Physiological impacts and bioaccumulation of dietary Cu and Cd in a model teleost: The Amazonian tambaqui (Colossoma macropomum)

Abstract

Increasing anthropogenic activities in the Amazon have led to elevated metals in the aquatic environment. Since fish are the main source of animal protein for the Amazonian population, understanding metal bioaccumulation patterns and physiological impacts is of critical importance. Juvenile tambaqui, a local model species, were exposed to chronic dietary Cu (essential, 500 μg Cu/g food) and Cd (non-essential, 500 μg Cd/g food). Fish were sampled at 10-14, 18-20 and 33-36 days of exposure and the following parameters were analyzed: growth, voluntary food consumption, conversion efficiency, tissue-specific metal bioaccumulation, ammonia and urea-N excretion, O consumption, P, hypoxia tolerance, nitrogen quotient, major blood plasma ions and metabolites, gill and gut enzyme activities, and in vitro gut fluid transport. The results indicate no ionoregulatory impacts of either of the metal-contaminated diets at gill, gut, or plasma levels, and no differences in plasma cortisol or lactate. The Cd diet appeared to have suppressed feeding, though overall tank growth was not affected. Bioaccumulation of both metals was observed. Distinct tissue-specific and time-specific patterns were seen. Metal burdens in the edible white muscle remained low. Overall, physiological impacts of the Cu diet were minimal. However dietary Cd increased hypoxia tolerance, as evidenced by decreased P, increased time to loss of equilibrium, a lack of plasma glucose elevation, decreased plasma ethanol, and decreased NQ during hypoxia. Blood O transport characteristics (P, Bohr coefficient, hemoglobin, hematocrit) were unaffected, suggesting that tissue level changes in metabolism accounted for the greater hypoxia tolerance in tambaqui fed with a Cd-contaminated diet.

The fallacy of thePcrit – are there more useful alternatives?

“…(A) Hyperbolic relationshipse.g. sturgeon (Nonnotte et al, 1993), epaulette shark (Routley et al, 2002;Speers-Roesch et al, 2012), grass shrimp (Cochran and Burnett, 1996), catfish (Zhang et al, 2010), tambaqui (Giacomin et al, 2018), goldfish . (B) As ambient P O2 declines, Ṁ O2 is initially close to stable, then increases before it eventually declinese.g.…”

The physiology of fish in acidic waters rich in dissolved organic carbon, with specific reference to the Amazon basin: Ionoregulation, acid–base regulation, ammonia excretion, and metal toxicity

“…DOC may have similar effects on the binding properties of the gill. High levels of dietary Cu also had negligible effects on the physiology of the tambaqui (Giacomin et al, 2018), again indicating that this species is unusually tolerant to Cu.…”

“…Acclimation to added Ca 2+ or added foreign DOC before Cd exposure was effective in decreasing Cd accumulation at the gills, even when these agents were no longer present, suggesting persistent protective changes in gill properties, as similarly seen with Cu exposure (Matsuo et al, 2005; Figure 4). In contrast to dietary Cu, dietary Cd, at the same level as used for Cu (500 μg Cd g −1 ), resulted in much greater internal accumulation, and marked effects on the internal metabolic physiology of tambaqui, again indicating its greater potency in this species (Giacomin et al, 2018).…”