Aeolosomatidae
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| Beddard , 1895 |
The Aeolosomatidae are a family of very small annelid worms in the order of the Aeolosomatida and the Aphanoneura class , of which around 30 species occur predominantly in freshwater .
features
The Aeolosomatidae, which mostly live in fresh water , are very small and thin with body lengths of 0.3 to 10 mm and widths of 0.04 to 0.06 mm. They have neither appendages nor parapodies on their heads. Colored glands in the epidermis, the cells of which contain vacuoles with red, green, blue-green, yellow or sometimes colorless fluid, often give the Aeolosomatidae a light color. The lobed prostomium, which is covered with numerous cilia on the abdomen , is set off by a conspicuous groove, which is also covered with cilia. The animals are clearly segmented, but without partition walls, whereby the 13 to 20 segments separated from one another by constrictions are zooids , which are formed by fragmentation (paratomy) and are used for asexual reproduction . There are four bundles of bristles on each zooid, with the bristles ( chaetae ) on both the back and the belly either smooth and thin (capillary-shaped) or S-shaped (sigmoid) hooks.
Similar to the belt worms , the Aeolosomatidae are also hermaphrodites . The sperm are formed by the testicle cells in the coelom and released into the open through modified nephridia in the posterior segments. The egg cells, on the other hand, are passed out through a female genital opening in the middle of the fifth segment. Depending on the species, there are two to five, but usually three, pairs of receptacula seminis on the front bristle bundles of the animal. Above the segment with the developing egg cells, the animal forms a glandular epithelium (“pseudo-clitellum”) on the abdomen and on the side to separate the egg cocoon from a layer of cells that does not cover the back. It is now no longer with the clitellum the clitellata homologated , but as analog viewed development.
Occurrence and distribution
Most of the 30 or so species of the Aeolosomatidae live in the fresh water of lakes, rivers and other inland waters. Few species live in brackish water or in estuaries , while only one marine species ( Aeolosoma maritimum ) has been described. The animals live between aquatic plants or in sediments, especially in sand that is rich in detritus. They are common worldwide.
Life cycle
The hermaphroditic Aeolosomatidae have not yet been observed during copulation, oviposition and embryonic development only in Aeolosoma quaternarium .
The animals reproduce mainly asexually . If an individual reaches a certain number of segments (depending on the species), several zooids detach themselves from the mother animal within a few days and thus form a clone. Each detached segment grows into a completely new animal. This enables high population densities to be reached quickly.
Some species can survive dry spells and spread between bodies of water over land by forming a protective cyst around their body.
nutrition
The Aeolosomatidae feed on microscopic algae and other microorganisms that live on the substrate. The animals suck in the substrate particles by placing their prostomium over them and creating a vacuum. The algae are digested in the intestine and the mineral components are excreted undigested.
Systematics
The sister group of the Aeolosomatidae is the family of Potamodrilidae , with which it forms the order of the Aeolosomatida and at the same time the class of Aphanoneura within the tribe of annelids .
The approximately 30 species of the Aeolosomatidae are divided into three genera :
Christian Gottfried Ehrenberg described Aeolosoma hemprichi as the first species of the Aeolosomatidae in 1828 , which he named after the Silesian zoologist Friedrich Wilhelm Hemprich , who died shortly before at the age of 29 . The generic name means "nimble body" ( ancient Greek αἰόλος aiólos "nimble", σῶμα sō̂ma "body"). The English zoologist Frank Evers Beddard described the family Aeolosomatidae with the then only genus Aeolosoma as small "freshwater oligochaetes " whose segments are not characterized by regular partitions and whose prostomium is ventrally occupied by eyelashes.
literature
- Frank Evers Beddard: A Monograph of the Order of Oligochaeta . Oxford at the Clarendon Press, 1895. pp. 176-187, Oligochaeta, Group Aphaneura, Family Aeolosomatidae.
- Jacob van der Land: Family Aeolosomatidae. In: Ralph O. Brinkhurst, Barrie GM Jamieson (1988): Aquatic Oligochaeta of the World. Oliver and Boyd, Edinburgh 1971, pp. 665-706.
- Pierre Lasserre: Clitellata - Aeolosomatidae. In: Arthur Giese, John S. Pearse (Eds.): Reproduction of Marine Invertebrates V3: Annelids and Echiurans. Academic Press, New York 1975. pp. 222f.
- Olav Giere, Olaf Pfannkuche: Biology and Ecology of Marine Oligochaeta - A Review. In: Harold Barnes, Margaret Barnes (eds.): Oceanography and Marine Biology, Volume 20. Aberdeen University Press, Aberdeen 2005. pp. 197-350, here p. 217, Aeolosomatidae.
- Emilia Rota, Yde de Jong: Fauna Europaea: Annelida - Terrestrial Oligochaeta (Enchytraeidae and Megadrili), Aphanoneura and Polychaeta. Biodiversity Data Journal 3: e5737. doi : 10.3897 / BDJ.3.e5737
- Adrian M. Pinder: Annelida: Aphanoneura. In: Catherine Mary Yule, Hoi-Sen Yong (Ed.): Freshwater Invertebrates of the Malaysian Region. Academy of Sciences Malaysia, Kuala Lumpur 2004. p. 191.