Glossworm
| Glossworm | ||||||||||||
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Lumbriculus variegatus with a double tail as a result of an injury |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Lumbriculus variegatus | ||||||||||||
| ( OV Müller , 1774) |
The gloss worm ( Lumbriculus variegatus ) is a kind süßwasserbewohnender annelid from the family of Lumbriculidae in the class of clitellata (Clitellata) located on the northern hemisphere is native, but was spread worldwide by humans.
features
The largest specimens of Lumbriculus variegatus , as found in the wild, grow to be about 10 cm long and about 1.5 mm wide, with about 200 to 250 segments . In the laboratory, they do not get as long as they divide beforehand. The front end of the glossworm is often greenish in color, but the rest of the animal is always red. The largely cylindrical gloss worm has a uniform thickness over almost its entire body and only tapers very far at the front or rear end.
On each segment of the glossworm there are 4 bundles of bristles, each with 2 bristles ( Chaetae ), a total of 8 bristles. All of the worm's bristles are forked with a large lower tip and a smaller upper tip. The approx. 200 µm long bristles are used to anchor the movement with the help of the longitudinal and circular muscles of the skin muscle tube .
In Lumbriculus variegatus, the red blood vessels, which branch out strongly in each segment, are noticeable . The pulsating lateral vessels branching off from the dorsal vessel in most segments are characteristic of worms of the genus Lumbriculus . The pulse rhythms of the back and side vessels are coordinated with one another, while the abdominal vessel does not pulsate. The blood flows forwards in the back vessel and backwards in the abdominal vessel. The rhythms of the blood vessels can be easily observed because the body wall of the glossworm is transparent. The red color of the blood is due to the blood pigment erythrocruorin dissolved in the plasma , which has a very strong affinity for oxygen and enables the glossworm to survive under low -oxygen conditions.
Like other lumbriculids, sexually mature hermaphroditic glossworms, which, in contrast to immature, asexually dividing individuals, are only rarely found, are quite variable in terms of the position and number of gonads . Usually there is 1 pair of testicles with associated sperm conductors and male genital orifices, which are somewhere in the 7th to 10th segment, but usually in the 8th segment. However, there can also be a male gender outlet on one side only. The animals have 1 or 2 pairs of ovaries in the segment or segments behind the testicles. The glossworms usually have 4 pairs of receptacula seminis , beginning one or two segments behind the segment with the atria - muscular end sections of the sperm ladder, which are either paired or only on one side in the 7th to 11th segment, mostly in pairs in the 8th segment.
Occurrence and distribution
The glossworm can often be found under leaves, wood, plants and stones in freshwater deciduous pools, at the edges of lakes and in shallow inland waters.
Lumbriculus variegatus is distributed across the entire northern hemisphere - Eurasia and North America . Meanwhile, the gloss worm is by humans to other continents introduced Service. It is now common in Australia and New Zealand , where its locations are concentrated in ponds in the vicinity of cities. However, it probably only came to North America, where it occurs very frequently, through humans.
Sexual development cycle
Sexually mature glossworms are very rare and have not yet been observed during copulation. Sexual maturity is believed to be reached only at full body length of 10 cm with at least 200 segments, and worms of this length have only been seen in the wild, not in the laboratory. It is assumed that, as with other belt worms, the sperm of the respective sex partner is absorbed into their own receptacula seminis during mating. The egg cocoons are transparent and contain 4 to 11 very yolk-rich eggs. Finished small worms develop from the fertilized eggs, which leave the cocoon after about two weeks with a length of about 1 cm.
Asexual reproduction and regeneration
Lumbriculus variegatus divides into small sections by architomy in order to reproduce asexually . This happens before he reaches sexual maturity. In the laboratory, this is the only mode of reproduction of the glossworm observed so far. A single segment of the glossworm can regenerate into a complete animal. In the case of unilateral injuries, this can lead to a segment still in the body forming a new end of the body to the side and thus a branch.
The glossworm divides in autotomy even when there is danger, especially when one end of the body is grabbed by a predator. The animal can cut itself cleanly within a fifth of a second. The surviving part of the body also benefits from the extremely high regenerative capacity, so that it grows back into a complete worm.
nutrition
The glossworm feeds on organic detritus, bacteria and other microorganisms that it digests with the substrate swallowed at the bottom of the water. The mineral components are excreted undigested.
Escape reactions
If you touch Lumbriculus variegatus at its rear end, it swims away in a screw-like (corkscrew-shaped) movement. When touched at the front end, he turns his body to escape. The glossworm has light-sensing cells in its skin, with which it perceives shadow movements, to which it is able to react quickly. This also plays a role when he holds his rear end out of the water in the air in order to absorb oxygen into the blood in the pulsating dorsal vessel just below the dorsal skin and to release carbon dioxide from it, but then withdraws completely into the water again in case of danger.
Importance to humans
The glossworm is used as fish feed and is therefore bred for trout farms and the aquarium trade, among other things . This is also one of the reasons for its worldwide spread.
literature
- Ralph O. Brinkhurst: Guide to the Freshwater Aquatic Microdrile Oligochaetes of North America. Canadian Special Publication of Fisheries and Aquatic Sciences 84, Ottawa 1986. pp. 24f., 237.
- Barrie GM Jamieson (1988): On the phylogeny and higher classification of the Oligochaeta. Cladistics 4, pp. 367-410.
- Tarmo Timm (2009): A guide to the freshwater Oligochaeta and Polychaeta of Northern and Central Europe. Lauterbornia 66, p. 170
- Ton van Haaren & Jan Soors (2013): Aquatic Oligochaeta of the Netherlands and Belgium. KNNV Publishing, Zeist, pp. 66-67
Web links
- Lumbriculidae in: Lexicon of Biology , online edition.
- C. Drewes (2004): Lumbriculus variegatus: A Biology Profile.
- Key to Australian Freshwater and Terrestrial Invertebrates - Lumbriculidae.