''Archaster typicus'' 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 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 ...
Archasteridae. It is commonly known as the sand star or the sand sifting star but these names are also applied to starfish in the genus ''
Astropecten''. It is found in shallow waters in the Indo-Pacific region.
Description
''Archaster typicus'' is a five-limbed star with long, slightly tapering arms with pointed tips. Occasionally three, four, or even six-armed individuals occur. Adults grow to in diameter, with males often being smaller than females. This starfish is adapted to life on the sandy seabed, where it buries in the sediment during high tides and moves over the sediment surface during low tides.
The general colour is grey or brownish, variously marked with darker and lighter patches, sometimes forming a chevron pattern. The underside is pale. The body is slightly inflated and there is a whitish
madreporite near the centre of the disc. The small armour plates that cover the upper surface of the arms are lined up in neat parallel rows which distinguishes it from the rather similar ''
Astropecten polyacanthus
''Astropecten polyacanthus'', the sand sifting starfish or comb sea star, is a sea star of the family Astropectinidae. It is the most widespread species in the genus ''Astropecten'', found throughout the Indo-Pacific region. The armspread is up t ...
'' which has similar habits and colouring. The spines, arranged in a marginal fringe, are short, flat and blunter than ''A. polyacanthus'' and the tube feet have suckers and not points.
[Common Sea Star – ''Archaster typicus'']
WildSingapore. Retrieved 2012-04-08.
Distribution and habitat
''Archaster typicus'' is found in the western Indian Ocean and the Indo-Pacific at depths down to . The range includes the
Maldive Islands, the
Bay of Bengal
The Bay of Bengal is the northeastern part of the Indian Ocean, bounded on the west and northwest by India, on the north by Bangladesh, and on the east by Myanmar and the Andaman and Nicobar Islands of India. Its southern limit is a line between ...
,
Singapore
Singapore (), officially the Republic of Singapore, is a sovereign island country and city-state in maritime Southeast Asia. It lies about one degree of latitude () north of the equator, off the southern tip of the Malay Peninsula, borde ...
, northern
Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
,
New Caledonia
)
, anthem = ""
, image_map = New Caledonia on the globe (small islands magnified) (Polynesia centered).svg
, map_alt = Location of New Caledonia
, map_caption = Location of New Caledonia
, mapsize = 290px
, subdivision_type = Sovereign st ...
, the
Philippines
The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no),
* bik, Republika kan Filipinas
* ceb, Republika sa Pilipinas
* cbk, República de Filipinas
* hil, Republ ...
,
China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
, southern
Japan
Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...
and
Hawaii
Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...
. It usually inhabits areas of the seabed with soft sediments including sand, silt and
seagrass meadow
A seagrass meadow or seagrass bed is an underwater ecosystem formed by seagrasses. Seagrasses are marine (saltwater) plants found in shallow coastal waters and in the brackish waters of estuaries. Seagrasses are flowering plants with stems and ...
s.
[ Larval settlement occurs among ]mangroves
A mangrove is a shrub or tree that grows in coastal saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evolution in several ...
, while individuals gradually move to seagrass
Seagrasses are the only flowering plants which grow in marine environments. There are about 60 species of fully marine seagrasses which belong to four families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae), all in the orde ...
and sandy habitats as they age.[
]
Feeding
''Archaster typicus'' is a detritivore
Detritivores (also known as detrivores, detritophages, detritus feeders, or detritus eaters) are heterotrophs that obtain nutrients by consuming detritus (decomposing plant and animal parts as well as feces). There are many kinds of invertebrates, ...
and eats detritus
In biology, detritus () is dead particulate organic material, as distinguished from dissolved organic material. Detritus typically includes the bodies or fragments of bodies of dead organisms, and fecal material. Detritus typically hosts commun ...
and anything else edible it comes across. To feed, it everts its stomach through its mouth which is situated centrally on its underside. The food item is engulfed and brought inside the starfish when its stomach is returned to its normal position.[
]
Reproduction
Like other starfish, ''Archaster typicus'' is a broadcast spawner, the male and female starfish each liberate their gamete
A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce t ...
s into the sea where fertilisation takes place. However, in contrast to most other starfish, ''Archaster typicus'' performs pseudocopulation. Specimens reach sexual maturity at a radius of 29 mm.gonad
A gonad, sex gland, or reproductive gland is a mixed gland that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gonad, the testicle, produces sper ...
al activity so that when the female is ready to spawn, so is the male. When she releases her eggs, he releases his sperm
Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, whi ...
almost simultaneously thereby increasing the chances that successful fertilisation will take place.The Sex Life of ''Archaster''! Pseudocopulation in Sand Stars!
Echinoblog. Retrieved 2012-04-08. Mating occurs in September and October in the Philippines and pair densities reach up to 7 pairs per square meter during full moon, whereas during new moon none are found.
References
{{Taxonbar, from=Q2242090
Archasteridae
Animals described in 1840