The Effects of Silkworm-Derived Polysaccharide (Silkrose) on Ectoparasitic Infestations in Yellowtail (<i>Seriola quinqueradiata</i>) and White Trevally (<i>Pseudocaranx dentex</i>)
2022
Takeshi Miura | Munenori Nishikawa | Yuki Otsu | Muhammad Fariz Zahir Ali | Atsushi Hashizume | Chiemi Miura
The effect of silkworm-derived polysaccharide silkrose on fish ectoparasites was investigated. When juvenile yellowtail (<i>Seriola quinqueradiata</i>) fed diets containing silkrose were artificially infected with <i>Benedenia seriolae</i>, a fish ectoparasite, the numbers of parasitized <i>B. seriolae</i> were significantly lower compared to that in fish in the control group without silkrose treatment. Furthermore, when juvenile yellowtails were severely infected with <i>B. seriolae</i>, no mortality was observed in the silkrose-treated group, compared to more than 60% in the control group. In field studies carried out at a fish farm with yellowtail and white trevally (<i>Pseudocaranx dentex</i>), oral treatment with silkrose significantly reduced <i>B. seriolae</i> parasitism in yellowtail and <i>Caligus longipedis</i> and <i>Neobenedenia girellae</i> parasitism in white trevally. Silkrose treatment also reduced blood levels of cortisol, a stress hormone in both species. The changes in gene expression in the epidermis of yellowtail by silkrose treatment were also investigated, showing that the expression of various genes, including factors involved in immunity, stress response, and wound healing, was changed by the treatment. These findings indicate that silkworm-derived silkrose effectively prevents infection by external parasites in yellowtail and white trevally.
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