Didelphodiplostomum, Dubois, 1944

Achatz, Tyler J, Chermak, Taylor P, Martens, Jakson R, Woodyard, Ethan T, Rosser, Thomas G, Pulis, Eric E, Weinstein, Sara B, Mcallister, Chris T, Kinsella, John M & Tkach, Vasyl V, 2022, Molecular phylogeny supports invalidation of Didelphodiplostomum and Pharyngostomoides (Digenea: Diplostomidae) and reveals a Tylodelphys from mammals, Zoological Journal of the Linnean Society 196 (1), pp. 124-136 : 133

STATUS OF DIDELPHODIPLOSTOMUM

The analysis of 28S ( Fig. 1 ) places Did. variabile (shown as Tylodelphis variabilis comb. nov. in the figure) in the cluster of Tylodelphys and Austrodiplostomum species. The morphology of adult Didelphodiplostomum and Tylodelphys spp. is remarkably similar ( Fig. 4A ; Dubois, 1968). Furthermore, Didelphodiplostomum and Tylodelphys have identical flame-cell formulas, 2 [(2+2)+(2+[2])] = 16 ( Harris et al., 1967; Dubois, 1968, 1970; Niewiadomska, 2002). Dubois (1968) emphasized the remarkable morphological similarity between Didelphodiplostomum and Tylodelphys species. However, the members of the two genera differ in the shape of anterior testis (asymmetrical in Didelphodiplostomum spp. vs. symmetrical in Tylodelphys spp. ) and the lack of a genital cone in Didelphodiplostomum spp. (present in Tylodelphys spp. , albeit weakly developed in some species).

Our molecular phylogeny ( Fig. 1 ) clearly demonstrates that Did. variabile belongs to one of the two major clades of Tylodelphys . Taking into account the results of our phylogenetic analysis ( Fig. 1 ) and minor morphological differences between Didelphodiplostomum and Tylodelphys , we consider Didelphodiplostomum to be a junior synonym of Tylodelphys . As such, we transfer Did. variabile and Did. nunezae into Tylodelphys as T. variabilis ( Chandler, 1932) comb. nov. and Tylodelphys nunezae ( Dubois, 1976) comb. nov., respectively. The partial 28S and cox1 sequences of T. variabilis and Tylodelphys sp. VVT1 of Achatz et al. (In press) are identical. It is clear that the larval specimens of Tylodelphys sp. VVT1 from the mole salamander Ambystoma talpoideum Holbrook, 1838 collected in Mississippi are conspecific with T. variabilis . An amended diagnosis of Tylodelphys is provided below.

Figures

Figure 1. Phylogenetic interrelationships among 54 diplostomoidean taxa based on BI analysis of partial 28S rDNA gene sequences including Didelphodiplostomum and Pharyngostomoides spp. BI posterior probability values lower than 80% are not shown. The new sequences generated in this study are indicated in bold. The scale bar indicates the number of substitutions per site.

Figure 4. Photographs of: A, Tylodelphys variabilis comb. nov.from Didelphis virginiana, Arkansas; B, Alaria arisaemoides from Canis latrans, Oregon; C, Alaria alata from Nyctereutes procyonoides, Ukraine; D, Alaria marcianae from Taxidea taxus, North Dakota; E, Alaria ovalis comb. nov. from Procyon lotor, Mississippi; F, Alaria procyonis comb. nov. from Procyon lotor, Minnesota; G, H, Alaria mustelae from Mephitis mephitis, North Dakota.