Oweniidae
| Oweniidae | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Oweniidae | ||||||||||||
| Rioja , 1917 |
Oweniidae is the name of a family of sessile, tube -building polychaeta (polychaeta) that live as filter feeders and that can be found in seas around the world.
features
The Oweniidae can be recognized by their characteristic living tubes, which they cement together from grains of sand and their own cement substance. A tentacle crown for breathing and for the vortex of food particles may be present or absent. They are usually small and, depending on the species, are a few millimeters to 3 cm long , only in the case of Owenia fusiformis up to 10 cm long and have comparatively few, elongated segments with weakly developed parapodia on which capillary-like bristles and hooks sit. The prostomium is fused with the peristomium . The head is either rounded in front or puffed up and bilobed , in the genus Owenia, however, flat and lobed. The peristomium forms a complete ring behind the prostomium. The animals do not have any antennae, but in most species there is a pair of palps on the prostomium , which in the genus Owenia have a lobed shape, are usually dorsally oriented and each have an eyelash groove. In contrast to the vast majority of bristles, the Oweniidae have no nuchal organs. On the other hand, eye spots are present in some species, but these may or may not appear in different populations of the same species.
On the first and second segment there are only notopodia , while from the 3rd segment onwards all parapodia have both notopodia and neuropodia . The notopodia are shaped like short, truncated cylinders, while the neuropodia are broad with a flattened torus . There are neither dorsal nor ventral cirrus organs, and gills, epidermal papillae, aciculae and a throat membrane are also absent. Cirrus on the Pygidium are only present in some species.
The evertable buccal organ lies ventrally, and the intestine is a straight tube. The Oweniidae have a well-developed, closed blood vessel system that lacks a central heart. In the genus Owenia , dissolved erythrocruorin serves as the blood pigment in the plasma, giving the tentacles , which are well supplied with blood and also used for breathing, their reddish-brown to greenish color. Paired Mixonephridien open individually into one or a few segments to the outside front.
Distribution, way of life and example species
The Oweniidae are widespread in seas around the world and live mainly on sandy or muddy surfaces. The Oweniidae build cylindrical living tubes from the body's own mucus and grains of sand. They feed the filter feeders of detritus . Even small grains of sand that stick to the mucus of the palps or tentacles are transported to the mouth via the eyelash grooves and swallowed, the attached organic components are digested and the mineral particles are excreted. Larger grains of sand are either repelled or - if necessary - used to build or repair the residential tube.
Development cycle
The Oweniidae are separate sexes and mate several times in life, in the genus Owenia with a lifespan of up to 3 years about once a year. In sexually mature animals, the coelom spaces of the posterior segments are filled with gametes , which are released through two pores in the anus, so that fertilization takes place in the open sea water. A female of Owenia fusiformis can lay 6,000 to 85,000 eggs at once, depending on size. Within 24 hours of fertilization, a mitraria larva develops, which develops into an actively swimming trochophora larva in 2 to 3 days . The pelagic stage as zooplankton lasts about 4 months until the mature larva finds a suitable substrate, sinks to the bottom and metamorphoses into a creeping worm .
Genera
The Oweniidae family includes 4 recognized genera :
- Galathowenia Kirkegaard, 1959
- Myriochele Malmgren, 1867
- Myriowenia Hartman, 1960
- Owenia delle Chiaje, 1844
literature
- Stanley J. Edmonds: Fauna of Australia, Volume 4A. Polychaetes & Allies. The Southern Synthesis 4. Commonwealth of Australia, 2000. Class Polychaeta. Pp. 235-238, Family Oweniidae.
Web links
Individual evidence
- ↑ Oweniidae Rioja, 1917. WoRMS , 2018. Accessed November 7, 2018.