Abstract
Given the growing interest in marine aquaculture, the current study sought to monitor and investigate some of the pathogens affecting marine fish that could pose a threat to marine aquaculture and result in high mortality rates in southern Iraq. The marine Soleidae, a species of importance in marine aquaculture because of its ease of rearing, was among a variety of marine fish that were examined. Only one of the thirty fish that were inspected had an infection rate of 3.3%, which is a very low percentage. The findings demonstrated that the nematode worm Huffmanela (Nematoda: Trichosomoididae: Huffmanelinae) lays its eggs in the intestinal tissues of the fish Brachirus orientalis (Bloch & Schneider, 1801) of the Soleidae family, which are unique sites for this kind of infection. Multiple tiny black spots, which are outward indicators of infection, were present on the serous and subcutaneous layers, characterizing the infection. Huffmanela species are known for their polyploid, thick-walled, and tissue-clustering eggs, which were observed both histologically and under a microscope. Additionally, pathological examinations showed that the eggs were rough, brown-shelled, oval to spindle-shaped, and encircled by localized fibrosis and tissue tears. This study adds to our understanding of the nematode biodiversity in the northern Arabian Gulf by being the first to report Huffmanela infection of B. orientalis in Iraqi marine waters.