[Morphological traits of indigenous field carps maintained in traditional rice-based farming systems.]

Rice-fish is an important traditional farming system. In the rice-fish system, common carp (Cyprinus carpio) is the major species raised in paddy field where the environment is characterized by shadow water. Under a long-term of natural selection and artificial selection, the carp would adapt to the paddy field environment. We investigated two indigenous carps (C. carpio qingtianensis and C. carpio congjiangensis) that originated and evolved in the Globally Important Agriculture Heritage System (GIAHS) 'rice-fish system' in Qingtian, Zhejiang Province and 'rice-fish-duck system' in Congjiang, Guizhou Province. We measured the morphological traits of indigenous carps by collecting carp samples from 'rice-fish system' and 'rice-fish-duck system'. We used mitochondrial gene (D-loop) to build phylogenetic tree. We also collected data of morphological traits of other carp populations from documented databases and published papers. Both traditio-nal morphometric analysis and landmark based geometric morphometric analysis showed that Qingtian field carp and Congjiang field carp differed in body shape. Compared with Qingtian field carp, Cong-jiang field carp had a longer and more narrow tail, and lower ratio of tail length to body length. The analysis of phylogenetic tree suggested that Qingtian field carp and Congjiang field carp were genetically independent populations. However, principal component analysis basing on morphometric traits showed that the field carps (Qingtian field carp and Congjiang field carp) were morphometrically similar to each other and were both significantly different from other common carp populations, especially in the traits of caudal fin and dorsal fin. All these results suggested that carps living and evolving in paddy field environment were significantly different in genetics and morphology from the carp populations living in other water environment and that Qingtian field carp was morphologically different from Congjiang field carp.