Kapsulotaenia tidswelli – an unusual cestode from the Australian goannas Varanus gouldii gouldii and V. giganteus

Kapsulotaenia tidswelli is a proteocephalidean cestode that utilizes varanid lizards as definitive hosts. Fresh specimens of this cestode were observed with endogenous red pigmentation in the neck region that disappeared rapidly if specimens were not preserved in glutaraldehyde. The ultrastructural characteristics of the red pigment, which are described, suggest it is a carotenoid. Phylogenetic analysis confirmed a close relationship between K. tidswelli and other species of Kapsulotaenia for which sequence information is available. There is thus no reason to consider that the red pigmentation is because K. tidswelli is atypical, and it is proposed the carotenoids are likely to be associated with the diet of its varanid host.