There are 4 different strains of Common carp Cyprinus carpio; each different strain has different scale patterns and very few different genetic traits.
The first strain is the common carp, as we know it, this strains is the closest descendant of the wild carp. Basically speaking, the common carp is genetically different to the wild carp through the possession of an inherited trait connected to its growth. If compared to the mirror, leather and linear strains of carp the common carp had been proven to have the best growth rate in terms of increase in size rather than potential weight; this is dependant on the environment it is subjected to. The common carp has both of its flanks full of neatly aligned uniform scales.
The mirror carp was the first mutation on from the common carp and its formation is related to alternative forms of two of its genes, the S and the N alleles. Both of these alleles are paired and they hold a major and minor version, the minor being the recessive of the two. The genetic term used for the mirror carp is ssnn (all minor). The behaviour of the s (minor) and the N (major) genes in carp have and effect on a wide range of its genetic traits in addition to scaling patterns, this is the reason that mirror carp often have fewer rays in its dorsal, pectoral and pelvic fins than common and wild carp. As with all the strains of carp the mirror carp possesses a number of other genes which determine the carps body length, bucal cavity (mouth) positioning and scale pattern. Some mirror carp have been proven of being able to reach heavier weights than common, linear and leather carp; this is related to its genes.
A leather carp is known for it scale less flanks though scientifically a leather carp can possess a few scales, the dorsal row of scales must either be absent or if present it must have breaks between scales. Leather carp have a reduced growth when compared with commons and mirrors; this is due to them having fewer red blood cells. This also means that they require higher oxygen levels in the water to maintain a healthy oxygen level in their blood. Leather carp also have fewer dorsal spines than the other strains, they quite frequently have genetic kinks or deformities in its fins and they are much less hardy than the rest of the Common carp family.
A true linear carp has a single row of scales along it lateral line giving them their distinctive looks. Like leather carp, linears have a restricted maximum growth potential and their growth rate is also a lot slower. Both linear and leather carp have a more intensive fat metabolism, meaning that fat amasses more quickly in both during the summer time and is utilized in greater amounts during the winter. This and the reduced potential growth of linear and leather carp is related to its reduced amount of gill rakers and its decreased number of pharyngeal teeth, both strains have 2 rows compared with the three rows found in common and mirror carp.