title: A dark cuticle allows higher investment in immunity, longevity and fecundity in a beetle upon a simulated parasite attack.
abstract: Cuticle melanism in insects is linked to a number of life history traits: a positive relationship is hypothesized between melanism, immune function, fecundity and lifespan. However, it is not clear how activation of the immune system affects trade-offs between life history traits in female mealworm beetles (Tenebrio molitor) differing in cuticle melanization. The females with tan, brown and black cuticles examined in the present study did not differ in the intensity of encapsulation response, fecundity and longevity when their immune system was not activated. However, we found that immune activation and cuticle melanization have a significant effect on life history traits. Offspring number and lifespan decreased in females with tan and brown cuticles, while the fecundity and lifespan of black females were not affected. Importantly, we inserted the implants again and found a significant decrease in the strength of encapsulation response in females with tan and brown cuticles. In contrast, black females increased melanotic reactions against the nylon implant, suggesting immunological priming. The results show that cuticle melanization plays an important adaptive role under the risk of being infected, while the lack of these benefits before the insertion of nylon monofilaments suggests that there are costs associated with an activated immunity system.
authors.affiliation: Department of Psychology, University of Tennessee, Knoxville, TN, USA. indrikis.krams@ut.ee.|Institute of Food Safety, Animal Health and Environment BIOR, Riga, Latvia. indrikis.krams@ut.ee.|Institute of Ecology and Earth Science, University of Tartu, Vanemuise 46, 51014, Tartu, Estonia. indrikis.krams@ut.ee.
authors.forename: Indrikis
authors.initials: I
authors.lastname: Krams
authors.affiliation: Departments of Psychology and Ecology & Evolutionary Biology, University of Tennessee, Knoxville, TN, USA.
authors.forename: Gordon M
authors.initials: GM
authors.lastname: Burghardt
authors.affiliation: Department of Biotechnology, Institute of Life Sciences and Technology, Daugavpils University, Daugavpils, Latvia.
authors.forename: Ronalds
authors.initials: R
authors.lastname: Krams
authors.affiliation: Department of Biotechnology, Institute of Life Sciences and Technology, Daugavpils University, Daugavpils, Latvia.|Center for Ecology and Environmental Research, Vilnius University, Vilnius, Lithuania.
authors.forename: Giedrius
authors.initials: G
authors.lastname: Trakimas
authors.affiliation: Institute of Ecology and Earth Science, University of Tartu, Vanemuise 46, 51014, Tartu, Estonia.
authors.forename: Ants
authors.initials: A
authors.lastname: Kaasik
authors.affiliation: English, Drama and Writing Studies & School of Psychology, University of Auckland, Auckland, New Zealand.
authors.forename: Severi
authors.initials: S
authors.lastname: Luoto
authors.affiliation: Department of Biology, Turku Brain and Mind Centre, University of Turku, Turku, Finland.
authors.forename: Markus J
authors.initials: MJ
authors.lastname: Rantala
authors.affiliation: Department of Plant Protection, Institute of Agricultural and Environmental Sciences, Estonian University of Life Science, Tartu, Estonia.
authors.forename: Tatjana
authors.initials: T
authors.lastname: Krama
mesh_terms: D000818:Animals; D001517:Coleoptera; D005260:Female; D005298:Fertility; D008136:Longevity; D010271:Parasites
keywords: Cuticle melanization; Fecundity; Immunological priming; Lifespan; Tenebrio molitor; Trade-offs