This strain originated from the Rio Papaloapan drainage in Veracruz, Mexico. A
Y-linked gene causes the expression of a red spot over the anal fin (Arsp) in adult males;
this is also known as ruby throat. Genes encoding additional pigment patterns mark two
X-chromosomes segregating in this population. One X-chromosome carries an allele at a
gene that encodes a yellow iris (Iy). The other X-chromosome carries two linked
pigment genes, one affecting dorsal fin color, dorsal red (Dr), and the other spotting on
the flank (Sp). This stock also has two alleles segregating at a gene for an autosomal tailspot pattern, the allelic designation reflecting the number of spots expressed: one spot (O)
and twin spot (T).
