Carp louse
| Carp louse | ||||||||||||
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Argulus spec. on a stickleback |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Argulus foliaceus | ||||||||||||
| ( Linnaeus , 1758) |
The carp louse ( Argulus foliacaeus ) is a fish parasite from the group of fish lice or Branchiura (family Argulidae ) and causes the fish disease argulose.
features
Argulus foliaceus , like all members of the genus, has a dorsoventrally (i.e. from top to bottom) flattened body which consists of two sections. The head and torso section or cephalothorax has a broad oval shield on the upper side, which appears slightly indented in the middle at the back by two posterolateral lobes projecting backwards. It covers the body with the exception of the abdomen and all limbs with the exception of the last pair of legs. On the upper side of the dorsal shield sit two conspicuous and quite large, dark-colored complex eyes . The undivided abdomen is drawn out backwards into two broad lobes. Visible from below are two very short pairs of antennae at the front edge of the cephalothorax, the basal limbs of which have thorns. The mouth opening sits on an elongated, extendable "trunk"; in front of this sits a strong stiletto-like thorn. The toothed mandibles inside the trunk are not visible from the outside. During the sucking process, the carp louse drills a wound with its thorn, injects toxins or enzymes and then sucks up the blood that emerges. The most striking feature and highly characteristic of the genus are two complexly built suction cups, which were created by reshaping the second maxilla and which sit on the side of the mouth. In their place, the youthful stages still have the thorny mouthparts, which are replaced by the suction cups during the last moults. The one-branched (uniramen) second maxillae sitting behind them have three strong thorns at their base. In the rear section of the cephalothorax in front of the abdomen are four pairs of two-branched (birame) legs that are used as swimming legs. In the lateral section there are two respiratory fields with a thinned cuticle.
The genus Argulus comprises 129 species worldwide, 85 of which live in freshwater. The eight Palearctic species are the only fish lice living here. In Germany, as in all of Central Europe, only three species occur. The species can be differentiated as follows: Argulus coregoni is considerably larger (almost twice as large) as the three to seven millimeter long carp lice, in addition the lobes of the abdomen are pointed at the end, not rounded, and smooth on the edge, not with small spikes occupied as with foliaceus . It is difficult to distinguish it from the Argulus japonicus , which was recently introduced from Japan with koi imports, and it is not always possible with absolute certainty, especially in the case of females. The males can be clearly identified by the shape of an extension on the hips (coxes) of their swimming legs. In females, only the combination of the following features helps: legs mostly pigmented (less often unpigmented and then difficult to distinguish from japonicus ), abdominal lobes more rounded at the back, the indentation between them is always less than half as long as the abdomen. The fourth pair of swimming legs is mostly free, in japonicus mostly covered by the dorsal shield.
distribution
Argulus foliaceus lives across Europe as well as West and Central Asia. They live in standing and flowing waters of all kinds, provided fish live in them.
Way of life
The carp louse is an obligatory, blood-sucking ectoparasite of fish in fresh water, more rarely in brackish water with a salt content of up to 12 per thousand . It is not very specific to the host and has been found in a large number of fish from numerous families, including carp , goldfish , pike , trout and rainbow trout ; there is even some information about infestation by amphibians. It can anchor itself anywhere on the fish's body with its thorns and suction cups, but prefers gill cavities and crevices. The animals can leave their host and actively swim around freely, males (for mating) and females (for laying eggs) do this regularly, transition between different host fish can also take place at other times with close contact. Argulus foliaceus can leave the host at lightning speed if the host fish is lifted out of the water.
Life cycle
Carp lice are separate sexes. Males and females can be recognized by their pigmentation, the males have two dark spots on the abdominal lobes, the females a dark strip of spots in the middle of the dorsal shield. The mating takes place on the host or off-site, but then on a solid surface. One mating is sufficient for all eggs to be fertilized. After mating at the latest, the female leaves the host and lays her eggs on hard substrate at the bottom of the water. The eggs laid in rows are coated with a substance that hardens on contact with water. Females can lay several clutches, but in between they have to seek out a fish to eat. It is not uncommon for a clutch of around 400 eggs to remain. The eggs are about 0.3 millimeters long. After approx. 25 to 50 days, the egg hatches into a larval stage, a metanauplius (the nauplius stage is still passed through in the egg), which, after each molt, is followed by nine juvenile stages, all of which are similar in morphology to the adults like the adults sucking blood on fish. The larvae hatch in Northern Europe when the water temperature rises around the end of April to the beginning of May. Sexually mature animals appear from the end of June, with a maximum in midsummer. New egg laying begins at the end of July. The overwintering stage is predominantly the egg, but, even in Finland, a certain proportion of adults overwinter. While in Scandinavia there is only one generation per year, several (up to three?) Can develop in a row in the same year in a warmer climate.
Adult carp lice can survive for 8 to 14 days, freshly hatched larvae for up to 5 days without contact with a host. A few longer survivors were then almost immobile and could no longer reach any fish successfully.
Clinical appearance
Carp lice injure the skin of the fish when sucking firmly with their mandibles, in order to then stab the wound with the poisonous sting. With the sting itself, a poisonous secretion is injected into the wound. This secretion contains enzymes which in the host break down the tissue surrounding the puncture site and promote blood flow. Bacteria and viruses that the fish louse use as an intermediate host are often transferred to the fish during blood sucking. Characteristic features are jerky swimming movements of the fish as a reaction to the puncture, as well as scrubbing movements to strip off the parasite. Due to the injury to the skin, an epidermal wall forms at the puncture site, combined with increased mucus formation and inflammatory foci. If young fish are attacked by carp lice, a single parasite can be fatal.
Carp lice also transmit a number of infectious diseases, e.g. B. Rhabdovirus carpio , the carrier of the spring viremia of carp or the Koi herpes virus . In Central and Western Europe, Argulus japonicus is now just as common or even more common than the native carp louse , especially in intensive breeding farms.
Individual evidence
- ^ William J. Poly (2008): Global diversity of fishlice (Crustacea: Branchiura: Argulidae) in freshwater. Hydrobiologia 595: 209-212. doi : 10.1007 / s10750-007-9015-3
- ↑ Erik Mauch, Ursula Schmedtje, Anette Maetze, Folker Fischer: Taxalist of the aquatic organisms in Germany for coding biological findings. Attachment. Information reports from the Bavarian State Office for Water Management, issue 01/03. Munich, 2003 - ISBN 3-930253-89-5
- ↑ DM Soes, PD Walker and DB Kruijt (2010): The Japanese fish louse Argulus japonicus new for The Netherlands. Lauterbornia 70: 11-17.
- ^ G. Fryer (1982): The parasitic Copepoda and Branchiura of the British freshwater fishes. A handbook and key. Freshwater Biological Association Scientific Publication 46, 87 S., Ambleside, Cumbria.
- ^ Argulus foliaceus at WoRMS
- ^ A b Fish Lice in the UK
- ↑ SK Rushton-Mellor & GA Boxshall (1994): The developmental sequence of Argulus foliaceus (Crustacea: Branchiura). Journal of Natural History Volume 28, Issue 4: 763-785. doi : 10.1080 / 00222939400770391
- ↑ Pasternak, AF; Mikheev, VN; Valtonen, ET (2000): Life history characteristics of Argulus foliaceus L. (Crustacea: Branchiura) populations in Central Finland. Annales Zoologici Fennici Vol. 37 No. 1: 25-35.
- ^ A b Peter D. Walker, Iain J. Russon, Raymond Duijf, Gerard van der Velde, Sjoerd E. Wendelaar Bonga (2011): The off-host survival and viability of a native and non-native fish louse (Argulus, Crustacea : Branchiura). Current Zoology 57 (6): 828-835.
- ↑ Robin M. Overstreet, Jean Jovonovich, Hongwei Ma (2009): Parasitic crustaceans as vectors of viruses, with an emphasis on three penaeid viruses. Integrative and Comparative Biology 49 (2): 127-141. doi : 10.1093 / icb / icp033
- ↑ Alexander cap: Parasitological studies of one and two year old carp (Cyprinus carpio) from pond farms in the Leipzig area during winter keeping. Diss., Faculty of Veterinary Medicine, University of Leipzig, 2004.
swell
- Fish diseases , Rudolf W. Hoffmann, Eugen Ulmer Verlag, Stuttgart 2005, pp. 175-176, ISBN 3-8001-2739-3 .
- Diseases in aquarium fish , Dieter Untergasser, Franckh-Kosmos Verlag, pp. 145–146, 2006, ISBN 3-440-10264-5 .
