Physonectae is a suborder of
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 ...
s. In
Japanese
Japanese may refer to:
* Something from or related to Japan, an island country in East Asia
* Japanese language, spoken mainly in Japan
* Japanese people, the ethnic group that identifies with Japan through ancestry or culture
** Japanese diaspor ...
it is called ().
Organisms in the suborder Physonectae follow the classic
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 ...
body plan. They are almost all pelagic, and are composed of a colony of specialized
zooid
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 zoo ...
s that originate from the same fertilized egg. While Physonectae are not generally well-known by the public, a related species also of the order Siphonophorae is the
Portuguese man o' war
The Portuguese man o' war (''Physalia physalis''), also known as the man-of-war, is a marine hydrozoan found in the Atlantic Ocean and the Indian Ocean. It is considered to be the same species as the Pacific man o' war or blue bottle, which is ...
, well-known for its painful sting.
Distribution
The majority of physonect siphonophores are pelagic, with the exception of
Rhodallidae, which are a family of benthic physonects first collected during the
''Challenger'' expedition and described by
Ernst Haekel in his ''Challenger'' monograph.
Physonects, and siphonophores in general, are known to be widely distributed globally, but are understudied. Few individuals have been collected and are often misidentified. As a result, their exact global distributions are unclear.
Morphology
All physonect siphonophores have an
aboral
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...
, apical pneumatophore filled with gas, which is formed by invagination of the superficial cell layers of the apical side of the larva.
In some species in the suborder Physonectae, the pneumatophore has a pore located either on the apical or basal pole of the organism and plays a role in controlling gas volume and pressure for buoyancy control.
Gas in the pneumatophore is high in carbon monoxide and is secreted by the pneumadenia, or gas gland.
Below the pneumatophore, an organism has a long stem with two distinct regions. The