Projects
Effects of sea
lice on the development of chronic stress and suppression of host Atlantic Salmon
defense
mechanisms This experiment was
conducted to determine the effects of sea lice on chronic stress parameters and on
non-specific defense mechanisms in Atlantic salmon. The salmon were infested with
sea lice at intensities ranging from 15-285 lice per fish, and were sampled at days 0, 3,
7, 14, and 21. Blood was sampled from each fish, as well as the head kidney for the
evaluation of blood cortisol and glucose (stress indicators) and for macrophage status. At the conclusion of
the experiment, it was determined that the blood cortisol and glucose levels rose
dramatically between day 14 and day 21, and that macrophage activity decreased by day 21.
These decreased levels corresponded with the development of the lice to the 4th
chalimus stage, supporting the perception that lice become more detrimental at later life
stages. Comparative
susceptibilities of salmonid species to sea lice infestations Previous studies have
demonstrated that resistance to infestation with sea lice (Lepeophtheirus salmonis)
differs between species. Coho salmon (Oncorhynchus kisutch) are the most
resistant to sea lice, followed by Chinook salmon (Oncorhynchus tshawytscha) and
then by Atlantic salmon (Salmo salar). In addition, an economically
important species, Steelhead trout (Oncorhynchus mykiss) is also known to be susceptible
to sea lice infestations. The objective of this
study is to determine stress parameters in the blood, mucus and tissues so that the effect
of the sea lice infestation on the development of chronic stress and the suppression of
host defense mechanisms in each species can be determined. Effect of
chemical treatments on re-infestation of sea lice on salmonids The objective of this
study is to determine if the stress of pesticide application has an effect on the fish's
susceptibility to re-infestation. Aquaculture fish that are treated are probably
re-exposed to sea lice almost immediately after treatments. The procedures required
to treat the fish with pesticides probably serves as a stressor. The test group of fish
will be treated with the pesticide Azamethiphos and then infected with sea lice, while the
controls will receive no treatment, and then be exposed to sea lice. After a given
period of time, the number of sea lice on the fish will be counted to determine if the
treated fish have a higher infestation rate than those which were not treated. Effect of
multiple sea lice infestations on Atlantic Salmon At the present time,
it is not known if sea lice induce a protective immune response in fish. The
likelihood of success for a vaccine against sea lice would be increased if this could be
determined. The objectives of this study are to determine if there is a protective
response in fish which have had previous sea lice infestations. The test group of
Atlantic salmon will be infested with sea lice and left for a period of 4 weeks, after
which they will be anaestatised and the sea lice mechanically removed. The control
group and the test group will then be infected with another batch of sea lice to determine
if the previously infected group shows any natural resistance to the
re-infestation. Effect of Sea
Lice on Mucus Pattern Distribution It is well known that
sea lice feed off the mucus, blood and skin cells of their hosts. This ultra structural
study's objectives are to determine what effect this browsing has on the
overall mucus coat of the infested fish. Sections of fresh skin from control and
infested fish are taken and prepared for both light and electron microscopy. Using
electron microscope techniques, it is possible to view and photograph the mucus coat of
the skin as well as the goblet cells which produce it. Preliminary results show that
control fish show a fairly even and smooth coat of mucus whereas sea lice infested fish
have washed out mucus.
Investigators: Dr. John
F. Burka
Dr. Ahmed Mustafa
Investigators: Dr. John
F. Burka
Dr. Ahmed Mustafa
Investigators: Dr. Gary
Conboy
Dr. Ahmed Mustafa
Investigators: Dr. Gary
Conboy
Dr. Ahmed Mustafa
Principal Investigator: Dr. David
Sims
This is normal fish skin viewed with light microscopy. The arrow shows the extent of the skin layer, the letter M depicts mucus producing cells, and the rectangle shows the portion of the skin that the following two diagrams represent.
Healthy skin looks very
uniform, and the mucus coat (surrounding the microridges) is thick and full
looking.
On the other hand, lice
infested skin has a mucus coat that is much thinner than in normal skin, and
that has a washed out appearance.
Pictures from: Horne, M.M. and Sims, D.E. Preliminary ultra structural studies of the surface mucus of Atlantic salmon. Bull. Aquacul. Assoc. Canada 98-2: 85, 1998.