Effects of Pinglu Canal Construction on Camouflage in Two Sesarmid Crab Species

Canal construction activities alter the visual characteristics of natural habitats, which in turn impairs the camouflage effectiveness of resident animals. To explore the impacts of habitat degradation induced by anthropogenic engineering on the camouflage strategies of sympatric crab species, this study investigated the camouflage performance of Chiromantes haematocheir and Orisarma dehaani in natural estuarine habitats and canal-modified estuarine habitats of the Pinglu Canal. The Chromatic Just Noticeable Difference (CJND) of C. haematocheir in canal-modified habitats was 16.272 ± 9.503, significantly higher than the value of 12.911 ± 7.982 in natural estuaries (Z = -6.514, p < 0.001). Within the same habitat type, the CJND value of O. dehaani was consistently and significantly lower than that of C. haematocheir, with significant differences observed in both natural estuaries (Z = -11.572, p < 0.001) and canal-modified habitats (Z = -13.413, p < 0.001). Meanwhile, the pattern energy difference (PED) of O. dehaani in canal-modified habitats (0.744 ± 0.119) was significantly higher than that in natural estuaries (0.726 ± 0.107; Z = -2.390, p = 0.017), and the PED of C. haematocheir in canal-modified habitats (0.750 ± 0.133) was significantly higher than that in natural estuaries (0.731 ± 0.122; Z = -2.742, p = 0.006). The Pinglu Canal's construction significantly exacerbated the reduction in background-matching camouflage effectiveness of both crab species. This study provides empirical evidence for evaluating the impacts of anthropogenic engineering activities on the camouflage adaptability of estuarine benthic animals, and offers a scientific reference for the conservation of benthic biological resources in canal-modified estuarine ecosystems.