| Chiridotidae | |
|---|---|
 | |
| Chiridota heheva | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Echinodermata |
| Class: | Holothuroidea |
| Order: | Apodida |
| Family: | Chiridotidae Östergren, 1898 |
| Genera | |
see Taxonomy | |
Chiridotidae is a family of sea cucumbers found in the order Apodida. Within the family, there are 16 recognized genera all with different ranges of body types and functions. [1] Sea cucumbers play a fundamental role in many marine ecosystems. [2]
Members in this family have 10, 12, or 18 pelto-digitate tentacles. They lack podia, radial canals, a respiratory tree, and papillae. [3] [4] [5] However, their body structure does include ossicles, tentacles, a calcareous ring, and a ciliary urn.
Chiridotidae typically undergo direct development and can usually be found in benthic ecosystems. Within their benthic systems they feed off of detritus meaning they must have a digestive tract.
The following genera are recognised in the family Chiridotidae: [6]
There is a subfamily of Chiridotidae, Chiridotinae, that is classified by the absence of an even number of tentacles. [7]
During the developmental stages of Chiridotidae, the gastrula develops directly into the doliolaria larvae, with no Auricularia stage, this means that they typically undergo direct development. [8] Direct development allows for the internal brooding of their young within the coelom or ovaries. [7] They gain their nutrition during developmental stages through a Lecithotrophic pathway, which is made easier by their benthic habitat during these stages. [8] Researchers have discovered that Chiridotidae reach their asymptotic range size at 10 cells. [8]
Sea cucumbers are a mostly nocturnal animals. [9] It has been found that they are dependent on light for the regulation of body processes. [9]
In the family Chiridotidae, there are roughly 110 identifiable species. [10] Chiridotidae can be found worldwide. Although they develop in benthic ecosystems they can be found anywhere in the ocean once they are fully matured. [8] Different species have adapted to the harsh conditions of deep-sea life, but because they primarily feed off detritus, they do not starve. Chiridotidae is specifically known for burrowing into the seafloor. [8]
Chiridotids have a very thin, mostly transparent body wall. There is an amino acid peptide called Stichopin that affects the stiffness in the body wall, connective tissues, and the contraction of muscles. [11] They often range in lengths from a few millimeters to up to 3 meters. [3] Because they lack podia, they also lack sensory cups. [3] [4] [5]
The only remnants of a skeleton within this family of sea cucumbers are the calcareous ring, microscopic sclerites within the body wall, sometimes the walls of internal organs, and the tentacles that surround the organism’s mouth. [12] However, the sclerites are absent in some genera of Chiridotidae (ex. Kolostoneura and Paradota). [12]
Sea cucumbers have a number of connective tissues that suspend their organs. Cells that contain the amino acid peptide, Stichopin, have been found within the connective tissues of the Chiridotidae. [11] These tissues perform in catch and autonomy manifestations. [13] The muscles that undergo catch manifestations exhibit reversible stiffening and softening properties. [13] [11] The muscles that undergo autonomy manifestations exhibit irreversible softening allowing for the loss of body parts. [13]
The digestive system is anchored to the body wall by mediodorsal mesentery muscles. [12] When sea cucumbers go though an autonomic loss of an organ, it regrows from the muscles that anchor them to the body wall. [14] This process starts with the thickening of the muscle along the mesentery edge. [14] Then the new organ arises from these thick places along the muscle. [14]
Mesenteries are made up of a coelomic epithelium layer that lies over a layer of muscles, this is known as the mesothelium. [14] The mesothelium is separated from the inner connective tissue layer by the basal lamina. [14]
Ossicles are generally wheel-shaped with six spokes. [7] Ossicles have rods, hooks, denticles, and miliary granules. [4] [7] Many have even developed elaborate wheel and anchor-shaped ossicles contained in the body wall. [4] The denticles are located on the inner rim and complex hub of the ossicles. [7] On the lower side of the ossicles the denticles branch to the lower side of the hub and it forms a star-shape in the center. [7] In the genus Chiridota, the ossicles attached to the body wall often occur in small clusters that are adjacent to the radii. [3] Some genera of Chiridotidae are thought to have lost their body wall ossicles independently. [5]
Hooks can only be found in three living genera of Chiridotidae: Taeniogyrus, Scoliorhapis, and Trochodota. [3] In these genera, the ossicles are curved to form a loop, or eye. [3]
Wheel ossicles located in Chiridotidae contain numerous tiny teeth. [3] For example, the Myriotrochid genus has teeth located in the inner margin and they can be either large and pronounced or completely absent. [3]
The calcareous ring is made up of many small plates bound together by connective tissues. [4] The radial plates contain a deep notch on the upper side of the ring. [7] In Chiridotidae the ring is composed of dense labyrinthic stereom, that is thickest in the center of the plate. [5] The stereom in this family is more porous than other families of sea cucumber. [5]
The ring provides structural integrity in these animals by providing support to the pharynx, tentacles, water vascular system, and the radial nerve ring. [5] Calcareous rings also serve as a point of insertion for the retractor muscle bands. [5]
The genus Gymnopipina has short anterior projections in the calcareous ring and a madreporite sitting at the end of the long stone canal that has allowed scientists to classify it in the family Chiridotidae. [4]
Ciliary urns are a coelomic organ that gathers and excretes waste. [15] It is thought that it aids in immunity. [15] The Ciliary urn can also be called ciliated funnels or vibratile urnae. [15]
The echinoderm immune system has components of cellular and humoral defenses. [15] Cellular defense comprises various types of coelomocytes with humoral defenses mediated by numerous immune-specific molecules. [15] Invertebrate immunity is an innate defense. [15]
Ciliary urns have a cornucopia-shaped body and an invaginated ciliary field that collects and accumulates coelomocytes. [15] They also take up waste materials from the coelom and dispose of them by deposition or release through the body wall. [15]
Ciliary urns vary in shape, size, and arrangement among species. [15] Because ciliary urns run up the entire length of adult sea cucumbers, it is known that the urns are not associated with digestion, but rather they serve an excretory role in the immune system. [15]
The development and formation of the urn is still unknown; however, its function is clear. [15]
All families within Apodida do not have tube feet, including the Chiridotidae. [5] [4] More recent studies have proven that anchors are important for movement. [4] Other body parts used for movement include; the body wall, tentacles, papillae, and dermal ossicles. [5] Apodids in general usually use peristaltic movements to navigate around the seafloor. [4] Because of the lack of podia, tube feet, it is assumed that species use their anchors to hold onto the substratum. [4]
In the family Chiridotidae, the tentacles around the mouth are forked. [16] For species within the family, there are always an even number of tentacles, except for in the subfamily Chiridotinae [7] . Tentacles are present in order to help the sea cucumbers guide food into their mouths. [17] [2]
The movement of tentacles changes with the movement of the water. [2] There are two different responses to flow rheotaxis response, direct, and rheokinesis response, non-direct. [2]
Sea cucumbers within the family Chiridotidae, feed on benthic sediments causing a change within the stability and stratification of the sediment. [2] The benthic sediments that they consume as food contain fungal, bacterial, and detrital organic matter. [18] The availability of food is the main driver for the Chiridotidae to move around the seafloor. [2]
There are two different feeding strategies that have been observed; those that conduct a continuous search for food and those that shelter during periods when they reduce feeding activity. [18]
Amongst all sea cucumbers, tentacles are linked to the mode of feeding conducted by the organism. [17] The structure and type of feeding is different within even a species of sea cucumber. [17]
When collecting food the sea cucumbers extend their tentacles out to grab the particles. [17] [2]
The Chiridotidae are a nocturnal family and because of this they contain light avoidance behaviors. [9] This is behavior is thought to be a response to predation. [18] Tentacles respond to changes in light at a molecular level, the response shown as a full body contraction when exposed. [9]
The rheotaxis response of their tentacles to water flow allows for muscles to turn when activated. [2] During the rheokinesis response is a random movement in the water. [2]
The burrowing behavior of sea cucumbers within the family Chiridotidae is effected by the salinity and temperature of the water around them. [19]
It has been observed by many researchers that abundance of sea cucumbers is affected by the moon phases. [18] [19] Specifically, Chiridotidae are spotted in larger groups closer to a new moon than when it is not a new moon, it is thought that this is due to the lack of light. [18] [19]
An echinoderm is any member of the phylum Echinodermata. The adults are recognisable by their radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the sea lilies or "stone lilies". Adult echinoderms are found on the sea bed at every ocean depth, from the intertidal zone to the abyssal zone. The phylum contains about 7,000 living species, making it the second-largest grouping of deuterostomes, after the chordates. Echinoderms are the largest entirely marine 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.
Apodida is an order of littoral to deep-sea, largely infaunal holothurians, sea cucumbers. This order comprises three families, 32 genera and about 270 known species, called apodids, "without feet".
Dendrochirotida are an order of sea cucumbers. Members of this order have branched tentacles and are suspension feeders. Examples include Thyonella and Cucumaria.
Evisceration is a method of autotomy involving the ejection of internal organs used by animals as a defensive strategy. Sea cucumbers (Holothuroidea) eject parts of the gut in order to scare and defend against potential predators such as crabs and fish. The organs are regenerated in a few days by cells in the interior of the sea cucumber.
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.
The orange-footed sea cucumber is the largest sea cucumber in New England, United States. It is one of the most abundant and widespread species of holothurians within the North Atlantic Ocean and the Barents Sea (Russia), being most abundant along the eastern coast of North America.
Enypniastes is a genus of deep-sea sea cucumber. It is monotypic, being represented by the single species Enypniastes eximia. Due to its unique appearance, the species has been dubbed the headless chicken fish, headless chicken monster, and the Spanish dancer. It is also known as the swimming sea cucumber, and some are called the pink see-through fantasia.
Molpadida is an order of sea cucumbers. The body shape is fusiform and unlike other sea cucumbers, their hind body is narrowed to form a distinct tail. Although they possess tentacles around the mouth derived from the water vascular system, they have no true tube feet, and are therefore believed to be related to the Apodida.
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.
Sclerodactyla briareus, commonly known as the hairy sea cucumber, is a species of marine invertebrate in the family Sclerodactylidae. It is found in shallow waters in the western Atlantic Ocean.
Euapta lappa, the beaded sea cucumber, is a species of sea cucumbers in the family Synaptidae in the phylum Echinodermata. It is found on coral reefs in the Caribbean region.
Ossicles are small calcareous elements embedded in the dermis of the body wall of echinoderms. They form part of the endoskeleton and provide rigidity and protection. They are found in different forms and arrangements in sea urchins, starfish, brittle stars, sea cucumbers, and crinoids. The ossicles and spines are the only parts of the animal likely to be fossilized after an echinoderm dies.
Leptosynapta dolabrifera, the snot sea cucumber, is a small sea cucumber under the class Holothuroidea (1), in the family Synaptidae. It is most closely related to another species in its genus of 34 species Leptosynapta known as Leptosynapta inhaerens.
Psolus chitonoides, also known as the slipper sea cucumber, armoured sea cucumber, creeping armoured sea cucumber, or creeping pedal sea cucumber, is a species of sea cucumber in the family Psolidae. It is found in shallow water on the western coast of North America. The scientific name "chitonoides" means resembling a chiton.
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.
Catch connective tissue is a kind of connective tissue found in echinoderms which can change its mechanical properties in a few seconds or minutes through nervous control rather than by muscular means.
Psychropotidae is a family of deep-sea swimming sea cucumbers. The geographic range of some psychropotids is very extensive at abyssal depths, whereas other species are found within more restricted ranges.
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 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.
