I’ve been out in the field around Illinois taking new photos (see right sidebar!) and neglecting my internet… um, responsibilities? Procrastinations? Whatever you call it. In any case, it’s far past time to answer Monday’s mystery.
The DNA sequence was a fragment from a carotenoid desaturase gene isolated from the oleander aphid, Aphis nerii. The fragment was obtained as part of a phylogenetic study pinning the origin of such genes in aphids to an ancient acquisition from fungi. Of the photographs I showed, only one aphid (B) had the brilliant yellow coloration of Aphis nerii.
Carotenoids are common pigments in plants, fungi, and other organisms. The color of carrots, for example, is due to carotenoids. But these useful molecules are notably missing from animals. When carotenoids turned up unexpectedly in aphids, their origin was something of a mystery until Nancy Moran’s research group figured out that aphid ancestors had somehow subsumed fungal carotenoid genes. A natural instance of genetic engineering, as it were.
6 points go to bioczw for getting to the correct ID first, and 4 points go to Guillaume D. for the fungal link.
sources: Moran NA, Jarvik T. 2010. Lateral transfer of genes from fungi underlies carotenoid production in aphids. Science 328: 624-627. DOI: 10.1126/science.1187113
Nováková E, Moran NA. 2012. Diversification of genes for carotenoid biosynthesis in aphids following an ancient transfer from a fungus. Mol Bio Evol. 29: 313-323. doi: 10.1093/molbev/msr206
A hungry aphid lion plucks a milkweed aphid from the herd
A few weeks ago the first Aphis nerii of the season showed up in our little prairie garden. These little orange globes multiplied to plague proportions within days. The butterfly weed was hit hard, dropping its plumes of orange flowers and withering.
The bounty of aphids didn’t go unnoticed for long. Lots of insects eat aphids, and before long the rows of aphids had succumbed to the developing larvae of aphid wasps, turning to hardened brown mummies. Armies of furry aphid lions appeared- larvae of the common green lacewings that frequent porch lights*- to pick among the survivors.
Aphid lions are particularly effective predators, perhaps more so than the ladybirds and preying mantids more commonly marketed as garden beneficials. Their mouthparts are elongated into sharp hollow needles that quickly pierce their prey and drain them dry within minutes.
The long jaws of aphid lions are hollow, allowing them to suck up the juices of their hapless prey
*Lacewings also visit bug zappers, unfortunately. Do you know what doesn’t visit bug zappers? Mosquitoes. You’re an idiot if you use those things, as bug zappers have a high kill rate against friendly insects while doing nothing against the most common biting insects.
As you may have noticed I’ve been experimenting recently with various forms of video. Time-lapse photography only requires a regular still camera, a tripod, and an interval timer, so it doesn’t need any video equipment save the software on the finishing end. The above clip is made from 1/2 second exposures taken every 4 seconds over a couple hours.
But time lapse is highly finicky in its own right. It wasn’t until after I viewed the video did I realize that the tripod wasn’t entirely stable (hence the occasional camera shake), and that I shouldn’t have left the camera on auto-white balance (hence the flickering). It’s a rather unforgiving medium, and I’ve still got plenty to learn.
The genome sequence of the pea aphid Acyrthosiphon pisum was published today in PLoS. Concurrently, a set of supporting papers has come out in Insect Molecular Biology. This genome is significant for a number of reasons- it’s the first Hemipteran genome to be sequenced, aphids have an unusual reproductive cycle, and this particular species is a serious agricultural pest.
I’ve not had time to fully digest the paper, but it seems the salient features of this genome are:
extensive gene duplications
a higher gene count than most other known genomes (including our own!), perhaps related to all the duplications
It’s been snowing aphids the past few days here in Champaign-Urbana. Trillions of them are drifting across town, settling out on our garden, getting caught in our hair. I’ve never seen anything like it.
I recently learned that this sternorrhynchan storm is composed of soybean aphids (Aphis glycines). That would explain all the aphid biomass. Illinois is a major producer of soy, and there’s no shortage of soy fields around here. Sensing the end of summer, the aphids are moving en masse to their winter host, buckthorn.
Soy has traditionally been easy to grow in North America as it lacked any major insect pests. Until about 10 years ago, that is. That’s when the first soybean aphids, an Asian species, showed up in Wisconsin. Given the sheer numbers of these insects, I can’t imagine this bodes well for soy yields this year.