title: Physiological effects of salinity on Delta Smelt, Hypomesus transpacificus.
abstract: Abiotic factors like salinity are relevant to survival of pelagic fishes of the San Francisco Bay Estuary. We tested the effects of 4 parts per thousand (ppt) salinity increases on Delta Smelt (DS) in a laboratory experiment simulating salinity increases that might occur around the low-salinity zone (LSZ) (<6 ppt). Adult DS, fed 2% body mass per day, starting at 0.5 ppt [freshwater (FW)], were exposed to weekly step-increases of 4 ppt to a maximum of 10 ppt saltwater (SW) over 19 days, and compared to FW controls. DS (n = 12/treatment per sampling) were sampled at 24, 72, and 96 h (1, 3, and 4 days) post-salinity increase for analyses of hematocrit, plasma osmolality, muscle water content, gill chloride cell (CC) Na(+)/K(+)-ATPase (NKA) and apoptosis after being weighed and measured (n = 3 tanks per treatment). No apparent increase in length or weight occurred nor did a difference in survival. Following step-increases in SW, hematocrit increased over time. Other fish responses generally showed a pattern; specifically plasma osmolality became elevated at 1 day and diminished over 4 days in SW. Percent muscle water content (%) did not show significant changes. CCs showed increased NKA, cell size and apoptosis over time in SW, indicating that CCs turnover in DS. The cell renewal process takes days, at least over 19 days. In summary, DS are affected by salinities of the LSZ and ≤10 ppt, though they employ physiological strategies to acclimate.
authors.affiliation: Department of Veterinary Medicine: Anatomy, Physiology, and Cell Biology, University of California, VM3B, 1089 Veterinary Medicine Drive, Davis, CA, 95616, USA. bdkammerer@ucdavis.edu.
authors.forename: Brittany D
authors.initials: BD
authors.lastname: Kammerer
authors.affiliation: Department of Biological and Agricultural Engineering, University of California, 11 One Shields Ave., Davis, CA, 95616, USA.
authors.forename: Tien-Chieh
authors.initials: TC
authors.lastname: Hung
authors.affiliation: California Department of Fish and Wildlife, Bay-Delta Region 3, 2109 Arch-Airport Rd., Suite 100, Stockton, CA, 95206, USA.
authors.forename: Randall D
authors.initials: RD
authors.lastname: Baxter
authors.affiliation: Department of Veterinary Medicine: Anatomy, Physiology, and Cell Biology, University of California, VM3B, 1089 Veterinary Medicine Drive, Davis, CA, 95616, USA.
authors.forename: Swee J
authors.initials: SJ
authors.lastname: Teh
mesh_terms: D000064:Acclimatization; D000818:Animals; D017209:Apoptosis; D049628:Body Size; D053148:Caspase 3 / Q000378:metabolism; D053179:Caspase 7 / Q000378:metabolism; D005880:Gills / Q000378:metabolism; D006400:Hematocrit; D009132:Muscles / Q000378:metabolism; D036441:Osmeriformes / Q000033:anatomy & histology / Q000378:metabolism / Q000502:physiology*; D054712:Salinity; D028021:Sodium-Potassium-Chloride Symporters / Q000378:metabolism; D014867:Water / Q000378:metabolism
chemical_list: D028021:Sodium-Potassium-Chloride Symporters; D014867:Water; D053148:Caspase 3; D053179:Caspase 7
keywords: Apoptosis; Chloride cells; Delta Smelt; Fluorescent confocal microscopy; Low-salinity zone; Na+/K+-ATPase; Physiology; Salinity