Chondrophore
Porpita porpita
The Porpitidae are a living exclusively in the sea family of hydroids ( Hydrozoa ) from the tribe of Cnidarians ( Cnidaria ). It is a very small family with currently only three species in two genera.
Features
The hydroid are colonial, but strongly differentiated. When mature, they are mobile and drive as a raft on the water surface. The soft body is supported by an inner Chitinstruktur. It contains the air chambers, which allow the floating of the colony on the water surface. The hydranths are polymorphic at the bottom of the raft. It is a large, central, tentacle -free feeding polyps, surrounded by Fress-/Geschlechtspolypen and military polyps. The tentacles are capitat or reduced to stinging cells stains.
The medusa has an evenly rounded umbrella and four or eight radial channels. An annular channel is also provided. On the Exumbrella sit an even number of rows of nematocysts ( Steno stelae ); these begin at the edge union buds. The manubrium is short and conical, the mouth roundish. The gonads are arranged perradial or irregular perradial and inter- radial. Two against permanent thin, randliche tentacles end in large, round nematocysts buttons. Two other adaxial tentacles can additionally be present. The two or six rand union buds are without tentacles. Ocelli absent. The Cnidom consists of roundish Steno steles makrobasischen Eurytelen and atrichen Haplonemen. Zooxanthellae are present.
Geographical occurrence
The three types of Porpitidae are particularly common in the warmer oceans around the world. The sail jellyfish penetrates even into the western Mediterranean.
System
The Porpitidae family includes only three genera with three species:
- Porpita porpita (Linnaeus, 1758) ( syn. P. pacifica Lesson, 1826 and P. linneana Lesson, 1843)
- Sail jellyfish ( Velella velella ) ( Linnaeus, 1758)