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Focal aggregates of leucocytes were present in the intestinal epithelium,
or adjacent to it, in 14.2% (8 of 127) of the gut tissues
examined. One case involved a large, loose aggregation of leucocytes
in the leydig tissue beneath the basement membrane. Another involved
small clumps of leucocytes between the columnar epithelial cells. Like
the general leucocytosis , this condition was difficult to judge. Leucocytes
are normally present in the epithelium, but more or less scattered
about. These clumps could be normal phagocytosis, although no foreign
matter was ever observed in such clumps. The intestinal epithelium
containing the above clumps appeared otherwise very healthy.
Focal necrotic areas were present in the gut epithelium of 3 (2.3%)
oysters examined. In two incidences, the gastric shield was involved.
This condition was characterized by a breakdown of the structure of the
a concentration of debris at the
gastric shield and/or epithelium,
affected area, and leucocytic inflammation of the gastric shield and/or
epithelium.
Ciliates were present in the gut lumen of one C. gigas. These
ciliates were the same type as described above in the digestive gland.
The plasmodial stage of an unidentified sporozoan was noted in the
epithelium of a single C. gigas. The Plasmodium was amoeboid in appearance
with several nuclei. The gut otherwise appeared in very good
condition.
Copepods were present in the stomach of 15.7% (20 of 127) of the
specimens examined. No oysters from Aber Wrac'h bore copepods. None of
the copepods observed were being phagocytized as was the case in the
digestive gland. Up to three copepods were observed in some sections.
4. Gonad . - Gonadal tissues of 130 C. gigas were examined. Generally,
two tissue samples were taken from each specimen (anterior and
psoterior visceral mass).
Gonadal tissues from C. gigas were a very difficult tissue type to
assess for non-symbiotic pathologies. Possible histopathologies were
noted in 38% (9 of 130) of the gonadal tissues examined. There were 50
incidences of the three non-symbiotic pathology (?) types and one symbiotic
pathology discussed below. Only six of the 50 conditions were of
an apparent symbiotic nature.
Half (36 of 71) of the female gonadal tissues examined exhibited
moderate to heavy aggregations, both focal and general, of eosinophilic
leucocytes. This presented a perplexing problem in determining if this
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