The present study was carried out to investigate parasites of one
from the most important seafood, the blue crab Portunus pelagicus. Samples
of crabs were caught seasonally fromRas El Bar, Damietta, Egypt. Results
showed that crabs were infested with two different parasites (protozoa and
nematode larvae). The identification of protozoa was confirmed by using the
electron microscope. The current study revealed that only 30% of P.
pelagicus were infected with parasites. Protozoan parasites showed a
prevalence of 79.63%, while nematode larvae showed a prevalence of
20.37%. Histological examination of infected tissues showed disruption of
tissue cells, loss of normal gill structure, interruption of lamellae, presence of
several granulomas. Also, gonad follicles showed degeneration in the infected
crabs. The histopathological effects of such parasites could induce host injury
especially in case of heavy infection. However, the highest infection of
parasites was recorded in the crabs with a medium size (carapace width 10.1-
15 cm & length 6.1-9 cm). whenever the least infection was recorded in the
heaviest crabs. Alternatively, the present study may lead to the conclusion that
heavy crabs are believed to be healthier for the consumers as it was less
susceptible to parasite infection.