P29-8

s119

P29-10

Sea lice, Lepeophtheirus salmonis (CopepodxCaligidae) in Atlantic salmon, Salmo salar: the dynamics host resistance and of parasite fecundity in infested fish

A. Mustafa, G. A. Conboy and J. F. Burka Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PEI, Canada C 1 A 4P3.

Non-specitic host resistance and parasite fecundity were tested by artificially infesting hatchery-reared post-smolts of Atlantic salmon with laboratory grown infective copepodids of sea lice (mean intensity 106). Plasma cortisol and glucose levels increased significantly and macrophage respiratory burst and phagocytic activities decreased significantly in the lice infested fish from 3 weeks post-infestation, when the lice became mobile. At 6 weeks post-infestation the lice on 10 fish randomly selected for a longer term study started to produce egg-strings. The numbers of surviving adult females and their egg-strings decreased over the next 6 months. Eggs from these parasites also lost their hatching ability or ability to develop into active copepodids. Over the same period, salmon on the other hand, brought their non-specific defence activities to the same levels as those of controls. This suggests that there may be an immunological strategy in Atlantic salmon against sea lice infestations. (Supported by the NSERCMRC Partnership Program)

P29-9

Life in the burrows: metabolic rate depression in two species of crayfish.

Powell ML and Watts SA Department of Biology, University of Alabama at Birmingham, Birmingham, Alabama, USA 35294-l 170

The hfe cycles of the crayfish Procambarus m and p. zonangulus, in Louisiana crayfish ponds, include an extended periomme (3-4 months) i;l burrows during the summer months. During this time females will extrude eggs which mature while the female is in the burrow and juveniles will emerge in the fall. Survival during prolonged starvation may depend on a species ability to suppress the overall metabolic rate. We examined the metabolic rate of P. clarkii and _P. zonangulus over a 5-month period of starvation. The metabolic rate of starved P. clarkii and p. zonangulus decreased significantly from fed controls by 4 and 5 months, respectively. At 5 months mean metabolic rates were 4.34 and 2.44 pmol02/sec/mg dry wt. for fed and starved P. clarkii, respectively. Metabolic rates for _P. zonangulus were 5.39 and 2.10 pmol Oyseclmg dry wt. for fed and starved groups, respectively after 5 months of starvation. Starved P. clarkii -7 which did not significantlv decrease their metabolz rate relative to fed controls during the first 4 months of starvation, experienced the lowest survivorship after 5 months of starvation (45% and 82% for males and females respectively). However, starved p. zonangulus, which showed a greater decrease in the metabolic rate relative to the fed controls, had higher survivorship after 5 months of starvation (71% and 89% for males and females, respectively). Although starvation delayed oviposition one to two weeks in both species there was no significant difference in the number of females extruding eggs between the fed and starved treatment groups.

Thermal acclimation in the early life stages of Arctic char, Salvelinus alpinus.

Shahsavarani A, Ballantyne JS and Wright PA Department of Zoology, University of Guelph, Guelph, Ontario, Canada, NlG 2Wl.

The effect of thermal acclimation to four temperatures (4, 6, 8 and 1 O°C) was studied in Arctic char, Salvelinus alpinus, from fertilization up to time of hatching. For each acclimation group, oxygen consumption was measured as an indicator of metabolism. Although oxygen consumption was positively correlated with experimental temperatures during acute exposure (less than 2 hours), there was no similar relationship with chronic exposure (weeks). This data suggests that S. alpinus is not capable of thermal acclimation during its early life stages. To further examine this process, a new method was developed to separate yolk from embryonic tissue by centrifugation. Amino acids, certain phospholipids and enzyme activities were examined in the yolk and tissue at various developmental stages. The findings indicate that the initial maternal contribution and/or the ability of the developing embryo to modify and utilize metabolites may be possible factors limiting thermal acclimation during these early life stages.

P29-11

The physiological effects of ectoparasite infection of coral trout, Plectropomus leopardus. Turner TB, Bennett MB and Bennett SM* Departments of Anatomical Sciences and *Parasitology, University of Queensland, Brisbane, Qld, Australia 4072

Coral trout are the subject of an important and expanding live- fish export industry and are a strong candidate for tropical marine aquaculture. Parasitic infection can adversely affect cultured finfish productivity. The project aimed to determine whether a causal relationship exists between ectoparasite load and physiological status. The physiological status was determined from assaying blood samples taken within 60 s of hooking. The results, indicative of baseline stress, were compared to the longer term stress response due to hooking, handling and captivity. Ectoparasite number was positively correlated with fish size. Copepods cause attachment trauma to the gills (D&onus manteri, 4-165Ifish; Hatschekia plectropomi, 35479/fish), and the upper palate (Lepeophtheirusplectropomi, 2-145Ifish). Dentigryps litus (l- 8/fish) move freely over the body surface. No significant correlation existed between ectoparasite load and physiological stress. Glucose concentrations of 15.7 mM occurred 2 h post- hooking, whereas initial samples never exceeded 2.6 mM. Equivalent values for osmolality were 494 and 434 mOsm/l, and for cortisol, 50 nm and 0.4 nm indicating that levels of ectoparasite infection on wild fish were insufficient to cause significant physiological disturbance to the host fish.