Humic acid and moderate hypoxia alter oxidative and physiological parameters in different tissues of silver catfish (Rhamdia quelen)

Abstract

Aquatic animals are naturally exposed simultaneously to environments with different concentrations of humic acid (HA) and seasonal or daily variations of dissolved oxygen (DO) levels. This study investigated the effects of simultaneous exposure to different HA and DO levels on plasma ion levels and some hematological and oxidative parameters in different tissues of silver catfish (Rhamdia quelen). The fish were exposed to 0, 2.5 or 5 mg L(-1) HA for 120 h. After this period, each group was divided into two groups: normoxia and hypoxia. Exposure to the different DO levels lasted 96 h, totaling 216 h of experimentation. At the end of the experimental period, blood sampling was performed, and the fish were euthanized prior to the excision of the gills and the brain to evaluate hematological and oxidative parameters. To verify the antioxidant capacity of HA, total phenolic compounds were measured. In general, all tissues of silver catfish exposed simultaneously to hypoxia and different HA concentrations showed a reduction in lipid peroxidation levels, as well as a modulation of the antioxidant system. These effects occurred in an HA concentration-dependent manner. Thus, HA is beneficial to silver catfish exposed to hypoxia. These beneficial effects can be attributed, most likely, to the action of the different HA constituents and functional groups, including phenolic compounds, which have antioxidant properties.

Effect of humic acid on survival, ionoregulation and hematology of the silver catfish, Rhamdia quelen (Siluriformes: Heptapteridae), exposed to different pHs

“…Inefficient gill ventilation triggers mechanisms such as splenic contraction in an attempted to absorb more oxygen, therefore elevating hematocrit and hemoglobin (SAMPAIO et al 2008). RIFFEL et al (2014) have similarly reported that the addition of HA to the water, though at low concentrations, induced hematocrit and hemoglobin rises in silver catfish at neutral pH.…”

“…MATHAN et al (2010) also observed higher plasma K + levels in the common carp, Cyprinus carpio, after exposure to acidic pH, and suggested that it could be due to a release of K + from the muscle cells as H + enters them. Another study assessing plasma ion levels in silver catfish exposed to Aldrich HA (0, 2.5 and 5 mg L -1 ) at pH ~ 7.0 observed a progressive increase in K + levels with increased HA concentrations, suggesting that HA could limit gill permeability (RIFFEL et al 2014). In this study HA did not influence K + levels at pH 7.0, while at the intermediate pH levels (4.0 and 4.2) its presence caused a marked decrease in ion levels.…”

“…According to some studies, the occurrence of various charged functional groups in the heterogeneous compounds of DOC may change fundamental properties of the gill epithelium, such as the transepithelial potential, thus altering membrane permeability and stimulating ion uptake (WOOD et al 2011). Humic acid also reduces respiratory stress in fish exposed to slightly acidic water, but increases it at more acidic waters (HOLLAND et al 2014) and decreases lipid peroxidation and modulates the antioxidant system (RIFFEL et al 2014). In opposition to the several findings regarding the effects of DOC on ionoregulatory disturbances, respiratory stress and antioxidant system, no evidence has been documented about its influence on the hematology of fish subjected to acidic pH.…”

Humic acid of commercial origin causes changes in gill morphology of silver catfish Rhamdia quelen exposed to acidic water

“…Additionally, Riffel et al. () reported Aldrich HA as beneficial for hypoxic silver catfish, since it reduced lipid peroxidation levels and modulated the antioxidant system.…”

“…Nonetheless, the likelihood of interspecific variations, as cited above, and the paucity of information regarding the effect of Aldrich HA in the course of an acidic challenge in silver catfish motivated the trials with the species. Additionally, Riffel et al (2014) reported Aldrich HA as beneficial for hypoxic silver catfish, since it reduced lipid peroxidation levels and modulated the antioxidant system.…”