Crested worms

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Crested worms
Lanice conchilega

Lanice conchilega

Systematics
Trunk : Annelids (Annelida)
Class : Polychaete (Polychaeta)
Subclass : Palpata
Order : Canalipalpata
Subordination : Terebellida
Family : Crested worms
Scientific name
Crested worms
Pit , 1851

The mop of worms ( Terebellidae ) are a diverse family often large and conspicuous polychaete (Polychaeta) in seas worldwide either slime tube-making can be found or without tube in the sediment.

features

The crested worms, which usually build tubes of mucus and sediment, typically have a robust body with numerous non-retractable buccal tentacles. Dorsally on their anterior segments are branched or simple gills , which, however, are absent in the non-tubular species living naked in the sediment. The latter also have an extensive tentacle membrane. The peristomium of the Terebellidae is fused both with the reduced prostomium (head lobe, on its rear edge) and with the first body segment and protrudes under the prostomium in the form of an enlarged upper lip. The buccal tentacles sit at the junction between the prostomium and the peristomium. Ventrally there is a non- evertable buccal organ . Most species of the Terebellidae have nuchal organs . The longitudinal muscles of the skin muscle tube are arranged in bundles. While the first segment, which is fused with the head, has neither parapodies nor bristles , the following segments usually have a characteristic shape that changes over the many segments. The parapodies are mostly forked, but are absent in some species, such as the genus Hauchiella . The cylindrical notopodia are slender or cut off and in many species only exist on the posterior segments. The neuropodia are designed as a torus , but can also be absent. Epidermal papillae and pygidial cirrus are absent. All segments have mixonephridia with a simple excretory canal that also serves as an exit for the gametes in the posterior segments . Bristles (Chaetae) are almost always present and often have a shape characteristic of the species, while Aciculae are absent.

The multi-bristle of the family Terebellidae have up to over 300 segments , depending on the species , the number of which increases with the age of the worm. The animals are between 1 and 2 mm and 30 cm long. In particular, many of the gillless, tubeless Amphitritinae are small. The segmented body can be divided into thorax and abdomen - as in species that have notochaetae only on the anterior segments - or have no larger sections. The various structures on the head and the side lobes are highly mobile.

The intestinal canal consists of a long, narrow esophagus , a wide, thin-walled front stomach and a muscular back stomach. The Terebellidae have a highly developed closed blood vessel system in which a section of the dorsal vessel above the esophagus is designed as a cylindrical heart . In addition to the heart's activity, general muscle movements ensure blood circulation. The gills and the lateral lobes are particularly well supplied with blood - if available. Hemoglobins are usually used as blood pigments to bind the oxygen , whereas in some species such as the Thelepodinae subfamily , chlorocruorins , which are freely dissolved in the blood and not bound to blood cells. In some species, hemoglobins are also found in the cells of the celomial fluid , albeit with a different molecular structure and a higher oxygen affinity, which enables survival in a less oxygenated environment.

Females and males are the same size in the Terebellidae and can only be distinguished during mating on the basis of their differently colored gametes , so that the females often appear pink to greenish and the males cream-colored. The gamete-forming tissue is shed in patches by the epithelium and the germ cells develop through the maturation in the body cavity. The mature gametes are released to the outside via the mixonephridia, where fertilization takes place in the seawater. The development after fertilization takes place in different ways depending on the species. In many species there are larvae that swim freely and feed on the yolk for several days as plankton and then metamorphose into crawling worms , while in other species the development in the jelly of the egg clutch takes place directly without a freely swimming larval stage. Some species hatch their eggs and either larvae or finished worms hatch. Asexual reproduction has not been observed in the Terebellidae.

The Terebellidae feed on detritus and microorganisms by grazing the food particles from the substrate with their non-retractable tentacles.

Some sample styles

A very widespread species that can be found from the North Sea to the coast of Australia is the tree tubeworm ( Lanice conchilega ) up to 30 cm long with up to 300 segments, which is the largest species in the family. The small species Terebella lapidaria also lives in the rock crevices of the middle tidal zone in the North Sea , which, with the help of its hemoglobin in the blood cells of the coelomic fluid , binds the oxygen much more strongly than the hemoglobin dissolved in the blood plasma of the blood vessels and survives the low-oxygen times of the ebb.

Genera

The family Terebellidae is divided into 50 genera :

literature

  • Stanley J. Edmonds: Fauna of Australia, Volume 4A. Polychaetes & Allies. The Southern Synthesis 4. Commonwealth of Australia, 2000. Class Polychaeta. Pp. 303-311, Family Terebellidae.

Web links

Commons : Terebellidae  - Collection of images, videos, and audio files

Individual evidence

  1. ↑ MJ de Kluijver et al .: Lanice conchilega (Pallas, 1766). Macrobenthos of the North Sea - Polychaeta, Marine Species Identification Portal.
  2. ↑ RMG Wells, RP Dales (1975): Hemoglobin function in Terebella lapidaria L., an intertidal terebellid polychaete. Journal of the Marine Biological Association of the United Kingdom 55 (1), pp. 211-220.
  3. ^ Terebellidae Grube, 1851. WoRMS , 2018. Accessed May 10, 2018.