Immunological vulnerability and adjustments to environmental thermal variability

Abstract

Ecological physiologists recognize the potential impacts of temperature on physiological traits, however less attention has been paid to changes in thermal variation on a scale that pertains directly to living organisms. Also, few studies have examined the effects of temperature variation or other climatic drivers on host-pathogen interactions. We evaluated the effect of acclimation to ambient temperature variability (0, 4 and 8 °C daily variability) on the immune performance in the insect Tenebrio molitor (Coleoptera). We observed that antibacterial activity differed signifi cantly between treatments. In addition, variances of antibacterial activity were larger under the more variable thermal conditions. Similarly to antibacterial responses, tyrosinase phenoloxidase activity was higher in animals living in the most variable thermal condition. We hypothesized that a stress-associated mechanism may affect negatively the constitutive immune activity in T. molitor. It is well known that acute stress can cause in insects a transient impairment in the resistance to bacterial infection. This increase in susceptibility to diseases is mediated, at least in part, by the release of neuro-hormones in response to stress.Key words: ecoimmunology, immune performance, mealworm beetles, temperature, tyrosinase phenoloxidase. RESUMENSi bien los ecofi siólogos reconocen el impacto de la temperatura sobre los atributos fi siológicos, se ha prestado poca atención a la variación térmica a escalas que afectan directamente a los organismos. Además, son pocos los estudios que han examinado el efecto de la variabilidad térmica y otros factores climáticos en las interacciones patógeno-hospedero. Evaluamos el efecto de la aclimatación a la variabilidad térmica ambiental (0, 4 and 8 °C variabilidad diaria) sobre la respuesta inmune en el insecto Tenebrio molitor (Coleoptera). Observamos que la actividad antibacteriana difi ere signifi cativamente entre tratamientos térmicos. Además, las varianzas en la actividad antibacteriana fueron mayores bajos las condiciones de mayor variabilidad térmica. Del mismo modo que las respuestas antibacterianas, la actividad de tirosinasa fenoloxidasa fue mayor en los animales viviendo bajo las condiciones térmicas más variables. Hipotetizamos que los mecanismos de estrés asociados podrían afectar negativamente la respuesta inmune constitutiva en T. molitor. Se conoce que el estrés agudo causa en insectos una discapacidad transiente en la resistencia a la infección bacteriana. Este aumento en susceptibilidad es mediado, al menos en parte, por la liberación de neurohormonas en respuesta al estrés.Palabras clave: ecoinmunología, gusano de la harina, rendimiento inmune, temperatura, tirosinasa fenoloxidasa.

Scientists' warning on climate change and insects

“…It is likely that climate-driven impacts on insect immunity will alter interactions between hosts, symbionts and pathogens. For instance, insects exposed to higher and more variable temperature regimes show higher levels of immunity than those exposed to lower and less variable temperature regimes (Bozinovic et al, 2013;Catal an et al, 2012;Van Dievel et al, 2017), whereas other studies report opposite findings (Karl et al, 2011). Mutualistic bacteria provide various ecological benefits, such as resistance to environmental stress, pathogen infections or natural enemies, yet their impact remains poorly understood at the level of ecological communities (Ferrari & Vavre, 2011;Oliver et al, 2010).…”

Physiological ecology meets climate change

“…Studies in thermal biology have often focused on the impact of shifting mean values on organisms but temperature variability may also act as a selective force (Pörtner and Knust ; Bozinovic et al. ; Clavijo‐Baquet et al. ).…”

“…Development of unifying concepts such as OCLTT is relevant for interpreting existing and future findings in a coherent way and for projecting the future ecological and evolutionary effects of climate change on whole‐organism and ecosystem functioning (Bozinovic et al. ,b, ,b; Folguera et al. ; Pörtner et al.…”

“…Increased variability and frequency of extreme events under climate change require consideration (Rahmstorf and Coumou 2011). Studies in thermal biology have often focused on the impact of shifting mean values on organisms but temperature variability may also act as a selective force (P€ ortner and Knust 2007;Bozinovic et al 2013a;Clavijo-Baquet et al 2014). The development of a widely accepted theoretical basis should relate physiology to population processes and address the role of temperature means and variability at higher ecological levels and their potentially nonadditive interaction shaping performance.…”

The multigenerational effects of water contamination and endocrine disrupting chemicals on the fitness of Drosophila melanogaster

“…Here, we evaluated the impact that dif- A major selective force in nature is exposure to environmental perturbations (Bijlsma & Loeschcke, 2005;Hoffmann & Hercus, 2000;Hoffmann & Parsons, 1991). Animals have evolved several strategies, from genetic (e.g., Alvarez, Espinoza, Inostroza B, & Arce, 2015;Hebbelmann et al, 2012;Lardies, Arias, & Bacigalupe, 2010;Silva, Bacigalupe, Luna-Rudloff, & Figueroa, 2012;Sørensen & Loeschcke, 2004), to physiological (e.g., Bozinovic, Catalán, & Kalergis, 2013;Castañeda et al, 2011;Chapin, Autumn, & Pugnaire, 2012;Hermes-Lima & Zenteno-Savìn, 2002;Uy, Leduc, Ganote, & Price, 2015) and behavioral (e.g., Kitaysky, Wingfield, & Piatt, 2001;Koolhaas et al, 1999;Ruiz-Aravena et al, 2014;Wingfield & Kitaysky, 2002) to deal with or avoid the effects of such stressors. Additionally, fitnessrelated traits are not an exception and are also affected by environmental stress (Bijlsma & Loeschcke, 2005).…”