Freshwater crab Freshwater crab There are around 1,300 species of freshwater crabs, distributed throughout the tropics and subtropics, divided among eight families. They show direct development and maternal care of a small number of offspring, in contrast to marine crabs which release thousands of planktonic larvae. This limits the dispersal abilities of freshwater crabs, so they tend to be endemic to small areas. As a result, a large proportion are threatened with extinction. There are more than 1,300 described species of freshwater crabs, out of a total of 6,700 species of crabs across all environments. The total number of species of freshwater
Food chain exist in the absence of sunlight. Chemosynthetic bacteria and archaea use hydrogen sulfide and methane from hydrothermal vents and cold seeps as an energy source (just as plants use sunlight) to produce carbohydrates; they form the base of the food chain. Consumers are organisms that eat other organisms. All organisms in a food chain, except the first organism, are consumers. In a food chain, there is also reliable energy transfer through each stage. However, all the energy at one stage of the chain is not absorbed by the organism at the next stage. The amount of energy from one stage