Increased Resin Collection after Parasite Challenge: A Case of Self-Medication in Honey Bees?

The constant pressure posed by parasites has caused species throughout the animal kingdom to evolve suites of mechanisms to resist infection. Individual barriers and physiological defenses are considered the main barriers against parasites in invertebrate species. However, behavioral traits and other non-immunological defenses can also effectively reduce parasite transmission and infection intensity. In social insects, behaviors that reduce colony-level parasite loads are termed “social immunity.” One example of a behavioral defense is resin collection. Honey bees forage for plant-produced resins and incorporate them into their nest architecture. This use of resins can reduce chronic elevation of an individual bee's immune response. Since high activation of individual immunity can impose colony-level fitness costs, collection of resins may benefit both the individual and colony fitness. However the use of resins as a more direct defense against pathogens is unclear. Here we present evidence that honey bee colonies may self-medicate with plant resins in response to a fungal infection. Self-medication is generally defined as an individual responding to infection by ingesting or harvesting non-nutritive compounds or plant materials. Our results show that colonies increase resin foraging rates after a challenge with a fungal parasite (Ascophaera apis: chalkbrood or CB). Additionally, colonies experimentally enriched with resin had decreased infection intensities of this fungal parasite. If considered self-medication, this is a particularly unique example because it operates at the colony level. Most instances of self-medication involve pharmacophagy, whereby individuals change their diet in response to direct infection with a parasite. In this case with honey bees, resins are not ingested but used within the hive by adult bees exposed to fungal spores. Thus the colony, as the unit of selection, may be responding to infection through self-medication by increasing the number of individuals that forage for resin

Interaction between Apis mellifera L. and Baccharis dracunculifolia DC, that favours green propolis production in Minas Gerais

In Minas Gerais, green propolis is produced from the collection of resinous substance found in shoot apices of Baccharis dracunculifolia. The aim of this study was to evaluate the biological parameters associated with the interaction Apis mellifera x Baccharis dracunculifolia, to elucidate the supply of resin for green propolis production in Minas Gerais. We selected male and female individuals of two populations of Baccharis dracunculifolia located on São Judas Tadeu Farm - FSJT, in the municipality of Betim, MG and the Experimental Garden of the Ezequiel Dias Foundation - HORTO, located in an urban area in Belo Horizonte, MG. We made weekly observations, from June 2007 to June 2008, and evaluated in both populations: richness and abundance of insect visitors; resin collecting visits of Apis mellifera; presence of Baccharopelma dracunculifoliae galls; growth of individuals and phenological phases. Statistical analyses were made using R software. The rainy season showed the highest number of visitors. A. mellifera collected resin in shoot apices of Baccharis dracunculifolia from August to April, only in the FSJT population, where galls of B. dracunculifoliae were also present. Ovoposition of gall inductor on host plants occurs during the rainy season, when there is a peak of visitants and resin collecting visits of honeybees. This fact stimulates plant defense strategies against parasitoids and predators, which includes the production of several secondary metabolites, and ultimately reduces competition for food by inhibiting the attack of other phytophagous insects, not adapted to the chemical environment of plant tissues. Green propolis production in Minas Gerais is related to the abundant supply of resin by Baccharis dracunculifolia, when they are parasitised by B. dracunculifoliae galls. They induce plant production of defense exudates, which attract Apis mellifera bees to collect resin and consequently favour the production of green propolis

Interaction between Apis mellifera L. and Baccharis dracunculifolia DC, that favours green propolis production in Minas Gerais

In Minas Gerais, green propolis is produced from the collection of resinous substance found in shoot apices of Baccharis dracunculifolia. The aim of this study was to evaluate the biological parameters associated with the interaction Apis mellifera x Baccharis dracunculifolia, to elucidate the supply of resin for green propolis production in Minas Gerais. We selected male and female individuals of two populations of Baccharis dracunculifolia located on São Judas Tadeu Farm - FSJT, in the municipality of Betim, MG and the Experimental Garden of the Ezequiel Dias Foundation - HORTO, located in an urban area in Belo Horizonte, MG. We made weekly observations, from June 2007 to June 2008, and evaluated in both populations: richness and abundance of insect visitors; resin collecting visits of Apis mellifera; presence of Baccharopelma dracunculifoliae galls; growth of individuals and phenological phases. Statistical analyses were made using R software. The rainy season showed the highest number of visitors. A. mellifera collected resin in shoot apices of Baccharis dracunculifolia from August to April, only in the FSJT population, where galls of B. dracunculifoliae were also present. Ovoposition of gall inductor on host plants occurs during the rainy season, when there is a peak of visitants and resin collecting visits of honeybees. This fact stimulates plant defense strategies against parasitoids and predators, which includes the production of several secondary metabolites, and ultimately reduces competition for food by inhibiting the attack of other phytophagous insects, not adapted to the chemical environment of plant tissues. Green propolis production in Minas Gerais is related to the abundant supply of resin by Baccharis dracunculifolia, when they are parasitised by B. dracunculifoliae galls. They induce plant production of defense exudates, which attract Apis mellifera bees to collect resin and consequently favour the production of green propolis