Immune responses of honeybees and their fitness costs as compared to bumblebees

Abstract

Immune responses of invertebrates imply more than developing a merely unspecific response to an infection. Great interest has been raised to unveil whether this investment into immunity also involves fitness costs associated to the individual or the group. Focusing on the immune responses of honeybees, we use the well-studied insect bumblebee for comparison. Bumblebees are capable of producing specific immune responses to infections whereas this has not been assessed for honeybees so far. We investigated whether a prior bacterial encounter provides protection against a later exposure to the same or a different bacterium in honeybees. Additionally, we studied whether the foraging activities of honeybees and bumblebees are affected upon immune stimulation by assessing the flight performance. Finally, the acceptance behavior of nestmates toward immune-challenged honeybees was determined. Results show that despite stimulating the immune system of honeybees, no protective effects to infections were found. Further, honeybees were not affected by an immune challenge in their flight performance whereas bumblebees showed significant flight impairment. Immune-challenged honeybees showed lower survival rates than naive individuals when introduced into a regular colony. Here, we reveal different immune response-cost scenarios in honeybees and bumblebees for the first time.Electronic supplementary materialThe online version of this article (doi:10.1007/s13592-014-0318-x) contains supplementary material, which is available to authorized users.

Genetic diversity confers colony-level benefits due to individual immunity

“…Also noteworthy is that we only found a difference relating to the immune response of challenged larvae across the gradient of genetic diversity and that there were no differences in the baseline immune production in unchallenged larvae. Since a high constitutive production of antimicrobial peptides can have costs for both individuals and colonies [13,16], selection may favour inducible expression rather than constitutive expression. A recent study has in fact shown that constitutive expression does not seem to correlate with subsequent ability to fight pathogen exposure [22], which supports the findings presented here.…”

“…It still remains unclear, therefore, if individuals from colonies with increased genetic diversity differ in their ability to mount an effective immune response after a pathogen challenge. This is a critically important distinction, given demonstrated colony-level fitness costs for individuals' upregulation in immune response [13], as well as costs at the individual level [16].…”

Immunity and survival response of Atta cephalotes (Hymenoptera: Myrmicinae) workers to Metarhizium anisopliae infection: Potential role of their associated microbiota

“…Similarly, an increase in hemolymph antimicrobial activity after immune challenge has been reported in solitary insects such as Galleria mellonella [ 65 ], Musca domestica [ 66 ] and Schistocerca gregaria [ 67 ], as well as in social insects. For instance, it has been reported that Bombus terrestris [ 68 ] and Apis mellifera [ 69 ] bee workers challenged by bacterial-associated molecular patterns showed an increase in hemolymph antimicrobial activity compared to the control or uninfected group. Furthermore, Camponotus fellah worker hemolymph has no antimicrobial properties but it acquires such properties after a trauma [ 70 ].…”

Factors Affecting Immune Responses in Honey Bees: An Insight

“…Another cost of immune activation could be the elimination of beneficial microflora from the gut of honey bees (Gilliam, 1997). Riessberger-Gallé et al (2015) provided experimental evidence that the cost of using the immune system reduces survival in immunechallenged bees as compared to control bees. In response to endogenous bacteria, honey bees activate their immune system by upregulating immunity-related genes, but at the same time, the gene-encoding storage protein (Hexamerin 70b) is downregulated (Janashia & Alaux, 2016).…”