Interspecific relationship between P.magnum and P.(N.) celatus in the intestine of ricefield eel were studied on the site occurring alone and together.The distribution of each species in the gut of hosts was extremely similar when the two helminths occurred alone,similarity coefficient is r =0.9226( P <0 01).With P.magnum growing,the distribution of P.magnum moved ahead and the distribution of P.(N.) celatus moved backwards significantly and the niche overlap of two parasites decre...