''Cenocrinus'' is a

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unisp ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of stalked

crinoid Crinoids are marine invertebrates that make up the class Crinoidea. Crinoids that remain attached to the sea floor by a stalk in their adult form are commonly called sea lilies, while the unstalked forms, called feather stars or comatulids, are ...

s in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Isselicrinidae. The great West Indian sea lily (''Cenocrinus asterius'') is the only species in the genus and is found in deep waters in the

Caribbean Sea The Caribbean Sea is a sea of the Atlantic Ocean, North Atlantic Ocean in the tropics of the Western Hemisphere, located south of the Gulf of Mexico and southwest of the Sargasso Sea. It is bounded by the Greater Antilles to the north from Cuba ...

and

Gulf of Mexico The Gulf of Mexico () is an oceanic basin and a marginal sea of the Atlantic Ocean, mostly surrounded by the North American continent. It is bounded on the northeast, north, and northwest by the Gulf Coast of the United States; on the southw ...

Description

Like other sea lilies, ''Cenocrinus asterius'' has a crown consisting of a calyx surrounded by feathery arms splayed out to create a filtration fan. The crown is supported by a long slender stem which is attached to the

substrate Substrate may refer to: Physical layers *Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached ** Substrate (aquatic environment), the earthy material that exi ...

at its base. The stem is semi-rigid but flexible and is made up of disc-shaped ossicles known as columnals, joined together by ligaments. At each node between the columnals there is a whorl of five cirri. These are also articulated and are tipped with claws and when the cirri come into contact with other objects, they cling to them and help stabilise the sea lily and keep it upright.

Distribution

''Cenocrinus asterius'' is found in the Caribbean Sea, the Gulf of Mexico and off the coast of Mexico.

Biology

''Cenocrinus asterius'' lives on areas of the seabed with strong currents at depths of more than . This enables it to maximise the capture of food particles by the sticky

tube feet Tube or tubes may refer to: * Tube (2003 film), ''Tube'' (2003 film), a 2003 Korean film * "Tubes" (Peter Dale), performer on the Soccer AM#Tubes, Soccer AM television show * Tube (band), a Japanese rock band * Tube & Berger, the alias of dance/e ...

on its arms without them being fouled by the collection of its own faecal matter. ''Cenocrinus asterius'' has been studied in a laboratory flow tank where it was found that, with the base of the stem detached, it could move itself along the substrate and climb objects. It took as long as twenty four hours to manoeuvre itself into its usual, near vertical posture and reattach itself. In its natural surroundings, it may be assisted in this process by the hydrodynamic lift provided by a strong current in elevating its fan of arms. In studies by cameras mounted on

submersibles A submersible is an underwater vehicle which needs to be transported and supported by a larger ship, watercraft or dock, platform. This distinguishes submersibles from submarines, which are self-supporting and capable of prolonged independent ope ...

, it has been found that sea lilies can drag themselves along the seabed by their arms. In the case of ''Cenocrinus asterius'', this may be in response to attack by the

sea urchin Sea urchins or urchins () are echinoderms in the class (biology), class Echinoidea. About 950 species live on the seabed, inhabiting all oceans and depth zones from the intertidal zone to deep seas of . They typically have a globular body cove ...

Calocidaris micans ''Calocidaris micans'' is a species of sea urchins of the family Cidaridae. Their armour is covered with spines. ''Calocidaris micans'' was first scientifically described in 1903 by Ole Mortensen.Kroh, A. (2010). ''Calocidaris micans'' (Mortense ...

'' which has been shown to feed on live crinoids. Although the rate of movement was slow, it was sufficiently fast to outpace the echinoid.

Autotomy Autotomy (from the Greek ''auto-'', "self-" and ''tome'', "severing", αὐτοτομία) or 'self-amputation', is the behaviour whereby an animal sheds or discards an appendage, usually as a self-defense mechanism to elude a predator's grasp ...

of the stalk may also take place in an effort to evade the

predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

. The sexes are separate in ''Cenocrinus asterius''. Like other sea lilies, it produces

gamete A gamete ( ) is a Ploidy#Haploid and monoploid, haploid cell that fuses with another haploid cell during fertilization in organisms that Sexual reproduction, reproduce sexually. Gametes are an organism's reproductive cells, also referred to as s ...

s in specialised areas of the pinnules and releases them into the sea. After fertilisation, the

eggs An egg is an organic vessel in which an embryo begins to develop. Egg, EGG or eggs may also refer to: Biology * Egg cell, the female reproductive cell (gamete) in oogamous organisms Food * Eggs as food Places * Egg, Austria * Egg, Switzerland ...

hatch into barrel-shaped doliolaria

larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

e. These have several bands of cilia which enable them to swim. The larvae are

plankton Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...

ic and after a few days settle on the seabed and undergo

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth transformation or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and different ...

into juvenile sea lilies.

References

{{Taxonbar, from=Q18606503 Isselicrinidae Crinoid genera Monotypic echinoderm genera Taxa described in 1864