''Actinopyga varians'', the Pacific white-spotted sea cucumber or Hawaiian sea cucumber, 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 ...

sea cucumber Sea cucumbers are echinoderms from the class Holothuroidea (). They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found on the sea floor worldwide. The number of holothuria ...

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 ...

Holothuriidae Holothuriidae is a family of sea cucumbers, a type of echinoderm. Description Members of the family Holothuriidae have thick fleshy bodies and several rows of tube feet which are used for moving around and for adhering to the surface. The body ...

. It is found in the Pacific Ocean near

Hawai'i 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 ...

and also in the

Indo-Pacific Ocean The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...

Distribution and Habitat

''Actinopyga varians'' is found in tropical waters, commonly seen in the Western Pacific and the Indo-Pacific. It has been seen in Hawai’i,

Fiji Fiji ( , ,; fj, Viti, ; Fiji Hindi: फ़िजी, ''Fijī''), officially the Republic of Fiji, is an island country in Melanesia, part of Oceania in the South Pacific Ocean. It lies about north-northeast of New Zealand. Fiji consists ...

, the

French Polynesia )Territorial motto: ( en, "Great Tahiti of the Golden Haze") , anthem = , song_type = Regional anthem , song = " Ia Ora 'O Tahiti Nui" , image_map = French Polynesia on the globe (French Polynesia centered).svg , map_alt = Location of Frenc ...

and other islands in

Micronesia Micronesia (, ) is a subregion of Oceania, consisting of about 2,000 small islands in the western Pacific Ocean. It has a close shared cultural history with three other island regions: the Philippines to the west, Polynesia to the east, and ...

. It tends to live in depths of about 0-25 m on living

corals Corals are marine invertebrates within the class (biology), class Anthozoa of the phylum Cnidaria. They typically form compact Colony (biology), colonies of many identical individual polyp (zoology), polyps. Coral species include the important C ...

and surrounding rubble areas of

reefs A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic processes— deposition of sand, wave erosion planing down rock out ...

on the crest of the ocean floor.

Description

The size of this species ranges from 15 cm to 20 cm (6 to 8 in.). The bivium is hard, is dark red or brown with distinct white spots, and can be wrinkled. Although the bivium is hard, all holothuroids have a reduced skeleton of isolated ossicles in the body wall. A distinct characteristic of the ''Actinopyga'' genus are the teeth surrounding the anus. However, this trait is not exclusive to the ''Actinopyga'' genus, and some other ''

Holothuria ''Holothuria'' is the type genus of the marine animal family Holothuriidae, part of the class Holothuroidea, commonly known as sea cucumbers. Members of the genus are found in coastal waters in tropical and temperate regions. They are soft bodied ...

'' can have similar characteristics.'' ''The Holothuriidae family, which the ''Actinopyga varians'' is a part of, is are known to have thick fleshy bodies and rows of tube feet. Papillae, which are blunt projections, cover the body. Their

spicules Spicules are any of various small needle-like anatomical structures occurring in organisms Spicule may also refer to: *Spicule (sponge), small skeletal elements of sea sponges *Spicule (nematode), reproductive structures found in male nematodes ( ...

are shaped like tubes and although most species in the Holothuriidae family are able to eject

cuvierian tubules Cuvierian tubules are clusters of fine tubes located at the base of the respiratory tree in some sea cucumbers in the genera ''Bohadschia'', ''Holothuria'' and ''Pearsonothuria'', all of which are included in the family Holothuriidae. The tubules ...

in self-defense, the genera ''Actinopyga'' is unable to do so. One of the main distinguishing feature of the order Holothuriida'','' of which the family Holothuriidae is a part of, is the leaf-like tentacles that surround the mouth, which aids in feeding.

Diet

''Actinopyga varians'' are

detritivores 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 trap particles and plankton on their tentacles. The papillae of the tentacles hold cells that secrete the mucus, which the particles and plankton are stuck on to. They are highly selective deposit feeders and generally consume highly organic material. The tentacles surround the mouth, which from the mouth goes to the esophagus, then the foregut to the intestine. This is where digestion occurs.

Reproduction

Although not much is known about the reproductive habits of ''Actinopyga varians,'' members of the class Holothuroidea are gonochoric and have only one

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 ...

. Spawning and fertilization are external; furthermore, species in the same genus, such as the ''

Actinopyga mauritiana ''Actinopyga mauritiana'', commonly known as the surf redfish, is a species of sea cucumber in the family Holothuriidae. It is native to the tropical West Indo-Pacific region and is harvested for food. Description ''Actinopyga mauritiana'' grows ...

,'' have shown that although there are many physical, chemical and biological cues that have been used to successfully stimulate spawning, thermal stimulation is the most successful method of repoduction.

Development

Echinoderm 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 ...

s are

deuterostomes Deuterostomia (; in Greek) are animals typically characterized by their anus forming before their mouth during embryonic development. The group's sister clade is Protostomia, animals whose digestive tract development is more varied. Some exampl ...

. The larvae begin with a bilateral symmetrical embryo, and pass through several stages before reaching adulthood. The larvae have a three-part paired

coelom The coelom (or celom) is the main body cavity in most animals and is positioned inside the body to surround and contain the digestive tract and other organs. In some animals, it is lined with mesothelium. In other animals, such as molluscs, it r ...

that eventually develop into different parts. The first stage of the larve is auricularia, which starts after three days. This first stage has a ciliated locomotor band which leads into the next stage where the ciliated band breaks up into "girdles" in a stage called

doliolaria Sea cucumbers are echinoderms from the class Holothuroidea (). They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found on the sea floor worldwide. The number of holothurian ...

. Eventually, after the larval metamorphosis, the sea cucumber settles down and becomes a fully grown species.

Predation

Sea cucumbers, as a species, are most vulnerable in the larval and juvenile stages; thus, they face predation most often during these stages. It is known that starfish, fish, gastropods and crustaceans are predators.

Uses

Although sea cucumbers have been known as a delicacy in many cultures, including those in the Pacific Islands, ''Actinopyga varians'' has not been known to be one of the edible species of sea cucumbers; however, ''Actinopyga mauritiana,'' a species in the ''Actinopyga'' The only known edible species in the ''Actinopyga'' genus is ''Actinopyga mauritiana''. In China a similar species in the same genus, ''Actinopyga echinites'', is held valuable for its pharmacological compound. It is unknown if the ''Actinopyga varians'' holds the same compounds that are thought of as valuable for such purposes.

References

External links

Family Holothuriidae HAWAII Actinopyga varians
Holothuriidae Fauna of the Pacific Ocean Animals described in 1867 {{Holothuroidea-stub