Short-term hyperthermia at larval age reduces sucrose responsiveness of adult honeybees and can increase life span

Abstract

Honeybees are very sensitive to their breeding temperature. Even slightly lower temperatures during larval development can significantly affect adult behavior. Several devices which are employed for killing the honeybee ectoparasite Varroa destructor rely on short-term hyperthermia in the honeybee hive. The device used here applies 43.7°C for 2 h, which is highly effective in killing the mites. We study how short-term hyperthermia affects worker brood and behavior of emerging adult bees. Sucrose responsiveness was strongly reduced after treatment of larvae early or late of larval development. Hyperthermia significantly enhanced life span, particularly in bees receiving treated early in larval development. To ask whether increased life span correlated with foraging performance, we used radio frequency identification (RFID). Onset and offset of foraging behavior as well as foraging trip duration and lifetime foraging effort were unaffected by hyperthermia treatment as prepupa.

Varroa Control by Means of a Hyperthermic Device

“…Hyperthermia applied using the Bee Ethic system at three-week intervals from late spring to autumn kept V. destructor population at tolerable levels, whereas alarming increases in mite number were observed in untreated controls. Even if hyperthermia is a rather old approach to varroa control [9,11], most of the tests were carried out in the laboratory [9,10,20] and several reports of apiary trials are of anecdotal nature [11,13,14]. The experimental conditions adopted in our trials (42 • C for 90 min) were intermediate among those adopted in other studies and proved to be effective in varroa control for most of the season.…”

“…Juvenile forms of honey bee, such as larvae, can tolerate up to 42-43 • C while adults can tolerate up to 48 • C; therefore, if they are exposed for a sufficiently long time to temperatures above 40 • C, they are not harmed, unlike the mites, which are killed. The time required to kill or seriously damage most of the mites is inversely proportional to temperature; times up to eight hours were applied in various experiments without hampering adult bee and brood survival [8,9], even extending worker lifespan [10].…”

Diverse communication strategies in bees as a window into adaptations to an unpredictable world

“…Since bees are not perfectly endothermic, their body temperature increases with ambient temperature ( 114 , 115 ), and an elevated body temperature of returning foragers ( 116 , 117 ) may be translated into more intense recruitment behavior, while the warmer nectar could lead to more efficient learning of food odors ( 118 ). Extreme heat events could also have delayed, negative effects on recruitment given that elevated temperatures during brood development result in reduced sensitivity to sucrose rewards later in life ( 119 ), which is likely to dampen the motivation of bees to forage and communicate ( 1 , 16 , 120 ). These temperature effects are especially relevant for tropical stingless bees and honey bees, which tend to have a reduced ability to control brood area temperature compared to temperate honey bees ( 22 , 121 ).…”

Coping with the cold and fighting the heat: thermal homeostasis of a superorganism, the honeybee colony

“…Thermal stress for a honeybee colony does not only occur in a cold ambience but also at high temperatures (Lindauer 1954 ; Abou-Shaara et al 2017 ). In scenarios of future global warming, increased environmental temperatures are expected to challenge also honeybee colonies (Kovac et al 2014 ; Bordier et al 2017 ; Medina et al 2018 ; Kablau et al 2020 ; McAfee et al 2020 ). If the hive is in danger of being overheated the bees cool it by fanning (Southwick and Moritz 1987 ; Sudarsan et al 2012 ; Cook and Breed 2013 ; Egley and Breed 2013 ; Cook et al 2016 ), and they collect water to spread it on the combs (Lindauer 1954 ; Kühnholz and Seeley 1997 ).…”