Roller gel
| Roller gel | ||||||||||||
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Eight-eyed throat leech ( Erpobdella octoculata ) |
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| Scientific name | ||||||||||||
| Erpobdellidae | ||||||||||||
| R. Blanchard , 1894 |
The roller gels (Erpobdellidae) are a family of predatory leeches in the order of the throat leeches that live in freshwater .
features
The small to medium-sized, but very elongated roller gels are elongated-round at the front and slightly flattened towards the back. The very muscular and firm body has a comparatively small rear suction cup and a well-developed clitellum . The roller gels have three to six pairs of eyes, which are arranged in two transverse rows in the head area. The mouth, arched by a strongly protruding lip, has muscular ridges. The pharynx is long and jawless, as with all throat leeches, the intestinal canal in adaptation to the predatory way of life without the blind sacs known from other, blood-sucking leech groups. The testicles arranged in numerous grape-like vesicles are characteristic of the family .
Distribution, habitat and way of life
The roller gels are common in North America , India and the entire Palearctic including China . The only species found in 1976 in New Zealand was Dina maoriana Mason .
The leeches are freshwater inhabitants who predatory feed on small animals. The prey is swallowed whole using the muscular pharynx.
The best studied of the spread in Europe until cm to 6 long is Achtäugige Schlundegel ( Erpobdella octoculata ), which is found in ponds, lakes and slow-flowing waters and especially midges - and blackfly larvae and sludge tube worms captured.
Reproductive cycle
Like all other leeches, the Rollegel are also hermaphrodites , who exchange their sperm when they mate. Two leeches wrap around each other with their fore bodies during a longer mating act. Roller gels do not have a penis; copulation takes place with the help of spindle-shaped, about 1 to 2 mm long pseudospermatophores, which are formed by glands at the male genital outlet and rammed through the skin of the sex partner at any part of the body during copulation. In the partner's body, the sperm leave the pseudospermatophores and swim to the egg cells to fertilize them. The emptied pseudospermatophores fall off after about a day, but the wounds they cause in the leech's skin take several weeks to heal. This hypodermic insemination (mutual injection of pseudospermatophores) is practiced not only with roller gels, but also with fish leeches and most flat leeches , which, in contrast to the jaw rules, also have no penises.
A few days after mating with each other, both roller gels involved form the first cocoon from a glandular secretion from the clitellum , in which the fertilized eggs are laid while it is still forming . After the leech has pulled its front body out of the cocoon, it attaches it to a hard surface. For a short time he fanned it with oxygen-rich water, but then left it. The initially soft, transparent cocoon solidifies within half an hour and turns brown. There are numerous small yolkless eggs in a cocoon. The embryos are nourished by the lecithin-rich gelatinous nutrient fluid in the cocoon. In Erpobdella octoculata , the 2 to 3 mm long young leeches hatch after 3 weeks. Rollegel live predatory from birth and devour small animals available to them.
Since the egg cocoons of the roller gel are not guarded, there are sometimes high rates of loss. Important predators include mud snails ( Lymnaea ), which, according to studies on the European and North American reel fish Erpobdella octoculata and Erpobdella punctata, ate up to 30% of the egg cocoons. Even cannibalism of freshly deposited, still soft cocoon plays a role, with only foreign nests are eaten.
Systematics
The internal systematics of the Erpobdellidae is controversial. Six genera are currently recognized. However, a molecular genetic analysis by Siddall (2002) showed that the genera Dina , Mooreobdella , Nephelopsis , Trocheta and Erpobdella s. st. not monophyletic groups and some are polyphyletisch why he all conducted under these genera species in the genus extended Erpobdella summarized and in addition to this, only the genus Motobdella left standing.
literature
- Ulrich Kutschera : Propagation strategies of worm-shaped hermaphrodites. In: Ulrich Kutschera: Evolutionary Biology. UTB, Verlag Eugen Ulmer, Stuttgart 2008, pp. 192–194.
- Mark E. Siddall (2002): Phylogeny of the leech family Erpobdellidae (Hirudinida: Oligochaeta). Invertebrate Systematics 16, pp. 1-6.
- Hasko Nesemann, Eike Neubert: Annelida, Clitellata: Branchiobdellida, Acanthobdellea, Hirudinea. Spectrum Academic Publishing House Heidelberg / Berlin 1999. Erpobdellidae , p. 109.
- Urania Tierreich , Volume 2. Urania-Verlag, Leipzig / Jena / Berlin 1966. P. 89, Family Herpobdellidae .
- Fauna of Meghalaya, Part 9. Editor-Director, Zoological Survey of India, Calcutta 1999. Erpobdellidae , pp. 457, 460.
- Fauna of Tripura. Editor-Director, Zoological Survey of India, Calcutta 2000. Erpobdellidae , p. 225.
Web links
- Erpobdellidae in: Lexicon of Biology , online edition.