Testing the effect of individual color morphology on immune response in bush‐crickets

Abstract

Despite the growing interest in how an individual's immune response is correlated to morphological and ecological factors, little empirical data has been available from wild insect populations. Many insects have different color morphs and exhibit differences in immune responses. Links are expected to exist between body colors and immune function in insects, because the same biochemical precursors involved in the immune response are responsible for melanin‐based color markings. In this study, I assay the immune response of two different color morphs of 377 wild‐caught bush‐crickets, Metrioptera roeseli, from 20 populations by measuring individual encapsulation responses to a surgically implanted nylon monofilament. There was no difference between green and brown bush‐cricket morphs (low melanin vs high melanin investment in cuticula color respectively) and their ability to mount an immune response to the implant. Further study is needed on the relationship between color morphology and immune response in wild insects, and whether trade‐offs occur between factors during an insect's development phase and long‐term health.

Detection of Temporal Changes in Insect Body Reflectance in Response to Killing Agents

“…Furthermore, there is ample evidence of the insect cuticle being highly dynamic with its chemical composition responding to age of individuals [ 9 – 13 ] and a wide range of behavioural [ 9 , 14 – 17 ] and environmental factors [ 9 , 14 ]. Melanin is responsible for brown or black colouring of insects, [ 18 – 20 ], and the biochemical precursors leading to melanin synthesis also trigger a range of immune responses [ 21 , 22 ]. Thus, there may be multiple and complex interactions between internal physiological processes and the biochemical composition of the cuticle.…”

A test of the relationship between cuticular melanism and immune function in wild‐caught Mormon crickets

“…For example, more heavily melanised morphs of the moth Mamestra brassicae are found to be less resistant to a nucleopolyhedrovirus (Goulson & Cory, 1995), and melanised morphs of the stone weta Hemideina maori have weaker encapsulation responses than unmelanised morphs (Robb et al , 2003). However, in the damselfly Coenagrion puella , female colour morphs show no differences in haemocyte count, phenoloxidase levels or resistance to a fungal pathogen (Joop et al , 2006); green and brown morphs of the bush‐cricket Metrioptera roeseli do not differ in encapsulation ability (Berggren, 2010); and there appears to be no relationship between encapsulation ability and pupal melanisation in the butterfly Lycaena tityrus (Karl et al , 2010).…”