Spawning Behaviour of Rudd, Scardinius erythrophthalmus infested with Plerocercoids of Ligula intestinalis

THE plerocercoid of Ligula intestinalis is found in the body cavity of cyprinid fishes, where it causes castration 1 . Kerr 2 in 1948 showed that the presence of the plerocercoid reduces the number of basophils in the pituitary of infested roach, with consequent virtual elimination of gonad stimulating hormone of the pituitary, and this work was afterwards confirmed 3,4 . More recently, it has been shown that this occurs not only in roach parasitizod by Ligula plerocercoids, but in other cyprinids as well.