Changes in circulating blood cell levels of rainbow trout, Salmo gairdneri Richardson, following acute and chronic exposure to copper

Significant leucopenia, predominantly the result of a large reduction in lymphocyte concentration, was observed in rainbow trout exposed to 301 μg1⁻¹ copper for 24h. A strong trend ( P = 0–085) toward reduced erythrocyte concentration was also apparent. The pattern of haematological change after chronic exposure (118 μg 1⁻¹ copper for 16 weeks) was substantially different. With the exception of a significant increase in neutrophil concentration (neutrophilia), all blood cell concentrations had returned to control levels.     

Effects of sampling on blood parameters in the rainbow trout, Salmo gairdneri Richardson

The effects of sampling and short-term storage of blood samples on the blood parameters of rainbow trout were evaluated by comparing values obtained from resting fish sampled via cannulae and from fish sampled by cardiac puncture. Sampling stress causes an increase in haematocrit value and a decrease in mean cellular haemoglobin concentration, indicating red cell swelling. These changes are aggravated by consecutive storage of samples. Also, blood ionic balance is affected. The K⁺ concentration of plasma increases and plasma Cl⁻ concentration decreases owing to sampling. During storage the plasma K⁺ concentration decreases far below resting levels in samples taken by cardiac puncture, whereas plasma Cl⁻ level returns to pre-stress levels. Owing to the sampling- and storage-induced changes in blood parameters, care must be taken to ensure that similar sampling procedure is employed throughout to allow reliable comparisons between groups to be made.     

The effect of exercise on plasma cortisol and blood sugar levels in the rainbow trout, Salmo gairdnerii Richardson

Preliminary experiments were performed to determine the diurnal variation in cortisol, using trout which had been cannulated three days previously. These results indicated that cortisol levels were reasonably stable between 10.00 and 18.00 hours, thus permitting experimentation during this period without diurnal fluctuations masking the cortisol response. Uncannulated fish were exercised in a flume for 2 h at 1, 2.6 and 5 bl s^-1 and plasma samples taken from groups of five animals at 15, 30, 60 and 120 min after the start of exercise and at 1½, 12 and 24 h after the exercise ceased. The cortisol levels in all cases were elevated after 15 min, but the magnitude of the elevation increased with swimming speed. At 1 bl s^-1 the cortisol levels increased from 76.4 (± 20.4) to 129.2 (± 20.4) ng ml^-1 [mean (± s.d. )]. At 2.6 bl s^-1 the increase was from 72.4 (± 17.1) to 254.4 (± 34.4) ng ml^-1 and at 5 bl s^-1 the increase was from 69.5 (± 27.5) to 326.4 (± 39.0) ng ml^-1. The cortisol levels were stable over the exercise period and all groups recovered to baseline levels after 24 h, though the sample taken 12 h after the termination of exercise was elevated due to regular nocturnal increases in cortisol levels. There were no dramatic changes in blood sugar levels during and after exercise at 1 and 3.2 bl s^-1.     

Some blood parameters of the rainbow trout (Salmo gairdneri Richardson)

Some of the blood constituents of male, female and immature rainbow trout of the Shasta variety, maintained in known environmental and dietetic conditions, were examined and the results statistically treated. The parameters for male and female trout were similar, only the erythrocyte count exhibiting a significant difference. Large but expected differences were evident between the parameters for mature and immature fish.     

Some blood parameters of the rainbow trout (Salmo gairdneri Richardson)

Fifty rainbow trout of the Kamloops strain were examined for 12 haematological parameters: erythrocyte sedimentation rate, haemoglobin, packed cell volume, erythrocyte count, erythrocyte diameters, mean cell volume, mean cell haemoglobin, mean cell haemoglobin concentration, leukocyte count, differential leukocyte count, plasma total protein and plasma glucose concentration. The fish had been held under known environmental and dietetic conditions, and at the time of sampling were 14 months old. The majority of results for erythrocyte sedimentation rate, haemoglobin, packed cell volume, erythrocyte count, erythrocyte diameters, total protein and differential leukocyte count fell within narrow ranges. The total leukocyte counts and glucose levels were more widely spread. The results are discussed and compared with those already published for Idaho and Shasta strains. It is impossible to say whether the differences that were observed between Kamloops and these other varieties were due to strain alone, since other variables were present. Some problems associated with establishing normal ranges for these parameters in fish are discussed.     

Cohort sampling, anaesthesia and stocking-density effects on plasma cortisol, thyroid hormone, metabolite and ion levels in rainbow trout, Salmo gairdneri Richardson

The effect of serial removal of fish from aquaria, anaesthesia and stocking density on plasma cortisol, thyroid hormone, metabolite and ion levels was examined in rainbow trout, Salmo gairdneri , to determine the consequences of normal handling and maintenance procedures on the activity of the pituitary-adrenal and pituitary-thyroid axes in the species.
The capture and handling associated with serial removal of fish from an aquarium resulted in a rapid elevation of plasma cortisol concentrations and a slower rise in plasma glucose, Mg²⁺ and Na⁺ concentrations; plasma K.+ levels showed a transient fall shortly after commencing the sampling, followed by a significant increase.
A lethal concentration of 3-aminobenzoic acid ethyl ester (MS 222) of 125 mgl⁻¹ (but not a sublethal concentration of 62.5 ng 1⁻¹) prevented the capture stressor-associated changes in most of the measured parameters, including plasma cortisol levels, although plasma protein and ion concentrations were elevated in fish sampled after MS 222-anaesthesia.
Stocking densities from 1 to 64 fish 80 1⁻¹ aquarium did not appear to effect changes in the measured parameters, except for plasma T3/T4 ratios which decreased with increasing stocking density. The exception was found in fish which were stocked in pairs: one member of each pair had a markedly elevated plasma cortisol level and there was a high incidence of mortality, probably related to aggressive social interaction.     

Oxygen uptake by rainbow trout blood, Salmo gairdneri

Oxygen uptake rate by rainbow trout red cells was measured in the temperature range 5° to 40° C. Between 5° and 20° C there was a steady increase in rate and at 20° C a maximum rate of 2.5 μl O₂/min/ml red cells occurred, followed by a decline in the rate as the temperature increased. A morphological investigation of the red cell was conducted and possible functions of the nucleus in fish red blood cells are discussed.     

Cadmium exposure of rainbow trout, Salmo gairdneri Richardson: effects on immune functions

Differential leucocyte counts, phagocytosis, humoral antibody response and the in vitro blasto-genetic response to mitogens (lipopolysaccharide and Concanavalin A) and to an antigen ( Vibrio anguillarum ) were studied in rainbow trout exposed to 0,0.7 or 3.6 μg Cd 1⁻¹ for 12 weeks.
Although the fish did not exhibit any clinical or histological changes, cadmium exposure was found to affect two of the immune parameters measured. The cellular response of fish immunized with V. anguillarum to the homologous antigen was significantly lower for splenocytes obtained from fish exposed to cadmium for 9 weeks (3.6 μg Cd 1⁻¹ group) than for splenocytes obtained from non-exposed fish. Conversely, the humoral antibody response to V. anguillarum O-antigen was higher in the 3.6 μg Cd 1⁻¹ group than in the non-exposed group. Protective immunity of fish vaccinated against V. anguillarum was equally as good in the cadmium-exposed group as in the non-exposed group. No cadmium-induced changes in differential leucocyte counts or in the proportions of phagocytic cells were observed.     

Plasma oestrogen levels in rainbow trout Salmo gairdneri Richardson

Levels of oestrogens in plasma of mature fall-spawning rainbow trout Salmo gairdneri were determined using a radio-immunoassay. No significant difference was found in oestrogen concentration between the sexes (male =2.5 ng/ml; female =4.4 ng/ml); between individual variability was great. Four blood samplings over a 24-h period via cardiac puncture of males revealed no diel variation or change in estrogen levels due to the stress of bleedings. Although no gonado-somatic index-estrogen relationship could be demonstrated for either sex, there was correlation between oestrogen and androgen levels in the female.     

The effects of aluminum and acid on the gill morphology in rainbow trout,Salmo gairdneii

Synopsis The objective was to determine the effects of acid and aluminum in acidified hard and soft water on the histology and morphometry of rainbow trout gills, and to determine relevant toxicity indicators within the gill tissue. Acid and aluminum promoted measurable primary epithelial hyperplasia which proved to be a reliable biological indicator of acid and aluminum contamination and possibly of some predictive value. Low levels of aluminum and acid resulted in hypertrophied chloride cells, suggesting a role in adapting to the contaminants. High concentrations of aluminum (>10 molI^-1) caused chloride cell necrosis and consequently a decline in cell numbers over time. Aluminum precipitates accumulating within the chloride cell cytoplasm probably lead to impaired function prior to cell degeneration. The morphological alterations resulted in a decrease in water space between secondary lamellae (up to 40% within 14 d) which may reduce the efficiency of gas exchange. Twice the aluminum was required in hard water to elicit a similar soft water tissue response. Pathological changes were more severe with aluminum at pH 5.2 than at pH 4.7; results of aluminum speciation suggest that both labile and non-labile fractions are responsible for the induction of gill lesions. Low levels of aluminum may protect fish from the effects of high hydrogen ion concentration.     

Changes in plasma thyroxine,triiodothyronine and cortisol associated with starvation in rainbow trout (Salmo gairdneri)

Synopsis Chronically starved rainbow trout (Salmo gairdneri) showed a significant fall in liver size, total liver glycogen, liver glycogen concentration and plasma glucose levels. Liver lipid concentration did not differ significantly from controls although total liver lipid reserves fell during the first 40 days of starvation but had partly recovered after 65 days of starvation. Plasma cortisol and T3 levels did not show consistent changes concomitant with food deprivation over the 65 day period of the experiment. However, plasma T4 levels in fish starved for 40 or 65 days were significantly lower than comparably fed animals. The involvement of T4 in intermediate metabolic processes in salmonids is discussed.     

Evaluation of oral administration of cortisol and metyrapone: the effects on serum cortisol in rainbow trout (Salmo gairdneri)

The effect of manipulating dietary levels of cortisol and metyrapone on peripheral concentrations of serum cortisol was examined in rainbow trout, Salmo gairdneri. Fish were fed 0, 10, 20, 30, 40 or 50 mg/kg body weight/day of metyrapone or cortisol for 7 days. All levels of cortisol tested increased peripheral levels of serum cortisol. Feeding a level of 30-40 mg/kg body weight/day of metyrapone depressed serum cortisol. We describe, herein, a noninvasive technique for suppression or stimulation of serum cortisol in rainbow trout.     

The effect of low pH and aluminum on the olfactory organ of rainbow trout,Salmo gairdneri

Synopsis The effects of acid ((H₂SO₄) and aluminum AIKSO₄ in acidified water on rainbow trout, Salmo gairdneri, olfactory organ were examined using scanning electron microscopy and electrophysiology. Exposure to pH 4.7 resulted in an increase in the number of mucus droplets over parts of the olfactory epithelium, primarily along the ridges of the secondary folds. The addition of aluminum (5.0, 9.5, 20.0 μmol · 1⁻¹) at pH 4.7 resulted in loss of receptor cell cilia, irregularly shaped olfactory knobs, clumped microvilli and swellings on microridge cells. Electrical responses recorded from the olfactory nerve in response to the amino acid L-serine were similar to controls in fish exposed to acidified water. When fish were exposed to acidified water and aluminum the response was depressed. These morphological and electrophysiological changes could be used to indicate metal-induced stress in fish from natural ecosystems.     

Effects of magnetic field exposure on fertilization success in rainbow trout,Salmo gairdneri

The sensitivity of trout ova and sperm to 1-T magnetic fields was investigated. It was determined that (1) overall test results combining seven independent Z-statistics demonstrated a significant (α < 0.0001) enhancement of fertilization when ova alone were exposed to the magnetic field prior to fertilization; (2) similarly, overall test results combining Z-statistics from eight independent experiments indicated a significant (α < 0.0004) enhancement when sperm alone were exposed; and (3) statistical analysis of nine independent experiments confirmed enhanced fertilization (α < 0.0001) when both ova and sperm were exposed to the magnetic field prior to fertilization. Although these data indicated that both ova and sperm were sensitive to magnetic fields, simultaneous exposure of both gametes did not have a greater total effect on fertilization rate than the sum of their individual effects.     

The effect of chlorine toxicity on certain blood parameters of adult rainbow trout (Salmo gairdneri)

Synopsis In an effort to assess the mode of chlorine action on rainbow trout (Salmo gairdneri), hematocrit percentage, and hemoglobin, methemoglobin, reduced glutathione, plasma protein, and plasma hemoglobin concentrations were determined in four tests in which duplicate groups of approximately 15 fish each were exposed to 3.86, 2.47, 2.75, and 1.09 mg 1^–1 TRC1₂ for 8, 19, 20, and 29 minutes, respectively. Blood from fish exposed to chlorine was darker and thicker than that of the control. Chlorine seemed to diffuse readily through the gills, oxidizing the hemoglobin to methemoglobin and disrupting the erythrocyte membranes, resulting in hemolysis. Stress polycythemia was also due to the substantial increase of the hematocrit values and hemoglobin concentration. Hemoconcentration led to a significant rise in the reduced gluthathione and plasma protein concentrations. The hemoconcentration seemed to interfere with the blood circulation and hinder the delivery of oxygen to tissues.