Interdemic variation in haematocrit and lactate dehydrogenase in the African cyprinid Barbus neumayeri

Authors

  • M. L. Martinez,

    1. Department of Biological Sciences, University of New Orleans, New Orleans, LA 70 148, U.S.A.,
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    • Present address: Department of Biology, Laurentian University, Sudbury, Ontario P3E 2C6, Canada.

  • L. J. Chapman,

    1. Department of Zoology, University of Florida, Gainesville, FL 32 611, U.S.A. and
    2. Wildlife Conservation Society, 2300 Southern Boulevard, Bronx, NY, 10 460, U.S.A.
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  • J. M. Grady,

    1. Department of Biological Sciences, University of New Orleans, New Orleans, LA 70 148, U.S.A.,
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  • B. B. Rees

    Corresponding author
    1. Department of Biological Sciences, University of New Orleans, New Orleans, LA 70 148, U.S.A.,
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¶Tel.: +1 504 280 6729; fax: +1 504 280 6121; email: brees@uno.edu

Abstract

This study evaluated whether the African cyprinid Barbus neumayeri from Rwembaita Swamp (low-oxygen) and Njuguta River (high-oxygen) in the Kibale National Park, Uganda differed in traits related to aerobic and anaerobic metabolic potential. Haematocrit was measured as an index of blood oxygen-carrying capacity, and tissue activities and isozyme composition of lactate dehydrogenase (LDH) were measured as indices of tissue anaerobic capacity. To address whether site-dependent differences were acute responses v. longer-term adjustments to environmental conditions, these variables were measured in fish sampled shortly after collection and after laboratory maintenance under well-aerated conditions. In fish sampled in the field, those from the low-oxygen site had significantly higher haematocrit, but this difference disappeared after long-term laboratory maintenance. In contrast, fish from the low-oxygen site had higher liver LDH activities than fish from the high-oxygen site, and this difference persisted during laboratory maintenance. Polymorphism was detected at both the LDH-A and LDH-B loci, and genotype frequencies for LDH-B differed significantly between collection sites. These results demonstrate physiological, biochemical and genetic differences in B. neumayeri from habitats differing in dissolved oxygen availability and suggest both acute and long-term responses to local environmental conditions.

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