MARTINEZ, M.L.; CHAPMAN, L.J.; GRADY, J.M.; REES, B.B.; University of New Orleans, Louisiana; University of Florida, Gainesville; University of New Orleans, Louisiana; University of New Orleans, Louisiana: Interdemic Variation in Lactate Dehydrogenase in the African Cyprinid Barbus neumayeri

This study evaluated whether Barbus neumayeri from habitats of high and low oxygen concentration differ in their capacity for anaerobic carbohydrate metabolism. Fish were collected from Nguguta River (dissolved oxygen >6 mg/l) and Rwembaita Swamp (D.O. <2 mg/l) in the Kibale National Park, Uganda, and frozen immediately (wild) or held in the laboratory for 10-15 months (lab). Lactate dehydrogenase (LDH) activities and isozyme composition were measured in white skeletal muscle, heart, liver and brain. Body size was significantly related to LDH activity in white skeletal muscle. Liver and brain LDH activities differed significantly between collection sites, with fish from the low oxygen (Rwembaita Swamp) having higher activities. The LDH activities differed significantly between collection groups (wild vs. lab) in heart, liver and brain, an effect possibly related to differences in nutritional or reproductive status of these two groups. Gel electrophoresis of tissue extracts showed that LDH-A predominates in skeletal muscle, a mixture of LDH-A and LDH-B occur in heart and brain, and both isozymes plus and additional tissue-specific isozyme are found in liver. In heart, the amount of LDH-A was greater than LDH-B among wild fish, but this pattern was reversed in lab fish. Populations were polymorphic at the LDH-A and LDH-B loci, and the frequencies of LDH-B genotypes differed between Nguguta River and Rwembaita Swamp. These results demonstrate biochemical differences in Barbus neumayeri from habitats differing in oxygen availability, document changes due to laboratory maintenance, and support earlier evidence of genetic differentiation between these collection sites.