An Opposite Pattern to the Conventional Thermal Hypothesis: Temperature-Dependent Variation in Coloration of Adults of Saccharosydne procerus (Homoptera: Delphacidae)

Abstract

Melanism is a common polymorphism in many insect species that also influences immune function. According to the thermal melanin hypothesis, ectothermic individuals from cooler environments have darker cuticles and higher polyphenol oxidase (PO) levels, which represent a better immunocompetence. In this study, the links among environmental temperature, melanism, and PO activity of Saccharosydne procerus (Matsumura) were examined. Most S. procerus have a black spot on their forewings at high temperatures in the field and in the laboratory. In PO activity assay, a positive association between PO level and temperature was found. Our results showed that a diversification of melanism occurred under different temperatures and that melanism in S. procerus presented an opposite pattern to the one proposed by the thermal hypothesis.

The Environmental Plasticity of Diverse Body Color Caused by Extremely Long Photoperiods and High Temperature in Saccharosydne procerus (Homoptera: Delphacidae)

“…A previous study has shown that the proportion of melanism in S. procerus increased under higher temperature in the laboratory. This finding was also obtained in a field study, previous field investigation in four primary water bamboo producing areas showed that the proportion of melanic morphs was highest in the areas that had highest mean temperature, field investigations in Wuhan (N30°28′ and E114°21′), China from June to October 2012 also proved that high temperature improve the melanic proportion (Yin et al, 2015 ). In the present study, our data showed that photoperiod also had marked effects on melanism in S. procerus besides temperature.…”

“…Some green slender planthoppers have a black spot on the terminus of the forewing (Figure 1 ). These phenotypes represent the melanic morph of the species (Yin et al, 2015 ). The black spot appears after emergence.…”

How and when melanic coloration is an advantage for lizards: the case of three closely-related species of Liolaemus

“…Up to now, evidence for the thermal melanism hypothesis in ectothermic animals has been contradictory, reporting either a clear relationship between colour and heat flux or a lack of influence ( Harris et al, 2013;Geen and Johnston, 2014;Yin et al, 2015;Zamora-Camacho et al, 2015;Moreno Azócar et al, 2016;Köhler et al, 2017;De Souza et al, 2017;Kuyuku et al, 2018;among others). We aimed to clarify the relevance of this hypothesis by comparing a study system that would allow us to reduce the noise produced by differences in traits such as body size, diet, and reproductive mode (for further details see Moreno Azócar et al, 2016), as well as colour polymorphism.…”

Colour lightness of butterfly assemblages across North America and Europe

“…Thus, if melanism provides protection against UV radiation, we should expect to observe a large-scale decrease of insect colour lightness with increasing solar radiation, which is in contrast to the prediction of the thermal melanism hypothesis. Additionally, if melanism provides protection against pathogens, we should expect to observe decreased colour lightness of insects in humid environments, where pathogen pressure is likely highest 33–35 .…”