Luidia ciliaris
Encyclopedia
Luidia ciliaris or the seven armed starfish is a species
of starfish in the family Luidiidae. It is found in the eastern Atlantic Ocean
and the Mediterranean Sea
.
with two valves. The tube feet
are long and numerous. They do not have suction pads but have two sets of terminal bulbs. The gonad
s are arranged in two rows along the length of the arms. There is a mouth at the centre of the underside, an oesophagus and a cardiac stomach but no intestine, pyloric stomach or anus.
in the eastern Atlantic Ocean
from Norway
and the Faroe Islands
southwards to Cape Verde
and the Azores
and in the Mediterranean Sea
. It is found in the neritic zone
at depths down to four hundred metres, mainly on soft sediments into which it sometimes burrows, but sometimes on rock.
and scavenger
and feeds predominantly on other echinoderm
s. A study in the Irish Sea found that the brittle star
s, Ophiothrix fragilis
and Ophiura albida, and the sea urchin
, Psammechinus miliaris
, formed the chief items of prey. The brittle star Ophiocomina nigra
was also consumed but in lesser quantities because it had more efficient escape strategies.
L. ciliaris moves rapidly in comparison with other starfish. It hoists itself up on the tips of its arms, in which position it can "walk", before launching itself at its prey
. The ring of plates around its mouth are extensible or can even be ruptured to enable it to ingest food items much bigger than the normal size of its mouth. In this way it can pounce on a brittle star twenty-five centimetres in diameter and completely engulf it. Undigested remains are ejected through the mouth.
L. ciliaris breeds in early summer. Each female releases millions of eggs
into the water column and this stimulates the release of sperm by the males. About four days after fertilisation, the zygote
s develop into bipinnaria
larva which form part of the plankton
. After several moults the seven arms can be seen developing in what is called the "rudiment" which is connected to a stalk which has several bands of cilia. The larva reaches a length of thirty-five millimetres in 3 to 4 months. It does not become a brachiolaria
larva as is the case in most starfish taxa
. Instead, it settles on the sea bed and metamorphosis
takes place. Functional tube feet appear in the juvenile before the larval tissue is fully reabsorbed.
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 starfish in the family Luidiidae. It is found in the eastern Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
and 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...
.
Description
L. ciliaris is an orangeish-brown colour and has seven long arms radiating from a small disk. It is a large but fragile starfish, growing to forty centimetres across, and easily losing its arms (which afterwards regenerate). The arms have parallel sides and taper only near the tip. They have a conspicuous fringe of white spines along the margins. The upper surface is clothed in paxillae, spines shaped like a pillar with a flat top bearing tiny spinules. There are also many-lobed, nipple-like papillae. There are no marginal plates on the upper side of the arms but those on the lower side bear pedicellariaePedicellariae
A pedicellaria is a small wrench or claw-shaped structure commonly found on Echinoderms, particularly in sea stars and sea urchins...
with two valves. The 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...
are long and numerous. They do not have suction pads but have two sets of terminal bulbs. The gonad
Gonad
The gonad is the organ that makes gametes. The gonads in males are the testes and the gonads in females are the ovaries. The product, gametes, are haploid germ cells. For example, spermatozoon and egg cells are gametes...
s are arranged in two rows along the length of the arms. There is a mouth at the centre of the underside, an oesophagus and a cardiac stomach but no intestine, pyloric stomach or anus.
Distribution and habitat
L. ciliaris occurs on the seabedSeabed
The seabed is the bottom of the ocean.- Ocean structure :Most of the oceans have a common structure, created by common physical phenomena, mainly from tectonic movement, and sediment from various sources...
in the eastern Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
from Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
and the Faroe Islands
Faroe Islands
The Faroe Islands are an island group situated between the Norwegian Sea and the North Atlantic Ocean, approximately halfway between Scotland and Iceland. The Faroe Islands are a self-governing territory within the Kingdom of Denmark, along with Denmark proper and Greenland...
southwards to Cape Verde
Cape Verde
The Republic of Cape Verde is an island country, spanning an archipelago of 10 islands located in the central Atlantic Ocean, 570 kilometres off the coast of Western Africa...
and 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 in the neritic zone
Neritic zone
The neritic zone, also called coastal waters, the coastal ocean or the sublittoral zone, is the part of the ocean extending from the low tide mark to the edge of the continental shelf, with a relatively shallow depth extending to about 200 meters...
at depths down to four hundred metres, mainly on soft sediments into which it sometimes burrows, but sometimes on rock.
Biology
L. ciliaris is a predatorPredation
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...
and scavenger
Detritivore
Detritivores, also known as detritophages or detritus feeders or detritus eaters or saprophages, are heterotrophs that obtain nutrients by consuming detritus . By doing so, they contribute to decomposition and the nutrient cycles...
and feeds predominantly on other echinoderm
Echinoderm
Echinoderms are a phylum of marine animals. Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone....
s. A study in the Irish Sea found that the brittle star
Brittle star
Brittle stars or ophiuroids are echinoderms in the class Ophiuroidea closely related to starfish. They crawl across the seafloor using their flexible arms for locomotion. The ophiuroids generally have five long slender, whip-like arms which may reach up to in length on the largest specimens...
s, Ophiothrix fragilis
Ophiothrix fragilis
Ophiothrix fragilis is a species of brittle star in the order Ophiurida. It is found around the coasts of northwestern Europe and is known in Britain as the common brittle star.-Description:...
and Ophiura albida, and 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...
, Psammechinus miliaris
Psammechinus miliaris
Psammechinus miliaris is a species of sea urchin in the family Parechinidae. It is sometimes known as the green sea urchin or shore sea urchin. It is found in shallow areas of the eastern Atlantic Ocean and the North Sea.-Description:...
, formed the chief items of prey. The brittle star Ophiocomina nigra
Ophiocomina nigra
Ophiocomina nigra, commonly known as the black brittle star or black serpent star, is a species of marine invertebrate in the order Ophiurida...
was also consumed but in lesser quantities because it had more efficient escape strategies.
L. ciliaris moves rapidly in comparison with other starfish. It hoists itself up on the tips of its arms, in which position it can "walk", before launching itself at its prey
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...
. The ring of plates around its mouth are extensible or can even be ruptured to enable it to ingest food items much bigger than the normal size of its mouth. In this way it can pounce on a brittle star twenty-five centimetres in diameter and completely engulf it. Undigested remains are ejected through the mouth.
L. ciliaris breeds in early summer. Each female releases millions of eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
into the water column and this stimulates the release of sperm by the males. About four days after fertilisation, the zygote
Zygote
A zygote , or zygocyte, is the initial cell formed when two gamete cells are joined by means of sexual reproduction. In multicellular organisms, it is the earliest developmental stage of the embryo...
s develop into bipinnaria
Bipinnaria
A bipinnaria is the first stage in the larval development of most starfish, and is usually followed by a brachiolaria stage. Movement and feeding is accomplished by the bands of cilia. Starfish that brood their young generally lack a bipinnaria stage, with the eggs developing directly into...
larva which form part of the plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
. After several moults the seven arms can be seen developing in what is called the "rudiment" which is connected to a stalk which has several bands of cilia. The larva reaches a length of thirty-five millimetres in 3 to 4 months. It does not become a brachiolaria
Brachiolaria
A brachiolaria is the second stage of larval development in many sea stars; it follows the bipinnaria. Brachiolaria have bilateral symmetry, unlike the adult sea stars, which have a pentaradial symmetry...
larva as is the case in most starfish taxa
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
. Instead, it settles on the sea bed and metamorphosis
Metamorphosis
Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation...
takes place. Functional tube feet appear in the juvenile before the larval tissue is fully reabsorbed.