''Marrus orthocanna''

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 ...

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 ...

siphonophore Siphonophorae (from Greek ''siphōn'' 'tube' + ''pherein'' 'to bear') is an order within Hydrozoa, which is a class of marine organisms within the phylum Cnidaria. According to the World Register of Marine Species, the order contains 175 specie ...

, a colonial animal composed of a complex arrangement of

zooids A zooid or zoöid is a single 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 zooi ...

, some of which are

polyps A polyp in zoology is one of two forms found in the phylum Cnidaria, the other being the medusa. Polyps are roughly cylindrical in shape and elongated at the axis of the vase-shaped body. In solitary polyps, the aboral (opposite to oral) end is ...

and some

medusae Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella- ...

. Swimming independently in the mid-ocean, it lives in the

Arctic The Arctic ( or ) is a polar regions of Earth, polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Canada (Yukon, Northwest Territories, Nunavut), Danish Realm (Greenla ...

and other cold, deep waters.Siphonophores
Retrieved 2011-10-01. It is a colonial creature that is born from a single egg which is fertilized. Later on, a protozoan form that eventually grows to form more duplicating members of the colony. It belongs to the order ''

siphonophorae Siphonophorae (from Greek ''siphōn'' 'tube' + ''pherein'' 'to bear') is an order within Hydrozoa, which is a class of marine organisms within the phylum Cnidaria. According to the World Register of Marine Species, the order contains 175 specie ...

'' and the family ''

Marrus ''Marrus'' is a genus of siphonophores. Species include: *'' Marrus antarcticus'' Totton, 1954 *'' Marrus claudanielis'' Dunn, Pugh & Haddock, 2005 *''Marrus orthocanna'' Kramp, 1942 *'' Marrus orthocannoides'' Totton, 1954 References *Mapstone ...

''. Other species in the family include the ''Marrus antarcticus, Marrus claudanielis, and Marrus orthocannoides''.

Description

Like other siphonophores, ''Marrus orthocanna'' is a colony composed of a number of specialised

linked together by a long stem. They have different functions such as locomotion, capturing prey, waste removal, and reproduction. At the front is the

pneumatophore Aerial roots are roots above the ground. They are almost always adventitious. They are found in diverse plant species, including epiphytes such as orchids (''Orchidaceae''), tropical coastal swamp trees such as mangroves, banyan figs ('' Fi ...

, an orange-colored, gas-filled float, the largest of which can reach estimated sizes of 5-10 centimeters in diameter . Behind this is the nectosome, a region where there are a number of translucent nectophores with red, unlooped radial canals. These are bell-shaped medusae specialised for locomotion. When they contract, water is expelled which causes the colony to move. The coordinations of the medusae contractions enable the organism to swim forwards, sidewards, or backwards. The remaining region is the

siphosome {{Short pages monitor