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

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. # 2004 The Fisheries Society of the British Isles

Population variation in hypoxic responses of the cichlid Pseudocrenilabrus multicolor victoriae

“…The observation that haematocrit was higher, regardless of acclimation treatment, in P. m. victoriae from Lwamunda Swamp (hypoxic site) than from Lake Kayanja (normoxic site) agrees with results found in Barbus neumayeri Fischer, 1884, a fish endemic from Africa, where fish from a hypoxic environment showed higher haematocrit levels than fish from a normoxic environment, even after normoxic maintenance (Martínez et al 2004). In the case of P. m. victoriae, the present study demonstrates that this population difference is maintained in F 1 offspring reared under common garden conditions.…”

“…Immediately prior to enzyme assays, supernatants were diluted in homogenization buffer to give an overall dilution of 100-fold relative to the starting tissue mass, except for the liver homogenates, which were used without further dilution. Assays of LDH activity were done as previously described (Martínez et al 2004), and reagents were purchased from either Sigma Chemical Co. (St. Louis, Missouri, USA) or Roche Diagnostics Corporation (Indianapolis, Indiana, USA).…”

“…One exception is the fish community of the Lake Victoria basin (Africa), where a number of studies have demonstrated population-level differences in respiratory morphology, behaviour, and physiology of several species of non-airbreathing fishes (Chapman and Liem 1995;Chapman et al 2000Chapman et al , 2002Chapman and Hulen 2001;Martínez et al 2004). Among these is the dwarf Victoria mouth-brooder (Pseudocrenilabrus multicolor victoriae Seegers, 1990), an endemic haplochromine cichlid that is widespread in the Nile River basin (Schierwater and Mrowka 1987).…”

Hypoxia drives plastic divergence in cichlid body shape

“…These adaptations can be physiological (e.g. anaerobic respiration, higher haematocrit; Cooper et al 2002;Martínez et al 2004Martínez et al , 2009, behavioral (e.g. increased use of aquatic surface respiration; Chapman and Liem 1995;Timmerman and Chapman 2004), or morphological (e.g.…”

Brood protection at a cost: mouth brooding under hypoxia in an African cichlid

“…However, long-term acclimation to normoxia may have reduced levels of variation among populations in hypoxia tolerance. In the African cyprinid Barbus neumayeri, Martinez et al (2004) found that fish collected from a low-oxygen site had significantly higher hematocrit and liver LDH activities than conspecifics from a nearby well-oxygenated site; however, the difference in hematocrit disappeared after long-term maintenance under normoxic conditions. Future studies exploring variation in ASR behavior in fish acclimated for various periods to hypoxia may be important in understanding population effects on ASR behavior.…”