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
Microscopic colitis of 7.1 per 100,000 person-years and 12.6 per 100,000 person-years for collagenous colitis for lymphocytic colitis, respectively. Prevalence has been estimated as 103 cases per 100,000 persons. People who develop microscopic colitis are characteristically, though not exclusively, middle-aged females. The average age of diagnosis is 65 but 25% of cases are diagnosed below the age of 45. The condition of microscopic colitis was first described as such in 1982. Lymphocytic colitis was described in 1989. Collagenous colitis was recognised earlier, in 1976. Microscopic colitis Microscopic colitis refers to two related medical conditions which cause diarrhea: collagenous colitis and lymphocytic colitis.