Many animals that live near shorelines (X-axes) perfonn horizontal movements perpendicular (Y-axes) to the nearest shore, which is referred to as Y-axis orientation (Ferguson and Landreth, 1966). Shore-directed (Y-axis) orientation was studied in the intertidal purple shore crab, Hemigrapsus nudus. The crabs were collected fr001 several shorelines with different compass directions in southern British Columbia, Canada; i) in Barkley Sound, on the West Coast of Vancouver Island, ii) in the Nanaimo area on the east coast of Vancouver Island, and iii) in the Vancouver city area on the mainland coast. The directional preferences of the crabs were tested in orientation arenas. A seaward Y-axis orientation ability was established for crabs fr001 the Vancouver Island shorelines. Vancouver city crabs showed a bimodal orientation parallel to the beach (X-axis orientation). Potential factors influencing Y-axis orientation were investigated. The di recti anal preference and directivity of the orientation were not affected by the time of day, temperature, tidal cycles, level of activity, the moon, or the position of the observer. The crabs were presented with visual and non-visual orientation cues to determine the guiding mechanisms of the orientation. The results. indicate that visual cues present in clear day and night skies are important for Y-axis orientation since high cloud cover and experimental interference with the natural sky visibility severely disrupted the orientation ability. Y-axis orientation based on non-visual cues was tested by subjecting crabs to altered magnetic fields. Results of these and other experiments suggest that non-visual cues may also be used in Y-axis orientation. Transplant experiments were conducted in which crabs from one area were relocated to a new beach with a· different Y-axis. The directional preference in the seaward Y-axis direction of the original 11 home" beach persisted after 48 days on the new beach. / Graduate

Phagocytosis by hyaline cells of the shore crab, Carcinus maenas, was investigated in vitro. In particular, the project examined the role of the prophenoloxidase activating system (proPO) in opsonisation, the metabolic requirements of the cells during phagocytosis and the extent of intracellular bacterial killing. Related work investigated the mechanism and regulation of bacterial killing. Uptake was assessed using monolayers of separated hyaline cells challenged with the bacterium, Psychrobacter iminobilis. The bacteria were pretreated with haemocyte lysate supernatant (HLS) to enhance uptake. The opsonic factor(s) were found to be freeze stable and to be generated during serine protease activation of the proPO system. Phagocytosis was also found to depend upon electron transfer and oxidative phosphorylation and to require an intact cytoskeleton for engulfment. Following ingestion, ca 84% of the bacteria were found to be killed within 3h. Experiments designed to investigate the mechanism of killing showed that treatment of the hyaline cells with phorbol 12-myristate 13-acetate, lipopolysaccharide, phytohaemagglutinin or concanavalin A, but not laminarin, sdmulates the production of superoxide ions (O2-). The semi-granular and granular cells did not produce O2- following stimulation. Incubation of the cells with superoxide dismutase (SOD) confirmed that O2- was produced. Parallel experiments were conducted on a range of marine invertebrates. In all cases O2- production was observed, showing that O2- production is a general phenomenon for invertebrate phagocytes. However, quantification of hydrogen peroxide (H2O2) production, using a H2O2 assay, showed that crab phagocytes produced more H2O2 than tunicate phagocytes indicating that the kinetics of the response varies between species. Using immunocytochemistry, the antioxidant enzymes, catalase, glutathione peroxidase and SOD were found to be located within the haemocytes and plasma of C. maenas. These enzymes may minimise the risk of damage to the host tissues by the O2- and H2O2 produced by the hyaline cells.

The aim of this work has been to make an overall study of the uptake accumulation, and excretion of inorganic mercury, and the effects of long term exposure to the metal, in the lobster, Homarus gammarus, using relatively simple techniques considered appropriate to pollution studies. In this way it was hoped to gain an under- standing of the way in which the lobster deals with mercury and to be able to predict what organs were likely to be affected by low levels of mercury. The initial approach was to measure background levels in the different organs of the lobster, and also of lobsters exposed to 100ppb. and 10ppb. mercury for varying periods of time, using neutron activation analysis. These results were amplified by radioisotope tracer experiments so that besides the sites of principal accumulation being identified the route of uptake could be determined. By the same means, the ability of lobsters to excrete mercury was investigated. Long term studies of the effects of exposure to mercury on organs identified as being susceptible to damage because they were sites of uptake, major accumulation, or excretion were studied by histological techniques which were amplified in part by electron microscopical examination. Since it was likely that the lobster larvae might be weak links in the life history, measurements of mercury uptake by the larvae was attempted using X-ray microanalysis. This was unsuccessful, and studies of the effects of mercury on the survival of the lobster larvae were inconclusive. It was found by these varied approaches that uptake was mainly through the gills where highest levels of mercury accumulated, but it is probable that most of this mercury was bound to the cuticle or in the cells. A small proportion passes into the blood and is taken up and gradually excreted by the green glands, Long term damage is found in these organs but not in either the gills or the digestive gland. It is therefore suggested that damage due to mercury only occurs at sites of active control. The damage in the green glands due to exposure to levels even as low as 10ppb is likely to lead to death if exposure is prolonged, but a more important finding was evidence of greater susceptibility at different stages of the moult cycle. This is worthy of more detailed investigation.

No description available.

Most models of the impacts of climate change on the distributions of animals have focused on limits to thermal tolerances of individual species. Such "bioclimatic envelope" models do not consider the importance of interactions among species, each of which may respond to climate change in its own way. Hermit crabs (Paguridae) cannot exist without shells produced by gastropods. Thus, their ranges are expected to depend not only on their own physiological tolerances, but also on tolerances of gastropod species that produce shells of suitable sizes for growing crabs that use successively larger shells. To assess their potential importance to range shifts of hermit crabs, I characterized these commensal relationships over a large area of the northern Bering Sea in May to early June. Of 1539 hermit crabs collected, Pagurus rathbuni comprised 55%, P. trigonocheirus 44%, and Labidochirus splendescens 1%, with only four individuals of three other Pagurus species. Species richness for all living gastropods in my study area was 26 species, of which 18 were used by hermit crabs. P. rathbuni used shells of mostly moon snails (Naticidae); only 7 to 19% used whelk shells (Buccinidae) in the first four size classes, and 34% in the largest size class. P. trigonocheirus also used shells of mainly moon snails, but its use of whelk shells ranged from 18 to 44% in the first four size classes, and 70% in the largest size class. Densities of P. rathbuni and P. trigonocheirus varied independently of each other (r2 = 0.08, p = 0.09, N = 36 stations). Other studies suggest that hermit crabs obtain most of their shells from gastropods that have recently died, and that such empty shells are available for a relatively short period before being buried in sediments; thus, available shells should resemble the local pool among living gastropods. Correlation of P. rathbuni densities with densities of living gastropods with suitable shells was weak (r2 = 0.18, p < 0.01, N = 36 stations), while there was no correlation for P. trigonocheirus (r2 < 0.01, p = 0.59). Density patterns of hermit crabs within the five size classes did not correspond to those of living gastropods with suitable shells (randomization tests of independence, all p < 0.002). These results suggest that in the northern Bering Sea, initial effects of climate change on hermit crab distributions will depend more strongly on factors other than concurrent effects on dispersion of gastropods.

Extracted from Summary, p. 172. The semi-terrestrial grapsoid crabs Cyclograpsus punctatus and Sesarma catenata have been studied in two ways. Part I of this thesis gives an account of their distribution in the Kowie River estuary in relation to certain environmental factors. Part II deals with further aspects of their biology as well as the ecological relationship between the two species.

In the San Juan Archipelago, cancer oregonensis (Dana) Rathbun (Fig. 1) is abundant and distributed from the low intertidal zone to -435 m subtidally (Rathbun, 1904). Ricketts and Calvin (1974) refer to c. oregonensis as the most common Cancer species in this area.

published_or_final_version / Ecology and Biodiversity / Doctoral / Doctor of Philosophy

published_or_final_version / Ecology and Biodiversity / Master / Master of Philosophy

published_or_final_version / Zoology / Doctoral / Doctor of Philosophy