| Holothuria difficilis | |
|---|---|
 | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Echinodermata |
| Class: | Holothuroidea |
| Order: | Holothuriida |
| Family: | Holothuriidae |
| Genus: | Holothuria |
| Species: | H. difficilis |
| Binomial name | |
| Holothuria difficilis Semper, 1868 | |
Holothuria (Platyperona) difficilis is a species of sea cucumber in the family Holothuriidae. [1] Holothuria comes from Latin but is originally taken from Greek. Its meaning is a plantlike animal whose origin is uncertain. [2]
H. difficilis is a member of the phylum Echinodermata meaning they share a general body plan with other members of the phylum. These traits include pentamerous radial symmetry, an endoskeleton, an oral side opposite of an aboral side, a water vascular system, and tube feet. [3] The oral side contains the mouth for feeding and the aboral side contains an anus used to rid of waste and for respiration. Tube feet is used for locomotion. H. difficilis also contains several mechanisms for defense. Structurally, their dermis is noxious and they also contain very thin Cuvierian tubules that can be ejected. [4] It has been hypothesized these defense mechanisms, that animals such as Holothurians have, are due to evolution against predation. [5] This species contains one gonad and can perform sexual reproduction. [6]
The species has been found in many seas and oceans across the globe such as the Red Sea, and near Central America. [1] However, its general distribution is in the Indian and Pacific Oceans. [1] [7] Typically, this species is benthic and lives inshore. [1] When observed in La Reunion Island fringing reefs, the species resided in outer reef flats and under large boulders. [8]
The genus, Holothurians, can be categorized as particulate feeders wherein there are two subgroups: suspension feeders and deposit feeders. When observed in Western Australia, it was found that H. difficilis that resided there were deposit feeders, where the species grazed on rocks and ate sediment. The mechanism by which H. difficilis feeds is unknown but other Holothurian deposit feeders have different shaped tentacles that catch food. [5]
Although the life cycle of H. difficilis is not specifically known, sea cucumbers can start off as fertilized eggs that either develop inside an adult sea cucumber or float freely through the water. During spawning, Holothurians tend to wave the front of their body. The hypothesized reason is to ensure that gametes do not get stuck in the sediment. [3] As an adult, this species mainly reproduces asexually but can also reproduce sexually. The means of reproducing asexually is done by fission of the body otherwise known as fragmentation. Depending on the fission site, the organism's internal organs may be affected. However, this species is able to regenerate and can rebuild their body. [6] H. difficilis, along with other species in the Holothuria genus living in the southern hemisphere have specific reproductive schedules. Asexual reproduction was at its highest in the winter season which correlated with lower water temperatures whereas sexual reproduction was at its highest in the late spring to summer seasons which correlated with warmer water temperatures. [6]
The main predator of H. difficilis are sea stars. However, they are also preyed upon by fish. Sea stars are able to wholly ingest sea cucumbers whereas fish typically can only eat certain because of H. difficilis' dermal toxicity. [9]
An echinoderm is any deuterostomal animal of the phylum Echinodermata, which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". While bilaterally symmetrical as larvae, as adults echinoderms are recognisable by their usually five-pointed radial symmetry, and are found on the sea bed at every ocean depth from the intertidal zone to the abyssal zone. The phylum contains about 7,600 living species, making it the second-largest group of deuterostomes after the chordates, as well as the largest marine-only phylum. The first definitive echinoderms appeared near the start of the Cambrian.
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. They are found on the sea floor worldwide. The number of known holothurian species worldwide is about 1,786, with the greatest number being in the Asia-Pacific region. Many of these are gathered for human consumption and some species are cultivated in aquaculture systems. The harvested product is variously referred to as trepang, namako, bêche-de-mer, or balate. Sea cucumbers serve a useful role in the marine ecosystem as they help recycle nutrients, breaking down detritus and other organic matter, after which bacteria can continue the decomposition process.
Sea apple is the common name for the colorful and somewhat round sea cucumbers of the genus Pseudocolochirus, found in Indo-Pacific waters. Sea apples are filter feeders with tentacles, ovate bodies, and tube-like feet. As with many other holothurians, they can release their internal organs or a toxin into the water when stressed.
Scotoplanes is a genus of deep-sea sea cucumbers of the family Elpidiidae. Its species are commonly known as sea pigs.
Isostichopus fuscus, commonly known as the brown sea cucumber, is a species of sea cucumber in the family Stichopodidae native to the eastern Pacific. It was first described to science by German biologist Hubert Ludwig in 1875.
Holothuria atra, commonly known as the black sea cucumber or lollyfish, is a species of marine invertebrate in the family Holothuriidae. It was placed in the subgenus Halodeima by Pearson in 1914, making its full scientific name Holothuria (Halodeima) atra. It is the type species of the subgenus.
Holothuria mexicana, the donkey dung sea cucumber, is commonly found in the Caribbean and the Azores. It is a commercially important aspidochirote sea cucumber that can reach a total length of 50 cm (20 in).
Colochirus robustus, commonly known as the robust sea cucumber or the yellow sea cucumber, is a species of sea cucumber in the family Cucumariidae. It is found in shallow seas in tropical parts of the central Indo-Pacific region. C. robustus belongs to the class Holothuroidea, a group of echinoderms called sea cucumbers and known for unusual behavior including evisceration, asexual reproduction, and regeneration. The robust sea cucumber has a soft body and lacks a spine, but it does have an endoskeleton consisting of microscopic spicules, or ossicles, made of calcium carbonate. C. robustus has a respiratory tree that allows it to extract oxygen for respiration, using the anus to pump water. The robust sea cucumber is an important dietary staple for many East and Southeast Asian populations, and has been used for medicinal purposes for hundreds of years. Recent research suggests that peptides from C. robustus enhance the activity of the immune system.
Lissocarcinus orbicularis, common names sea cucumber crab, red-spotted white crab, and harlequin crab is a species of crab in the family Portunidae. This species gains one of its names from its close-knit relationship with holothuroids, the sea cucumbers. L. orbicularis should not be confused with L. laevis, a similar species of swimming crab, or Camposcia retusa, both of which are also commonly referred to as the harlequin crab. L. orbicularis displays numerous morphological and social adaptations for feeding and has a large distribution throughout the Indo-West Pacific.
Holothuria parvula, the golden sea cucumber, is a species of echinoderm in the class Holothuroidea. It was first described by Emil Selenka in 1867 and has since been placed in the subgenus Platyperona, making its full scientific name Holothuria (Platyperona) parvula. It is found in shallow areas of the Caribbean Sea and Gulf of Mexico and is unusual among sea cucumbers in that it can reproduce by breaking in half.
Holothuria edulis, commonly known as the edible sea cucumber or the pink and black sea cucumber, is a species of echinoderm in the family Holothuriidae. It was placed in the subgenus Halodeima by Pearson in 1914, making its full scientific name Holothuria (Halodeima) edulis. It is found in shallow water in the tropical Indo-Pacific Ocean.
Ophiactis savignyi is a species of brittle star in the family Ophiactidae, commonly known as Savigny's brittle star or the little brittle star. It occurs in the tropical and subtropical parts of all the world's oceans and is thought to be the brittle star with the most widespread distribution. It was first described by the German zoologists Johannes Peter Müller and Franz Hermann Troschel in 1842. The specific name honours the French zoologist Marie Jules César Savigny.
Coscinasterias muricata is a species of starfish in the family Asteriidae. It is a large 11-armed starfish and occurs in shallow waters in the temperate western Indo-Pacific region.
Holothuria grisea, the gray sea cucumber, is a mid-sized coastal species of sea cucumber found in shallow tropical waters of the Atlantic Ocean from Florida to Southern Brazil and West Africa. They have a variety in color and can range from red to more yellowish with brown markings. They are also a food source for local and international markets with the majority of harvesting taking place in Brazil. This species is currently not over-fished and is not endangered or threatened.
Holothuria hilla is a species of sea cucumber in the subgenus Mertensiothuria of the genus Holothuria. Some common names include the contractile sea cucumber, the sand sifting sea cucumber and the tigertail sea cucumber, and in Hawaii it is known as the light spotted sea cucumber. It is found in the Indo-Pacific region and the Red Sea.
Actinopyga varians, the Pacific white-spotted sea cucumber or Hawaiian sea cucumber, is a species of sea cucumber in the family Holothuriidae. It is found in the Pacific Ocean near Hawaii and also in the Indo-Pacific Ocean.
Holothuria pervicax is a species of sea cucumber in the genus Holothuria. It is commonly called the stubborn sea cucumber due to its inability to be kept alive in captivity. It is commonly found buried beneath rocks on reefs in warm waters.
Holothuria stellati, also known as the Brown sea cucumber,is a species of sea cucumber in the family Holothuriidae. First described by Delle Chiaje in 1824. There are two accepted subspecies, Holothuria stellatidakarensis and Holothuria stellati mammata, though there is still debate on whether or not they are separate species.
Holothuria (Thymiosycia) impatiens, commonly known as the impatient sea cucumber or bottleneck sea cucumber, is a species of sea cucumber in the genus Holothuria, subgenus Thymiosycia.
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