08/28/2003
Troubles in the Hive
After the Columbia Space Shuttle disaster, the Russians came to our rescue by bringing down the astronauts who had served their time on the International Space Station. Once again, “The Russians are Combing”. That’s not a misprint, but the title of an article by Gabriel Gluck in the August 19 issue of the New Jersey newspaper The Star Ledger. The article detailed the travails of Dianne, our town arboretum’s beekeeper. Last winter, on a cold December day, Dianne went out to check her 50,000 charges in the box housing the hive. To her dismay, the door to the box was open (a curious visitor?) and every last bee had expired!
These were not your typical American honeybees. They were Russian immigrants or their descendants. Dianne started out with 5,000 bees and everything was going great, the population soaring to the above-mentioned 50,000. Why the Russians? They are good groomers and more hygienic in their habits than the less fastidious American bees, which have been decimated by a couple types of mites. It isn’t the loss of honey that’s the main concern. It’s the some $15 billion dollars worth of produce in this country that requires pollination by the bees.
The Russian bees not only groom themselves but each other, brushing off and killing the mites in the process. They’re also better housekeepers, cleaning the cells and tossing out those that are infested with mites. By breeding American colonies with a Russian queen, the local bees’ resistance to mites is doubled.
Speaking of breeding, it’s well known that bees have this tidy arrangement wherein a lone female establishes herself as the one and only queen bee. The other females are relegated to jobs as workers. Her royal status entitles the queen to have the other females fawn over her and provide her with food and protection. The price she pays is having to single-handedly produce all those eggs to perpetuate the hive. But, in New Zealand, this orderly social structure has broken down and given way to anarchy.
In 1994, Ben Oldroyd, an associate professor at the University of Sydney in Australia, and his colleagues published a paper about a colony of bees in New Zealand in which workers were violating the code and were producing their own offspring. I was tipped to this anarchy by a brief item by K. M. Reese in the Newscripts column of the August 18 issue of Chemical & Engineering News (C&EN). The article discusses more recent studies of Oldroyd and his colleagues, who are trying to determine whether there is a genetic reason for this errant behavior. What they did was to take some of these anarchists from New Zealand and propagate their own colonies of anarchists in Australia.
To learn more, I visited the Web sites of the University of Sydney and nature.com. I was provided with a whole new perspective on life in the normal beehive. An article dated April 25, 2002 on the Nature site titled “The Police State” by John Whitfield suggests that the hive is every bit as brutal as the police states that we humans manage to come up with. Aside from the infighting and maneuvering that the queen employs to establish her royal status, maintaining order in the hive requires the cooperation of the loyal female workers to quash any deviations from the norm.
The New Zealanders are not the only bees that break the rules. A few workers may deviate by laying their own eggs. When the other workers realize what has happened they promptly eat the deviant worker’s eggs. The queen maintains the devotion of her subjects by emitting a pheromone, a substance that shuts down the workers’ ovaries. In a hive of a few tens of thousands of bees, only a handful ignore this pheromone signal and lay eggs of their own. These eggs lack the royal scent, however, and the workers devour them.
What happens to the eggs that don’t get eaten? Have you heard of the term “haplodiploidy”? It seems that bees, wasps and ants share this unusual means of determining the sex of offspring. The anarchist worker bees that lay the eggs have not mated; hence, the eggs are unfertilized. Yet they give birth to bees, all of them male! The queen, who has mated, perhaps with more than one suitor, produces fertilized eggs, all of which yield females. The females are “diploid”, that is, they have two sets of chromosomes, one set from the father and one from the royal mother. The males from the worker eggs are “haploid”, that is, they only have one set of chromosomes, from the worker mother.
This haploid-diploid business makes for some interesting relationships. Since all the workers share the queen’s chromosomes, they have a close relationship with her and with each other. By tending to her needs and to her eggs they encourage the propagation of their own genes. If the queen is monogamous all the worker sisters also share the chromosomes from the father and the sisterly bonds are especially close. When one of the workers lays her own eggs, the resulting males are not as closely related to the sisters and, lacking the sentimental attachment to the future males, the sisters eat the eggs.
In those anarchistic colonies in New Zealand, it appears that a substantial number of workers developed an insensitivity to the queen’s pheromone. Not only were their ovaries active but they also seem to have developed the capacity to camouflage their own eggs to mimic the royal scent. Consequently, the other workers tend to the eggs and a bunch of males are the result. An alternate possibility is that the queen’s pheromone is weaker than normal and doesn’t work as effectively in shutting down the ovaries. In either case, the consequence for the hive can be catastrophic. More and more unproductive males are produced and the workers can’t keep up with the demand for food and care and the hive degenerates into chaos.
In recent work, Oldroyd and colleagues have found a possible genetic link to the anarchist bee phenomenon. Their idea is that the queen’s pheromone somehow affects production of a protein or proteins that switch off the ovaries. Perhaps a gene is highly expressed. “Alien” is the name given to a gene that is known to be associated with reproduction in other insects. This gene is quite active (highly expressed) in queen bees that are not laying eggs. The Australians found that Alien is highly expressed in sterile worker bees but is lightly expressed in the anarchist egg- laying workers. They speculate that the Alien gene could be a key in keeping order in the normal honeybee colony.
We started off mentioning our problem with mites. South Africa has another problem, the parasitic Cape honeybee. The Cape bees are freeloaders and counterfeiters who come into a normal honeybee hive and start laying their own diploid female eggs. They counterfeit the royal scent and the hive’s original occupants tend them as their own. The invaders do little work and produce so rapidly that in a few months the hive is destroyed and the Capes move into another unsuspecting hive.
Let’s all root for the “good” honeybees to evolve some sort of effective defenses against these invaders and subverters. We need those fruits and veggies! And if you’re in an arboretum, please shut the door when you leave!
Allen F. Bortrum
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