The Pesticidal Effects of Chinese Herbal Medicine on the Trophonts and the Theronts of Ciliate Cryptocaryon irritans and the Influence of Temperature and Salinity on the Cyst Rupture

Abstract:

In this study we performed in vitro study on the pesticidal effects of 15 Chinese herbal medicines on the trophonts and theronts of ciliate Cryptocaryon irritans, including Betel nut (Areca catechu), Bitter ginseng (Sophora flavescens), Rhubarb (Rheum officinale), Cyrtomium rhizome (Cyrtomium Rhizoma), Radix scutellariae (Scutellaria baicalensis) and Wild chrysanthemum (Dendranthema indicum). We also explored the optimum temperature and salinity for the cyst rupture. At the concentration of 4.55 g/L, Betel nut could kill both the trophonts and the theronts of the ciliate, but Rhubarb and Wild chrysanthemum could only kill theronts. At the concentration of 9.09 g/L, both Bitter ginseng and Cyrtomium rhizome were able to kill the trophonts and the theronts. At the concentration of 18.18 g/L, Radix scutellariae, Toosendan fruit (Melia toosendan) and Fructus aurantii (Citrus aurantium) could kill the trophonts and the theronts, and Wild chrysanthemum could kill the trophonts. Other herbs could annihilate the trophonts and the theronts at much higher concentrations (45.45 g/L to 90.91 g/L), such as Astragalus root (Astragalus membranaceus), Heartleaf houttuynia herb (Houttuynia cordata), Isatis root (Isatis tinctoria), Chinese bulbul (Anemone chinensis), Honeysuckle (Lonicera japonica), Radix rehmanniae preparata (Rehmannia glutinosa), and Rhizoma coptidis (Coptis chinensis). These results suggested that Betel nut, Bitter ginseng, Rhubarb, Cyrtomium rhizome, Radix scutellariae, Toosendan fruit, Fructus aurantii, and Wild chrysanthemum might be more pesticidal than the other herbs, and hence they could be used to control the ciliate. Our study also revealed that the optimum temperature and salinity for the cyst rupture were 26℃and 20-30 respectively.