Morphological and molecular identification of nematodes of digestive system of Sorkhu (Lutjanus johnii) and Ghobad (Scomberomorus guttatus) fishes in Persian Gulf waters of Hormozgan province

Abstract

Introduction: Marine fish are important in providing animal protein and human health. The study of pathogenic factors of these fish, including parasitic factors, plays an important role in applying preventive policies and quality control of fishery products. Therefore, it seems necessary to identify the morphology and molecular parameters of fish parasites in the Persian Gulf, which are considered to be one of the main sources of food in Iran. Materials & Methods: In the present study, 20 pieces of infected Sorkhu and Ghobad fish were caught and analyzed separately from the coastal areas of the Qeshm, and kish in Hormozgan province. For each fish, morphological characteristics including length and width, body weight, standard length in Sorkhu, fish and fork length in Ghobad fish were measured and recorded. Each infected fish peritoneum, viscera, and entire digestive tract of each infected fish were examined macroscopically for the presence of gastrointestinal nematodes and isolated. Then, the collected nematodes were identified after washing and storing in preservative and clarifying solutions. Nematode larvae were examined by PCR method to confirm the diagnosis by molecular method with specific primers of each genus. Results: 18 (90%) and 20 (100%) fish pieces were infected with nematodes from Sorkhu cidentified in Scomberomorus guttatus fish were Terranova and Ascarophis, respectively. Ascarophis and Raphidoscaris species were detected as the most abundant nematodes in Lutjanus johnii; It should be mentioned that the nematode species of Ascarophis, Hystrotilacium and Paracamalanos in Scomberomorus guttatus fish and Capillaria, Eustrongyloides and Cosmoxynemoides in Lutjanus johnii fish had the lowest level of contamination. In molecular studies, larvae and parasitic nematodes suspected by PCR method with specific primers of each genus, infection of Scomberomorus guttatus and Lutjanus johnii fish with nematode species Tranova, Anisakis, Ascarophis and Hysterothylacium after sequencing and comparing the degree of similarity of their genomes with other species. Nematode was confirmed by the World Gene Bank (NCBI).
Conclusion: This study showed that due to the high level of nematode contamination, especially zoonotic nematodes in bony fishes of the Persian Gulf, it is important to monitor the stages of preventing the transmission of infectious parasitic agents parasites and to monitor the stages of processing and consumption of marine fish to ensure their health safety and quality.