Temperature Acclimation Ability by an Oceanic Sea Skater, Halobatesgermanus, Inhabiting the Tropical Pacific Ocean.

Takahiro Furuki,Hiroki Fujita,Mitsuru Nakajo,Tetsuo Harada

doi:10.3390/insects9030090

Abstract

Temperature acclimation and heat shock experiments were performed on adult oceanic skaters, Halobates germanus, inhabiting the tropical Pacific Ocean. Acclimation for 10 or 24 h to 25 °C or 28 °C promoted significantly lower cool coma temperatures by specimens than acclimation to 31 °C. After heat shock by exposure to the relatively moderate temperature of 32.5 °C for 12 h, 52.9% or 61.1%% of specimens died in the 24 h period following acclimation at 28 °C or 31 °C, respectively, whereas all survived when there was no experience of heat shock. The average cool coma temperature was 14 to 17 °C in the specimens which had suffered no heat shock, whereas it was much higher (22 to 23 °C) in specimens that had suffered heat shock. The lower survival rate and the higher cool coma temperature can be attributed to damage suffered by exposure to 32.5 °C. The upper limit of the surface water temperature in the tropical ocean (15° N to 15° S) is currently around 30 to 31 °C, and Halobates appear to have no experience in 32 to 33 °C environments. Nevertheless, 32 °C, i.e., a temperaturethat is only slightly higher than 30 to 31 °C, may occur in the future due to global warming. This species may develop resistance to 32 to 33 °C in the near future.

Highlights

(1) Acclimation means “physiological or behavioral changes occurring within an organism and itis caused by experimentally induced stressful changes in particular climatic factors”. (2) Heat shock means “a rapid, short acting molecular process associated with the synthesis of several families of heat shock proteins of different molecular weights, such syntheses can be elicited as a result of acute short sub-lethal heat injury.” (3) Hardening means “a quick, transitory adaptation to an extreme temperature that followed brief exposure at a sub-lethal temperature including hsps related to enhancement of cold hardiness” [2]
Mosquitoes, Culex pipiens, were reared in a full factorial design at 18 or 26 ◦ C as larvae and adults, and critical thermal maxima (CTmax) and metabolic rate-temperature (MR-T) relationships were determined for all treatments
Insect cold hardiness and effects of acclimation at relatively lower temperature have been studied in depth [22,23]

Summary

Introduction

Heat Shock, Hardening and Acclimation in Ectotherms. Bowler [1] defined the terms, ‘acclimation’, ‘heat shock’, and ‘hardening’ in regard to temperature response based on thermal physiology in ectotherms. Mosquitoes, Culex pipiens, were reared in a full factorial design at 18 or 26 ◦ C as larvae and adults, and critical thermal maxima (CTmax) and metabolic rate-temperature (MR-T) relationships were determined for all treatments. High temperature acclimation induces a high metabolic rate [3]. Mosquitoes, Culex pipiens, were reared in a full factorial design at 18 or 26 °C as larvae and adults, and critical thermal maxima

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