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RESULTS
Tissues from 134 specimens of Cvassostvea gigas from four sites were
examined for histopathologies over five sampling trips. From the specimens
collected, tissue samples of 131 adductor muscles, 127 stomach/
intestines, 129 digestive glands, 130 gonads, 134 gills, and 130 mantles
were examined for a total of 781 tissues out of a possible 804.
A total of nine types of pathologies were found with an incidence
of 241 occurrences (Table 1). Five-hundred and ninety of the 781 (75.6%)
tissues examined were free of pathologies; or, 191 of the 781 (24.3%)
tissues examined bore one or more pathologies. Of the 241 pathologies
found, 77 (32.0%) were various types of symbioses, while 164 (68.0%)
cases apparently were not correlated with symbioses. Table 2 summarizes
the distribution of pathologies among the tissues examined. Adductor
muscle had the lowest incidence (3.8%). Digestive gland tissue had the
highest incidence (23.9%) followed by gill (22.0%), mantle (21.4%), gut
(17%), and gonad (11.9%). The number of tissues with pathologies was
nearly evenly distributed among the collecting sites. Oysters from
reference stations had a higher incidence of lesions, particularly in
gonad and gill, than oysters from oil-polluted sites. Thirty percent of
the oyster tissues from both Aber Wrac'h and Aber Benoit bore one or more
pathologies. Forty percent of the tissues from Rade de Brest and lie
Tudy combined contained one or more pathologies.
Overall, mantle bore the lowest number of pathology types (3) while
digestive gland contained the most types of pathologies (9) followed by
gut (7), gill (6), gonad (5), and muscle (4).
Pathologies and their distributions among organs and sites are
described below.
1. Muscle . - Muscle tissues were examined from 131 C. gigas.
Samples for microscopic examination were dissected from the adductor
muscle and both fast and catch muscles were examined when possible.
Generally, two tissue samples were taken from each muscle and oriented
to give both longitudinal and cross sections.
Histopathologies occurred in 4.6% (6 of 131) of the muscle samples
examined. There were a total of 9 incidences of. the three pathologies
described below. Muscle from reference stations contained the widest
variety of pathologies. No pathologies were found in muscles from Aber
Benoit.
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