Sick Honey Bees Buzz Away From Their Hives

honey-bees

By Lisa Jancarik

Research from the French National Institute for Agricultural Research suggests that honey bees (Apis mellifera) infected with pathogens leave the hive permanently, limiting the spread of infection. Scientists in Avignon infected honey bees with either of two known parasites, Varroa destructor (a mite) and Nosema ceranae (a fungus) and observed their behavior and the behavior of other bees in the hive.

Bees with the parasites on board showed changes in which genes were active in the bees’ brains. The up-regulated genes (genes that were switched on or made more active) involved foraging and neural function, among other things. Infection also altered the “family scent” by which honey bees from the same hive recognize each other.

Self-exile From The Hive

Curiously, uninfected honey bees do not treat the infected bees differently in spite of the change in “family scent”. Social interactions like grooming and antennal contact continued as usual, and the sick bees were not expelled from the hive. Instead, study leader Cynthia McDonnell hypothesizes that the honey bees infected with these parasites leave the hive voluntarily, possibly as a result of the changes in the bees’ brain chemistry. She went on to suggest that voluntarily leaving the hive may be a response to other parasitic infections, too, because the two parasites studied were very different.

University of North Carolina bee researcher Olav Rueppell commented on the study to NBC News, saying that this study does not explain the widely reported problem of declining honey bee population. His team’s own earlier research predicted her findings, when they simulated infection using carbon dioxide to make bees feel sick. He also takes McConnell’s conclusion that the behavior of leaving the nest to limit contagion spread as speculative. The overlap in expression of genes in the bees’ brains that McDonnell views as significant strikes him as a “small amount of neurogenomic overlap”.

Classroom Discussion

  • Why does Dr. McDonnell think that honey bees may abandon the hive as a response to infection generally, not just infection with the two parasites her team studied?
  • This behavior by infected bees from the hive has been described as “altruistic”. Do you agree with that characterization? Why or why not?