アニサキスは宿主の中で何をしているのか？

抄録

The parasitic nematode Anisakis is one of major parasites frequently found in fish, squid, and marine mammals including dolphins and whales, and cases severe abdominal pain if human eats infected fish or squid. However, little knowledge is available in what the parasites are doing in the host fish species and how they can survive and remain infective in their unique life cycles. In the present study, to enhance our knowledge on the parasite, we investigated trophic level (TL) and potential diet resources (δ¹⁵N_Resource) based on stable nitrogen isotopic composition (δ¹⁵N) of glutamic acid and phenylalanine in Anisakis larvae and their host fish Pleurogrammus azonus. The TL of Anisakis larvae (2.6-2.9) is considerably smaller than that of muscle in the host fish (3.6). Moreover, the δ¹⁵N_Resource values largely vary among individual Anisakis larvae specimens (2.4‰-4.7‰), and several specimens are clearly smaller than the value of muscle in the host fish (4.3‰). These results reveal that Anisakis larvae have never fed on the host fish tissues/organs even though they are found in the fish, and suggest that Anisakis larvae can survive as a dormant phase, remain infective, and be accumulated in the paratenic host fish for the effective infection to the definitive hosts.