title: Effects of salinity on short-term waterborne zinc uptake, accumulation and sub-lethal toxicity in the green shore crab (Carcinus maenas).
abstract: Waterborne zinc (Zn) is known to cause toxicity to freshwater animals primarily by disrupting calcium (Ca) homeostasis during acute exposure, but its effects in marine and estuarine animals are not well characterized. The present study investigated the effects of salinity on short-term Zn accumulation and sub-lethal toxicity in the euryhaline green shore crab, Carcinus maenas. The kinetic and pharmacological properties of short-term branchial Zn uptake were also examined. Green crabs (n=10) were exposed to control (no added Zn) and 50μM (3.25mgL(-1)) of waterborne Zn (∼25% of 96h LC50 in 100 seawater) for 96h at 3 different salinity regimes (100%, 60% and 20% seawater). Exposure to waterborne Zn increased tissue-specific Zn accumulation across different salinities. However, the maximum accumulation occurred in 20% seawater and no difference was recorded between 60% and 100% seawater. Gills appeared to be the primary site of Zn accumulation, since the accumulation was significantly higher in the gills relative to the hepatopancreas, haemolymph and muscle. Waterborne Zn exposure induced a slight increase in haemolymph osmolality and chloride levels irrespective of salinity. In contrast, Zn exposure elicited marked increases in both haemolymph and gill Ca levels, and these changes were more pronounced in 20% seawater relative to that in 60% or 100% seawater. An in vitro gill perfusion technique was used to examine the characteristics of short-term (1-4h) branchial Zn uptake over an exposure concentration range of 3-12μM (200-800μgL(-1)). The rate of short-term branchial Zn uptake did not change significantly after 2h, and no difference was recorded in the rate of uptake between the anterior (respiratory) and posterior (ion transporting) gills. The in vitro branchial Zn uptake occurred in a concentration-dependent manner across different salinities. However, the rate of uptake was consistently higher in 20% seawater relative to 60% or 100% seawater - similar to the trend observed with tissue Zn accumulation during in vivo exposure. The short-term branchial Zn uptake was found to be inhibited by lanthanum (a blocker of voltage-independent Ca channels), suggesting that branchial Zn uptake occurs via the Ca transporting pathways, at least in part. Overall, our findings indicate that acute exposure to waterborne Zn leads to the disruption of Zn and Ca homeostasis in green crab, and these effects are exacerbated at the lower salinity.
authors.affiliation: Department of Biology, University of Saskatchewan, Saskatoon, SK, Canada; Toxicology Centre, University of Saskatchewan, Saskatoon, SK, Canada; Bamfield Marine Sciences Centre, Bamfield, BC, Canada. Electronic address: som.niyogi@usask.ca.
authors.forename: Som
authors.initials: S
authors.lastname: Niyogi
authors.affiliation: Bamfield Marine Sciences Centre, Bamfield, BC, Canada; Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada; Department of Biology, McMaster University, Hamilton, ON, Canada.
authors.forename: Tamzin A
authors.initials: TA
authors.lastname: Blewett
authors.affiliation: Toxicology Centre, University of Saskatchewan, Saskatoon, SK, Canada.
authors.forename: Trevor
authors.initials: T
authors.lastname: Gallagher
authors.affiliation: Bamfield Marine Sciences Centre, Bamfield, BC, Canada; Department of Biological Sciences, University of Manitoba, Winnipeg, MB, Canada; Department of Zoology, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Sandra
authors.initials: S
authors.lastname: Fehsenfeld
authors.affiliation: Bamfield Marine Sciences Centre, Bamfield, BC, Canada; Department of Biology, McMaster University, Hamilton, ON, Canada; Department of Zoology, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Chris M
authors.initials: CM
authors.lastname: Wood
mesh_terms: D000818:Animals; D003386:Brachyura / Q000187:drug effects* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D005880:Gills / Q000187:drug effects / Q000378:metabolism; D006458:Hemolymph / Q000187:drug effects / Q000378:metabolism; D017136:Ion Transport / Q000187:drug effects; D008297:Male; D054712:Salinity; D012623:Seawater / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000378:metabolism / Q000633:toxicity*; D015032:Zinc / Q000378:metabolism / Q000633:toxicity*
chemical_list: D002712:Chlorides; D014874:Water Pollutants, Chemical; D015032:Zinc; D002118:Calcium
keywords: Branchial uptake; Calcium homeostasis; Green crab; Sub-lethal toxicity; Tissue accumulation; Waterborne zinc