Laboratory experiments were conducted to study the effects of dehydro-abietic acid (DHA) on the physiology of the adaptation of sockeye salmon smolts (Oncorhynchus nerka) to sea water. Dehydroabietic acid occurs in the rosin of commercially important coniferous trees and is found in the untreated effluents of the pulp and paper industry at concentrations acutely toxic to salmonids. As this resin acid is known to be one of the more persistent toxic components of kraft mill effluent (KME) and although its concentrations are greatly reduced by biological treatment, DHA is nevertheless discharged in the effluents of the pulp mills situated on the Fraser River system as well as of those located on the coast of British Columbia. As sockeye salmon utilize both the Fraser and Thompson Rivers during their downstream migration, this species may be exposed to DHA before entering the sea. An attempt was made to simulate this situation in the laboratory by exposing sockeye salmon smolts to a sublethal concentration of DHA (0.65 mg/L) in fresh water for 120 h and then transferring them into sea water (28 °/oo) containing no DHA. Hydromineral balance was studied by monitoring changes in plasma osmolality, plasma NA⁺, K⁺ , Ca⁺⁺, Mg⁺⁺ and Cl⁻, blood hematocrit and muscle water content at the end of the freshwater DHA exposure and at 24 h intervals during the adaptation to sea water (120 h). After 24 h in sea water the gill permeability to water and the water transport ability of the gut were also determined. Supportive experiments measured changes in the size of red blood cells, the levels of plasma bilirubin as well as the uptake and tissue distribution of DHA in sockeye salmon smolts. Lipid extracts of various tissues were analyzed for DHA residues by gas chromatography coupled with mass spectrometry (GC-MS). The exposure of sockeye salmon to DHA in fresh water resulted in a hydromineral disturbance characterized by a drop in plasma osmolality, sodium, and chloride, indicating a general hydration which was reflected by increased muscle water content. A lowering of dissolved oxygen to 75% saturation markedly increased the toxicity of DHA and the osmotic imbalance may have been a secondary result of an adaptive respiratory response to a hypoxic stress brought on by DHA exposure. Increases in blood hematocrit were caused by a swelling of the red blood cells related to lowered plasma osmolality. When these fish were transferred to sea water, the hydration was replaced by dehydration and a rise in osmolality was caused by abnormally elevated levels of all the plasma ions. The added salinity stress resulted in some mortality and considerably greater excursions in plasma electrolytes occurred in fish which were experiencing locomotor difficulty. Plasma magnesium showed the greatest elevation and took the longest (96 h) to return to normal levels. Prior DHA exposure increased the permeability of the gill. During acute DHA exposure in fresh water a gradual deterioration in schooling and fright response was followed by hypersensitivity to mechanical stimuli and abnormal swimming behavior. After sublethal exposure, the reduction in schooling and fright response generally became most evident during the first 24 h of sea water adaptation. These results of the study are discussed in terms of the possible roles played by the gills, gut and kidney in the DHA-induced perturbations of hydromineral balance. The implications of the accompanying alterations in behavior are discussed in the context of the ecological survival of sockeye salmon smolts during adaptation to sea water. Residue analyses showed that sockeye salmon accumulated DHA from the water to high levels in the brain (954 x), liver (428 x) and kidney (404 x) as well as in other tissues. The presence of DHA metabolites in the bile, which also contained the highest DHA residues (647.3 μg/g), indicates that the hepatobiliary route is important in the excretion of DHA by fish. The possibility of the bioaccumulation of DHA by fish in the wild is discussed in relation to the setting of water quality criteria for pulp mill effluent. / Science, Faculty of / Zoology, Department of / Graduate

The purposes of this investigation were to measure the relative levels of enzymatic and respiratory metabolism of some vertically migrating mesopelagic fishes collected from the ocean waters off Oregon and to modify and adapt an enzyme method for use as a measure of metabolic activity at sea with a minimum of equipment. A knowledge of the quantitative measure of the respiratory and metabolic rates of these organisms could be usefully applied to several problems of interest; oxygen minimum layers, vertical migration, and vertical distribution. Ten species of fishes were studied with regard to their respiratory potential as measured by succinic dehydrogenase activity. Oxygen consumption for two species was measured at various temperatures for comparative purposes. The metabolic rates calculated from the enzyme data fell within the limits of the standard metabolic rate - temperature relationships compiled from the data of several authors for fishes of the same size from various environments. The fish from the greatest depths had low metabolic rates comparable to those reported for some Antarctic and Arctic species. Metabolic rates of species of mesopelagic fish differed significantly and declined with the general depth and temperature at which the species was found. / Graduation date: 1965

In higher vertebrates, normal digestion and absorption by the gastrointestinal tract are dependent on the orderly and controlled transit of intraluminal contents. A relationship between fluid passage through the gut and absorption from the gut has yet to be examined in fish. In marine teleosts, the osmolality and ion concentration of the ingested seawater (SW) must be lowered before water absorption is initiated. By assuming that these processes are related to fluid transit, it is likely that alterations in these processes as well as in the water-electrolyte balance (WEB) of the animal would result with changes in the transit of intraluminal fluid. I hypothesized that marine teleosts regulate gut motility to achieve essential water absorption and thereby maintain the WEB. To test this, the gut of a marine teleost, the buffalo sculpin (Enophrys bison G.), was challenged in situ with forced drinking (continuous perfusion) at rates above and below that of the measured drinking rate (DR). Initially, the sensitivity of the WEB of the sculpin to preparatory manipulations that were essential for testing the above proposal was determined. The WEB was monitored before, during and after manipulation that included handling, containment, benzocaine-induced anesthesia, arterial and esophageal cannulation and serial sampling of blood. To monitor the WEB, indicators of the osmotic status and the intravascular volume were measured. Within one to three hours after surgery, a hyper-osmotic hemodilution resulted from an influx of hyper-osmotic fluid. Blood volume increased about 18% after surgery. The osmotic imbalance was corrected within 24 hours after surgery, whereas, the volume disturbance persisted. The occurrence of plasma hyper-osmolality after surgery was inhibited with esophageal occlusion. This implicated the gut as the origin of the osmotic and volume disturbances. Further data evaluation suggested that the surgery-induced WEB disturbance was a resultant of enhanced ion and water absorption in the upper and lower gut. Next, the DR and drinking behavior of the buffalo sculpin were determined. Also assessed was the influence of the manner of SW ingestion (ab libitum drinking or forced drinking) and of the rate of ingestion on SW modification by the gut. DR was variable within as well as among experimental groups. DR appeared to increase with the animal's capture duration suggesting that water permeability of the sculpin was gradually increasing after capture. The fluid volume and resident duration, and water modification in the upper gut and lower gut were consistent over a broad range of DRs. This demonstrated that the sculpin were ingesting SW frequently, perhaps in a manner similar to sipping. In respect to estimates made in sculpin allowed to drink ab libitum, forced drinking had a negative effect on desalting. Finally, a relationship was looked for between gut motility and the WEB of the sculpin. Several indicators of gut motility, water absorption, and the WEB were monitored while the gut was perfused at several different rates. If gut motility is regulated to achieve essential water absorption, then changes in gut motility would result in response to alterations in the forced drinking rate, so that adequate water modification and absorption would be accomplished and the WEB maintained. Over the levels of perfusion administered, the WEB was not maintained. With the elevation in perfusion rate, the intravascular volume increased and yet intestinal water absorption was maintained or gradually increased. It appears that under the circumstance of enhanced SW ingestion, the mechanisms regulating gut motility and water absorption are not integrated with mechanisms maintaining the WEB of the buffalo sculpin. It remains unclear if, without SW ingestion, gut motility and the WEB are actively related. / Graduation date: 1982

There is no abstract available for this dissertation.

Graduation date: 1986

This is a study of the structure and functions of the endocrine tissues in the head-kidney of the teleost fish, the homologous tissues to the mammalian adrenal cortex (=adrenocortical tissue) and adrenal medulla (=chromaffin tissue). The study is divided into three main sections: 1.The first section comprises a study of the general morphology, at the anatomical and histological level, of the different types of head-kidney which occur in teleost fish. The range of types is illustrated by studies on twenty-four species, some of which have been previously investigated, and including in particular sixteen marine species from the Red Sea coast of Saudi Arabia collected by the author. 2. The second section of this thesis comprises a detailed study of the morphology of the head-kidney of one particular species, Phoxinus phoxinus (Linnaeus), and a two year study of seasonal variations in the activity of its adrenocortical and chromaffin tissue. Samples of fish were collected from a population in the Walton Reservoir, Scotland, at monthly intervals. The activity of the adrenocortical tissue was assessed by measuring nuclear diameter of the adrenocortical cells, a criterion already widely used for this purpose. The activity of the chromaffin cells was similarly assessed, though the methodology is less well established in this case. The effects were compared of electro-fishing followed by anaesthesis and immersion in Bouin's fixative while still under electronarcosis. Both proved to be relatively stress-free methods. 3. The third section of this thesis comprises a study of the fine structure of the endocrine tissues of the head-kidney of Phoxinus phoxinus and Salmo qairdnerii. Electron micrographs were prepared using fish caught under stress-free conditions in the Walton Reservoir, and from aquarium-maintained fish. The adrenocortical cells in both species are characterised by having a great many conspicuous mitochondria with tubule-vesicular internal structure. The nucleus is circular in section, and centrally situated in the cell. There is an extensive smooth endoplasmic reticulum and numerous ribosomes, Microvilli occur on cell surfaces in contact with veins. There is a wide range in the structure of the adrenocortical cells of individual fish; mitochondria range from small, elongated structure, with dark matrix to large, circular structures in which the internal structures eventually breaks down. The cytoplasm as a whole tends to be pale in cells with small dense mitochondria, and dense in cells with large, paler mitochondria. Pale highly vacuolated cytoplasm is associated with cells in which the mitochondria are breaking down; the vacuoles are probably associated with cells in which the mitochondria are breaking down; the vacuoles are probably associated with the degenerating mitochondria, In Phoxinus maintained in aquaria for twenty-four hours before killing, the proportion of adrenocortical cells with small mitochondria with dark matrices, -. as compared to fish caught by stress-free methods and fixed immediately. In Salmo which had been maintained in aquaria for longer periods, the proportion oft- cells showing mitochondrial degeneration and cytoplasmic vacuolation is higher. It is concluded that small, dark matrix mitochondria are typical of early stages of adrenal activity; dense cytoplasm and an increased number of large, circular mitochondria are typical of maximum activity; and mitochondrial degeneration and vacuolation of the cytoplasm is typical of exhaustion. Chromaffin cells, not hitherto described in teleost fish, are of the type found in other vertebrates, with many chromaffin vesicles containing varying amounts of granular inclusion. Synaptic contacts occur commonly, apparently all of cholinergic type. In Salmo the chromaffin and adrenocortical cells lie separately, but in Phoxinus the adrenocortical cells form a sheath round the posterior cardinal veins and their main tributaries, and the chromaffin cells lie beyond them, against the haemopoietic tissue. These chromaffin cells communicate with the vein by elongated projections running amongst the adrenocortical cells.

Previous electrophysiological research on the fish olfactory system is reviewed and the conclusion reached that present knowledge concerning, in particular, the fundamental physiology of neuronal connections within the olfactory bulb, was rudimentary and confused. Field potentials were evoked in the olfactory bulb of teleost fish by electrical stimulation of the olfactory tract and nerve. The potential wave recorded at the bulbar surface consists of four components, N1, N2, N3, AND P, all of which appear to be of post-synaptic origin when the nerve is stimulated, whence they are usually preceded by a triphasic potential thought to represent the compound action potential of olfactory nerve fibres. The N1 wave evoked by olfactory tract stimulated is not of synaptic origin. It probably represents the synchronous antidromic activation of secondary neurons. The waves analysed with respect to voltage and time related to the underlying histology. The results indicate that the extracellular current flow around bulbar neuronal elements is essentially similar to that already described for mammals and is probably generated by similar pathways. This is surprising in view of fundamental anatomical dissimilarities, particularly regarding the dendritic field of mitral cells. The field potentials proved to be useful in the identification of single units at the time of recording. The spontaneous and evoked activity of identified mitral and granule cells could often be inhibited by stimulation of either the nerve or tract. The evoked field potentials could usually be similarly inhibited. Evidence has been obtained that this inhibition is mediated GABA and that it may well take place via a recurrent pathway involving reciprocal dendrodendritic synapses as in the mammalian system. Evidence was also obtained that this inhibition may, in part, result from the activation of granule cells by andrenergic centrifugal fibres when the olfactory tract is stimulated. Natural chemical stimulation of the olfactory mucosa with amino acid solutions produced a complex pattern of responses. Each odorant normally produced a unique pattern of excitatory and inhibitory responses across all units. Chi-square values were calculated for stimulatory effectiveness between forty-five pairs of odours. L-serine and L-alanine consistently showed a high degree of similarity with several other odours. The converse was true for GABA and L-histidine, although this pair had a high chi-square value when mutually compared. Enantiomeric pairs of amino acids were often found to have opposite stimulatory effects on bulbar units. These results are discussed in relation to the possible properties and configurations of odorant receptor sites for amino acids in the fish olfactory mucosa.

vi, 50 leaves : ill. ; 29 cm Typescript. (Another copy on microfilm is located in Archives) Thesis (M.S.)--University of Oregon Vita Bibliography: leaves 46-50

Energy demands for osmotic regulation and the possible osmoregulatory role of the thyroid gland were investigated in the euryhaline starry flounder, Platichthys stellatus. Using a melting-point technique, it was established that flounder could regulate body fluid concentration independent of widely divergent environmental salinities. Small flounder experienced more rapid disturbances of body fluid concentration than large flounder after abrupt salinity alterations. The standard metabolic rate of flounder adapted to fresh water was consistently and significantly less than that of marine flounder. In supernormal salinities standard metabolic rate was significantly greater than in normal sea water. These findings agree with the theory that energy demands for active electrolyte transport are greater in sea water than fresh water. Thyroid activity was studied in flounder adapted to fresh water and salt water. Correlative with the higher metabolic rate of small flounder was the more rapid turnover and excretion of radioiodine and greater thyroid uptake of small than large flounder. Percentage uptake of radioiodine by the thyroid was shown to be an insensitive and inaccurate criterion for evaluating thyroid activity in different salinities because removal rates of radioiodine from the body and blood differed between fresh water and marine flounder. Using thyroid clearance of radioiodine from the blood as a measure of activity, salt water flounder were shown to have much greater thyroid clearance rates and, hence, more active thyroid glands than flounder adapted to fresh water. The greater activity of the thyroid of marine flounder correlates with greater oxygen demands in sea water and suggests a direct or adjunctive osmoregulatory role of the thyroid gland of fish. / Science, Faculty of / Zoology, Department of / Graduate

The relationship between osmoregulatory stress and locomotor performance has been investigated in juvenile salmonids during their adjustment to sea water. Transfer from fresh water to sea water produced a statistically significant depression of the maximum swimming speed of chum salmon fry (Oncorhynchus keta). The effect of sea water was immediate and reached a maximum fourteen hours after transfer. From thirty-six to eighty hours (the duration of the experiment) relatively stable performance levels were recorded. Some recovery from the initial effects of sea water was apparent but the swimming speeds of "recovered" fish were significantly lower than those of fry in fresh water. Statistically significant correlations between swimming speed changes and changes in total body chloride and water concentrations have been demonstrated. Since chum fry were too small to allow separate sampling of plasma and tissue, the Steelhead trout (Salmo gairdneri gairdneri) was used to investigate the sequence of events in the osmoregulatory adjustment of salmonids to sea water. Transfer into sea water was accompanied by increases in plasma concentrations of chloride, sodium and potassium, but not of calcium. Cellular dehydration resulted from transfer of cellular fluids to the extracellular phase, and from loss of water to the environment. Cellular levels of calcium and sodium rose markedly. Smaller increases in cellular potassium and chloride were noted. Changes in cellular sodium and calcium were primarily due to ion uptake. Increases in cellular potassium were the result of cellular dehydration since tissue levels of this cation fell slightly in sea water. The data indicate that impairment of the efficiency of physiological processes sensitive to altered electrolyte concentrations, and the utilization of energy in the restoration of body fluid electrolyte concentrations to regulated levels may account, at least in part, for reduced locomotor ability in salmonid migrants during their adjustment to sea water. Body size was shown to influence the extent and duration of changes in plasma and tissue electrolyte concentrations and distributions. In chum fry the governing factor appeared to be size, larger animals adapting more rapidly, and undergoing less extensive changes than did smaller fish. In Steelhead trout efficiency of osmoregulation was highest at certain stages of growth, and suggested that adjustment to sea water was best achieved during a restricted phase of their life history. This stage appeared to be that of late parr-smolt transformation. The operation of plasma electrolyte homeostatic mechanisms was indicated in the Steelhead trout and the possible roles of the withdrawl of ions from the circulating fluids by complex formation and by active excretion have been considered. / Science, Faculty of / Zoology, Department of / Graduate