Physiological basis for large differences in resistance to nitric among freshwater and freshwater-acclimated euryhaline fishes

Joseph R. Tomasso, Martin Grosell

Research output: Contribution to journalArticlepeer-review

52 Scopus citations


Uptake of environmental NO2- by most freshwater fishes occurs at the gills where NO2- is actively transported into the blood by the Cl- uptake pathway. Some freshwater fishes do not concentrate NO2- in their plasma, regardless of environmental NO2- exposure and exhibit a high degree of resistance to NO2-. Recent studies indicate that freshwater-adapted killifish (Fundulidae: Fundulus heteroclitus) and European eel (Anguillidae: Anguilla anguilla) have no or minimal Cl- uptake activity at the gills relative to most freshwater fishes; rather, Cl - requirements are met in other ways (probably dietary). We hypothesized that different rates of Cl- uptake by the gill may explain the observed differences in NO2- uptake and consequent toxicity among freshwater fishes. Cl- influx rates of channel catfish (lctaluridae: lctalurus punctatus), a species that concentrates NO2- in the plasma and is sensitive to NO2 -, and bluegill (Centrarchidae: Lepomis macrochirus), a species that does not concentrate NO2- in the plasma and is resistant to NO2-, were determined over a range of environmental Cl- concentrations. Channel catfish actively transported chloride into the plasma (Km = 155.6 ± 101.2 μmol/L Cl-; Jmax = 414.9 ± 51.4 nmol/g/h; ± SEM). In contrast, bluegill exhibited no observable Cl- uptake. We placed our results and previously reported results in a phylogenetic context and concluded that differences in Cl- uptake mechanisms among groups of freshwater fishes may explain, in large part, the wide range of sensitivity to environmental NO2-. NO2- uptake determinations may also prove to be an easy screening method when studying the phylogenetic distribution and nature of Cl- uptake mechanisms in the gills of fishes.

Original languageEnglish (US)
Pages (from-to)98-102
Number of pages5
JournalEnvironmental Science and Technology
Issue number1
StatePublished - Jan 1 2005

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry


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