Headworm
| Headworm | ||||||||||||
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Headworm ( Capitella capitata ) |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Capitella capitata | ||||||||||||
| ( Fabricius , 1780) |
The head worm ( Capitella capitata ) is a cosmopolitan marine annelid from the genus Capitella within the polychaete - family of Capitellidae .
features
The headworm has a long, quite fragile, cylindrical body that tapers at the ends but is wider in front and can contract and stretch considerably. It becomes up to 12 cm long and then has about 100 segments , of which the thorax comprises 9 bristle-bearing segments. Gills are not found on any segment. The cone-shaped prostomium is as long as it is wide, has two small eyes on the abdomen and two nuchal organs behind them .
The first 6 to 7 segments only have capillary-like bristles , while on the 7th segment there are both capillary-like bristles and hooks and from the 8th or 9th segment there are only hooks. Between the 8th and 9th bristle-bearing segment there is a single genital opening in the middle of the back, which in the female is an oval swelling and in the male it is an opening between four strong bristles - genital hooks or genital spines - arranged in the form of a diagonal cross are. The pygidium does not show any cirrus.
The animal is red-brown to pink. Specimens preserved in ethanol turn reddish brown to transparent.
Distribution, habitat and way of life
Capitella capitata is cosmopolitan in all of the world's oceans, including the North Sea and up to the Skagerrak and Kattegat .
The headworm lives on sandy subsoil rich in mud, in mud and under stones from the upper tidal zone down to a depth of 1000 m.
It feeds on detritus that adheres to the substrate. The food particles are collected with the everted sac-like proboscis .
Life cycle
Capitella capitata is sexually separated with females and males of roughly equal size and external fertilization. Two different reproductive strategies have been observed within a population on the coast of Massachusetts, for which genetic studies have shown a common gene pool: Under favorable environmental conditions, crawling young animals (benthic larvae) develop from the eggs, which can make favorable use of the organic matter on site. In unfavorable conditions, on the other hand, free-swimming trochophora larvae develop, which can repopulate more distant habitats and therefore, after a stage as metatrochophora, only later metamorphose into crawling worms .
literature
- PJ Hayward, JS Ryland: Handbook of the Marine Fauna of North-West Europe. Oxford University Press, Oxford 1995, p. 187.
Web links
- J. Masterson: Capitella capitata (Fabricius, 1780). Smithsonian Marine Station, Indian River Lagoon Species Inventory
- MJ de Kluijver et al .: Capitella capitata (Fabricius, 1780). Macrobenthos of the North Sea - Polychaeta, Marine Species Identification Portal
Individual evidence
- ↑ J. Frederick Grassle, Judith P. Grassle (1974): Opportunistic life histories and genetic systems in marine benthic polychaetes. Journal of Marine Research 32 (2), pp. 253-284.