Dennis C. Haney

Physiological and hematological changes in chum salmon artificially infected with erythrocytic necrosis virus

Abstract Chum salmon Oncorhynchus keta were injected with erythrocytic necrosis virus (ENV) to study the physiological and hematological consequences of ENV infection. Infected and control fish were held in pathogen-free seawater and sampled for 5 weeks. Physiological tests included measures of plasma cortisol, glucose, protein, and osmolality; blood lactic acid; and liver glycogen. In general, ENV-infected fish had lower plasma glucose and blood lactic acid, and higher liver glycogen concentrations than did control fish. Hematological tests included red and white blood cell (RBC and WBC) counts, hematocrit, measurement of blood hemoglobin concentration, and a determination of erythrocyte fragility. Infected fish had lower RBC counts, hematocrits, and hemoglobin concentrations; higher WBC counts; and less fragile erythrocytes than did control fish. The hematology data indicated that erythrocytes of infected fish had higher mean corpuscular volume, depressed mean corpuscular hemoglobin concentration, and s...

Influence of Environmental Salinity on Routine Metabolic Rate and Critical Oxygen Tension of Cyprinodon variegatus

We examined the influence of a wide range of environmental salinities on routine metabolic rate and critical oxygen tension in Cyprinodon variegatus, a common coastal resident of the western Atlantic Ocean and Gulf of Mexico. C. variegatus lives in ambient salinities ranging from freshwater to 142%, with fish used in this study obtained from a Gulf of Mexico salt marsh near Cedar Key, Florida. In a steady state experiment, routine metabolic rate and critical oxygen tension were determined at salinities ranging from 0% to 100%. Measures of routine metabolic rate and critical oxygen tension were unaffected by changes in salinity between 0% and 40%. However, routine metabolic rate declined and critical oxygen tension increased progressively at salinities above 40%. The reduction in routine metabolic rate and rise in critical oxygen tension correlates with a reduced ability of C. variegatus to osmoregu‐late effectively at high salinities. The variations in routine metabolic rate and critical oxygen tension at high salinities suggest that C. variegatus responds to high salinities by reducing energy expenditures, effectively increasing the time that individuals can tolerate hypersaline conditions.

Comparisons of Salinity Tolerances and Osmotic Regulatory Capabilities in Populations of Sailfin Molly (Poecilia latipinna) from Brackish and Fresh Waters

Sailfin mollies, Poecilia latipinna, inhabit both fresh and brackish waters throughout their native range. In laboratory analyses, following extensive acclimation, individuals taken from freshwater populations tolerated a range of ambient salinities from fresh water through 70%o (parts per thousand), whereas individuals from brackish water tolerated salinities ranging from fresh water through 80%0o. Plasma osmotic concentrations of the two groups were not significantly different at common ambient salinities over the range from fresh water through 75%0o. Isolation in nature of populations in fresh and brackish waters has not greatly altered their physiological capabilities with respect to ambient salinity.

Plasma Osmotic Regulation and Routine Metabolism in the Eustis Pupfish, Cyprinodon variegatus hubbsi (Teleostei: Cyprinodontidae)

We assessed the influence of salinity on plasma osmotic regulation and routine metabolism in the freshwater Eustis pupfish Cyprinodon variegatus hubbsi and compared these results to published data for the widely distributed, euryhaline sheepshead minnow C. v. variegatus. The Eustis pupfish was able to tolerate salinities twice that of normal seawater. Plasma osmotic concentration increased with increasing salinity. In freshwater, Eustis pupfish maintained plasma osmotic concentrations lower than sheepshead minnow. However, this pattern reversed with increasing salinity. Routine metabolism did not differ between the Eustis pupfish and sheepshead minnow when the effect of body mass was statistically removed. The Eustis pupfish, although long isolated in fresh waters, has retained the physiological plasticity generally characteristic of the cyprinodontoids.

Adaptations in salt marsh teleosts to life in waters of varying salinity

Abstract Salt marsh environments are stressful, partially because of regular or unpredictable variations in ambient salinities, limiting habitability to a few teleost fish species. This study reviews capabilities of physiological response to ambient salinity in 10 teleost species of Florida Gulf coast salt marshes, nine permanent residents, and one a seasonal inhabitant. Two additional species found in marshes elsewhere in Florida, but absent from the study site, were also included. We examined salinity tolerances and osmotic regulatory capabilities among these teleosts, and related differences in their physiological responses to patterns of utilization of salinity‐habitat zones, fresh to hypersaline waters. Lower salinity tolerance varied from fresh water to dilute brackish water, while upper salinity tolerance varied from 25 ppt to >100 ppt within this group. Osmotic regulatory capabilities also varied within the group, with the ambient salinity zone of most consistent plasma osmotic regulation varying ...

Temperature Tolerance in Three Mycophagous Drosophila Species: Relationships with Community Structure

Patterns of host use at several spatial and temporal scales suggest that temperature tolerance may influence the structure of mycophagous fly communities. For instance, Drosophila putrida is more abundant than D. falleni and D. tripunctata in dry sites, at dry periods, and in small, desiccation-prone mushrooms. In this experiment, we acclimated flies from these species at different temperatures (15°C, 20°C, 25°C, and 30°C) for 5 d, and then measured their responses to acute thermal stress (increasing temperature 0.5°C/min). ANOVA were used to describe the effects of sex, species, and acclimation temperature on: 1) survivorship after 5 d, and 2) Critical Thermal Maxima (CTMax). Critical Thermal Maximum was measured as the temperature at which 50% of the flies in a sample were incapable of righting themselves. Survivorship was uniformly high for all species from 15°C to 25°C. However, at 30°C, D. putrida survival (74%) was significantly higher than either D. falleni (39%) or D. tripunctata (23%). When averaged across all acclimation temperatures, D. putrida also had a higher CTMax than the other species (40.7°C, compared to 40.2°C for D. falleni and 39.9°C for D. tripunctata). D. putrida was the only species with a CTMax that increased significantly after acclimation at 30°C. Thus, D. putrida was more tolerant to chronic and acute thermal stress than the other species, and was the only species to show an adaptive physiological response to high temperature exposure. These species differences are consistent with spatial and temporal abundance patterns, and may contribute to patterns in community structure.

Influence of Simulated Tidal Changes in Ambient Salinity on Routine Metabolic Rate in Cyprinodon variegatus

Cyprinodon variegatus, a common resident of coastal Atlantic and Gulf of Mexico waters from Cape Cod, Massachusetts, to northern South America, lives in salinities ranging from freshwater (0 ppt) to at least 142 ppt. We studied the metabolic patterns of C. variegatus as influenced by rapid changes in ambient salinity (approximating tidal changes in native habitats) of individuals from a Florida Gulf of Mexico coastal salt marsh. Fish were acclimated to a series of salinities from 0 ppt to 60 ppt, with routine metabolic rates (RMR) determined at each acclimation salinity. The salinity was then changed (? 20 or 30 ppt) at a uniform rate over 6 h to simulate an extreme tidal change. Metabolic rates were then remeasured after the system attained a new steady state. Routine metabolic rate was unaffected by changes in salinity between 2 and 40 ppt. However, at salinities outside this range, RMR was affected by changes in ambient salinity. Individuals of C. variegatus responded to fluxes at salinity extremes by reducing metabolism and energy expenditures.

Biomarker responses in sunfish species and largemouth bass from the Saluda River, South Carolina.

The upstate and Piedmont region of South Carolina is a rapidly urbanizing area as a result of a steadily growing population. This increase in population and development has the potential to negatively impact local aquatic systems like the Saluda River due to increased pollution from runoff, and effluents from industrial and wastewater treatment facilities. During the summer months of 2010, 159 fish from the Centrarchidae family (sunfish species (Lepomis) and largemouth bass - Micropterus salmoides) were collected from 13 sites along the Saluda River. A suite of biomarker assays, including ethoxyresosufin-O-deethylase, bile fluorescence, glutathione S-transferase, thiobarbituric acid reactive substances, bile estrogens, acetylcholinesterase inhibition, metallothionein and tissue metal levels were applied to investigate the impacts of diminished water quality on fish health. Results indicate that fish from the Saluda River are responding to contamination in a site specific manner, with up to four significant biomarker responses in the most impacted sites. Sampling sites in the lower portion of the Saluda watershed are less impacted by pollution than the upper and central sections. The observed biomarker responses can be explained by the proximity of urban areas, point sources and general land use, and demonstrate the applicability of biomarkers in environmental biomonitoring programs.

Physiological tolerances of juvenile robust redhorse, Moxostoma robustum: Conservation implications for an imperiled species

The robust redhorse, Moxostoma robustum (Teleostei: Catostomidae), is an imperiled sucker native to large rivers of the Atlantic slope of the southeastern United States. Juvenile M. robustum were tested for tolerances to temperature, salinity, pH, and hypoxia in order to evaluate basic early life-history requirements. Static (acute) tests resulted in estimates of mean lower temperature tolerances (5.3–19.4 °C) that varied with prior thermal acclimation and indicated no apparent difference in tolerance among fish 30, 60, and 90 days old. Fish acclimated to 20 °C and 30 °C had significantly different mean critical thermal maxima (34.9 °C and 37.2 °C, respectively) and exhibited pronounced increased opercular ventilation rates with elevated temperatures. Fish exposed to acute and chronic increases in salinity showed unusual patterns of mortality above the isosmotic point (9 ppt) that reflected possible differences in body mass and prior acclimation conditions (i.e., water ionic composition); small fish and those held in soft water were the least tolerant of increased salinity. Abrupt exposure to extreme pH values resulted in greater than 50% mortality at pH values below 4.3 and above 9.5 within a 96-hour period. Fish exposed to progressive hypoxia utilized aquatic surface respiration at a mean oxygen concentration of 0.72–0.80 mg O2 l-1 (20 °C and 30 °C acclimated fish, respectively), and lost equilibrium at 0.54–0.57 mg O2 l-1. Juvenile M. robustum are moderately tolerant of a wide range of ambient physicochemical parameters, but further research is needed to determine how both abiotic and biotic factors have contributed to population decline and extirpation of this species.

Osmoregulation in the sheepshead minnow, Cyprinodon variegatus: Influence of a fluctuating salinity regime

Cyprinodon variegatus (sheepshead minnow), a common coastal resident of the western Atlantic Ocean and Gulf of Mexico, can live in ambient salinities ranging from 0‰ to greater than 140‰. Fish in this study were obtained from a Gulf of Mexico salt marsh near Cedar Key, Florida. This study examined the ability of individual C. variegatus to regulate plasma osmolality under the influence of a cycling salinity regime. Individuals of C. variegatus were exposed for 21 d to one of seven cyclical salinity regimes. Each cycle lasted for 2 d, with salinity varied between 10‰ and 30‰ each day. Plasma osmolality of fish from each group was determined on five dates during the course of the experiment. C. variegatus efficiently regulated plasma osmolality, even when fishes were exposed to large fluctuations in salinity. Fish previously exposed to large salinity fluctuations regulated plasma osmolality better than fish that previously had experienced no change or small changes in salinity. Increasing salinity had a greater impact on osmoregulation than did decreasing salinity.