First detection of the parasitic dinoflagellate Hematodinium sp in the blue swimming crab Portunus segnis from the Suez Canal, Egypt

Background

The bitter crab disease was recorded for the first time in the blue swimming crab Portunus segnis inhabiting the Suez Canal. This study aimed to assess the presence of the parasitic dinoflagellate Hematodinium sp. in P. segnis in the Suez Canal lakes and investigate the infection levels in the crab’s tissues. We collected monthly samples from Timsah and the Bitter Lakes between October 2020 and September 2021. Crabs’ carapace width and weight were measured, and hemolymph smears were prepared for examination. Samples from the hepatopancreas, gills, heart, and muscles were taken for histopathological studies.

Results

In both lakes, crabs were found infected with the parasitic dinoflagellate Hematodinium sp. More than a quarter of the population in both areas had pathogens in their bodies (≥ 26%). Infection prevalence varied insignificantly with the body weight in the two lakes. The investigated internal organs were found to be invaded by the pathogen that caused significant damage to their tissues. The hemolymph lacked the capacity to clot in such a way that the heart’s spongy texture was apparently lost, and the muscles had disrupted connective tissue and edematous fibers. There was also a widening of the distance among the hepatopancreatic tubules as well as a distention of gill filaments.

Conclusion

This work highlights that over 25% of the P. segnis population in the Suez Canal is infected with Hematodinium sp.. In this respect, the study recommended the immediate and continuous monitoring of the P. segnis in the Suez Canal lakes in order to prevent future disease outbreaks.