Spontaneous long-range calcium waves in developing butterfly wings

Abstract

Background: Butterfly wing color patterns emerge as the result of a regular arrangement of scales produced b epithelial scale cells at the pupal stage. These color patterns and scale arrangements are coordinated throughou the wing. However, the mechanism by which the development of scale cells is controlled across the entire win remains elusive. In the present study, we used pupal wings of the blue pansy butterfly, Junonia orithya, which ha distinct eyespots, to examine the possible involvement of Ca2+ waves in wing development Results: Here, we demonstrate that the developing pupal wing tissue of the blue pansy butterfly displaye spontaneous low-frequency Ca2+ waves in vivo that propagated slowly over long distances. Some waves appeared t be released from the immediate peripheries of the prospective eyespot and discal spot, though it was often difficult t identify the specific origins of these waves. Physical damage, which is known to induce ectopic eyespots, led to th radiation of Ca2+ waves from the immediate periphery of the damaged site. Thapsigargin, which is a specific inhibito of Ca2+-ATPases in the endoplasmic reticulum, induced an acute increase in cytoplasmic Ca2+ levels and halted th spontaneous Ca2+ waves. Additionally, thapsigargin-Treated wings showed incomplete scale development as well a other scale and color pattern abnormalities Conclusions: We identified a novel form of Ca2+ waves, spontaneous low-frequency slow waves, which travel ove exceptionally long distances. Our results suggest that spontaneous Ca2+ waves play a critical role in the coordinate development of scale arrangements and possibly in color pattern formation in butterflies.