Linking organismal growth, coping styles, stress reactivity, and metabolism via responses against a selective serotonin reuptake inhibitor in an insect

Abstract

Evidence suggests that brain serotonin (5-HT) is one of the central mediators of different types of animal personality. We tested this assumption in field crickets Gryllus integer using a selective serotonin reuptake inhibitor (SSRI). Crickets were selected for slow and rapid development and tested for their coping styles under non-stressful conditions (time spent exploring a novel object). Resting metabolic rate, maximum metabolic rate and latency to resume activity were measured under stressful conditions (stress reactivity). Measurements were taken (i) before and (ii) during the SSRI treatment. Before the SSRI treatment, a strong negative correlation was observed between coping style and stress reactivity, which suggests the existence of a behavioral syndrome. After the SSRI treatment, the syndrome was no longer evident. The results of this study show that 5-HT may be involved in regulating behavior not only along a stress reactivity gradient but also along a coping styles axis. The relationship between personality and the strength and direction of 5-HT treatment on observed behaviors indicates trait-like individual differences in 5-HT signaling. Overall, these findings do not support recent ideas arising from the pace-of-life syndrome (POLS) hypothesis, which predict higher exploration and metabolic rates in rapidly developing bold animals.

Spontaneous activity rates and resting metabolism: Support for the allocation model of energy management at the among‐individual level

“…This provides evidence for the "allocation" model of energy management (Daan et al, 1990, Ricklefs et al, 1996, Nilsson, 2002, see also reviews in Careau et al, 2008, Auer et al, 2017. This is a seemingly rare observation in the literature given that most correlations are very low but in the positive direction, whereas very few studies show evidence of a negative correlation (Careau, Beauchamp, Bouchard, & Morand-Ferron, 2019;Krams et al, 2017Krams et al, , 2018Royauté et al, 2018). Given that the observed negative covariance between RMR and activity did not match our expectations under the performance model, this…”

“…This provides evidence for the “allocation” model of energy management (Daan et al, , Ricklefs et al, , Nilsson, , see also reviews in Careau et al, , Auer et al, ). This is a seemingly rare observation in the literature given that most correlations are very low but in the positive direction, whereas very few studies show evidence of a negative correlation (Careau, Beauchamp, Bouchard, & Morand‐Ferron, ; Krams et al, , ; Royauté et al, ). Given that the observed negative covariance between RMR and activity did not match our expectations under the performance model, this suggests that activity and underlying metabolic variation are not always linked together in ways as predicted by the majority of recent theoretical advances in this area (Biro et al, ; Biro & Stamps, , ; Burton et al, ; Réale et al, ; Sih & Bell, ).…”

Seasonal time constraints shape life history, physiology and behaviour independently, and decouple a behavioural syndrome in a damselfly

“…A faster life history has been associated with higher metabolic rates (Réale et al 2010, Arnqvist et al 2017, for damselfly larvae: Stoks et al 2006), yet many counterexamples exist. For example, the lines of the cricket Gryllus integer selected for a faster life history showed even a lower resting metabolic rate (Krams et al 2017, 2018).…”

Ecological Stoichiometry: A Link Between Developmental Speed and Physiological Stress in an Omnivorous Insect

“…Importantly, selection for slower development confers higher levels of anxiety/neuroticism along the stress reactivity axis in crickets (Krams et al, 2017 ). The observed anxiety in behavior and resting metabolic rate (RMR) in slowly developing crickets under stressful conditions decreased after a selective serotonin reuptake inhibitor (SSRI) treatment (Krams et al, 2018 ). On the other hand, slower development may be associated with longer lifespan (Brooks and Garratt, 2017 ; Kecko et al, 2017 ) which may require an improved immune system (Niemelä et al, 2013 ; Krams et al, 2015 , 2016a ).…”