The Differences of Anisakis Larvae Infection on Scads (Decapterus spp.) in the Indian Ocean off the Southern Coast of East Java Indonesia

This study investigated the Anisakis larvae infection in the scads (Decapterus spp.) in the Indian Ocean off the southern coast of East Java. A fish sample of approximately 450 individuals, consisting of three scad species, i.e., the Indian scad (D. russelli), the shortfin scad (D. macrosoma), and the redtail scad (D. kurroides), were obtained from Prigi and Muncar fishing port, East Java. Fish samples were measured individually for length and weight and subsequently dissected and examined in detail to detect the presence of Anisakis larvae in the abdominal cavity, intestinal tract, gonad, liver, and muscle. The collected larvae were preserved in 100% ethanol for the further identification process. The study indicates that the Decapterus spp. were receptive to the Anisakis larvae infection, with varying prevalence and mean intensity across species and locations. The redtail scad (D. kurroides) exhibited the highest prevalence and mean intensity; all of the sample were infected with Anisakis larvae (P= 100%), with a mean intensity of 22.54 larvae/individual.The shortfin scad (D. macrosoma), on the other hand, showed the lowest prevalence (P= 30.61%) and a mean intensity of MI = 1.29 larvae/individual. Most Anisakis larvae (52.30–76.61%) were located within the body cavity, followed by the digestive tract (16.78–18.40%), and only a small number of the larvae were detected in the liver, gonads, and muscles. The morphological identification indicated that the larva infecting the scad was Anisakis Type I, and it was confirmed as Anisakis typica throughout molecular identification. Anisakis typica parasitizes the redtail and shortfin scads in the Indian Ocean off the southern coast of East Java, indicating genetic variation, which is shown by the differences in nucleotide composition. The differences in Anisakis larvae infection and its genetic variation might be developed as biological indicators for various ecological investigations of the Decapterus spp.