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antenai, and longitudinal spiral rows of short, stout cilia. They
did not appear to damage the diverticula.
Sporozoa were present in the diverticular epithelium of 16 (12.4%)
of the specimens examined. All but two of the cases were from Aber
Benoit or Rade de Brest and lie Tudy (Table 3). Sporozoans were spherical
and stained very intensely. They were often surrounded by a clear
(lysed ?) zone.
The digestive gland of one specimen bore a nematode which elicited
an inflammatory response, an aggregation of eosinophilic leucocytes.
Remains of copepods were noted in the diverticula of 3 C. gigas
from Aber Benoit. They were accompanied by heavy leucocytic inflammation
and were being phagocytized as evidenced by the presence of leucocytes in
the copepods.
3. Gut . - Samples consisting of stomach, intestine and often esophageal
and rectal tissues were examined from 127 C. gigas. Generally,
two tissue samples were taken from each specimen (anterior and posterior
portions of the visceral mass).
Histopathologies were noted in 32.2% (41 of 127) of the gut samples
examined. There were 62 cases of the 6 pathology types discussed below.
Thirty-five percent (22) involved a symbiont while 40 cases (65%)
apparently were not symbiotic in nature, although there may be some
question about this. Specimens from the combined reference stations bore
more than two and a half times the pathologies as Aber Wrac'h specimens.
Oysters from Aber Benoit contained slightly fewer pathologies than those
from the reference stations and twice the number of pathologies as specimens
from Aber Wrac'h.
Abnormally high numbers of eosinophilic leucocytes (general leucocytosis)
were noted in the intestinal epithelium, and sometimes surrounding
all
leydig tissue, of 15% (19 of 127) of the C. gigas examined. Almost
cases were in oysters from Rade de Brest. This condition was difficult
to judge. Oyster intestinal epithelium normally has some leucocytes
between columnar cells. However, the large number of leucocytes in the
intestinal epithelium of these 14 specimens appeared abnormally high,
the number was considered abnormally high if the basal portion of columnar
cells was completely, or almost completely, obscured by leucocytes.
However, there still is some doubt about whether- this is a "pathology"
or a normal condition. Except for the large number of leucocytes, the
intestinal tissues appeared very healthy.
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