Spermiogenesis in the rainbow trout (Salmo gairdneri)

In an ultrastructural study on the spermiogenesis of the rainbow trout (Salmo gairdneri R.) four spermatogenetic stages were identified. In young round spermatids, the nuclear chromatin was first heterogeneous (euchromatin and heterochromatin). Subsequently, it became more homogeneous and started to condense in the form of coarse granules and fibers and then into fibrils associated in ribbon-like elements which eventually partly fused together. During early spermiogenesis, a juxtanuclear vacuole appeared in the area where the nuclear envelope was specialized due to condensation of material between the two envelopes and a slight accumulation of nuclear material. This area was finally located in the anterior part of spermatids and spermatozoa; it probably plays a role during fertilization. A flagellar rootlet appeared early in spermiogenesis; it may play a role in the attachment of the flagellum to the nucleus since it persisted until the centriolar complex was definitively fixed in the implantation fossa. The flagellum did not display a plasma membrane and was first located in the cytoplasm, but when it was later extruded from the cell, it acquired a membrane. The cytoplasm was rich in ribosomes (free or in small groups) but poor in membranous organelles. The few mitochondria polarized around the centriolar complex were finally organized into an annular mid-piece. The spermatids remained connected by intercellular bridges until the end of spermiogenesis. The complexity of trout spermiogenesis is intermediate between that in poecilids and that in carp and pike, which have very simple spermatozoa. The role of the material from the nucleus and the cytoplasm reaching the Sertoli cell in the control of spermatogenesis has been discussed.     

Apomorphine-induced vomiting in rainbow trout (Salmo gairdneri)

1. The LD50 for a 7-day period following intraperitoneal injection of apomorphine-HCl was calculated to be 158 mg/kg in rainbow trout. 2. Intraperitoneal injection of apomorphine at doses of 60 mg/kg or greater caused vomiting of plastic balls which had been placed in the stomachs of rainbow trout. 3. Apomorphine-induced effects included vomiting, vomiting behavior, toxicity, increased respiration, impaired motor control and equilibrium, and increased aggression. 4. The vomiting control mechanism of trout may be similar to that described in mammals.     

Changes in selected blood component concentrations of rainbow trout, Salmo gairdneri Richardson, exposed to hypoxia or sublethal concentrations of phenol or ammonia

Rainbow trout were exposed to sublethal phenol or non-ionized ammonia concentrations or to hypoxia. Blood samples were taken after various exposure periods and the packed cell volume (PCV) value, the whole blood glucose concentration and the plasma cortisol and chloride ion concentrations measured. At low pollutant concentrations there were no significant changes in the blood components compared to control fish values. At higher concentrations the general response to the stressors was significant increases in the PCV value and the glucose and cortisol concentrations during the first few hours of exposure, followed by a gradual return to normal values in the subsequent exposure time. The increases in glucose and cortisol concentrations were approximately proportional to the pollutant concentrations no such correlation was found for the PCV values. No clear pattern of plasma chloride ion changes was found in any experiment. Levels of no acute effect, in terms of toxic units (TU) based on the pollutants' 48 h LC₅₀ values, were estimated for phenol as 0.3 TU and for un-ionized ammonia as 0.1 TU, using the plasma cortisol concentration measurements. The use of fish blood component measurements as general indicators of a stress response is discussed.     

The effect of ammonia exposure on gill structure of the rainbow trout (Salmo gairdneri)

Gill structure has been studied in fish exposed to various ammonia concentrations. Gill damage resulting from exposure to acutely lethal concentrations was relatively minor and unlikely to have been a primary cause of death. Alternative toxic mechanisms have been discussed. Following long-term exposure to ammonia there were severe histopathological changes in gill structure and oxygen uptake may have been seriously impaired. A high incidence of disease was also observed.     

Chromosome polymorphism in the rainbow trout (Salmo gairdneri Richardson)

Chromosome preparations from lymphocyte cultures of 50 rainbow trout were studied. Diploid chromosome numbers of 59, 60, 61, 62 and 63 were found in different individuals in which the arm number (NF) was 104. Intraindividual polymorphism was found at a low level in 25 of the fish. The results suggest that numerous chromosome polymorphisms exist in rainbow trout.     

Crystallization of the rainbow trout (Salmo gairdneri) haemoglobin IV

Crystals of rainbow trout (Salmo gairdneri) haemoglobin IV were grown in mini batches from a solution of ammonium sulphate. Large single crystals grew over five days and were up to 2 mm in length. X-ray diffraction experiments indicated a space group of C222(1) with unit cell dimensions of a = 85.3 A, b = 94.6 A and c = 105.7 A. The crystals diffract to better than 2.5 A but exhibit some mosaicity along the c axis.     

The effects of temperature on contractile mechanisms of rainbow trout (Salmo gairdneri) intestine

Experiments were designed to determine whether contractility of trout smooth muscle in vitro varied with temperature and if changes occurred at the receptor or intracellular levels. The role of calcium in contractility at various temperatures was also investigated. Isolated trout intestinal segments, approximately 2 cm in length, were suspended isometrically under 2 g tension in 10-mL organ baths containing trout Ringer's solution aerated with O2 and CO2 (95:5). Contractions of trout intestine were not statistically different at 10 and 20 degrees C for carbachol, 5-hydroxytryptamine, and KCl. However, the efficacy, but not the potency, of each agonist was decreased at 2 degrees C. Receptor-induced contractions were reduced to a greater extent at 2 degrees C and did not recover to the same extent when returned to 10 degrees C in comparison with those induced by depolarization. The calcium source for contractility was also dependent on temperature. As temperatures increased, utilization of intracellular calcium increased, as indicated by increased contractility in the absence of extracellular calcium. Thus, low temperatures decrease smooth muscle contractility by affecting receptor-mediated events rather than the intracellular contractile mechanisms. Receptor-operated agonists appear to have a higher capability of using intracellular calcium than depolarizing agents.     

Induction of hepatic aryl hydrocarbon hydroxylase activity in rainbow trout (Salmo gairdneri) exposed to coal liquids

1. The hepatotoxic response of rainbow trout (Salmo gairdneri) to a middle distillate (MD) and heavy distillate (HD) coal liquid was determined following administration by injection or in food. Hepatic aryl hydrocarbon hydroxylase (AHH) activity was compared to the known AHH inducer, benzo(a)pyrene. 2. Acute toxicities (LD50) of 1500 and 1410 mg/kg were obtained 120 hr after intraperitoneal injection (i.p.) for MD and HD coal liquids, respectively. Only the HD induced AHH activity when injected at 5% and 10% of the acute LD50. 3. Ingestion of 7 or 70 mg HD/kg body weight for 1 week resulted in AHH induction at 5-7 times that of control values. Levels of hepatic AHH activity in fish treated at 7 mg HD/kg declined to 2.6 times control values 7 days after exposure. Maximum induction was observed for the 70 mg HD/kg group that was provided control food for 1 week following 2 weeks of exposure. 4. The hepatic index (HI) or liver to body weight ratio generally increased along with increased activity in the enzyme response system.     

Ultrastructure of the physostomatous swimbladder of rainbow trout (Salmo gairdneri)

Summary Rainbow trout swimbladder epithelium consists of non-ciliated and ciliated cells in the ratio of greater than 21. Non-ciliated cells contain vesicles filled with a mucus-like material and similar material is found lining the surface of the swimbladder lumen. Morphological evidence for discharge of the vesicle contents was obtained. In addition, nonciliated cells contain osmiophilic lamellar bodies which resemble the cytosomes of lung alveolar cells of air-breathing vertebrates. The non-ciliated cells do not appear to be involved in a process of active gas secretion.Supported by a research grant from the American Cancer Society, Oregon Division, Inc.     

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.     

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.     

Acute toxicity of nitric acid to fingerling rainbow trout (Salmo gairdneri)

The acute toxicity of nitric acid to fingerling rainbow trout was measured in 7 day bioassays at 11 degrees C. The LC50 was about pH 4.0. Fish which died at low pH (3.0-4.0) exhibited classical symptoms of acid toxicity. Comparison of our results with other toxicity measurements suggests that nitric acid is intermediate in toxicity between H2SO4 and HCl at pH 3.0 and less toxic than either acid at pH 3.3 and above.     

Ventilation and metabolic rate of young rainbow trout (Salmo gairdneri) exposed to sublethal environmental pH.

Differences between ventilatory response and metabolic rates of young rainbow trout tested within the sublethal range of pH 6 to pH 9 were observed using a flowing water respirometer. The oxygen consumption was monitored at swimming speeds of 12 cm/sec and 24 cm/sec. The oxygen consumption rates at 24 cm/sec and pH 6 (423 mg/kg-hr) and pH 9 (367 mg/kg-hr) were considerably higher than those determined near neutrality (328 mg/kg-hr). Ventilation rate increased to either side of neutrality, but significantly fewer respiratory reversals, or "coughs," were observed at pH 6 and a greater number at pH 9 than occurred at pH 7 and 8 or in untested fish. The respiratory-cough response is shown to be pH-dependent in rainbow trout and may therefore not be as reliable an indication of pollutant-caused stress in studies where the experimental pH has not been specified or controlled.     

Seasonal changes in reproductive function of the rainbow trout (Salmo gairdneri)

The sequential changes in serum oestradiol 17β (measured by specific radioimmunoassay), vitellogenin (measured by phosphoprotein phosphorus content) and total calcium (measured by fluorimetry) in male and female rainbow trout under a simulated natural photoperiod cycle were investigated. Resting levels of 130 pg/ml serum oestradiol in both male and female fish were found in April and May. In the female, levels reached a peak of 4800 pg/ml in October, and almost returned to resting levels just prior to spawning in mid-January. No significant change from resting levels was seen in the male fish.
In both male and female fish levels of 25 μg/ml serum phosphoprotein phosphorus and 10–14 mg % total serum calcium were found from April to July. Coincident with the rise in oestradiol 17β, in the females serum levels of phospho-protein phosphorus and total calcium increased to 400 uβg/ml and 58 mg% respectively just prior to spawning. In the males no significant change in either of these values was observed throughout the cycle. These results strongly support the hypothesis that photoperiod is the major factor in the environmental control of reproductive activity in the rainbow trout.     

Changes in urine flow rate and haematocrit value of rainbow trout Salmo gairdneri (Richardson) exposed to hypoxia

Measurements were made of urine flow rates and haematocrit of rainbow trout exposed to hypoxic conditions (3 mg O₂/1) for 3, 4, 5 or 24 h. Elevated urine flow rates during short time exposure and concomitant increased haematocrit, followed by lower than normal urine flow rates on return to normal aerated water, suggest that haemoconcentration is the initial response to anoxia. Results from longer exposure to hypoxic conditions suggest that the initial period of haemoconcentration is followed by a period of water retention and a return of the blood volume to normal; the sustained elevated haematocrit is thought to be derived from release of erythrocytes from storage organs. During prolonged exposure rainbow trout also become more permeable to water.     

Ultrastructural development of the saccus vasculosus in rainbow trout (Salmo gairdneri)

Summary The morphology of crown cells and supporting cells of the saccus vasculosus has been described by numerous investigators. A third type of cell has been mentioned by several authors and referred to variously as undifferentiated crown cells, pseudo-coronet cells, pear-shaped cells and, most recently, as liquor-contact neurons. A developmental study of the organ was undertaken as a possible means of characterizing this third cell type and determining its origin.The epithelium of the saccus vasculosus and the ependyma of the third ventricle are different and distinguishable at the time of hatching in rainbow trout. Initially, apical protrusions from crown cells extend slightly into the lumen and a few end knobs or motile cilia project from them. Basal bodies with cross-striated rootlets occur frequently. In swim-up fry, end knobs are more numerous and heavily vacuolated, although cross-striated rootlets are less apparent.Evidence is presented that is consistent with a hypothesis of secretory activity in the crown cells. Further, portions of end knobs containing this material appear to be pinched off from the remainder of the crown cell. The possible presence of bipolar neurons is also discussed.Supported by Research Grant 5 R01 NS0627 from the National Institute of Neurological Diseases and Stroke.