Combworms

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Combworms
Lagis koreni (with and without a residential tube)

Lagis koreni (with and without a residential tube)

Systematics
Trunk : Annelids (Annelida)
Class : Polychaete (Polychaeta)
Subclass : Palpata
Order : Canalipalpata
Subordination : Terebellida
Family : Combworms
Scientific name
Combworms
Quatrefages , 1866

The comb worms or comb bristle worms ( Pectinariidae ) are a family of mostly small polychaeta (polychaeta) that live in characteristic cone-shaped living tubes and that can be found in fine-grained soils in oceans around the world as detritus eaters .

features

The Pectinariidae are usually about 1 to 2 cm long; only the Amphictene favona , which lives in Australian waters, can grow to be almost 10 cm long and up to 2.6 cm wide. Unlike most of the many bristles, the Pectinariidae have a constant number of segments , 22 segments for all species. The body is divided into three sections: thorax, abdomen and an end-scaphe, a bowl-shaped ( ancient Greek σκάφη skáphē "bowl"), formed from the last five fused segments and laterally occupied with spiky bristles . The head consists of a reduced prostomium that is fused with the peristomium , which is reduced to lips around the mouth . Antennas are missing. The non-retractable buccal palps , on which an eyelash groove runs , sit on the lips or around them . On the notopodia of the first segment are conspicuous paleae surrounded by a head veil (a tentacle membrane) . The Notopodien the remaining segments are short and cut the cylindrical Neuro stages as Tori formed. Capillary-shaped bristles and spines sit on the notopodia, and hooks on the neuropodia. The peristomium forms a more or less well developed operculum, the raised edges of which are smooth or divided into triangular lobules and can also carry cirrus . Leaf-shaped gills sit dorsally on the 4th and 5th segments . The anterior segments have paired glandular areas ventrally and a small central shield.

Lateral organs run between the notopodia and neuropodia, pits with lashes on the inside. The longitudinal muscles are arranged in bundles. The animals have a throat membrane and a ventral buccal organ between the first and second segments . The intestinal canal runs in a loop. The closed blood vessel system includes a central heart on the back as well as a back and an abdominal vessel , which are connected to one another by side vessels, capillaries and lacunae on the intestinal canal. In the anterior segments there are a few pairs of mixonephridia , which are used for excretion, and gonoducts in the posterior segments .

Residential tube

The Pectinariidae can easily to their conical on ice cream cones reminiscent burrows are detected, they zusammenzementieren with autologous mucus from sand grains. It is noticeable that the wider end is pointing downwards in the sediment with the head.

Habitat and way of life

The Pectinariidae live in their conical living tubes with the head down in a sessile manner as substrate eater in fine-grained sediment soils . With their gold-colored paleae they dig into the substrate, while with their palps they collect the substrate particles that they swallow. The organic components on the substrate - debris and microorganisms - are digested while the mineral components are excreted. Likewise, some of the collected particles are not ingested with the mouth, but are repelled as pseudofaeces .

Development cycle

In the Pectinariidae, hermaphroditism occurs, such as in Lagis koreni , which can probably form egg cells and sperm on the same germinal epithelium . The lenticular egg cells are released into the open sea water before meiosis is complete , where fertilization also takes place. The zygotes develop into free-swimming Trochophora larvae and later Metatrochophora posing as zooplankton of phytoplankton feed. The mature larvae, in which the characteristic paleae are already visible, actively seek out a suitable, fine-grained substrate before they settle, metamorphose into crawling worms and build a living tube .

Asexual reproduction is unknown in the Pectinariidae and probably does not occur.

Genera and species

The species of the family Pectinariidae are divided into either 2 or 5 genera :

  • Pectinaria Savigny in Lamarck, 1818
  • Petta Malmgren, 1866
  • Amphictene Savigny, 1822 (also as a subgenus of Pectinaria )
  • Cistenides Malmgren, 1866 (also as a subgenus of Pectinaria )
  • Lagis Malmgren, 1866 (also as a subgenus of Pectinaria )

literature

Web links

Commons : Pectinariidae  - collection of images, videos and audio files

Individual evidence

  1. ↑ Pectinariidae Quatrefages, 1866. WoRMS , 2018. Retrieved October 7, 2018.