''Siderastrea radians'', also known as the lesser starlet coral or the shallow-water starlet coral, is a stony coral in the family Siderastreidae. It is found in shallow parts of the western Atlantic Ocean as small, solid mounds or encrusting sheets.

Description

''Siderastrea radians'' is either encrusting or grows in small, dimpled hummocks up to across but most colonies are much smaller than this. Occasionally it occurs as small calcareous pebbles that roll around in seagrass meadows or as loose flat discs in shallow rocky places. The

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 are not circular but are triangular or four-sided and deep, with 30 to 40 small ridges called septa. They have a dark interior that contrasts in colour with the pale surface of the coral which is greyish, greenish or light brown. The polyps are retracted back into these corallites during the day but emerge at night, extending their tentacles to feed. Each of these has a small knob of stinging cnidocytes at its tip. The lesser starlet coral can be confused with the closely related massive starlet coral (''

Siderastrea siderea ''Siderastrea siderea'', commonly known as massive starlet coral or round starlet coral, is a stony coral in the family Siderastreidae. It is found in shallow parts of the western Atlantic Ocean as solid boulder-shaped or domed structures. Des ...

'') but that usually grows at greater depths, is larger and has less deep, more rounded corallites, each with 50 to 60 septa.

Distribution and habitat

''Siderastrea radians'' is common in tropical parts of the western Atlantic Ocean at depths of less than but is most common in under of water. Its range extends from Bermuda, the Bahamas, Florida and the Caribbean Sea south to Brazil and it also occurs in the eastern Atlantic off the coast of Africa. It is found on rocks in various reef habitats and can tolerate silty environments and tide pools. It is an adaptable species and in the

Indian River Lagoon The Indian River Lagoon is a grouping of three lagoons: the Mosquito Lagoon, the Banana River, and the Indian River, on the Atlantic Coast of Florida; one of the most biodiverse estuaries in the Northern Hemisphere and is home to more than 4,300 ...

it has been found to tolerate temperatures varying between and and a wide range of salinities.

Biology

''Siderastrea radians'' feeds at night on zooplankton which it catches with its tentacles. During the day it benefits from the

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 that are found in the tissues. These unicellular algae live within the host's cells and produce carbohydrates by photosynthesis and the coral makes use of these. The sexes are separate in the lesser starlet coral. Each of the twenty-eight ovaries in a female polyp produces a flattened oval

egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...

. Spawning takes place all through the year but may be related to the phase of the moon. Well developed planula larvae have been found being brooded inside female polyps shortly before the full moon. Growth rates of the lesser starlet coral are low but, because of its great tolerance to an increase in sediment levels and to elevated temperatures, it is an important species for maintaining and restoring damaged reefs and may be useful for this purpose if sea temperatures continue to rise.

References

{{Taxonbar, from=Q3945920 Siderastreidae Corals described in 1766 Taxa named by Peter Simon Pallas