Morphological and molecular characterization of Anisakids Larvae from Thunnus tonggol and Nemipterus japonicus in Iran

Anisakids, common Ascaridoid nematodes of marine fish; has been reported in throughout the world. Fish is an important source of nutrients, and the consumption of raw or uncooked fish can cause the fish-borne zoonotic diseases. There are few differences in the morphology of Anisakid nematodes larvae; therefore, molecular methods have been used for accurate identification and differentiation of Anisakid nematodes. The present study aimed to identify Anisakids Larvae isolated from Longtail tuna ( Thunnus tonggol ) and Japanese threadfin bream ( Nemipterus japonicas ) using morphological and molecular approaches. A total of 20 Thunnus tonggol and 20 Nemipterus japonicas were caught from the Persian Gulf. Morphological features using existing keys and PCR-sequencing of ITS region were applied for the identification of Anisakid larvae. The parasitological method showed that 14 out of the 20 Japanese threadfin bream (70%) and one out of the 20 Longtail tuna (5%) were infected with anisakids larvae. The isolated larvae were identified as Hysterothylacium amoyense and H. reliquens based on morphological characteristics, polymerase chain reaction, and sequencing. Based on morphological criteria; ventricle, intestinal caecum, ventricular appendix and the posterior end of two species were similar. In the anterior part of H. amoyense , a boring tooth surrounded by underdeveloped lips was observed, while they were not seen in H. reliquens. Fish is an important source of nutrients for humans, and the fish-borne zoonotic diseases are transmitted to humans via the consumption of raw or uncooked fish or fish products. Therefore, preventive measures include proper cooking and avoiding raw fish are suggested.