Male mealworm beetles increase resting metabolic rate under terminal investment.
Harmful parasite infestation can cause energetically costly behavioural and immunological responses, with the potential to reduce host fitness and survival. It has been hypothesized that the energetic costs of infection cause resting metabolic rate (RMR) to increase. Furthermore, under terminal investment theory, individuals exposed to pathogens should allocate resources to current reproduction when life expectancy is reduced, instead of concentrating resources on an immune defence. In this study, we activated the immune system of Tenebrio molitor males via insertion of nylon monofilament, conducted female preference tests to estimate attractiveness of male odours and assessed RMR and mortality. We found that attractiveness of males coincided with significant down-regulation of their encapsulation response against a parasite-like intruder. Activation of the immune system increased RMR only in males with heightened odour attractiveness and that later suffered higher mortality rates. The results suggest a link between high RMR and mortality and support terminal investment theory in T. molitor.
Institute of Systematic Biology, University of Daugavpils, Daugavpils, Latvia.|Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia.|Department of Biology, University of Turku, Turku, Finland.
I A
IA
Krams
Institute of Systematic Biology, University of Daugavpils, Daugavpils, Latvia.
T
T
Krama
School of Psychology, University of Dundee, Dundee, UK.
F R
FR
Moore
Institute of Systematic Biology, University of Daugavpils, Daugavpils, Latvia.
I
I
Kivleniece
Department of Plant Protection, Institute of Agricultural and Environmental Sciences, Estonian University of Life Science, Tartu, Estonia.
A
A
Kuusik
Department of Psychology and Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN, USA.
T M
TM
Freeberg
Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia.
R
R
Mänd
Department of Biology, University of Turku, Turku, Finland.
M J
MJ
Rantala
Institute of Food Safety, Animal Health and Environment "BIOR", Riga, Latvia.
J
J
Daukšte
Department of Plant Protection, Institute of Agricultural and Environmental Sciences, Estonian University of Life Science, Tartu, Estonia.
M
M
Mänd
D000818:Animals; D001481:Basal Metabolism; D001517:Coleoptera / Q000378:metabolism* / Q000502:physiology; D008297:Male; D009812:Odorants; D012726:Sexual Behavior, Animal; D015996:Survival Rate
Tenebrio molitor; immunity; metabolism; reproductive strategy; sexual selection; survival