Procambarus clarkiired swamp crawfish

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Geographic Range

Although crayfish inhabitat many regions of the Earth, members of the genus Procambarus are located in North America. Procambarus clarkii are mostly found south-central United States, and northeastern Mexico (areas to which this species is native). The red swamp crayfish has also been transplanted to Hawaii, Japan, and even the River Nile (Safra, et al 1999; Jarmon 1999).

Habitat

As the common name implies, red swamp crayfish are found mainly in swamps, sloughs, and ditches. This species avoids streams and areas with strong current. During periods of drought or cold, the red swamp crayfish burrows itself for survival (McDonald 1996).

Physical Description

Adults of this species are about 2.2 to 4.7 inches in length. Crayfish are characterized by a joined head and thorax, and a segmented body. In the case of the species Procambarus clarkii, the body is a very dark red color, with a wedge-shaped black stripe on the abdomen. Crayfish have a sharp snout and moveable eyes on their heads. Like all arthropods, crayfish have a thin but tough exoskeleton that they shed during development. Crayfish have 5 pairs of walking legs, the first of which are large pinchers used for feeding. On the red swamp crayfish, the pinchers tend to be narrow and long. They have long antennae with sensory organs on them. This along with appendages used for feeding, are characteristic of the subphylum Mandibulata. There are also five pairs of smaller appendages called swimmerets on the abdomen. The carapace of this species, located on the dorsal side, are not separated by a space. The most posterior pair of appendages are called uropods. Uropods are flat, broad extentions that surround the telson, which is the last abdominal segment. Uropods are also used for swimming (Safra, et al 1999; McDonald 1996; Vodopich and Moore 1999; Barnes 1974).

Reproduction

The red swamp crayfish mate in late autumn. Sexes are separate, but the location of gonads are similar in both males and females -just anterior to the heart. Testes are usually white, while ovaries are usually orange. The sperm cells (crayfish sperm lack tails and are sometimes referred to as spermatophores) are released from the body of male crayfish through a pore at the base of the fifth pair of walking legs. Fertilization is internal. Sperm enters the female at the base of the third pair of walking legs, where the eggs are fertilized and released. The female crayfish then lies on her back and curls her abdomen forward. By beating her pleopods, or swimmerets, the female creates a water current which drives the fertilized eggs into the swimmerets where they will remain for approximately 6 weeks. By spring, the eggs will become larvae, and remain on the mother until sexually mature. The red swamp crayfish reach maturity in as little as three months, and in warm climates can reproduce two generations per year. Large healthy females typically produce over 600 viable young (Barnes 1974; Vodopich and Moore 1999; Safra, et al 1999).

Behavior

The behavior most characteristic of the red swamp crayfish is burrowing. Crayfish burrow to find moisture, food, warmth, and just to pass the time. Crayfish, along with many other arthropods molt their exoskelton several times throughout their life (most frequently during development). The crayfish take a break from regular activity, and burrow deep down for most of the molting process. The animal begins to secrete a new exoskeleton underneath the current one. Once the old cuticle separates from the epidermis, the new soft endocuticle is exposed. The endocuticle then experiences a calcification and hardening phase. This takes the most amount of time. Once the endocuticle is hardened, the crayfish returns to its regular routines. Crayfish are most active at night, and during the day often conceal themselves under rocks or logs (Safra, et al 1999; Barnes 1974; McDonald 1996)

Food Habits

Although some crayfish are known to feed on vegetation, the red swamp crayfish is carnivorous, eating insect larvae, tadpoles, and snails. When traditional food sources are scarce, the crayfish eat the remains of dead animals and worms as well (Safra, et al 1999; Barnes 1974).

Economic Importance for Humans: Positive

The red swamp crayfish, along with many other species of crayfish are an important source of food for humans. Especially in areas where Cajun communities are common, crayfish are the main ingredient in many everyday meals. Louisiana alone has 48,500+ ha of culture ponds. Procambarus clarkii was introduced to Japan as a food source for bullfrogs, and is now a common family pet all over the main island. This species also appears in many European pet markets. This species is very selective when it comes to its diet. There are many aquatic and semi-aquatic snails that are vectors for human pathogens such as Schistosomiasis. The red swamp crayfish significantly contribute to the control of these snail populations (Barnes 1974; Jarmon 1999).

Economic Importance for Humans: Negative

Because of the success of commercial aquaculture in its native southern USA, the red swamp crayfish has been introduced to many other areas. Most of these introductions have had negative consequences. Many of these areas have sophisticated irrigation systems in which the crayfish have burrowed. The burrowing activity has damaged the levees, dams, and water control structures. In addition, Procambarus clarkii is an intermediate host for many parasitic helminths of vertebrates, which may create new health problems in areas where the species is successfully established. Because of such adverse effects, many areas introduced to the red swamp crayfish are now trying to eradicate them (Jarmon 1999).

Conservation Status

Procambarus clarkii is a large prolific species of crayfish. Characterized by its aggressive burrowing, this speices is well adapted to life even when water levels fluctuate drastically. It is not surprising, that this species survives in very simple, shallow burrows (Jarmon 1999).

Contributors

Julia Rogers (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

native range

the area in which the animal is naturally found, the region in which it is endemic.

References

Barnes, R. 1974. Invertebrate Zoology. Philadelphia, PA: W. B. Saunders Company.

Jarmon, S. March 2, 1999. "Texas Gulf Coast Environmental Data Center; Summary of Work" (On-line). Accessed February 24, 1999 at http://texged.ips4.pvamu.edu/summary_crayfish.html.

McDonald, S. May 15, 1996. "Freshwater Resources" (On-line). Accessed February 24, 1999 at http://www.aqualink.com/fresh/z-crayfish2.html.

Safra, J., C. Yannias, J. Goulka. 1999. Encyclopedia Britannica. Chicago: Encyclopedia Britannica Inc..

Vodopich, D., R. Moore. 1999. Biology Laboratory Manual. USA: The McGraw Hill Companies Inc..