Measurement of urine production by the crab, Hemigrapsus nudus, gives an indication of the excretion, in absolute amounts, of substances whose concentrations in the urine are presently known. In this way, it is possible to judge the degree of participation of the antennary glands in the functions of ionic and osmotic regulation. Urine production was measured, firstly, by blockage of nephropores to prevent urination and detection of resulting weight increases. The adhesive, methyl 2-cyano-acrylate monomer (M2C-2), provided a virtually perfect block against leakage by fusing the operculum to the surrounding exoskeleton. Secondly, the rate of inulin excretion following injection was employed for determination of urine production. Blockage with M2C-2 and inulin excretion gave urine production values of 15% to 17% body weight/24 hours in 2 5% salinity. With M2C-2 blockage, in 75% salinity, urine production was about 6% body weight/24 hours, however, inulin excretion indicated the rate in this salinity to be 12% body weight/24 hours. The M2C-2 values are believed to be the more reliable since they were more directly obtained and were replicated. It is evident, thus, that urine production increases with decrease in salinity. In both salinities, winter and summer crabs were used. Although seasonal differences in urine production were not entirely consistent, there is evidence to suggest that urine flow is greater in winter than in summer crabs in the low salinity. Urine production is independent of weight of crabs over the range sampled. It appears that urine production is proportional to the osmotic gradient existing between blood and the external salinity (blood is hypertonic to the salinities considered). Thus, seasonal and salinity effects on urine production presumably are related to changes in this osmotic gradient. It is hypothesized that the antennary glands function in this species for volume regulation by excreting excess osmotic water. / Science, Faculty of / Zoology, Department of / Graduate

Spermatogenesis in Cancer productus Randall was studied to determine the availability of cells and chromosomes suitable for the localization of crab dAT. It was found that throughout most of the year the reproductive tract contained resting spermatogdnial cells and a few residual spermatophores. Between April and July there was a burst of meiotic activity observed both cytologically and by the incorporation of a radioactive DNA precursor, tritiated-thymidine. The mean haploid chromosome number for C. productus was found to be 47.0 ± 4.1, lower than the previously reported number of 58. / Science, Faculty of / Zoology, Department of / Graduate

Typescript. / Bibliography: leaves 142-149. / Microfiche. / xi, 149 leaves ill

Thesis (Ph. D.)--University of Hong Kong, 1996. / Includes bibliographical references (leaf 135-154).

published_or_final_version / abstract / Biological Sciences / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--University of Hong Kong, 1996. / Includes bibliographical references (leaf 177-196).

Thesis (M.Sc.). / Written for the Dept. of Biology. Title from title page of PDF (viewed 2009/07/07). Includes bibliographical references.

Means of improving yield and quality of cooked meat from Dungeness crab (Cancer magister) were investigated. Processing factors of cooking time, cooking medium, and condensed phosphate treatment were evaluated. The effect of condensed phosphate treatment and its interrelationship with cooking time and medium on meat was determined. Meat yield (wet and dry weight) decreased with respect to cooking time according to well defined linear regression functions. Cooking induced solubilization of proteins and reduced water holding capacity. Significant yield losses occurred during the first twelve minutes of cooking. Condensed phosphate treatment significantly increased the yields of meat through steam and water cooking and was directly related to treatment solution concentration and exposure time. Condensed phosphate treatment concentrations between 7 and 10% and treatment times of 90 to 120 minutes provided optimum meat yield. Treatment of crab with a 10% condensed phosphate solution for 120 minutes increased wet weight meat yields over controls ranging from 0.91 to 4.95 percentage points based on raw crab section weight. Action of condensed phosphate produced better meat yields wet weight in water than in steam cooking and was related to a slightly higher retention of moisture. Cooking time and cooking medium did not significantly effect yields of cooked meat. No yield advantage was found for steam over water cooking or for cooking times between 8 and 12 minutes. Phosphorus levels in treated and untreated meat did not vary significantly (p=.05). Levels were not affected by cooking time or medium. A slight increase (NS, P [less than or equal to] .05) in phosphorus levels was observed after condensed phosphate treatment. Sensory evaluation of frozen stored meat showed that steam cooking significantly (P [greater than or equal to] .001) increased overall desirability. This was directly related to a superior (P [greater than or equal to] .05) flavor and a slightly better (NS, P [less than or equal to] .05) texture. Condensed phosphate treatment favorably affected meat quality only after extended storage (406 days). / Graduation date: 1984

No description available.

Respirometers were designed which allowed the exercise physiology of Carcinus maenas (L.) and Homarus vulgaris (M.E.) to be examined in an aquatic environment. A treadmill system, incorporated into each respirometer, was used to induce exercise at a known velocity. The rate of oxygen consumption, (VO2), of Carcinus maenas exercised at different velocities was examined. It was found that at each velocity, VO2 reached a steady state. The steady state VO 2 was found to be linearly related to velocity. The VO2 of inactive animals, and the maximal rate of oxygen consumption were both found to be linearly related to animal live weight. The VO2, rate of heart beat (fH) and rate of scaphognathite beat (fScaph) of both C. maenas and H. vulgaris were measured prior to, during and after exercise, at one specific velocity. Various haemolymph gas parameters were also measured. In both species, the VO2, f H and FScaph increased at the onset of exercise until a steady state was achieved. Estimates of the rate of branchial water flow for C. maenas suggest that this parameter also increased as a result of exercise. The rate of blood flow increased as a result of excerise in both species, achieved by an increase in the rate of heart beat and stroke volume of the heart. In vitro oxygen equilibrium curve determinations suggest that at the velocities examined, a Bohr shift plays a minimal role in increasing oxygen delivery to the tissues during exercise of the two species. No significant change in haemolymph carbon dioxide tension or total gas content was found in either species, suggesting that gas exchange across the respiratory surface was not impared during exercise. In C. maenas, whole body and haemolymph L-lactate concentration increased as a result of exercise. No increase in haemolymph L-lactate was observed after exercise in H. vulgaris.