The Biologist Is In: September 2016

Tuesday, September 27, 2016

When A Fly Dies, Do We Question Why?

A housefly dead and holding onto a mint stem.

Dead fly on basil.

While recently visiting with my brother, he mentioned he had a biology question for me. He was wondering what might be behind the dead flies he was finding stuck to the basil and other plants in his garden. I asked him to show me what he was talking about, as there are many reasons a dead bug could end up stuck to a plant.

What he ended up pointing out was several house-flies that had become deceased while visiting floral structures on the various plants. Now, flies are dying all the time and they are often found feeding on flowers, so it wouldn't be surprising for them to die while at flowers. That these dead flies seemed to have a stubborn grip on the flowers they passed-on at made me consider an alternate model for their demise.

There are certain types of fungus that infect ants and take over the minds of the ants in the process, leading the ant to behave in a manner to help spread the fungus. Zombie ants. The zombie ants will clamp their jaws onto stems above where a colony of the host ant species has major highways, whereupon the fungus grows its spore-body and drops infectious spores on other unsuspecting ants. The ant-zombie-fungus in turn has its own parasite. This hyperparasite will help keep the zombie-fungus in check, thus supporting the health of the ant colonies. (Similar to the population dynamics between plankton and large fish.)

Closer.

Even closer.

So, how does this relate to the flies? They were all found deceased and holding securely to flowers. Close-up photos of the fly (at left) reveal the body to be covered with strands (fibers, webs?) and splotches that look like tiny yeast (single-celled fungus) colonies. Being stuck on a flower means that another fly dropping by for a feed would have a decent chance of getting exposed to whatever is on this fly. One type of fungus can make zombies out of ants, and there are many types of fungi that do this with different tropical insects, but I've never heard of one being found this far north.

It could easily be that dead flies, wherever they are, end up growing microbial colonies like this. It really isn't clear. To see if this is unusual, I'd have to collect a bunch of dead flies from different environments and determine what the normal decay process is for a fly cadaver. If ones like this are unusual, then I can imagine exposing lab-living flies to whatever is growing on the dead and seeing if they have altered behavior due to becoming a zombie.

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Ants etc.:

Tuesday, September 20, 2016

Ichneumon Wasp

Large female wasp with elongated ovipositor the length of the rest of the body. Wasp is climbing a vertical wooden post.

Between recently traveling on vacation and subsequent computer issues, I haven't posted much lately. I'm back from vacation and have fixed most of the computer issues. This has allowed me to produce the images I wanted to for my last post on the status of my carrot breeding efforts.

I've got several posts in the works, but for now I'm just going to show you this cool wasp I found a few months back. It, like most wasps, is female. When I found her she was probing the wood surface with her dramatically extended ovipositor. The ovipositor, and my limited entomological knowledge, identifies this as an ichneumon wasp of the family Ichneumonoidea.

Wasps in this family are parasitoids, meaning they inject their eggs into other insects for their larva to feed upon. I suspect this lady was trying to find a wood-boring beetle larvae to inject her eggs into, since the wood itself wouldn't provide for her children.

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Thursday, September 1, 2016

Making My Own Carrots 6

Two carrot roots, pale pink with darker pink tops. Bottom half of root was cut away and remaining top is sitting upright. One has new green leaves.

The only surviving roots.

My ongoing project to breed my own carrot variety had a couple of unexpected twists this year. At the end of last year I saved all the roots which appeared to be grown by F1 hybrid plants. Such roots were the most interesting to me because they were the ones that could later produce diverse F2 seeds. I was most pleased with the ones that had some purple or red coloring, since I want my carrot population to be full of rich red/purple colored roots in later years. Most of the roots seemed to make it through winter, but when I warmed them up this spring to start growing, most proceeded to rot. This left me with only two large roots that had a lovely blush color (at right). Two plants is a limited genetic pool to work with, but I figured it would be fine because they were both F1s.

During the growing season, one of these potential mother plants bloomed and seeded furiously. The second potential mother plant grew luxuriantly, but decided not to bloom at all. My population has gone through a severe genetic bottleneck. One individual.

Two large pots of carrot plants on balcony.

The sterile and floriferous mother plants.

Fortunately, this one plant is a F1 hybrid, so it is likely to have a relatively high amount of genetic heterozygosity. One of the parents was likely an intense red/purple, while the other was likely pale/white. White roots are generally a dominant trait over orange in carrots, but it seems the red/purple trait has a co-dominant expression pattern. The result of this is the next generation of carrots will likely have a widely diverse mix of phenotypes for me to select from, even with the genetic population having been reduced down to one individual. Next year, I plan to save many more roots to minimize the chance of this happening again.

I'll try to keep the non-blooming plant alive over this next winter. Maybe it will flower next year, maybe it won't. Either way, I won't be allowing its genetics to contaminate my main carrot breeding project. If it lives long enough and grows monstrous enough... I might decide to initiate a new carrot breeding project. We shall see.

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