony is a territory subject to a form of foreign rule. Though dominated by the foreign colonizers, colonies remain separate from the administration of the original country of the colonizers, the ''metropole, metropolit ...
of ''Astrangia solitaria'' consists of a small number of cylindrical
corallite
A corallite is the skeletal cup, formed by an individual stony coral polyp, in which the polyp sits and into which it can retract. The cup is composed of aragonite, a crystalline form of calcium carbonate, and is secreted by the polyp. Corallit ...
s (stony cups), in diameter and high, each secreted by the polyp that sits inside it. New polyps grow on short
stolon
In biology, stolons (from Latin '' stolō'', genitive ''stolōnis'' – "branch"), also known as runners, are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are external s ...
s and the coenosarc (soft tissue) does not cover the skeleton in a continuous sheet as it does in most coral species. The stolons may become abraded leaving the individual polyps completely or semi-separated. The corallites can have 48
septa
The Southeastern Pennsylvania Transportation Authority (SEPTA) is a regional public transportation authority that operates bus, rapid transit, commuter rail, light rail, and electric trolleybus services for nearly 4 million people in five coun ...
(stony ridges) but 36 is a more usual number. The septa of adjoining corallites are connected by wide, flat, granular
costae (ridges). The colour of this coral is usually pale brown, but the corallites may have brown extremities and white bases, or even be completely white.
''A. solitaria'' can be confused with the
northern cup coral (''Astrangia poculata'') but that species usually forms clumps with more numerous, smaller corallites. ''A. poculata'' often contains
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 ...
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 ''Sy ...
in its tissues
while ''A. solitaria'' does not.
[
]
Distribution and habitat
''Astrangia solitaria'' is found down to depths of about in the western Atlantic Ocean and Caribbean Sea, including Florida, the Bahamas, the Gulf of Mexico, Mexico, Costa Rica, Panama, Colombia, Venezuela and Belize. It is found on hard surfaces including coral rubble and the underside of plate corals.[ This coral is found in sheltered shallow water but on a particular stretch of coast on ]Grand Cayman
Grand Cayman is the largest of the three Cayman Islands and the location of the territory's capital, George Town. In relation to the other two Cayman Islands, it is approximately 75 miles (121 km) southwest of Little Cayman and 90 miles ( ...
, a large onshore boulder was found to harbour the remains of numerous colonies of ''A. solitaria'' that were carbon-dated
Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for Chronological dating, determining the age of an object containing organic material by using the properties of carbon-14, radiocarbon, a radioactive Isotope ...
to an age of six hundred years. This boulder was likely shifted onshore by a hurricane three hundred and thirty years ago, an event which would have resulted in the death of the corals.
References
{{Taxonbar, from=Q3942935
Rhizangiidae
Animals described in 1817