title: Effects of sodium chloride exposure on ion regulation in larvae (glochidia) of the freshwater mussel Lampsilis fasciola.
abstract: The salinization of freshwater can have negative effects on ecosystem health, with heightened effects in salt-sensitive biota such as glochidia, the larvae of freshwater mussels. However, the toxicological mechanism underlying this sensitivity is unknown. Therefore, Lampsilis fasciola glochidia were exposed to NaCl (nominally 0.25 and 1.0 g/L) prepared in reconstituted moderately-hard water (control), as well as to a dilution of that water (1:4) with ultrapure reference water (diluted control). Unidirectional Na(+) influx (measured with (22)Na) was evaluated after 1, 3 and 48 h of exposure. In addition, unidirectional Cl(-) influx (measured with (36)Cl), whole-body ion (Cl(-) and Na(+)) concentrations, and glochidia viability (measured as the ability to close valves) were assessed after 48 h of exposure. Significantly reduced glochidia viability (56%) was observed after exposure to 1.0 g/L NaCl. Na(+) influx was significantly higher in glochidia exposed to both 0.25 and 1.0 g/L NaCl for 1h than in those kept under control conditions. After 3 and 48 h of exposure, differences in Na(+) influx rate between salt-exposed and control glochidia were generally reduced, indicating that larvae may be able to, at least temporarily, recover their ability to regulate Na(+) influx when exposed to elevated NaCl concentration. Compared to the moderately-hard water control, whole-body Na(+) and Cl(-) concentrations were relatively unchanged in glochidia exposed to 0.25 g/L NaCl, but were significantly elevated in glochidia exposed to 1.0 g/L NaCl and the diluted control. While Na(+) influx rate had recovered to the control level after 48 h of exposure to 1.0 g/L NaCl, Cl(-) influx rate remained elevated, being ~7-fold higher than the Na(+) influx rate. These findings suggest that the loss of viability observed when glochidia were exposed to a high NaCl concentration (1.0 g/L) could be caused by ionoregulatory disturbances mainly associated with an elevated Cl(-) influx.
authors.affiliation: Instituto de Ciências Biológicas, Universidade Federal do Rio Grande-FURG, Av. Itália, km 8, 96201-900 Rio Grande, RS, Brazil. Electronic address: nogueiralygia@gmail.com.
authors.forename: Lygia S
authors.initials: LS
authors.lastname: Nogueira
authors.affiliation: Instituto de Ciências Biológicas, Universidade Federal do Rio Grande-FURG, Av. Itália, km 8, 96201-900 Rio Grande, RS, Brazil.
authors.forename: Adalto
authors.initials: A
authors.lastname: Bianchini
authors.affiliation: Department of Biology, McMaster University, Hamilton, ON, Canada L8S 4K1; Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4.
authors.forename: Chris M
authors.initials: CM
authors.lastname: Wood
authors.affiliation: Departamento de Química, Universidade Federal de Santa Maria (UFSM), Av. Roraima 1000, Santa Maria 97105-900, RS, Brazil.
authors.forename: Vania L
authors.initials: VL
authors.lastname: Loro
authors.affiliation: Department of Biology, McMaster University, Hamilton, ON, Canada L8S 4K1.
authors.forename: Sarah
authors.initials: S
authors.lastname: Higgins
authors.affiliation: Aquatic Contaminants Research Division, Water and Science Technology Directorate, Environment Canada, Burlington, ON, Canada L7R-4A6.
authors.forename: Patricia L
authors.initials: PL
authors.lastname: Gillis
mesh_terms: D000818:Animals; D002170:Canada; D002713:Chlorine / Q000378:metabolism*; D004784:Environmental Monitoring; D005618:Fresh Water / Q000737:chemistry*; D007477:Ions; D007814:Larva / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D054712:Salinity; D012621:Seasons; D012964:Sodium / Q000378:metabolism*; D012965:Sodium Chloride / Q000032:analysis / Q000633:toxicity*; D018675:Toxicity Tests; D049876:Unionidae / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*
chemical_list: D007477:Ions; D014874:Water Pollutants, Chemical; D012965:Sodium Chloride; D002713:Chlorine; D012964:Sodium
keywords: Chloride influx rate; Fresh water salinization; Freshwater mussels; Ion regulation; Sodium chloride toxicity; Sodium influx rate