Eyespot color patterns in butterfly wings are determined by the putative morphogenic signals from organizers. Previous experiments using physical damage to the forewing eyespots of the peacock pansy butterfly, Junonia almana (Linnaeus, 1758), suggested that the morphogenic signals dynamically interact with each other, involving enhancement of activation signals and interactions between activation and inhibitory signals. Here, we focused on the large double-focus fusion eyespot on the hindwing of J. almana to test the involvement of the proposed signal interactions. Early damage at a single focus of the prospective double-focus eyespot produced a smaller but circular eyespot, suggesting the existence of synergistic interactions between the signals from two sources. Late damage at a single focus reduced the size of the inner core disk but simultaneously enlarged the outermost black ring. Damage at two nearby sites in the background induced an extensive black area, possibly as a result of the synergistic enhancement of the two induced signals. These results confirmed the previous forewing results and provided further evidence for the long-range and synergistic interactive nature of the morphogenic signals that may be explained by a reaction-diffusion mechanism as a part of the induction model for color-pattern formation in butterfly wings.
Part of the book: Lepidoptera
Butterfly wing color patterns are developmentally determined by morphogenic signals from organizers in the early pupal stage. However, the precise mechanism of color-pattern determination remains elusive. Here, mechanical and surface disturbances were applied to the pupal hindwing of the peacock pansy butterfly Junonia almana (Linnaeus, 1758) to examine their effects on color-pattern determination. Using the forewing-lift method immediately after pupation, a small stainless ball was placed on the prospective major eyespot or background of the developing dorsal hindwing to cause a wing epithelial distortion, resulting in deformation of the major eyespot. When the exposed dorsal hindwing was covered with a piece of plastic film or placed on a surface of a glass slide, an adhesive tape, or a silicone-coated glassine paper, the major eyespot was effectively reduced in size without a direct contact with the covering materials. The latter two treatments additionally induced the size reduction of the minor eyespot and proximal displacement and broadening of parafocal elements through a direct contact, being reminiscent of the temperature-shock-type modifications. These results suggest the importance of mechanical force and physicochemical properties of planar epithelial contact surface (i.e., extracellular matrix) to propagate morphogenic signals for color-pattern determination in butterfly wings.
Part of the book: Lepidoptera
Many reports about the biological effects of the Fukushima nuclear accident on various wild organisms have accumulated in recent years. Results from field-based laboratory experiments using the pale grass blue butterfly have clearly demonstrated that this butterfly is highly sensitive to “low-dose” internal exposure from field-contaminated host-plant leaves. These experimental results are fully consistent with the filed-collection results reporting high abnormality rates. In contrast, this butterfly is highly resistant against the internal exposure to chemically pure radioactive cesium chloride under laboratory conditions. To resolve this field-laboratory paradox, I propose that the field effects, which are a collection of indirect effects that work through different modes of action than do the conventional direct effects, play an important role in the “low-dose” exposure results in the field. In other words, exclusively focusing on the effects of direct radiation, as predicted by dosimetric analysis, may be too simplistic. In this chapter, I provide a working definition and discuss the possible variation in the field effects. I include an example on the misunderstanding of the field effects In the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) 2017 Report. Lastly, I discuss a theoretical application of the butterfly model to humans.
Part of the book: New Trends in Nuclear Science