The main purpose of this study was to establish the pattern of variability
of some hemato-immunological parameters in the mangrove oyster, Crassostrea rhizophorae, from 3 different environmental conditions in Santa Catarina Island: two natural
habitats (mangrove and rocks of the coastal bay) and one oyster culture
station. The water quality was adequate in all localities. The animals were
collected seasonally over a period of one year (n = 30, per locality). The
oyster hemolymph comprised two basic cell populations, hyaline (HH) and
granular hemocytes (GH). Both cell populations contained carbohydrates and
glycogen in their cytoplasm (periodic acid Schiff reaction, PAS staining)
and the occurrence of lysosomes was suggested by the detection of acid
phosphatase (Gomori's method). Both hemocyte populations were able of
phagocytosis of zymosan particles in vitro and producing cytotoxic
molecules, such as the superoxide anions (nitroblue-tetrazolium, NBT
reduction). The oyster hemograms significantly differed in the different
habitats and also among seasons. The total circulating hemocyte counts (THC)
and the percentage of GH in the mangrove and rock oysters always differed
from each other, but not from those of the cultured oysters. The highest THC
and the lowest percentage of GH were always found in summer. The total
plasma protein concentration (PC) exhibited a similar seasonal pattern in
all oyster populations, with a marked decrease in spring. The PC of the
cultured oysters was almost always significantly lower than that of the
other oyster populations. The plasma agglutinating titer was higher in the
cultured oysters regardless of season. The histological organization of the
oyster digestive gland and gills was basically similar to that of other
oyster species. Their structural aspect did not show any detectable
alteration, corroborating that the oysters were in good health. The results
of this study will serve as a basis for further analyses on the monitoring
of C. rhizophorae health status and environmental quality in different aquatic habitats.