[Determination of some hematological aspects of Oncorhynchus mykiss (Salmonidae), in Cundinamarca, Columbia].

Thirty-five normal, adult specimens of the rainbow trout Oncorhynchus mykiss (Richardson, 1836) cultured in the Neusa Fishculture Station (73 degrees 38'28" W; 5 degrees 8'30" N) were studied to establish normal blood values; the hematopoietic tissues (pronefros, spleen and thymus), and other organs such as the stomach were also structurally studied. The rainbow trout collected in the second half of 1990 and the beginning of the first half of 1991 had 1,415,000 erythrocytes and 22,000 leukocytes per mm3 of blood. Their hemoglobin concentration was 6.99 g/100ml. They had three types of circulating leukocytes: lymphorytes 65%, polimorphonuclears 24% and monocytes 11%. The pronephros is the major hematopoietic organ in the rainbow trout. It produces mainly the polimorphonuclears; the spleen and the thymus are linfopoietics. The study of the hemocytometric values in the peripheral blood frotis and the structure of the hematopoietic organs of the rainbow trout is very useful, accessible and inexpensive. It produces data which yield information about physiological and pathological conditions.