Thesis (Ph. D.)--University of Delaware, 2008. / Principal faculty advisor: Charles E. Epifanio, College of Marine & Earth Studies. Includes bibliographical references.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 163-171). Also available via the Internet.

Thesis (Ph. D.)--University of Pennsylvania, 1943. / Bibliography: p. 195-197.

Thesis (Ph.D.)--University of Delaware, 2009. / Principal faculty advisor: Charles E. Epifanio, College of Marine & Earth Studies. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. Includes bibliographical references.

Thesis (Ph.D.)--University of Iowa, 2006. / Supervisors: George Constantinescu, Larry J. Weber. Includes bibliographical references (leaves 288-296).

Thesis (M.S.)--University of Delaware, 2009. / Principal faculty advisor: George R. Parsons, College of Earth, Ocean, & Environment. Includes bibliographical references.

Crabs of the species Hemigrapsus oregonensis, when held at temperatures of 5° and 18°C for eight days and then observed at temperatures approximating these holding conditions and at intermediate temperatures, showed greatest locomotor activity and frequency of behaviour patterns at highest temperature conditions. At intermediate temperatures, locomotor activity was greater in crabs from the higher holding condition, and the greatest variability was recorded for females at an observation temperature of 19°C. Observations made at 0530, 1030, 1630 and 2230 hours of the day showed that a peak activity period occurred at 0530 hours in male crabs at most temperature conditions. This may have been caused by the low intensity of illumination used at night. Presentation of chemical food stimuli in the form of a solution of liver to crabs, elicited feeding and probing movements and an increase in locomotor activity. Pieces of art eraser simulating tactile stimuli of meat elicited feeding movements, but no response could be shown to sight of sculpins or minced liver. Visual stimuli appeared ineffective even when combined with other stimuli. Combinations of chemical and tactile stimuli, however, appeared to sum, and responses were increased above those obtained by separate presentation. Starvation increased the frequency of all behavior that occurred as a response to food stimuli. / Science, Faculty of / Zoology, Department of / Graduate

Weight-specific oxygen consumption of midgut gland tissue of Hemigrapsus nudus has been investigated at three levels of salinity (35%, 75% and 125% sea water), two levels of experimental temperature (5°C and 20°C) and four acute (Warburg) temperatures (5°, 10°, 15° and 20°C) in all combinations for each season (summer and winter). Metabolic-temperature curves reveal that at standard baseline conditions where the animals are held 24 hr at their respective seasonal temperature and salinity, midgut gland respiration is highest at all acute temperatures in the summer animals. Acutely measured metabolic-temperature curves for midgut gland tissue show that winter animals acclimated to their opposite seasonal conditions of temperature and salinity for 10 days demonstrate the greatest degree of acclimation. The effect of experimental temperature is statistically and biologically significant. The highest respiration rate is at 5°C. Low temperature (5°C) may provide a greater thermal stress than a high temperature (20°C) resulting in a higher rate of oxygen consumption. Experimental temperature also influences the seasonal respiratory response of midgut gland tissue to salinity. In summer animals there is no correlation of midgut gland respiration to salinity at 5°C. There is a increase in respiration rate as the osmotic gradient between the blood and medium increases at the seasonal baseline temperature of 20°C. Winter animals held at the seasonal baseline temperature of 5°C demonstrate a "V-shaped" relationship to salinity with the lowest respiratory response in 75% sea water where the gradient between the blood and medium is minimal. Animals held at 20°C increase respiration with an increase in salinity. It is suggested that the metabolic activity of midgut gland from summer animals may be related to the maintenance of a osmotic gradient between the blood and medium or alternatively to the energy demands associated with new exoskeleton formation. The proposal is put forth that midgut gland respiration in winter animals may indicate osmotic work being done to maintain the osmotic gradient between the blood and medium. The production of a urine hypotonic to the blood may also assist winter animals in regulation of blood electrolytes. The regression coefficients of weight-specific oxygen consumption as a function of body weight were not significantly different from zero at the 0.01 probability level. / Science, Faculty of / Zoology, Department of / Graduate

A structural analysis of the compound eye of Hemigrapsus nudus expands the basis of functional analysis of decapod Crustacean eyes. Contradictory evidence for disintegration of rhabdomeric microvilli in the absence of light prompted observation of H. nudus eyes after 146 days in darkness. Eyes were fixed with formalin and glutaraldehyde and post fixed with osmium tetroxide for electron and light microscopy. Light- dark-adapted eyes were also observed with hot water fixation and paraffin embedment. The eye of H. nudus is typical of decapod Crustacean compound eyes. Corneagenous cells underlie the transparent cuticle cone cells secrete the composite crystalline cone which contacts the rhabdom proximally. The single fused rhabdom is composed of layers of microvilli from two groups of retinular cells. The layers are oriented at right angles to each other, and perpendicular to the optic axis of the ommatidium. A presumptive four-lobed eighth retinular cell makes up the distal end of the rhabdom. Distal, proximal and reflecting retinal pigments are located in the distal pigment cells, retinular cells and tapetal cells, respectively. Distal and proximal pigments surround the rhabdom during light-adaptation, and withdraw during dark-adaptation. Reflecting pigment is found above the basement membrane in light-adapted eyes and below it in dark-adapted eyes. The crystalline cone may change length during light- and dark-adaptation. Prolonged darkness does not cause disintegration of the rhabdomeric microvilli. H. nudus lives in conditions of dim illumination. The fused, layered rhabdom is an efficient mechanism of light absorption. Internal reflection within the rhabdom is enhanced by the palisade and further increases light absorption. Functional units exist within the ommatidium. Mutually perpendicular rhabdomeric layers suggest intraretinal polarized light perception. Eighth retinular cells may respond individually to light focused on the distal rhabdom by the dioptric apparatus in mosaic image formation.