Coloration Characteristics of the Chinese Giant Salamander (Andrias davidianus) in Zhangjiajie and Their Associations with Water Quality.

Body colour is an important phenotypic trait of the Chinese giant salamander and may reflect its responses to environmental variation. However, quantitative comparisons of body colour among captive environments remain limited. We examined 56 individuals from six breeding facilities in Zhangjiajie, China. The lightness, red-green coordinate and yellow-blue coordinate of the dorsal surface, ventral surface and body markings were measured, along with water quality variables at each facility. Analysis of variance, principal component analysis, cluster analysis and Pearson correlation analysis were used to compare populations, classify colour types and assess environmental relationships. Body-colour characteristics differed significantly among facilities, although overall colour differences between the body background and markings were not significant. Four colour types were identified, with 87.5% of individuals showing either an orange-brown dorsal surface with greyish-black markings or a grey dorsal surface with black markings. Body colour was significantly associated with water physicochemical variables. Higher pH and dissolved oxygen were mainly related to lower lightness and greater ventral redness, whereas higher total phosphorus and ammonia nitrogen were associated with increased lightness and yellowness. Water temperature mainly affected yellowness. These findings support captive-environment optimisation, body-colour management, conservation breeding and germplasm-resource protection.