Science Daily puts the beekeeper’s foe, the varroa mite (believed to be a key player in Colony Collapse Disorder), in a new light. The parasite had long been thought to be a blood-sucker, with various anti-mite strategies devised around that assumption. But it turns out the hive-killing pests are draining young bees of fat:
Based on research from the 1970s, scientists thought that the parasitic mites feed on the bee version of blood, called hemolymph. But the mites are actually after the fat of young and adult honeybees, says entomologist Samuel Ramsey, who is joining the U.S. Department of Agriculture’s Bee Research Laboratory in Beltsville, Md.
That insight might aid the largely failed efforts to develop antimite compounds for feeding to bees, says toxicologist Aaron Gross of Virginia Tech in Blacksburg. He has documented mites resisting some of the current controls and hopes for new options.
Ramsey’s rethink started with Varroa biology. For instance, the mites don’t have the more flexible body that can swell with a lot of incoming fluid or a gut specialized for elaborate liquid filtering that many other bloodsuckers do. And insect hemolymph looked to Ramsey like a weak, watery choice for exclusive nutrition.
So Ramsey spent about a year while at the University of Maryland in College Park developing artificial bee larvae from gelatin capsules that let him test how well mites survived when fed different proportions of fat from an organ called the bee fat body versus hemolymph. Mites lived for just 1.8 days on average on pure hemolymph. The only ones to survive the entire seven-day tests — though few in number — ate 50 percent or 100 percent fat.
Those tests plus other evidence show that the mites need bee fat, Ramsey and colleagues argue January 15 in the Proceedings of the National Academy of Sciences. Rather than sucking blood, the mite “is feeding on flesh more like a werewolf,” he says.
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Refocusing on fat suggests how mites damage bees in many ways, Ramsey says. The bee fat body detoxifies pesticides and, among other jobs, helps orchestrate the development of the unusually long-lived generation needed to survive winter. Damaging the organ may also reduce bees’ immune response, worsening damage from the viruses they spread, says evolutionary ecologist Lena Wilfert of the University of Ulm in Germany.