Echinocardium cordatum
Encyclopedia
Echinocardium cordatum, or the sea potato, is a sea urchin
in the family
Loveniidae
. It is found in sub-tidal regions in temperate seas around the world and lives buried in the sandy sea floor.
s and mostly point backwards. The upper surface is flattened and there is an indentation near the front. It is a fawn colour but the tests
that are found on the strandline
have often lost their spines and are white. The spines trap air which helps prevent asphyxiation for the buried urchin. The ambulacrum forms a broad furrow in a star shape extending down the sides of test. There are two series each of two rows of tube feet
. The test reaches from six to nine centimetres in length.
. It is found in temperate seas in the north Atlantic Ocean, the west Pacific Ocean, around Australia, New Zealand, South Africa and the Gulf of California at depths of down to 230 metres. It is very common round the coasts of the British Isles in the neritic zone
.
collects. This organic debris is used by the buried animal as food and is passed down by means of the long tube feet found in the front of the ambulacrum.
The sexes are separate in the sea potato and the males and females both liberate gamete
s into the water table
in the spring. The echinoplutei larva
e that develop after fertilisation have four pairs of arms and are laterally flattened. In late stage larvae, tube feet may be seen developing round the skeleton. The larva
e are pelagic
and form part of the zooplankton
. Metamorphosis
take place about 39 days after fertilisation with the larvae settling out and burrowing into the substrate
. The lifespan of the sea potato is thought to be ten or more years.
molluscs
Tellina fabula
, Ensis ensis
and Venus striatula
.
The bivalve Tellimya ferruginosa
is often found living inside the sea potato's burrow as a commensal
. Up to fourteen have been found in one burrow with the young being attached to the spines of the urchin by byssus
threads. Another species that makes use of the burrow is the amphipod
crustacean, Urothoe marina
.
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...
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...
Loveniidae
Loveniidae
Loveniidae is a family of heart urchins in the order Spatangoida.-Genera:* Echinocardium Gray, 1825 * Lovenia Desor, 1847...
. It is found in sub-tidal regions in temperate seas around the world and lives buried in the sandy sea floor.
Description
The sea potato is a heart shaped urchin clothed in a dense mat of furrowed yellowish spines which grow from tubercleTubercle
A tubercle is generally a wart-like projection, but it has slightly different meaning depending on which family of plants or animals it is used to refer to....
s and mostly point backwards. The upper surface is flattened and there is an indentation near the front. It is a fawn colour but the tests
Test (biology)
A test is a term used to refer to the shell of sea urchins, and also the shell of certain microorganisms, such as testate foraminifera and testate amoebae....
that are found on the strandline
Strandline
The strandline, or high water mark, is the area at the top of a beach where debris is deposited. Where there are tides, this line is formed by the highest position of the tide, and moves up and down the beach on a fortnightly cycle...
have often lost their spines and are white. The spines trap air which helps prevent asphyxiation for the buried urchin. The ambulacrum forms a broad furrow in a star shape extending down the sides of test. There are two series each of two rows of 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...
. The test reaches from six to nine centimetres in length.
Distribution
The sea potato has a discontinuous cosmopolitan distributionCosmopolitan distribution
In biogeography, a taxon is said to have a cosmopolitan distribution if its range extends across all or most of the world in appropriate habitats. For instance, the killer whale has a cosmopolitan distribution, extending over most of the world's oceans. Other examples include humans, the lichen...
. It is found in temperate seas in the north Atlantic Ocean, the west Pacific Ocean, around Australia, New Zealand, South Africa and the Gulf of California at depths of down to 230 metres. It is very common round the coasts of the British Isles 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...
.
Biology
The sea potato buries itself in sand to a depth of ten to fifteen centimetres. It occurs in sediments with a wide range of grain sizes but prefers sediments with a size of 200 to 300 µm and a low mud content. It makes a respiratory channel leading to the surface and two sanitary channels behind itself, all lined by a mucus secretion. The location of burrows can be recognised by a conical depression on the surface in which detritusDetritus
Detritus is a biological term used to describe dead or waste organic material.Detritus may also refer to:* Detritus , a geological term used to describe the particles of rock produced by weathering...
collects. This organic debris is used by the buried animal as food and is passed down by means of the long tube feet found in the front of the ambulacrum.
The sexes are separate in the sea potato and the males and females both liberate gamete
Gamete
A gamete is a cell that fuses with another cell during fertilization in organisms that reproduce sexually...
s into the water table
Water table
The water table is the level at which the submarine pressure is far from atmospheric pressure. It may be conveniently visualized as the 'surface' of the subsurface materials that are saturated with groundwater in a given vicinity. However, saturated conditions may extend above the water table as...
in the spring. The echinoplutei 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 that develop after fertilisation have four pairs of arms and are laterally flattened. In late stage larvae, tube feet may be seen developing round the skeleton. 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 are pelagic
Pelagic zone
Any water in a sea or lake that is not close to the bottom or near to the shore can be said to be in the pelagic zone. The word pelagic comes from the Greek πέλαγος or pélagos, which means "open sea". The pelagic zone can be thought of in terms of an imaginary cylinder or water column that goes...
and form 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"...
. 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...
take place about 39 days after fertilisation with the larvae settling out and burrowing into the substrate
Substrate (biology)
In biology a substrate is the surface a plant or animal lives upon and grows on. A substrate can include biotic or abiotic materials and animals. For example, encrusting algae that lives on a rock can be substrate for another animal that lives on top of the algae. See also substrate .-External...
. The lifespan of the sea potato is thought to be ten or more years.
Ecology
In the sandy sea bed that it favours, the sea potato is often found in association with the bivalveBivalvia
Bivalvia is a taxonomic class of marine and freshwater molluscs. This class includes clams, oysters, mussels, scallops, and many other families of molluscs that have two hinged shells...
molluscs
Mollusca
The Mollusca , common name molluscs or mollusksSpelled mollusks in the USA, see reasons given in Rosenberg's ; for the spelling mollusc see the reasons given by , is a large phylum of invertebrate animals. There are around 85,000 recognized extant species of molluscs. Mollusca is the largest...
Tellina fabula
Tellina fabula
Tellina fabula is a species of marine bivalve mollusc in the family Tellinidae. It is found off the coasts of north west Europe where it lives buried in sandy sediments....
, Ensis ensis
Ensis ensis
Ensis ensis, or the sword razor, is a marine bivalve mollusc in the family Pharidae. It lives buried in the sand and is found off the coasts of north west Europe....
and Venus striatula
Chamelea gallina
Chamelea gallina is a species of small saltwater clam, a marine bivalve mollusc in the family Veneridae, the venus clams.-Taxonomy:Linnaeus originally described Venus gallina from the Mediterranean in 1758. Other zoologists may have consequently assumed that Da Costa's 1778 Pectunculus striatulus...
.
The bivalve Tellimya ferruginosa
Tellimya ferruginosa
Tellimya ferruginosa is a species of small marine bivalve mollusc in the family Montacutidae. It is found on the eastern side of the Atlantic Ocean....
is often found living inside the sea potato's burrow as a commensal
Commensalism
In ecology, commensalism is a class of relationship between two organisms where one organism benefits but the other is neutral...
. Up to fourteen have been found in one burrow with the young being attached to the spines of the urchin by byssus
Byssus
Byssus means both a silky filament by which certain molluscs attach themselves to hard surfaces, and a rare fabric, also called sea silk and its fibre source.-Word:...
threads. Another species that makes use of the burrow is the amphipod
Amphipoda
Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. The name amphipoda means "different-footed", and refers to the different forms of appendages, unlike isopods, where all the legs are alike. Of the 7,000 species, 5,500 are classified...
crustacean, Urothoe marina
Urothoe marina
Urothoe marina is a species of small marine amphipod crustaceans in the family Urothoidae. It is found on and burrowing in coarse sediments in shallow coastal waters off northwestern Europe.-Description:...
.