Journal of Marine Biology

Tuna are among the most economically important fish for many countries and are of considerable significance in terms of industrial fisheries and economic value. Among fish parasitic infections, acanthocephalan infections occupy a distinctive position. All worms belonging to the phylum Acanthocephala are obligate parasites, and all stages of their life cycle except the egg stage are completed within the host’s body. In the present investigation, a total of 10 tuna caught in the Persian Gulf and subsequently frozen, and referred to the Department of Aquatic Animal Health and Diseases, Shahid Chamran University of Ahvaz, were examined. Twenty-seven cysts were isolated from the musculature. The mean cyst dimensions were 4 mm × 2 mm. After opening the cysts and staining the cystacanths, morphological characteristics indicated that the identified cystacanths belonged to Tenuisentis niloticus. In addition, using a drawing microscope, the mean length and width of the cystacanths were 2.30 mm and 0.54 mm, respectively. Because the cystacanth develops in the intermediate host, the internal organs are typically observed clearly and completely. If a fish serving as the intermediate host ingests infective larvae, it may subsequently function as the definitive host. It is evident that the accidental migration of larvae into sensitive organs could lead to serious complications. Nonetheless, it should be noted that, in general, infection of the musculature of Thunnus tonggol with these parasitic cysts can directly affect marketability. Therefore, where feasible, reducing infection may be achieved through elimination of intermediate hosts, removal or control of disease reservoirs, and implementation of appropriate management and organizational measures.