Life-stage related responses to combined effects of acclimation temperature and humidity on the thermal tolerance of Chilo partellus (Swinhoe) (Lepidoptera: Crambidae)

Reyard Mutamiswa; Honest Machekano; Frank Chidawanyika; Casper Nyamukondiwa

doi:10.1016/j.jtherbio.2018.12.002

Life-stage related responses to combined effects of acclimation temperature and humidity on the thermal tolerance of Chilo partellus (Swinhoe) (Lepidoptera: Crambidae)

J Therm Biol. 2019 Jan:79:85-94. doi: 10.1016/j.jtherbio.2018.12.002. Epub 2018 Dec 11.

Authors

Reyard Mutamiswa¹, Honest Machekano², Frank Chidawanyika³, Casper Nyamukondiwa⁴

Affiliations

¹ Department of Biology and Biotechnological Sciences, Botswana International University of Science and Technology (BIUST), Private Bag 16, Palapye, Botswana; Department of Zoology and Entomology, University of the Free State, P.O. Box 339, Bloemfontein 9300, South Africa.
² Department of Biology and Biotechnological Sciences, Botswana International University of Science and Technology (BIUST), Private Bag 16, Palapye, Botswana.
³ Department of Zoology and Entomology, University of the Free State, P.O. Box 339, Bloemfontein 9300, South Africa.
⁴ Department of Biology and Biotechnological Sciences, Botswana International University of Science and Technology (BIUST), Private Bag 16, Palapye, Botswana. Electronic address: nyamukondiwac@biust.ac.bw.

PMID: 30612691
DOI: 10.1016/j.jtherbio.2018.12.002

Abstract

Adaptive thermal plasticity plays a key role in mitigating the effects of seasonal and diurnal thermal fluctuations among ectotherms at various life-stages. While the role of thermal history in conferring such plasticity is widely documented, its interaction with relative humidity (RH), another important driver of ectotherm survival and activity, is relatively underexplored. Yet the potential responses to these combinational stressors across ontogeny remain largely neglected. Against this background, we used a full-factorial design to test the combined acclimation effects of RH (45%, 65% and 85%) and temperature (23, 28 and 33 °C) on various indices of thermal sensitivity of laboratory reared spotted stemborer, Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) following acclimation beginning at larval, pupal and adult life-stages. Traits measured included critical thermal limits (CTLs), supercooling points (SCPs), chill coma recovery time (CCRT) and heat knockdown time (HKDT). Larval acclimation at 23 °C; 85% RH recorded the lowest critical thermal minima (CT_min) whereas adult acclimation at 28 °C; 45% RH recorded the highest critical thermal maxima (CT_max). There were no significant differences (P > 0.05) in SCPs across all temperature × RH acclimations. Larval and pupal acclimations at 23 °C; 85% RH and adult acclimation at 23 °C; 45% RH significantly improved CCRT. Similarly, commencing acclimation at larval, pupal and adult stages at 28 °C; 85% RH improved HKDT whereas larval and pupal acclimations at 33 °C; 45% RH impaired it. Our results indicate that combinational interactions of temperature and RH have significant thermal fitness costs and benefits and are dependent on the life-stage acclimation timing. Results also imply that both the vulnerability and adaptive potential of C. partellus populations under rapid climate variability varies with ontogeny. This therefore calls for the consideration of the role of ontogeny and multi-factors in better understanding the impact of environmental stress on ectotherms.

Keywords: Climate change; Ontogeny; Phenotypic plasticity; Stress resistance.

MeSH terms

Animals
Hot Temperature
Humidity
Lepidoptera / growth & development
Lepidoptera / physiology*
Life Cycle Stages*
Thermotolerance*