The First Evidence for STDs in Honeybees
Nosema is a unicellular fungus that causes nosemosis, the most widespread disease of honeybees. Diseased bees are often afflicted with dysentery, disjointed wings, and an absent sting reflex, among many other symptoms.
The most common way Nosema is passed is via spore-ridden fecal matter. Bees swallow the spores, which make their way to the insects' guts and germinate. But it turns out that spores can also get into the semen of male bees, and when these bees copulate with the queen, she can also become infected.
Researchers primarily based out of the University of Leeds collected sexually mature male bees from 39 colonies infested by Nosema. They then harvested the insects' semen (very delicately, as one would surmise) and inseminated a group of queens. One out of every five of the queens developed nosemosis.
Luckily for the colony, infected queens do not pass Nosema onto their young. None of the 400 eggs laid by queens in the experiment carried the parasite. However, unluckily for parasite-ridden queens, their days are usually numbered once they take on the parasite. An infected queen's ovaries quickly degenerate, severely reducing her egg-laying capacity. Sensing the queen's infertility, workers then set about rearing replacement queens. When one is ready to take the throne, workers encircle the old queen and sting her to death.
"The results provide the first quantitative evidence of a sexually transmitted disease (STD) in social insects," the researchers said of the study.
STDs have been found in insects before, though, unlike vertebrate STDs, which are commonly caused by bacteria or viruses, insect STDS are usually caused by parasites -- mites, nematodes, fungi, and protists.
Source: Roberts, K. E. et al. The cost of promiscuity: sexual transmission of Nosema microsporidian parasites in polyandrous honey bees. Sci. Rep. 5, 10982; doi: 10.1038/srep10982 (2015)