Crayfish

. Establishing a breeding population from introduced captive-bred animals. Crayfish, crawfish, or crawdads are freshwater crustaceans belonging to the infraorder Astacidea, which also contains lobsters. Taxonomically, they are members of the superfamilies Astacoidea and Parastacoidea. They breathe through feather-like gills. Some species are found in brooks and streams, where fresh water is running, while others thrive in swamps, ditches, and paddy fields. Most crayfish cannot tolerate polluted water, although some species, such as Procambarus clarkii, are hardier. Crayfish feed on animals and plants, either living or decomposing, and detritus. The term "crayfish" is applied to saltwater species in some countries.

. Establishing a breeding population from introduced captive-bred animals. Crayfish, crawfish, or crawdads are freshwater crustaceans belonging to the infraorder Astacidea, which also contains lobsters. Taxonomically, they are members of the superfamilies Astacoidea and Parastacoidea. They breathe through feather-like gills. Some species are found in brooks and streams, where fresh water is running, while others thrive in swamps, ditches, and paddy fields. Most crayfish cannot tolerate polluted water, although some species, such as Procambarus clarkii, are hardier. Crayfish feed on animals and plants, either living or decomposing, and detritus. The term "crayfish" is applied to saltwater species in some countries. ==Diet== Crayfish are opportunistic omnivorous scavengers, with the ability to filter and process mud. In aquaculture ponds using isotope analysis they were shown to build body tissue selectively from the animal protein portion of pelleted food and not the other components of the pellet. They have the potential to eat most foods, even nutrient poor material such as grass, leaves, and paper, but can be highly selective and need variety to balance their diet. The personalities of the individual crayfish can be a key determinant in the food preference behaviour in aquaria. Crayfish all over the world can be seen in an ecological role of benthic dwellers, so this is where most of their food is obtained – at the sediment/water interface in ponds, lakes, swamps, or burrows. When the gut contents are analysed, most of the contents is mud: fine particulate organic matter (FPOM) and mixed particles of lignin and cellulose (roots, leaves, bark, wood). Some animal material can also be identified, but this only contributes a small portion of the diet by volume. They feed on submerged vegetable material at times, but their ability to catch large living animal material is restricted. They can feed on interstitial organisms if they can be grasped in the small feeding claws. They can be lured into traps with an array of baits from dog biscuits, fish heads, meat, etc., all of which reinforces the fact that they are generalist feeders. On a day-to-day basis, they consume what they can acquire in their immediate environment in limited space and time available – detritus. At a microbial level, the FPOM has a high surface area of organic particles and consists of a plethora of substrate and bacteria, fungi, micro-algae, meiofauna, partially decomposed organic material and mucus. This mucus or "slime" is a biofilm and can be felt on the surface of leaves and sticks. Also crayfish have been shown to be coprophagic – eating their own faeces, they also eat their own exuviae (moulted carapace) and each other. They have even been observed leaving the water to graze. Detritus or mud is a mixture of dead plankton (plant and animal), organic wastes from the water column, and debris derived from the aquatic and terrestrial environments. Mostly detritus is in the end phase of decomposition and is recognised as black organic mud. The crayfish usually ingest the material in only a few minutes, as distinct from grazing for many hours. The material is mixed with digestive fluids and sorted by size. The finer particles follow a slower and more exacting route through to the hindgut, compared to the coarser material. The coarser material is eliminated first and often reappears in approximately 10 to 12 hours, whereas the finer material is usually eliminated from 16 to 26 hours after ingestion. All waste products coming out through the hindgut are wrapped in a peritrophic membrane, so they look like a tube. Such an investment in the wrapping of the microbial free faeces in a protein rich membrane is most likely the reason they are coprophagic. Such feeding behaviour based on selection, ingestion, and extreme processing ensures periodic feeding, as distinct from continuous grazing. They tend to eat to satiation and then take many hours to process the material, leaving minimal chance of having more room to ingest other items. Crayfish usually have limited home range and so they rest, digest, and eliminate their waste, most commonly in the same location each day. Feeding exposes the crayfish to risk of predation, and so feeding behaviour is often rapid and synchronised with feeding processes that reduce such risks – eat, hide, process and eliminate. Knowledge of the diet of these creatures was considered too complex since the first book ever written in the field of zoology, The Crayfish by T.H. Huxley (1879), where they were described as "detritivores". This is why most researchers have not attempted to understand the diet of freshwater crayfish. The most complex study which matched the structure and function of the whole digestive tract with ingested material was performed in the 1990s by Brett O'Brien on marron, the least aggressive of the larger freshwater crayfish with aquaculture potential, similar to redclaw and yabbies. America's Crayfish: Crawling In Troubled Waters Louisiana Crawfish Research and Promotion Board Species of Ontario Crayfish

Text derived from https://en.wikipedia.org/w/index.php?oldid=1378671415 under CC BY-SA 4.0; modifications have been made.