Abnormal spicule development in a laboratory strain of trichostrongylus vitrinus

The occurrence of specimens in a laboratory strain of Trichostrongylus vitrinus exhibiting unusual spicules resembling those of T. minor and T. angistris is reported and the abnormal spicules described. The specimens include individuals with one spicule typical of T. vitrinus and the other spicule of the abnormal type. Possible reasons for the occurrence of such abnormalities are discussed.