The Effects of Salinity on Acute Toxicity of Zinc to Two Euryhaline Species of Fish, Fundulus heteroclitus and Kryptolebias marmoratus.

*Department of Biology, Valdosta State University, 1500 North Patterson St, Valdosta, GA 31698, USA; University of North Florida, 1 UNF Dr., Jacksonville, FL 32224, USA.
Integrative and Comparative Biology (Impact Factor: 3.02). 04/2012; DOI: 10.1093/icb/ics045
Source: PubMed

ABSTRACT It is well known that the toxicity of zinc (Zn) varies with water chemistry and that its bioavailability is controlled by ligand interactions and competing ions. Zn toxicity in freshwaters with varying water chemistry has been well characterized; however, far less attention has been paid to the toxicity of Zn in estuarine and marine systems. We performed experiments using two euryhaline species of killifish, Fundulus heteroclitus and Kryptolebias marmoratus, to investigate the effects of changing salinity on acute toxicity of Zn. Larvae (7- to 8-days old) of each species were exposed to various concentrations of Zn for 96 h at salinities ranging from 0 to 36 ppt and survival was monitored. As salinity increased, Zn toxicity decreased in both fish species, and at salinities above 10 ppt, K. marmoratus larvae were generally more sensitive to Zn than were those of F. heteroclitus. The protection of salinity against Zn toxicity in F. heteroclitus was further investigated to determine the role of Ca(2+). Increased Ca(2+) in freshwater protected against Zn toxicity to the same extent as did saline waters with an equal Ca(2+) concentration up to ∼200 mg/L Ca for F. heteroclitus and ∼400 mg/L Ca for K. marmoratus. These results suggest that these two species may have differing Ca(2+) requirements and/or rates of Ca(2+) uptake in water of intermediate to full-strength salinity (∼200-400 mg/L Ca(2+)) and thus differ in their sensitivity to Zn. The overall goal of this study was to better understand Zn toxicity in waters of different salinity and to generate data on acute Zn toxicity from multiple species over a range of salinities, ultimately for use in development of estuarine and marine biotic ligand models.

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    ABSTRACT: The mangrove rivulus, Kryptolebias marmoratus, (hereafter, rivulus) is one of the only two vertebrates known to self-fertilize, with the other being a recently named close relative, Kryptolebias hermaphroditus (Tatarenkov et al. 2012). Rivulus is also the first fish species found to have environmental sex determination, whereby lower temperatures inhibit ovarian development, thus providing one potential route that avoids inbreeding depression (Harrington 1967; Conover 2004). Wild rivulus exist as androdioecious populations in which both hermaphrodites and, although relatively rare, males are found (Taylor 2000). In the laboratory, individual adult rivulus can produce isogenic embryos. Under as yet unknown environmental conditions, males develop and outcrossing between the hermaphrodites and males occurs (Taylor 2000; Mackiewicz et al. 2006a, 2006b). It is intriguing to consider the behavioral, neurological, and endocrinological control necessary to accommodate this reproductive strategy (Sakakura et al. 2006; Orlando et al. 2006; Earley et al. 2008). In addition to environmental sex determination and androdioecious reproduction, rivulus is also known to emerge from its aquatic surroundings and assume a transitory, terrestrial existence (Ong et al. 2007; Taylor et al. 2008; Cooper et al. 2012). Rivulus is an emerging and potentially powerful model for integrative and comparative biological research and, in part, this emergence has been catalyzed by this first symposium on its biology. The well-attended symposium comprised 11 speakers, which included four women and seven men, with academic ranks ranging from postdoctoral fellow to full professor, who came from four countries. This symposium will help drive future research within this taxon and will facilitate collaborations among researchers. It has already facilitated networking between heads of laboratories and current and potential future postdoctoral fellows and students. The organizing committee looks forward to the next rivulus symposium with great anticipation.
    Integrative and Comparative Biology 07/2012; · 3.02 Impact Factor
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    ABSTRACT: Exposure of adult Fundulus heteroclitus for 96 h to an environmentally relevant Zn concentration (500 μg L- 1) at different salinities (0, 3.5, 10.5, and 35 ppt) revealed the following sublethal effects of waterborne Zn: (i) Plasma [Zn] doubled after exposure at 0 ppt, a response which was attenuated at 3.5 and 10.5 ppt, and eliminated at 35 ppt. Tissue [Zn] also increased by 40-80% in gill, liver, intestine, and carcass at 0 ppt, but not at higher salinities. (ii) Both branchial and intestinal Ca2 + ATPase activities decreased in response to Zn at 0 ppt and were elevated at 35 ppt (10-20% changes), with no effects at intermediate salinities. Plasma [Ca] decreased by 50% at 0 ppt, by 30% at 3.5 ppt, did not change at 10.5 ppt, and increased by 20% at 35 ppt. Gill [Ca] decreased by 35% at 0 ppt and increased by about 30% at all higher salinities; these effects of Zn did not occur in other tissues. (iii) Branchial Na+,K+ ATPase activity decreased by 50% at 0 ppt, did not change at 3.5 ppt, and increased by 30% and 90% at 10.5 and 35 ppt respectively in response to Zn. Intestinal Na+,K+ ATPase activity was reduced by 30% at 0 ppt, with no effects at higher salinities. (iv) Plasma [Na] decreased by 30% at 0 ppt in Zn-exposed fish, with no changes at higher salinities. Zn exposure also disturbed the homeostasis of tissue cations (Na+, K+, Ca++, Mg++) in a tissue-specific (gills, intestine, liver, carcass) and salinity-dependent manner. (v) Drinking rate was not significantly altered by Zn exposure, but increased with salinity. In toxicity tests, acute Zn lethality (96-h LC50) increased in a close to linear fashion from 9.8 mg L- 1 at 0 ppt to 75.0 mg L- 1 at 35 ppt. We conclude that sublethal Zn exposure causes pathological changes in both Ca++ and Na+ homeostasis, and that increasing salinity exerts marked protective effects against both sublethal and lethal Zn toxicity.
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    PLoS ONE 01/2014; 9(2):e88723. · 3.53 Impact Factor


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