Holothuria forskali
Encyclopedia
Holothuria forskali, the black sea cucumber or cotton-spinner, is a species
of sea cucumber
in the family
Holothuriidae
. It is found at shallow depths in the eastern Atlantic Ocean and the Mediterranean Sea. It was placed in the subgenus Panningothuria by Rowe in 1969 and is the typetaxon
of the subgenus.
Sea cucumbers are marine invertebrates and are closely related to the sea urchin
s and starfish. All these groups tend to be radially symmetric and have a water vascular system that operates by hydrostatic pressure
, enabling them to move around by use of many suckers known as tube feet
. Sea cucumbers are usually leathery, gherkin-shaped animals with a cluster of short tentacles at one end.
for walking and climbing while the upper side has two rows of rudimentary suckers. The anterior end has a bunch of twenty yellowish short, retractable tentacle
s encircling the mouth. At the posterior end, near the anus, there are Cuvierian tubules or cotton glands which can eject a tangle of sticky white threads to confuse or enmesh predators
.
, the Azores
and in the Mediterranean Sea
. It is found on boulders and rocks, particularly vertical surfaces, from the intertidal zone down to a depth of about fifty metres.
Adult black sea cucumbers are normally either male or female. The gonads take a long time to mature and gametes are released synchronously into the water column in early spring, probably as a result of a rise in water temperatures. The larva
e become part of the zooplankton
. After several moults they grow tentacles and settle out onto the sea floor. Juveniles are seldom seen so it is surmised that they live by day in crevices and under rocks for protection from predators whereas the adults take no particular care to remain hidden.
Asterocheres boecki is an endoparasite
of the black sea cucumber.
It has been found that twenty-six saponin
s (triterpene glycosides) are present in the Cuvierian tubules and twelve in the animal's body wall. During stressful times, such as the presence of a predator, saponins are released into the surrounding water. It is thought that, though these are insufficient to harm a potential predator, they may serve as a warning that the cucumber is unpalatable.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of sea cucumber
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. There are a number of holothurian species and genera, many of which are targeted...
in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Holothuriidae
Holothuriidae
Holothuriidae is a family of sea cucumbers, a type of echinoderm.-Description:Members of the Holothuriidae family have thick fleshy bodies and several rows of tube feet which are used for moving around and for adhering to the surface. The body is often covered with blunt projections known as papillae...
. It is found at shallow depths in the eastern Atlantic Ocean and the Mediterranean Sea. It was placed in the subgenus Panningothuria by Rowe in 1969 and is the typetaxon
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
of the subgenus.
Sea cucumbers are marine invertebrates and are closely related to the sea urchin
Sea urchin
Sea urchins or urchins are small, spiny, globular animals which, with their close kin, such as sand dollars, constitute the class Echinoidea of the echinoderm phylum. They inhabit all oceans. Their shell, or "test", is round and spiny, typically from across. Common colors include black and dull...
s and starfish. All these groups tend to be radially symmetric and have a water vascular system that operates by hydrostatic pressure
Fluid statics
Fluid statics is the science of fluids at rest, and is a sub-field within fluid mechanics. The term usually refers to the mathematical treatment of the subject. It embraces the study of the conditions under which fluids are at rest in stable equilibrium...
, enabling them to move around by use of many suckers known as tube feet
Tube feet
Tube feet are the many small tubular projections found most famously on the oral face of a sea star's arms, but are characteristic of the water vascular system of the echinoderm phylum which also includes sea urchins, sand dollars and sea cucumbers and many other sea creatures.Tube feet function in...
. Sea cucumbers are usually leathery, gherkin-shaped animals with a cluster of short tentacles at one end.
Description
This sea cucumber has a cylindrical body and can grow to thirty centimetres long. It is usually deep brown or black but sometimes has an underlying yellowish mottling, especially on the underside. The skin is soft yet coarse and tough and is covered with fleshy papillae which are often tipped with white. The papillae are believed to be sensory organs sensitive to touch and possibly to chemicals dissolved in the water. The underside has three rows of tube feetTube feet
Tube feet are the many small tubular projections found most famously on the oral face of a sea star's arms, but are characteristic of the water vascular system of the echinoderm phylum which also includes sea urchins, sand dollars and sea cucumbers and many other sea creatures.Tube feet function in...
for walking and climbing while the upper side has two rows of rudimentary suckers. The anterior end has a bunch of twenty yellowish short, retractable tentacle
Tentacle
A tentacle or bothrium is one of usually two or more elongated flexible organs present in animals, especially invertebrates. The term may also refer to the hairs of the leaves of some insectivorous plants. Usually, tentacles are used for feeding, feeling and grasping. Anatomically, they work like...
s encircling the mouth. At the posterior end, near the anus, there are Cuvierian tubules or cotton glands which can eject a tangle of sticky white threads to confuse or enmesh predators
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
.
Distribution
The black sea cucumber occurs around the Atlantic coasts of northwest Europe, the Canary IslandsCanary Islands
The Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union...
, the Azores
Azores
The Archipelago of the Azores is composed of nine volcanic islands situated in the middle of the North Atlantic Ocean, and is located about west from Lisbon and about east from the east coast of North America. The islands, and their economic exclusion zone, form the Autonomous Region of the...
and in the Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
. It is found on boulders and rocks, particularly vertical surfaces, from the intertidal zone down to a depth of about fifty metres.
Biology
The black sea cucumber is a detrivore and feeds mostly at night. When feeding, it bends its body down towards the substrate, presses the ring of oral papillae against the surface and opens its mouth wide. It then extends and retracts its short tentacles repeatedly and "vacuums" up sediment, extracts the nutritious part and deposits the unmetabolised portion as a sausage-like string of droppings. When not feeding, the mouth is closed and the tentacles retracted and it is difficult to tell which is the head end of the animal.Adult black sea cucumbers are normally either male or female. The gonads take a long time to mature and gametes are released synchronously into the water column in early spring, probably as a result of a rise in water temperatures. The larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e become part of the zooplankton
Zooplankton
Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...
. After several moults they grow tentacles and settle out onto the sea floor. Juveniles are seldom seen so it is surmised that they live by day in crevices and under rocks for protection from predators whereas the adults take no particular care to remain hidden.
Ecology
The parasitic copepodCopepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
Asterocheres boecki is an endoparasite
Parasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
of the black sea cucumber.
It has been found that twenty-six saponin
Saponin
Saponins are a class of chemical compounds, one of many secondary metabolites found in natural sources, with saponins found in particular abundance in various plant species...
s (triterpene glycosides) are present in the Cuvierian tubules and twelve in the animal's body wall. During stressful times, such as the presence of a predator, saponins are released into the surrounding water. It is thought that, though these are insufficient to harm a potential predator, they may serve as a warning that the cucumber is unpalatable.