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Cambarus bartoniiAppalachian brook crayfish

By Stephanie Jenkinson

Geographic Range

Cambarus bartonii can be found in the eastern and southern parts of the United States as well as the southeastern part of Canada. They are most often found, however, in the range from New Brunswick, Canada to northern Georgia and in eastern parts of Kentucky and Tennessee. (Green, 1967)

Habitat

Cambarus bartonii dwell on the bottoms of streams, creeks, and small rivers and lakes. They construct burrows, sometimes called "chimneys". Their burrows can be simple hollows under stone or more intricate, with lateral passageways. Chimneys are found along the water's edge. Most of the structure is under water, but the top sticks out and resembles a chimney. Chimneys vary in size, the largest opening being about eight centimeters. (McMan, 1960)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams

Physical Description

Cambarus bartonii is a freshwater crustacean. On first inspection it looks rather "lobster-like". It has a sharp snout, and its eyes are on movable stalks. The thin, but tough exoskeleton is dark brown in color - sometimes with a slightly red tint. The exact shade depends on what the bottom substrate of the habitat looks like.

In terms of appendages, the most noticeable ones are its chelipeds. These appendages are attached to the thorax and are also referred to as the first walking legs. However, these appendages have claws and are used for protection and catching food, not walking. Cambarus bartonii also has four other pairs of walking legs attached to the thorax. The abdominal appendages of Cambarus bartonii are called swimmerets or pleopods, and they are much smaller than walking legs and not suitable for swimming. The male swimmerets are modified to transfer sperm packets to the female during reproduction and have a spatulate shape. What looks like a fan on the end of the abdomen is really many broad flat appendages called uropods. All of these appendages are attached on the ventral side of Cambarus bartonii, and they are all biramous. In general, the abdomen is large and usually extended; it can however, be flexed under the cephalothorax. The first abdominal segment is usually smaller than those posterior to it.

Cambarus bartonii has an open circulatory system. It possesses a diamond-shaped heart which lies just anterior to the abdominal segments on the dorsal midline. The heart is surrounded by a thin pericardial sac. Just anterior to the heart lie the gonads. The testes are white, and the ovaries orange. Along the dorsal midline of the cephalothorax lie the cardiac stomach and the pyloric stomach. Just posterior and laterally to the stomachs lies a large digestive gland. The ventral nerve cord lies beneath the internal organs, and the brain lies between and beneath the eyestalks. (Russel-Hunter, 1979; Vodopich and Moore, 1999)

Reproduction

Mating occurs most commonly in the spring and may also occur during the summer. Mating usually takes place at night because the chances of male and female encountering each other is nine times greater at night.

Reproduction involves pairing and can occur in two ways. The first is the deposit of sperm into a seminal receptacle in the female. This occurs when a sperm from the male flows down the grooves of the first pleopods and into the female receptacle. Sperm exits the male crayfish at the base of the fifth pair of walking legs through a pore. Eggs are released at the base of the third pair of walking legs. The other form of reproduction involves the transfer of a spermatophore, in which case fertilization is internal.

Either way, the fertilized eggs are retained for maturation on the pleopods of the female. They hatch on the pleopods and stay attatched to the mother until shortly after their second molt. A female carrying eggs is said to be "in berry" because the mass of eggs look like a berry. Females are most commonly "in berry" during May and June. (Roberts, 1994; Vodopich and Moore, 1999)

Behavior

Cambarus bartonii walk slowly on the bottom of ponds, creeks or streams when searching for food. If threatened, they can shoot backwards to quickly escape danger. They accomplish this rapid backward motion by contracting powerful abdominal muscles. Cambarus bartonii use their chelipeds for protection and for finding food. Predators on C. bartonii include various bird and turtle species. Cambarus bartonii is most active at night because this is when it feeds. (Buchsbaum, et al., 1987)

Food Habits

Cambarus bartonii is a predator and a scavenger. It feeds on decaying organic remains but also catches small animals. Its main sources of food include snails, alga, insect larva, various types of worms, and tadpoles. It finds its food on the bottom of the water source it inhabits or in the soil near the water. (Banister and Campbell, 1985)

  • Animal Foods
  • amphibians
  • eggs
  • insects
  • mollusks
  • aquatic or marine worms
  • aquatic crustaceans
  • Plant Foods
  • algae

Economic Importance for Humans: Positive

Crayfish are a huge industry for many countries, especially France and the United States. Each year between 400,000 - 800,000 Kg are consumed (880,000 to 1,960,000 lbs). There are also 2.6 million pounds of crayfish reared in artificial impoundments each year. This creates many jobs for people in the fishing industry.

Crayfish are good to eat and provide a source of protein. They are now eaten throughout the United States and many countries around the world.

The crayfish may have medicinal benefits as well. In Kenya, a microscopic blood fluke. a schistome, is causing infection in many people. The schistome burrows through skin and moves to the bladder and other major organs, causing much damage. Scientists have found that the schistome larva hatch in freshwater snails. They have also found that the crayfish has an appetite for these freshwater snails. Putting many crayfish (although it does not say which exact species would be used; most species have an appetite for snails) in these lakes may reduce the snail population, and in turn reduce the number of infections.

Cambarus bartonii digs in the soil along streams, ponds, and rivers. It helps with agriculture because the digging causes the soil to become richer in nutrients. In many rice farms, crayfish are the second crop because farmers bring them in after the rice has been harvested to help the soil gain many nutrients. The farmers then harvest the crayfish when it is rice season again. This is not a species specific benefit, because there are many rice farms around the world.

Crayfish are also used to monitor the environmental condition of streams and rivers. Specifically, one can analyze them for the presence of particular pollutants in their tissues. ("Crayfish", 1998; Banister and Campbell, 1985)

Economic Importance for Humans: Negative

There are no known adverse effects of Cambarus bartonii on humans.

Conservation Status

This species is not known to be endangered.

Contributors

Stephanie Jenkinson (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.

detritus

particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).

ectothermic

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

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

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

nocturnal

active during the night

omnivore

an animal that mainly eats all kinds of things, including plants and animals

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

terrestrial

Living on the ground.

References

1998. Crayfish. World Book Encyclopedia. London: World Book Inc..

Banister, K., A. Campbell. 1985. Lobsters and Freshwater Crayfish. Pp. 236-239 in The Encyclopedia of Aquatic Life. New York: Equinox Ltd.

Buchsbaum, R., M. Buchsbaum, J. Pearse, V. Pearse. 1987. Animals Without Backbones. Chicago: The University of Chicago Press.

Green, J. 1967. Crustaceans. Pp. 172-175 in The Larousse Encyclopedia of Animal Life. New York: Mc Graw-Hill Book Company.

McMan, L. 1960. An Occurence of Chimney Construction by the Crayfish *Cambarus bartonii*. Ecology, 41: 383-385.

Roberts, T. 1994. Light, Eyestalk Chemical, and Certain Other Factors as Regulators of Community Activity for the Crayfish. Ecological Monographs, 14: p 376-378.

Russel-Hunter, W. 1979. A Life of Invertebrates. New York: McMillan Publishing Co Inc.

Vodopich, D., R. Moore. 1999. Biology Labratory Manual. Burr Ridge: W. H. Freeman and Company.

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