Characters that differ between diploid and haploid honey bee (Apis mellifera) drones

Area of Science:

• Entomology
• Genetics
• Chemical Ecology

Background:

• Hymenoptera typically exhibit haplo-diploid sex determination.
• Diploid male honey bees (Apis mellifera) are usually eliminated by worker cannibalism shortly after hatching.
• A hypothesized 'cannibalism substance' inducing this behavior has not been identified.

Purpose of the Study:

• To investigate the chemical basis for the differential treatment of diploid versus haploid honey bee larvae by workers.
• To identify potential pheromonal cues on the surface of newly hatched larvae.

Main Methods:

• Extraction of cuticular secretions from newly hatched diploid and haploid honey bee larvae.
• Chemical composition analysis using gas chromatograph-mass spectrometry (GC-MS).
• In vitro rearing of larvae for up to three days.
• Comparison of physical parameters and vitellogenin levels in adult diploid and haploid drones.

Main Results:

• GC-MS analysis revealed alkanes as major compounds in larval cuticular secretions, with differences noted between diploid and haploid larvae.
• Adult diploid drones showed fewer wing hooks and smaller testes compared to haploid drones.
• Sperm DNA content confirmed a 2:1 ratio between diploid and haploid drone gametocytes.
• Vitellogenin titers were significantly lower in adult diploid drones.

Conclusions:

• The study identified chemical differences in cuticular secretions between diploid and haploid honey bee larvae.
• These chemical cues likely influence worker behavior, explaining why older diploid larvae are not cannibalized.
• Physical and physiological differences exist between adult diploid and haploid drones, impacting their reproductive potential.