Some exceptions in biology: Worm-catching fungi

Credit: microecos.wordpress.com
When most of us hear the word “predator” in the context of the natural sciences, the first thing that comes to mind is something terrifying. Something with fangs, sharp claws, venom or all of the above. Something that is to be reckoned with. Think lions, tigers, wolves, T-Rexes, you get the picture.
Did you know that there are many species of predatory fungi?
We do not usually think of fungi (yeast, mold, mushrooms) os predators. Well, as I said at the end of my previous post on biological exceptions, nature does not care about what we think! Some of these fungi trap small organisms like rotifers and amoebas.
I, for one, was amazed when I recently learnt about these fungi. As most people, I considered fungi as organisms that degraded decaying matter or as disease-causing agents. I was particularly surprised to lean that predatory fungi have been known since the 1800s! The first recorded observation of this behavior (in 1888) is attributed to Friedrich Wilhelm Zopf, a German mycologist (mycologists are scientists who study fungi & friends). He specifically studied fungi of the Arthrobotrys genus; this kind of fungi actively captures small worms, generally classified as nematodes or roundworms.
Nematodes are widely considered the most abundant multicellular organisms on Earth. There are some 15,000 described species, but as with most small organisms in our neck of the woods, this is most likely an underestimation. The study of nematodes is economically important in the sense that many species are agricultural pests. In fact, predatory fungi are being studied to design possible strategies to control nematode infestation.
These fungi are able to trap nematodes by two main techniques, by secreting adhesive substances that stick to the worm and by actually “lassoing” worms via a so-called hyphal loop or ring (hyphae are filament-like structures in fungi and certain bacteria).
The hyphal loop (HL) mechanism that the fungi use to trap the worms is fascinating. The HL is made of three cells as shown in the picture below:

Credit: microbewiki.kenyon.edu
When a worm touches the interior part of the ring, the cells rapidly gain water and swell as shown above, constricting the loop’s aperture and trapping the worm in the process. Look how cool it looks!

Credit: www.uoguelph.ca
A short time after the worm is trapped, the ring cells germinate and invade the worm, consuming it.
Better than a horror movie right?
IF YOU WANT TO KNOW MORE
microbewiki.kenyon.edu/index.php/Nematode_trapping_fungi
taxusbaccata.hubpages.com/hub/The-Hidden-World-of-Carnivorous-Fungi
Meio JJ (1958) Predatory fungi. Scientific American 199:1. July.
Yang et al. (2012) Origin and evolution of carnivorism in the Ascomycota (fungi). Proc Natl Acad Sci USA. 109(27):10960-5.
uoguelph.ca/~gbarron/N-D%20Fungi/n-dfungi.htm
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