Morphometric analysis of nymphalid butterfly wings: number, size and arrangement of scales, and their implications for tissue‐size determination

Abstract

Animal body size and tissue size depend on genetic and environmental factors, but the precise mechanisms of how tissue size is determined in proportion to body size remain unknown. Here we focused on wings from three nymphalid butterflies, Junonia orithya (Linnaeus), Vanessa cardui (Linnaeus) and Danaus chrysippus (Linnaeus) (Lepidoptera: Nymphalidae), to examine the contributions of the number and size of scales to macroscopic structures, represented by wing compartments, and to investigate the positional dependence of scale size, density and arrangement. The whole wing area and wing compartment area exhibited a high correlation in all three species. Similarly, the wing compartment area and the blue or orange area showed a high correlation in three species, indicating isometric relationships among wings of different sizes. However, only in J. orithya, the blue area was highly correlated with the number of constituent scales and, to a lesser extent, with scale size. In contrast, reasonable correlations were obtained between the blue or orange area and the number of rows in all three species. These results suggest that variations of the background area accompany changes in the number of scales through changes in the number of rows. In a background region of the compartment, scale size gradually decreased and scale density increased from the proximal to the distal side in all three species. Our findings suggest that butterfly wing tissue size is determined primarily by the number of scale cells and secondarily by the size change of scale cells before or during the period of row arrangement.

Spatial patterns of correlated scale size and scale color in relation to color pattern elements in butterfly wings

“…Scale size distribution analyses have revealed a size gap between the black and non-black rings of a single eyespot and that eyespot foci have scales that are larger than their surroundings (Kusaba and Otaki, 2009). We also found a proximodistal size gradient in Vanessa cardui and Danaus chrysippus, although the gradient of the latter species was small (Dhungel and Otaki, 2014). Based on these data, we proposed that a morphogenic signal that is released from a prospective eyespot focus determines scale size as well as color (Kusaba and Otaki, 2009) and that this signal is a train of wave-like pulses, as described in the induction model (Otaki, 2011a-c).…”

“…Based on these data, we proposed that a morphogenic signal that is released from a prospective eyespot focus determines scale size as well as color (Kusaba and Otaki, 2009) and that this signal is a train of wave-like pulses, as described in the induction model (Otaki, 2011a-c). Because scale size is probably determined by the size of scale cells, and because cell size can be altered by cell ploidy, we speculated that morphogenic signals for scale size and color may be identical to ploidy signals (Kusaba and Otaki, 2009;Dhungel and Otaki, 2014). From this perspective, the characterization of scale cell development is required to understand the nature of the putative morphogenic signal.…”

Self-Similarity, Distortion Waves, and the Essence of Morphogenesis: A Generalized View of Color Pattern Formation in Butterfly Wings

“…Scale size distribution is graded from the basal to peripheral areas of a wing in butterflies and moths Simonsen and Kristensen 2003). Similar size gradation has been found in the background scales in Junonia orithya, J. almana, Vanessa indica, and V. cardui (Kusaba and Otaki 2009;Dhungel and Otaki 2013;Iwata and Otaki 2016b). What about the size of scales that constitute elements?…”

“…This leads us to propose the ploidy hypothesis (Fig. 7.11a) (Dhungel and Otaki 2013;Iwata and Otaki 2016a, b). This hypothesis states that morphogenic signals induce polyploidization of signal-receiving cells.…”

Biomechanics of a moth scale at ultrasonic frequencies

“…A typical moth scale is anchored into a socket in the wing membrane with a narrow pedicel and widens into a flattened blade (9). Each scale itself is a highly sculptured porous structure, and scales show diverse morphologies even on a single wing (10). The highly sculptured scale structure implies sophisticated evolutionary adaptations, analogous to the highly organized nanoscale photonic structures for visual signaling (11,12).…”