title: The Effects of Acute Copper and Ammonia Challenges on Ammonia and Urea Excretion by the Blue Crab Callinectes sapidus.
abstract: Copper (Cu) is a persistent environmental contaminant that elicits several physiological disturbances in aquatic organisms, including a disruption in ammonia regulation. We hypothesized that exposure to Cu in a model crustacean (blue crab, Callinectes sapidus) acclimated to brackish water (2 ppt) would lead to hyperammonemia by stimulating an increase in ammonia production and/or by inhibiting ammonia excretion. We further hypothesized that urea production would represent an ammonia detoxification strategy in response to Cu. In a pilot experiment, exposure to 0, 100, and 200 µg/L Cu for 6 h caused significant concentration-dependent increases in ammonia excretion (Jamm). Based on these results, an acute 24-h 100 µg/L Cu exposure was conducted and this similarly caused an overall stimulation of Jammduring the 24-h period, indicative of an increase in ammonia production. Terminal haemolymph total ammonia content (Tamm) was unchanged, suggesting that while ammonia production was increased, there was no inhibition of the excretion mechanism. In support of our second hypothesis, urea excretion (Jurea) increased in response to Cu exposure; haemolymph [urea] was unaffected. This suggested that urea production also was increased. To further test the hypothesis that Jureaincreased to prevent hyperammonemia during Cu exposure, crabs were exposed to high environmental ammonia (HEA; 2.5 mmol/L NH4HCO3) for 12 h in a separate experiment. This led to a fourfold increase in haemolymph Tamm, whereas Jureaincreased only transiently and haemolymph [urea] was unchanged, indicating that urea production likely does not contribute to the attenuation of hyperammonemia in blue crabs. Overall, Cu exposure in blue crabs led to increased ammonia and urea production, which were both eliminated by excretion. These results may have important implications in aquaculture systems where crabs may be exposed to elevated Cu and/or ammonia.
authors.affiliation: Department of Biology, University of Ottawa, Gendron Hall, Ottawa, ON, K1N 6N5, Canada. azimmer@uottawa.ca.|Department of Biology, McMaster University, Hamilton, ON, L8S 4K1, Canada. azimmer@uottawa.ca.|Instituto de Ciências Biológicas, Universidade Federal do Rio Grande, Rio Grande, RS, 96203-900, Brazil. azimmer@uottawa.ca.
authors.forename: Alex M
authors.initials: AM
authors.lastname: Zimmer
authors.affiliation: Instituto de Ciências Biológicas, Universidade Federal do Rio Grande, Rio Grande, RS, 96203-900, Brazil.
authors.forename: Marianna Basso
authors.initials: MB
authors.lastname: Jorge
authors.affiliation: Department of Biology, McMaster University, Hamilton, ON, L8S 4K1, Canada.|Department of Zoology, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.
authors.forename: Chris M
authors.initials: CM
authors.lastname: Wood
authors.affiliation: Instituto de Ciências Biológicas, Universidade Federal do Rio Grande, Rio Grande, RS, 96203-900, Brazil.
authors.forename: Camila M G
authors.initials: CM
authors.lastname: Martins
authors.affiliation: Instituto de Ciências Biológicas, Universidade Federal do Rio Grande, Rio Grande, RS, 96203-900, Brazil.
authors.forename: Adalto
authors.initials: A
authors.lastname: Bianchini
mesh_terms: D000641:Ammonia / Q000633:toxicity*; D000818:Animals; D003386:Brachyura / Q000187:drug effects / Q000502:physiology*; D003300:Copper / Q000633:toxicity*; D005880:Gills / Q000187:drug effects / Q000378:metabolism; D014508:Urea / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; D000641:Ammonia; D003300:Copper; D014508:Urea