Title

Thermal Environment Shapes Cuticle Melanism And Melanin-Based Immunity In The Ground Cricket Allonemobius Socius

Keywords

Body size; Encapsulation; Pro-phenoloxidase; Season length; Thermal melanism; Trade-off

Abstract

The thermal melanin hypothesis posits that ectothermic individuals of larger size or from colder environments exhibit darker cuticles due to melanin's efficacy in absorbing solar radiation. However, melanin is also a crucial component of arthropod immunity. Thus, thermal selection for increased cuticle darkness may profoundly influence melanin-based immune function. In this study, we address the relationships between the thermal environment (season length), cuticular melanism and two aspects of melanin-based immunity across nine thermally distinct populations of the cricket Allonemobiussocius. We found that season length (i. e. degree days) and body size had a positive association with cuticle melanism in both sexes across populations, supporting the thermal melanism hypothesis. Despite their smaller size, males were found to have darker cuticles and superior melanin-based immunity. This pattern may be the result of additional selection on males due to sex-specific temperature-dependent activities, such as male calling song. Perhaps most interestingly, we found that short season length populations (i. e. colder) exhibited a greater phenoloxidase activity (aspect of the melanin-based immune system) in addition to darker cuticles in both sexes. This pattern is consistent with direct thermal selection on cuticular color, coupled with indirect selection on melanin-based immunity due to pleiotropy. Thus, thermal selection on cuticle darkness appears to indirectly shape the evolution of pathogen resistance in this system, and potentially for other terrestrial arthropod systems whose ranges encompass a significant thermal gradient. © 2012 Springer Science+Business Media Dordrecht.

Publication Date

5-1-2013

Publication Title

Evolutionary Ecology

Volume

27

Issue

3

Number of Pages

521-531

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1007/s10682-012-9620-0

Socpus ID

84875384898 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/84875384898

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