SciELO - Scientific Electronic Library Online

 
vol.64 issue1Phytoplankton nyctemeral variation at a tropical river estuary (Itamaracá - Pernambuco - Brazil)Spatial distribution of chromium and lead in the benthic environment of coastal areas of the Río de la Plata estuary (Montevideo, Uruguai) author indexsubject indexarticles search
Home Pagealphabetic serial listing  

Brazilian Journal of Biology

Print version ISSN 1519-6984

Abstract

MORAES, G.; POLEZ, V. L. P.  and  IWAMA, G. K.. Biochemical responses of two Erythrinidae fish to environmental ammonia. Braz. J. Biol. [online]. 2004, vol.64, n.1, pp. 95-102. ISSN 1519-6984.  http://dx.doi.org/10.1590/S1519-69842004000100011.

The non-ionized form of ammonia is very toxic to many aquatic species. It is especially important in several aspects of fish biology. A large range of organismal strategies for coping with environmental stressors is usually observed in living organisms. Among those, the responses for managing chemical stressors are well studied. The present work compares biochemical responses of two evolutionarily close species, Hoplias malabaricus and Hoplerythrinus unitaeniatus, exposed to environmental ammonia. Adult fish were submitted to 1.0 mg/L of ammonium chloride for 24 hours, and plasma ammonia and urea levels were determined. The activities of OUC enzymes OCT and ARG, and the accessory enzyme GS, were quantified in liver extract and are expressed below in mmol/min/mg of wet tissue. Increases in OUC enzymes (GS from 1.14 to 2.43, OCT from 0.81 to 1.72, and ARG from 3.15 to 4.23), plasma ammonia (from 0.95 to 1.42 mmol/L), and plasma urea (from 0.82 to 1.53 mmol/L) were observed (p < 0.05) in H. malabaricus exposed to 1 mg/L of ammonia chloride. The GS in H. unitaeniatus increased from 1.43 to 1.84, however the OCT, ARG, and plasma urea from H. unitaeniatus did not change. These data indicate that each species responds differently to the same environmental stressor.

Keywords : Hoplias malabaricus; Hoplerythrinus unitaeniatus; ammonia; biochemical adaptation; fish; Ornithine-urea cycle enzymes.

        · abstract in Portuguese     · text in English     · pdf in English