Fish lice
| Fish lice | ||||||||||||
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Argulus spec. on a stickleback |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Branchiura | ||||||||||||
| Thorell , 1864 |
The fish lice or carp lice (Branchiura) also fish ticks are a taxon of the crustaceans (Crustacea). They live as ectoparasites on changing hosts. About 130 species are known today.
features
External anatomy
Carp lice are up to ten millimeters in size, but usually stay smaller than two millimeters. They are strongly flattened dorsoventrally and have a large carapace that largely covers a large part of the body. The body structure in the head, chest area ( thorax ) and abdomen ( abdomen ) is very clearly visible. The last thoracic segment and the bilobed, fin-shaped abdomen protrude from the rear under the carapace.
The animals have clearly recognizable complex eyes on their heads , and there is also a central nauplius eye . The head extremities and mouthparts are adapted to the ectoparasitic way of life. The two pairs of antennas are designed like hooks and are used to hold onto the host's skin. The 1st maxilla also has suction cups on its base and the 2nd maxilla has claws on the underside and rasp surfaces on the top. The mandible is formed into a spine, either in a suction pipe installed between the upper and the lower lip (Proboscis) or is (in the genus Dolops ) and is extendable.
The thorax legs are two-branched and serve as floating branches. The abdomen is unsegmented and flattened, the furca is reduced to two short appendages.
Internal anatomy
The midgut consists of two main ventricles that are heavily ramified. The food ingested is digested and stored in them. For excretion , they have nephridia on the maxillary bases. The blood circulation is driven by the heart in the fourth thoracic segment, four areas with a thinned cuticle on the underside of the thorax are used for breathing .
Carp lice are separate sexes. In the female animals, the ovary is unpaired in the thorax and merges into a genital space behind the fourth thorax segment. In the abdomen it has seminal receptacles ( Receptacula seminis ), which also open into the genital area. In the males, the testicles in the abdomen open out via an unpaired seminal vesicle between the last pair of legs. The males have special attachments on the last pair of legs for mating .
Way of life
Carp lice parasitize various species of fish and other vertebrates in the water (such as tadpoles ). They can be found in fresh water as well as in marine water and reproduce well in the aquarium .
The hosts are first nudged when swimming around and then swam at specifically. The orientation takes place against the current , which is created by breathing in the area of the gills and behind the fins of the fish. In this way, the carp lice find the gills and the fin bases, which they cling to with their mouthparts. In order to find an optimal place to pierce, they can crawl along the skin of the fish with the help of their antennae. They can affect the entire body surface of the fish. Once they have found a good spot, the stinger is used. The carp lice use it to inject an anticoagulant saliva , after which the wound is opened with the mandibles until the proboscis can be brought to a vessel .
The animals ingest both blood and tissue fluids as food, which are then absorbed and digested in the midgut branches. The animals can consume a lot of food through the ramified intestine, a blood meal can be sufficient for up to three weeks. By injecting saliva and sucking, the pathogen causing ascites Pseudomonas punctata can be transmitted. The actual sting of carp lice, on the other hand, is largely harmless to the fish. In the case of high infestation, however, the hosts are weakened, which is noticeable in an increased mortality . After the blood meal, the parasites let go of their host and get back into the open water.
Since fish lice damage host animals due to their parasitic way of life, their control is of great importance in the fishing industry. It is usually done with trichlorfon .
Reproduction and development
It usually takes place on the host, with the male first collecting the sperm in the seminal vesicle and then releasing it into the receptacula of the female. These are individual sperm cells, only representatives of the genus Dolops have packets of seeds ( spermatophores ).
The females lay the fertilized eggs on stones or other hard substrates, with the water swelling the egg shell and causing the eggs to stick. The females form egg balls or strings. The female carp louse Argulus foliaceus , for example, produces an average of four clutches with a total of well over 1000 eggs within the 15-day breeding period.
After a short time, larvae with a shortened carapace hatch from the eggs ( Copepodit stages ). The first larval forms are parasites, but the suckers do not form until the third stage. In total, the development runs over nine stages.
Systematics
Today about 130 species of carp lice are known, which are classified into four genera, of which Dolops is considered the most original:
- Dolops
- Chonopeltis
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Dipteropeltis until 2014 was just that species
- Dipteropeltis hirundo became known in January 2014
- Dipteropeltis campanaformis described
- Argulus
In Central Europe there are only three Argulus species, the best-known species is the carp louse ( Argulus foliaceus ), which parasitizes on all freshwater fish and also on tadpoles . It is widespread in the Holarctic and is quite large with a body length of almost 10 millimeters. The species Argulus coregoni is even larger . The fish louse Argulus japonicus was introduced with ornamental fish from Japan .
Individual evidence
- ↑ Lourelle Alicia Martins Neethling, José Celso de Oliveira Malta, Annemariè Avenant-Oldewage: Additional morphological information on Dipteropeltis hirundo Calman, 1912, and a description of Dipteropeltis campanaformis n. Sp. (Crustacea: Branchiura) from two characiform benthopelagic fish hosts from two Northern rivers of the Brazilian Amazon. In: Zootaxa. 3755, 2, 2014, pp. 179-193.
literature
- Horst Kurt Schminke: Crustacea, crayfish. In: Wilfried Westheide (Ed.): Special Zoology. Part 1: Protozoa and invertebrates. Gustav Fischer Verlag, Stuttgart 1996, ISBN 3-437-20515-3 .
- Rolf Siewing (Ed.): Textbook of Zoology. Volume 2: Systematics. Gustav Fischer Verlag, Stuttgart 1985, ISBN 3-437-20299-5 .
