Thesis (M. Oc. E.)--Oregon State University, 1970. / Typescript. Includes bibliographical references (leaves 60-61). Also available on the World Wide Web.

The behavior of the shore crab Hemigrapsus oregonensis was assessed with and without exposure to polychlorinated biphenyls (Aroclor 1260). After describing the crab's behavioral repertoire, activity budgets were developed from observations of the time crabs spent in 20 categories of shelter use, posture, and activity while held in habitat replicas with sinusoidal tides of 12.4 hours. Without PCBs exposure female crabs spent more time sheltered and feeding but less time displaying than males. The sexes also differed in the kinds of displays given. For both sexes certain activities prevailed at certain tidal stages. Crabs readily accumulated PCBs from contaminated sand. Whole body burdens reached as high as 190 ppm PCBs and were related to sex and time spent in feeding. In two experiments the primary effect of PCBs exposure upon the activity budgets of both sexes was to decrease the time spent in pre-feeding and feeding behaviors. When given a variety of food types in a third experiment, crabs under exposure shifted from feeding upon PCBs-contaminated sand to uncontaminated food. By changing its feeding behavior Hemigrapsus oregonensis actively reduced the received dose of PCBs and its presumed adverse effects from what they would otherwise have been. / Graduation date: 1977

Thesis (M.S.)--Oregon State University, 1978. / Typescript (photocopy). Includes bibliographical references. Also available via the World Wide Web.

Thesis (Ph. D.)--Oregon State University, 1975. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Heart rates and amplitudes were measured for both intact animals (in situ) and isolated hearts (in vitro) of the Dungeness crab, Cancer magister, exposed to low levels in oxygen. Recordings were also made of gill ventilation rate by measuring the frequency of scaphognathite (gill bailer) beats. Both the in vitro heart and the in situ heart beat showed a marked decrease in amplitude and frequency under hypoxic stress. Upon the return of oxygen to the environment, the recovery of the hearts of the intact animals showed very short latent periods while the recovery of the isolated hearts was very slow. The response of the scaphognathites to hypoxia was biphasic. Upon the initial decrease in oxygen concentration, they showed an increase in beating frequency; with continued lowering of the oxygen concentration, the rate fell off considerably. In analysing the results it was concluded that such a decrease in heart rate could be adaptive in that it could result in a lowered energy demand at low oxygen concentrations. The rapid recovery of the in situ hearts may indicate the presence of a receptor for oxygen. / Graduation date: 1970

No description available.

Issued also as Thesis (Ph. D.)--George Washington University, 1917.

Thesis (M. Phil.)--University of Hong Kong, 1997. / Includes bibliographical references (leaf 132-147).

Estuarine animals are faced with environmental conditions which favour dilution of the body fluids by water uptake and ion loss. The mechanisms employed by two species of estuarine crabs, Hemigrapsus nudus and Hemigrapsus oregonensis, to maintain ionic stability in sea water of varying salinity were investigated. The concentrations of sodium, potassium, calcium and magnesium ions in the blood and urine of these species were measured at eight salinities (6-175% sea water), three temperatures (5°, 15° and 25°C.) and in summer and winter. In dilute salinities (6-75% sea water), concentrations of sodium, potassium and calcium ions in the blood of both species were considerably hypertonic to the media concentrations. In high salinities (100-175% sea water), the concentrations of these ions approached isotonicity with the media. Hypertonic ion regulation appears to be primarily effected by extra-renal mechanisms since the urine-blood ratios (U/B) approximate unity. It is suggested that the principal site of ion uptake in dilute sea water may be the lamellar cells in the gill epithelium. Magnesium ion concentrations in the blood were maintained in both species at constant, hypotonic levels in all salinities above 12% sea water. This appeared to result solely from kidney activity since the U/B magnesium ratios were markedly greater than unity over most of the salinity range. It is thought that low blood magnesium levels are necessary to facilitate neuromuscular impulse transmission. Changes in blood and urine concentrations of sodium, potassium and calcium ions in 25, 75 and 125% sea water required at least 24 hours to be completed, whereas the response of blood concentrations of magnesium ion was comparatively rapid, the major changes occurring after 12 hours. Although seasonal differences in the ability of Hemigrapsus to regulate sodium and potassium were not consistent, in dilute salinities calcium was found to be more effectively regulated by winter animals than by summer ones. Magnesium levels in the blood of both species were equivalent in the two seasons. No effect of temperature on the body fluid concentrations of sodium, potassium, or calcium was demonstrated at either season in Hemigrapsus. The magnesium regulatory mechanism in both species, however, appeared to be gradually impaired as the temperature increased from 5° to 25°C. This may have resulted from a decrease in available energy, since all other metabolic processes were accelerated. Hemigrapsus oregonensis was more effective in regulating winter blood concentrations of sodium in high salinities than H. nudus. The ability to regulate blood magnesium levels was almost identical in the two species. Higher urine magnesium concentrations in H. oregonensis, as compared to H. nudus, were related to the more permeable exoskeleton in the former species. / Science, Faculty of / Zoology, Department of / Graduate

Two species of intertidal crabs, Hemigrapsus oregonensis and H. nudus ocour in large numbers at Spanish Bank, Vancouver, British Columbia. The area is characterized by sea water of high temperature and low salinity in summer and low temperature and high salinity in winter. The crabs osmoregulate strongly in low salinities, keeping blood considerably hypertonic to the external medium. They do not regulate strongly in salinities higher than those normally found in the field in winter (70-80% sea water). This study attempts to establish the role of the excretory organs (antennary glands) in osmoregulation. Effects on their function of seasonal adaptation, temperature, osmotic stress and body size were also investigated. Experimental temperatures of 5°, 15° and 25° C and media of 6%, 12%, 25%, 75%, 100%, 125%, 150% and 175% sea water were used (100% sea water: 31.88% salinity). Animals were brought into the laboratory and equilibrated in 75% sea water for 36-48 hours at the experiments temperature. After equilibration, groups of 10-15 animals were transferred to each of the experimental salinities. After 3, 24 and 48 hours, 10 urine samples were drawn from each group, sealed in separate capillary tubes and quick-frozen. Osmotic concentration was measured by the method of melting point determination. Identical series of experiments were carried out, summer and winter. Procedures differed only in that summer animals were damp-dried and weighed before sampling. For each species and experimental temperature, a series of urine osmotic response curves was drawn. Data for summer-adapted animals at 15° C and winter-adapted animals at 5° C were used for most comparisons. These approximated seasonal mean field temperatures. Osmotic gradients between urine and media at 4-8 hours formed the basis for comparison of seasonally-adapted responses. Data were analysed for salinity and temperature effects and seasonal differences by means of Student's “t" test, which was used also to evaluate differences between urine and blood concentrations. Differences attributable to weight, and interspecific differences in U/B ratios were analysed by means of Wilcoxon's Matched-Pairs Signed-Hanks test. Concentration of urine was found to fall in dilute, and rise in concentrated media at rates, directly related to osmotic stress, which declined with time and were influenced by the seasonal adaptation of the animals and the experimental temperature. New equilibria were generally established by 48 hours, at levels, particularly in concentrated media (above 100% sea water), which were considerably higher in summer- than in winter-adapted animals. Hyper-osmotic regulation was achieved in summer-adapted animals with the production of blood-isotonic urine, implicating extra-renal mechanisms. In winter-adapted animals, hyper-osmotic regulation was enhanced by production of blood-hypotonic urine. Summer-adapted animals appeared to resist blood change in 100-150% sea water by producing blood-hypertonic urine, and although this resistance was maintained longest in 100% and 125% sea water, blood soon became hypertonic. In general, cooling retarded, and warming stimulated salt absorption and regulation. Winter-adapted animals in high salinities did not effectively resist blood change, and both urine and blood quickly became hypertonic. Effects on urine concentration of cooling or warming summer-adapted animals and warming winter-adapted animals were significant only in low and intermediate salinities. Body size had, in some cases, significant effects on urine concentration. Small H. nudus. taken from summer field conditions, had urine significantly hypertonic to that of large animals. This was also true of H. oregonensis at 15° in concentrated media. In winter-adapted animals, H. oregonensis had total osmotic U/B ratios significantly higher (nearer unity) than H. nudus for the whole range of experimental salinities at 50 C. In summer-adapted animals at 15° C, U/B ratios approached unity in both species. Seasonal adaptation of osmoregulatory mechanisms in both species altered the balance of active processes so that urine was lower, both in absolute concentration and relative to blood, in winter than in summer. / Science, Faculty of / Zoology, Department of / Graduate