Starch gel electrophoresis was used for examining the transferrin gene locus (Tf) and two esterase gene loci (Est-1 and Est-D1) of a pirarucu (Arapaima gigas) population sample collected from Santa Cruz Lake, Tefé River, Amazonas, Brazil. The Tf locus was tentatively classified as being polymorphic, showing two double-banded patterns (Tf 12 and Tf 22) of the three theoretically expected ones (Tf11, Tf 12 and Tf 22), presumably controlled by two co-dominant alleles, Tf 1 and Tf 2.
The discus is a very popular and expensive aquarium fish belonging to the family Cichlidae, genus Symphysodon, formed by three Amazon basin endemic species: Symphysodon aequifasciatus, S. discus and S. tarzoo. The taxonomic status of these fish is very controversial, with a paucity of molecular research on their population genetic structure and species identification.
About 98 species of Manihot are known. All of them are native to the New World and are concentrated in four regions in Brazil and Central America. All the Manihot species so far examined have 2n = 36 chromosomes. Interspecific hybrids between cassava and its wild relatives show relatively normal meiosis, and further generations can be obtained. Electrophoresis shows affinity among wild species of different sections, and between some of them and cassava. Both polyploidy and apomixis may have contributed to speciation in this genus.