Potamotrygonidae, Garman, 1877

Elasmobranch, Its Implications For Global, Parasitology, Diversity And, Naylor, G. J. P., Sc, Caira, J. N., Ct, Jensen, K., Ks, Rosana, K. A. M., Fl, White, W. T., Csiro, Tas, Last, P. R., Csiro & Tas, 2012, A Dna Sequence-Based Approach To The Identification Of Shark And Ray Species And Its Implications For Global Elasmobranch Diversity And Parasitology, Bulletin of the American Museum of Natural History 2012 (367), pp. 1-262 : 78-79

Potamotrygonidae (river stingrays)

Potamotrygon species ( fig. 60)

Much confusion surrounds the identities of the potamotrygonid stingrays from the rivers of South America. In total, the analysis included nine specimens of the South American freshwater stingray genus Potamotrygon , five of which were collected from the Madre de Dios River in Peru. The results of the analysis suggest that these nine specimens represent perhaps as many as six distinct lineages. However, the molecular results are not necessarily congruent with the color patterns of the specimens involved. Given this, in combination with the fact that only two of the nine specimens have been deposited in a museum (GN5881 5 MZUSP 95411 and GN5880 5 MZUSP 107670), and in light of the concerns raised by Toffoli et al. (2008), we have only limited confidence in the identifications of the specimens included here.

The analysis yielded a group comprised of all nine specimens, with a cluster comprised of five specimens collected from the Madre de Dios River in Peru. Within the Madre de Dios cluster, the genetic identities of three specimens were much closer to one another than to either of the other two specimens in the cluster. These three specimens had a range of pairwise differences of 2–3 (with an average of 2.7). However, the color patterns of these five specimens are inconsistent with their genetic identities. Given the issues raised by Toffoli et al. (2008), the identities of these specimens have been assigned here are based in large part on color pattern. We are confident that GN5880 is P. tatianae because it was among the voucher specimens examined by da Silva and de Carvalho (2011) in their description of P. tatianae , which is known only from the Madre de Dios River. Two specimens have been identified as P. cf. tatianae because, although they are consistent with the color pattern of that species, they differ from it by 26.5 bases. The color pattern of the remaining two specimens resembles that of P. motoro . However, in the absence of definitively identified specimens of P. motoro , in combination with the fact that these specimens differ from one another by 37 bases, we have given these specimens the designations Potamotrygon cf. motoro 1 and P. cf. motoro 2. The remaining four specimens were purchased from pet stores and, as a consequence, are of unknown provenance and their identities are uncertain. These have been given the designation Potamotrygon sp. 1 and Potamotrygon sp. here, but it is important to note that these specimens may represent described species that were not included in the analysis. The two specimens of Potamotrygon sp. 1 differed from one another by one base and the two specimens of Potamotrygon sp. 2 differed from one another by one base. The average of the pairwise differences between specimens of Potamotrygon sp. 1 and those of Potamotrygon sp. 2 was 104. Clearly, much work remains to be done to resolve the identities of these specimens relative to confirmed material.

Paratrygon aiereba (discus ray) ( fig. 60)

A single specimen of this currently monotypic genus, also collected from Peru, was included in the analysis. This grouped along with but outside the Potamotrygon specimens. This specimen is deposited in the Zoology Museum in Sao Paulo, Brazil (GN5874 5 MZUSP 95406).

Himantura schmardae (Chupare stingray) ( fig. 60)

A single specimen of this species, collected from Guyana, was included in the analysis. This specimen clustered along with, but outside those of Potamotrygon and Paratrygon . This specimen was deposited at the Royal Ontario Museum (GN6488 5 ROM 66845). The grouping of this species with the Potamotrygonidae rather than with the Dasyatidae warrants further taxonomic investigation.