''Morchellium argus'', the red-flake ascidian, is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of colonial sea squirt, a

tunicate Tunicates are marine invertebrates belonging to the subphylum Tunicata ( ). This grouping is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords (including vertebrates). The subphylum was at one time ...

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 ...

Polyclinidae. It is native to shallow water in the northeastern Atlantic Ocean, especially round the coasts of Britain.

Description

A colony of ''Morchellium argus'' consists of a clump of vase-shaped

zooid A zooid or zoöid is an animal that is part of a colonial animal. This lifestyle has been adopted by animals from separate unrelated taxa. Zooids are multicellular; their structure is similar to that of other solitary animals. The zooids can ...

s up to long, each supported by a conical stalk about wide, to which sand adheres. Each zooid has a buccal siphon with eight flaps and a tongue-like process underneath. This siphon opens into a large

pharynx The pharynx (: pharynges) is the part of the throat behind the human mouth, mouth and nasal cavity, and above the esophagus and trachea (the tubes going down to the stomach and the lungs respectively). It is found in vertebrates and invertebrates ...

through which water is drawn into the interior, but the colony has a single exit siphon through which the water from several zooids is expelled. The zooids are translucent white, pale pink, or red, and there are four small red spots at the entrance to the pharynx, which distinguishes this tunicate from similar species.

Distribution and habitat

''Morchellium argus'' is native to the northeastern Atlantic Ocean. It is common round the coasts of Britain, as far north as the

Shetland Isles Shetland (until 1975 spelled Zetland), also called the Shetland Islands, is an archipelago in Scotland lying between Orkney, the Faroe Islands, and Norway, marking the northernmost region of the United Kingdom. The islands lie about to the ...

. It is also known from the west of France including

Arcachon Bay Arcachon Basin or alternatively Arcachon Bay (, ; ) is a bay of the Atlantic Ocean on the southwest coast of France, situated in Pays de Buch between the Côte d'Argent and the Côte des Landes, in the region of Aquitaine. The bay covers an ar ...

. It is found at depths down to about mainly in caves, under overhangs and on vertical surfaces, often among foliose algae.

Biology

''Morchellium argus'' draws in water through its buccal siphon, filters out

zooplankton Zooplankton are the heterotrophic component of the planktonic community (the " zoo-" prefix comes from ), having to consume other organisms to thrive. Plankton are aquatic organisms that are unable to swim effectively against currents. Consequent ...

and other food particles and then expels the water. Gas exchange takes place at the same time. ''Morchellium argus'' is a

hermaphrodite A hermaphrodite () is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic. The individuals of many ...

. The

gonad A gonad, sex gland, or reproductive gland is a Heterocrine gland, mixed gland and sex organ that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gon ...

s are in the body cavity and sperm passes out with the exhalent water. When this sperm is drawn into another individual zooid, internal fertilisation can occur. The early developmental stages take place inside the zooid and the

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 are later liberated into the sea. After a short free-living stage, these attach themselves to a surface, 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 ...

, and start a new colony. Further development is by

budding Budding or blastogenesis is a type of asexual reproduction in which a new organism develops from an outgrowth or bud due to cell division at one particular site. For example, the small bulb-like projection coming out from the yeast cell is kno ...

of new zooids. The function of the red spots in the pharynx is unclear.

References

External links

* {{Taxonbar, from=Q4919381 Polyclinidae Animals described in 1841