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Pontastacus leptodactylus Eschscholtz 1823 |
Narrow-Clawed
Crayfish
Galizienkrebs
écrevisse
à pattes grêles
racul-de-lac |
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General description. Distribution |
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Large size and robust crayfish, the adults
being often larger than 14 cm. The dorsal colour of the crust
changes from yellow brown to dark brown depending on the last
molting, the age or the habitat. The ventral side has a lighter
colour, almost a dirty white colour. The rostrum has the margins
parallel and strong, denticulate with a visible median prominence.
The apex is long and sharp. It has two post-orbital ridges that end
with a thorn. It has a strong thorn at the lower part of the
antennal scale. The cervical section and the cephalothorax margins
have thorns. The males have longer claws that look more like a clip.
The propodit and the dactilopodit are smooth having small roughness
when touching them. Sometimes the claws can look
like a sickle.
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Sexual dimorphism |
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The male claws which are usually longer and stronger and the female abdomen which is larger are criteria's to distinguish the sex. In order to precisely distinguish the sex, especially at the juveniles, one may observe the sternal disk and the pleopodes. The male has the first couple of pleopodes strong and towards the front (for the transfer of the spermatophores) while the female has all the pleopodes equal. The shape of the two pleopodes at the males is an important criteria in order to distinguish form similar species, so that the first pleopod (Pl. I) has the distal lobe almost 1/2 of the total length while the second pleopod (Pl. II) has the exopodit almost the same length as the endopodit, the distal lobe of the endopodite being almost 1/2 of its length. |
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Habitat and Ecology |
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It lives in running water, lakes, ponds and channels trying to find places to hide in ground banks, submerse vegetation or in different objects found in water. It also lives in saltiest water or even sea. It is active day and night eating almost every kind of food, that` s why it represents a truly water sanitary. The adults, when they cannot find animal food they eat submerse plants. Sometimes the crayfish leaves the water in search for food. It is less sensitive to low concentration of oxygen, it can live several days outside water at low temperatures. Like other species of crayfish it is very sensitive to chemical pollution. Its natural enemies are the otter, the muskrat, the rats, the mink, the coypu, the fox, the badger, water birds – for the adults, fishes for the juveniles, especially the salmon, the pike, the perch and the sturgeons being the largest consumers. One of the major problems is that of parasitical diseases of viral nature, bacterial or the fungus. The oomycet Aphanomyces astaci was introduced in Europe once with the introduction of the North-American species. Compared to this one the local species are very vulnerable because of the lack of antibodies. Ectoparasitism, without producing any damage, is frequently found at the branhiobdelides, chironomides, ostracodes species and others. Bivalves colonies can often be attached on the adults (Dreissena sp.). | ||||
Life history |
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The narrow-clawed crayfish mate in autumn, between October and November or even in December, when the females have white spermatophores on the sternal plate. The laying contains a big number of eggs (180- 600) and it is carried by the female between the pleopodes until the juveniles become independent. The age is determined taking into consideration the total length as following 0+ 15-35 mm; 1+ 38-50 mm; 2+ 45-95 mm; 3+ 86-112 mm, 4+ 110-150 mm, 5+ >155 mm. The molt is more frequent to young age (about 4 to 5 molting per year) while the adults molt once or twice per year, between May and June. The next couple of days after molting are very critical for the crayfish because it loses the protection of the crust and can be easily attacked by fishes or even by other crayfish that have stronger crust. After this period the lost or hurt appendix can regenerate but usually a broken claw grows up smaller. The sexual maturity varies a lot, the males become fertile when they have 60-70 mm and can fecundate each year. The females begin to lay eggs when they are 2 or 3 years old. | ||||
Selective bibliography |
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1. Băcescu MC (1967) Fauna
Republicii Socialiste România - Crustacea, Decapoda. Editura
Academiei Republicii Socialiste România, Bucureşti 4; 4. Pârvulescu L (2010) Crayfish field guide of Romania. Editura Bioflux, Cluj-Napoca. |
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