Crayfish of Romania

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Orconectes limosus (Rafinesque 1817)
spiny-cheek crayfish Kamberkrebs écrevisse américaine racul dungat

General description. Distribution

identification guide

It's a suppler crayfish, medium size, the adults having between 6 and 12 cm long. The colour of the crust goes from brown olive to light brown to dark brown, sometimes blue brown, depending on the several factors (factors like the period from the last moulting, the age or the habitat). Usually one may distinguish red brown strips on the abdomen segments and on the pleura. The ventral part of the claws is lighter in colour but never turns red or brown red and the top is orange with black aspect that is visible on the ventral part of those. The rostrum is long and has parallel margins that end with teeth. The apex is long and sharp. Post orbital there is a single long ridge that ends with a thorn. The cephalothorax is smooth when touching it but on the sides of the cervical section and on the margins of the cephalic section there are several thorns, one or two larger and 3 or 6 smaller. The strong and smooth claws have the propodit without any section and the dactilopodit has a median tubercle. There is a prominent and curved thorn on the internal margin of the carpus. There is a robust thorn on the ventral part of the ischiopodit of the third pair of legs.

The species was deliberately introduced in Europe in 1890 by an import from North America. They introduced them in a pond from Barnowko (Poland). Since then his area extended and nowadays includes a major part from West and Central Europe, France, Great Britain, Italy to Serbia, Romania, Poland, Belarus and Lithuanian (Souty-Grosset et al. 2006). In Romania the species was recently noticed in Danube (Pârvulescu et al. 2009). The presence of this species in Romania overlaps that of narrow-clawed crayfish (Astacus leptodactylus) – for details visit the Distribution page.

Sexual dimorphism

For this species, the claws dimension doesn't constitute a relevant information to determine the sexes. The females have visibly larger abdomen. In order to precisely distinguish the males from the females, especially when we are talking about young crayfish/juveniles, one may verify the sternal disk and the pleopodes to be sure. Male crayfish have the first two pairs of pleopodes strong and oriented towards the back (for the transfer of the spermatophores) while the female has all the pleopodes equal. The shape of the first two males pleopodes also constitute an important criteria to distinguish it from similar species, so that the first pleopod (Pl. I) has the distal lobe almost 2/3 of the total length while the second pleopod ( Pl. II) has the exopodit almost 4/5 from the length of the endopodit, the distal lobe of the endopodite being almost1/5 of its length and being very twilled.

Habitat and Ecology

It prefers to live in muddy and turbid waters from the plains, large rivers, canals, lakes or ponds. In North America it was found even in current streams that have rocks on the bottom. In Europe it is present almost everywhere including cold and fast waters but preferring deep and cool waters, being frequent in ponds and lakes. It is active day and night eating almost every kind of food. The adults frequently eat vegetal food. It is very resistant to low concentration of oxygen or to bad quality of the water that helps him in the invasion process. It can successfully resist even several days without water.
The natural enemies are the otter, the muskrat, the rats, the mink, the nutria, the fox, the badger and water birds- for the adults, the fishes being a real threat for the juveniles; the sheatfish, the pike, the perch and the sturgeons being the larger consumers. It is very resistant to parasitical diseases and to Aphanomyces astaci fungus to which it has 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 cycle

A great advantage compared to aboriginal species is that of the great reproductive capacity of this species. The spiny-cheek crayfish copulates in autumn and spring and even during winter. The laying contains a big number of eggs (around 400) and it is carried by the female between the pleopodes until the juveniles become independent. The growing speed is also very favourable, in 6 or 7 weeks the juveniles can become independent.
The age is determined taking into consideration the total length as following 0+ 18-30 mm; 1+ 25-35 mm. The moulting is more frequent to young ages (up to 4 to 5 periods per year) while at the adults the moult happens once or twice a year, usually during spring or summer. The next couple of days after this period of losing its skin 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 spiny-cheek crayfish become sexual active after its first year of life, at a total length of almost 25-35 mm.

Selective bibliography

1. Ingle, R. (1997): Crayfishes, lobsters and crabs of Europe - an illustrated guide to common and traded species. Chapman & Hall
2. Pârvulescu, L., Paloş, C., Molnar, P. (2009): First record of the spiny-cheek crayfish Orconectes limosus (Rafinesque, 1817) (Crustacea: Decapoda: Cambaridae) in Romania. North-Western Journal of Zoology – in press
3. Souty-Grosset, C., Holdich, D. M., Noël, P. Y., Reynolds, J. D., Haffner, P. (Eds). (2006): Atlas of Crayfish in Europe. Muséum national d’Histoire naturelle, Paris (Patrimoines naturels, 64)

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Orconectes limosus (Rafinesque 1817)		spiny-cheek crayfish Kamberkrebs écrevisse américaine racul dungat

General description. Distribution	identification guide
	It's a suppler crayfish, medium size, the adults having between 6 and 12 cm long. The colour of the crust goes from brown olive to light brown to dark brown, sometimes blue brown, depending on the several factors (factors like the period from the last moulting, the age or the habitat). Usually one may distinguish red brown strips on the abdomen segments and on the pleura. The ventral part of the claws is lighter in colour but never turns red or brown red and the top is orange with black aspect that is visible on the ventral part of those. The rostrum is long and has parallel margins that end with teeth. The apex is long and sharp. Post orbital there is a single long ridge that ends with a thorn. The cephalothorax is smooth when touching it but on the sides of the cervical section and on the margins of the cephalic section there are several thorns, one or two larger and 3 or 6 smaller. The strong and smooth claws have the propodit without any section and the dactilopodit has a median tubercle. There is a prominent and curved thorn on the internal margin of the carpus. There is a robust thorn on the ventral part of the ischiopodit of the third pair of legs. The species was deliberately introduced in Europe in 1890 by an import from North America. They introduced them in a pond from Barnowko (Poland). Since then his area extended and nowadays includes a major part from West and Central Europe, France, Great Britain, Italy to Serbia, Romania, Poland, Belarus and Lithuanian (Souty-Grosset et al. 2006). In Romania the species was recently noticed in Danube (Pârvulescu et al. 2009). The presence of this species in Romania overlaps that of narrow-clawed crayfish (Astacus leptodactylus) – for details visit the Distribution page.


Sexual dimorphism
	For this species, the claws dimension doesn't constitute a relevant information to determine the sexes. The females have visibly larger abdomen. In order to precisely distinguish the males from the females, especially when we are talking about young crayfish/juveniles, one may verify the sternal disk and the pleopodes to be sure. Male crayfish have the first two pairs of pleopodes strong and oriented towards the back (for the transfer of the spermatophores) while the female has all the pleopodes equal. The shape of the first two males pleopodes also constitute an important criteria to distinguish it from similar species, so that the first pleopod (Pl. I) has the distal lobe almost 2/3 of the total length while the second pleopod ( Pl. II) has the exopodit almost 4/5 from the length of the endopodit, the distal lobe of the endopodite being almost1/5 of its length and being very twilled.


Habitat and Ecology
It prefers to live in muddy and turbid waters from the plains, large rivers, canals, lakes or ponds. In North America it was found even in current streams that have rocks on the bottom. In Europe it is present almost everywhere including cold and fast waters but preferring deep and cool waters, being frequent in ponds and lakes. It is active day and night eating almost every kind of food. The adults frequently eat vegetal food. It is very resistant to low concentration of oxygen or to bad quality of the water that helps him in the invasion process. It can successfully resist even several days without water. The natural enemies are the otter, the muskrat, the rats, the mink, the nutria, the fox, the badger and water birds- for the adults, the fishes being a real threat for the juveniles; the sheatfish, the pike, the perch and the sturgeons being the larger consumers. It is very resistant to parasitical diseases and to Aphanomyces astaci fungus to which it has 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 cycle
A great advantage compared to aboriginal species is that of the great reproductive capacity of this species. The spiny-cheek crayfish copulates in autumn and spring and even during winter. The laying contains a big number of eggs (around 400) and it is carried by the female between the pleopodes until the juveniles become independent. The growing speed is also very favourable, in 6 or 7 weeks the juveniles can become independent. The age is determined taking into consideration the total length as following 0+ 18-30 mm; 1+ 25-35 mm. The moulting is more frequent to young ages (up to 4 to 5 periods per year) while at the adults the moult happens once or twice a year, usually during spring or summer. The next couple of days after this period of losing its skin 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 spiny-cheek crayfish become sexual active after its first year of life, at a total length of almost 25-35 mm.

Selective bibliography
1. Ingle, R. (1997): Crayfishes, lobsters and crabs of Europe - an illustrated guide to common and traded species. Chapman & Hall 2. Pârvulescu, L., Paloş, C., Molnar, P. (2009): First record of the spiny-cheek crayfish Orconectes limosus (Rafinesque, 1817) (Crustacea: Decapoda: Cambaridae) in Romania. North-Western Journal of Zoology – in press 3. Souty-Grosset, C., Holdich, D. M., Noël, P. Y., Reynolds, J. D., Haffner, P. (Eds). (2006): Atlas of Crayfish in Europe. Muséum national d’Histoire naturelle, Paris (Patrimoines naturels, 64)

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