''Oikopleura cophocerca'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of small

pelagic The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or wa ...

tunicate A tunicate is a marine invertebrate animal, a member of the subphylum Tunicata (). It 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 ca ...

found in the surface waters of most of the world's oceans. It superficially resembles a tadpole and is surrounded by a transparent mucus net known as a "house".

Description

The trunk of ''Oikopleura cophocerca'' is oval and slightly arched and a few millimetres in length. A mouth at one end opens into a funnel-shaped

pharynx The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs). It is found in vertebrates and invertebrates, though its struc ...

and the anus is half way along the ventral surface. The

endostyle The endostyle is an anatomical feature found in invertebrate chordates and larval lampreys. It is an organ which assists chordates in filter-feeding. It is found in adult urochordates and cephalochordates, as well as in the larvae of the vertebra ...

is small and equidistant between the mouth and the anus. The branched ovary lies between the two testes. The tail is long, broad and muscular and contains remnants of the

notochord In anatomy, the notochord is a flexible rod which is similar in structure to the stiffer cartilage. If a species has a notochord at any stage of its life cycle (along with 4 other features), it is, by definition, a chordate. The notochord consis ...

as small, globular cells. The tail is attached just behind the anus and is bent forward to pass near the mouth. The tail has ventral and dorsal fins running along its length. However, because it is twisted through a right angle, it appears to have fins on its left and right sides and it undulates up and down rather than from side to side. The exoskeleton of this class of tunicates consists of a mucus net which is known as a "house" and surrounds the animal's body like a bubble.

Distribution

''Oikopleura cophocerca'' has a

cosmopolitan distribution In biogeography, cosmopolitan distribution is the term for the range of a taxon that extends across all or most of the world in appropriate habitats. Such a taxon, usually a species, is said to exhibit cosmopolitanism or cosmopolitism. The ext ...

and is found, mainly in the surface layers, in temperate and tropical parts of the Atlantic Ocean, the Caribbean Sea, the Gulf Of Mexico, the Mediterranean Sea, the Red Sea, the Indian Ocean and the Pacific Ocean. In the

Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an oceanic basin, ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of ...

it is found on the Tabasco–Campeche shelf where its maximum abundance is associated with the up-welling of water caused by the Yucatán Current.

Biology

''Oikopleura cophocerca'', like other appendicularians, secretes a

mucus Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It is ...

net known as a "house" (Greek ''Oikos'', house) inside which it lives. Periodically this gelatinous house is rolled up and abandoned, a new house being secreted within about a minute. This structure is inflated with sea water by undulations of the tail and further tail movements maintain a flow of water through it. The house has two inflow entrances and one outflow, between which are various passageways and two fine filters to catch food particles. The mucus net is a very efficient means of concentrating the minute planktonic particles on which this animal feeds and the appendicularian is in effect, swimming in a concentrated planktonic broth. At 20 °C, ''Oikopleura cophocerca'' builds and discards two houses each day. Appendicularians are

hermaphrodite In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many Taxonomy (biology), taxonomic groups of animals (mostly invertebrate ...

s and sexual reproduction is the only means of reproduction in this species. The testes ripen first and sperm is shed into the sea. When the

ovary The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the body. ...

ripens, the body wall of the animal ruptures to release the

eggs Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...

and the animal dies in the process. The development of the

zygote A zygote (, ) is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual organism. In multicellula ...

is rapid and direct and the

embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...

starts to feed and secrete a mucus net within twenty four hours.

References

{{Taxonbar, from=Q10608063 Appendicularia Animals described in 1855