REMARKS ON TYLODELPHYS

Based on our analysis, Tylodelphys spp. belong to at least three distinct clades (Fig. 1). Achatz et al. (In press) recently suggested that Tylodelphys americana (Dubois, 1936) (see Dubois, 1936b) and Tylodelphys sp. 4 may need to be placed in a novel genus. However, the inclusion of the DNA sequence of T. excavata in the present analysis has further complicated the situation. It is possible that Tylodelphys as currently recognized may represent a complex of genera and requires the establishment of at least two new genera. DNA sequences from adult specimens of T. clavata (von Nordmann, 1832) are necessary for a conclusive decision regarding the status of Tylodelphys.

The majority of Tylodelphys spp. and members of the closely related Austrodiplostomum and Diplostomum are known to primarily parasitize piscivorous birds (Achatz et al., In press). Achatz et al. (In press) recently revealed the presence of two Diplostomum spp. parasitizing North American river otters Lontra canadensis (Schreber, 1777) in the USA. Based on the results of the present study, T. variabilis represents the first species of Tylodelphys that secondarily switched from avian to mammalian definitive hosts. Transitions between birds and mammals may happen when hosts occur in the same environments and have overlapping diets; similar to many aquatic birds, otters and raccoons feed on fishes and amphibians.