Cyprinidae: Colossoma Bidens Metynnis

Sunday 22 July 2012

Colossoma Bidens Metynnis

Both pacus and silver dollars are not exclusive, yet are not totally inclusive if one simply lumps these vulgar names as common names of a particular group. The group which forms the silver dollars and pacus (for example, Mylossoma, and Myleus) is very complicated genera due to the number of synonyms and poor historical taxonomic measurement of species. The problem also seems centered around the pet industry which has lumped the genera into common names for the pet industry benefit to separate from the carnivorous Serrasalminae. The term silver dollars is an artificial group defined by the body color, not by synapomorphies. The group is not evolutionarily correct and all silvers dollars are pacus, with the noted exception of Metynnis (see below; Patterns of Nucleotide Changes in Mitochondrial Ribosomal RNA Genes and Phylogeny of Piranhas 42: 169-182, Orti, et al. 1996). Most look similar to each other during ontogeny, but those within the same species might even look like an entirely different species as they mature. Some of the larger pacus (genus Piaractus and Colossoma also called tambaqui) are imported for the aquarium trade as vegetarian piranha which is a gross mistake not only in classification,