Short-term changes in juvenile hormone titers in honey bee workers due to stress

Abstract

-Juvenile hormone (JH) is well studied in honey bees because it regulates caste determination in immatures and division of labor in adult workers. However it is not clear whether JH titers change significantly under stresses commonly experienced by workers in experimental manipulations. In this study we determined the effect of caging and cold-anaesthesia on JH titers in both nurses and foragers. The JH titers of nurses and foragers kept in cages at room temperature, or anaesthetized on ice, for up to 24 hours were determined at various time intervals. Nurses displayed a significant and sustained increase in JH titers by 1-2 hours in 2 out of 3 colonies, regardless whether being cold-anaesthetized or caged. Nurses in 4 out of 4 colonies showed remarkable JH titer elevations 24 hours after being caged. The increase ranged from 3-142 fold compared to their initial baseline JH titers. In foragers, changes in JH titers depended on their initial JH titers: foragers with low JH titers increased while those with high JH titers decreased. These results suggest that nurses and foragers respond to stress differently. The fact that JH did not always increase under stress conditions suggests that JH apparently does not function as a "stress-hormone" in honey bees under the two conditions we studied. Apis mellifera / juvenile hormone / radioimmunoassay / stressAbbreviations: JH Juvenile hormone; RIA radioimmunoassay; CA corpora allata

Starvation stress during larval development facilitates an adaptive response in adult worker honey bees (Apis mellifera L.)

“…Studies in the fruit fly Drosophila melanogaster indicate that elevated JH levels can enhance stress resistance, at least in the short term (Gruntenko et al, 1996(Gruntenko et al, , 2003(Gruntenko et al, , 2010. The role of JH in the stress response of honey bees is less clear (Even et al, 2012), but various stressors (temperature changes, experimental handling and transitioning to activities outside the protective nest) induce or are associated with increased JH levels (Sullivan et al, 2000;Lin et al, 2004;Page, 2013). It remains to be tested whether the changes in JH that we observed in this study can contribute to starvation resilience.…”

Reproductive status, endocrine physiology and chemical signaling in the Neotropical, swarm-founding eusocial wasp,Polybia micansDucke (Vespidae: Epiponini)

“…As for hymenopterans, honeybee workers showed a JH response to being caged and cold anesthetized (Lin et al, 2004). Although caged nurse bees experienced a dramatic upswing in JH, overall the response to the stressors was inconsistent (and sometimes reversed), leading the authors to conclude that JH is not a 'stress' hormone in honeybees (Lin et al, 2004).…”

“…Stress by way of crowding in caste-totipotent workers of the termite Coptotermes formosanus causes an increase in JH levels that induces the development of soldiers whose presence lessens the density-dependent rise of JH in workers (Mao and Henderson, 2010). As for hymenopterans, honeybee workers showed a JH response to being caged and cold anesthetized (Lin et al, 2004). Although caged nurse bees experienced a dramatic upswing in JH, overall the response to the stressors was inconsistent (and sometimes reversed), leading the authors to conclude that JH is not a 'stress' hormone in honeybees (Lin et al, 2004).…”

Social reversal of immunosenescence in honey bee workers

“…Care was taken to avoid contaminating the samples with tissue fragments and foregut content. Hemolymph (0.5-2 µl) was drawn within 1 h after the bees had been collected (Lin et al, 2004) and stored in 500 µl ice cold acetonitrile for JH titer determination, and 1 µl hemolymph was dissolved in 50 µl TRIS-buffer (20 mM TRIS-HCL, 150 mM NaCl, 5 mM EDTA, pH 7.5, 1 mM phenylmethylsulfonyl fluoride, 5 mM benzamidin, 0.7 µM pepstatin, 8 µM chymostatin, 10 µM leupeptin and 0.8 µM aprotinin) for quantification of vitellogenin (Amdam et al, 2004b). Further, 1 µl hemolymph was dissolved in 3 µl staining solution (16.2 g NaH 2 PO 4 , 4.2 g NaOH, 1 g methylene blue in 0.1 l formalin (40%) and 0.9 l d-H 2 O), or processed by the DeadEnd™ Fluorometric TUNEL System (Promega), for classification and count of hemocytes.…”