ABSTRACT
Common carp are closely related to goldfish (Carassius auratus) and both species are thought to be naturally tetraploid because they have around twice the number (2n = 100) of chromosomes compared to other cyprinid fishes. David et al (2003) estimates that genome duplication occurred around 12 million years ago and the two species subsequently diverged around 11 million years ago. Four modern subspecies of common carp were identified by Kirpitchnikov (1967): C. c. carpio (Europe), C. c. aralensis (central Asia), C. c. haematopterus (east Asia) and C. c. viridiviolaceus (southeast Asia). Recent genetic studies confirm the divergence of at least two subspecies of common carp (Gross et al, 2002; Kohlmann et al, 2003) presumably resulting from Pleistocene glacial separation. Cyprinus carpio carpio is now commonly regarded as central Eurasian/eastern European and C. carpio haematopterus is the main east Asian subspecies, although some evidence suggests that the southeast Asian subspecies (C. c. viridiviolaceus) is also genetically distinct (Chistiakov and Voronova, 2009). Although many authors discount the existence of C. c. aralensis, Murakaeva et al (2003) found genetic support for the distinctiveness of wild central Asian populations. The separation between European and Asian subspecies is regarded as ancient (Gross et al, 2002), and Mabuchi et al (2006) further found that carp from the ancient
Japanese Lake Biwa (4 million years ago) were also clearly distinct genetically. However, Kottelat (2001) regards the Asian coloured carp as an entirely separate species (C. rubrofuscus) and rejects C. c. haematopterus. A significant problem with studies of carp genetics is the considerable translocation and interbreeding that has occurred across the species’ natural range over the last few hundred years (Matsuzaki et al, 2010). In addition, many genetically distinct varieties of carp have been bred
for particular characteristics useful for their aquaculture, such as increased growth rate, greater cold tolerance or improved disease resistance (Hulata, 1995), and particular characteristics of the European carp such as the mirror scale form have been introduced into koi carp culture.
