Nematodes under the microscope

I'm in week six and the labwork is still going. I feel at least vaguelly competent at maybe half of the techniques now. Supervisor continues to be very busy, so in between running experiments under his direction, me and Smith have been investigating some worms from the museum's collections. And I've been doing hours of bioinformatics practice, but that's too dry and technical for a blog post. Even here!

So, back in the US, Smith's group work on parasitic worms found in marine mammals, especially seals. Among other things, they identify them when an infected animal washes up or comes into a rescue centre. However, they're having trouble with one sample of worms. They come from the heart of an elephant seal, but the scientists who found them have identified them as Otostrongylus circumlitus. This species instead lives in the lungs of harbour seals.

I know which one I'd rather parasitise.
Sources: https://pixabay.com/p-18440/?no_redirect
https://upload.wikimedia.org/wikipedia/commons/e/e3/Northern_Elephant_Seal%2C_Piedras_Blancas%2C_San_Simeon%2C_CA_02feb2009.jpg

Is the identification wrong, or is this a cool new host situation, maybe because the worms got into the elephant seal by mistake, got confused, and migrated to the wrong organ? That's what Smith's group want to find out.

Unfortunately, sequencing the DNA of the mystery worms wasn't helpful. The results came out all over the place, which might be true of that whole group of worms. The other way to identify them is good old-fashioned morphology. This is challenging for nematodes because they basically all look like this:

These ones were about 15 mm long but you still needed a microscope to see any, erm, identifiable features. And the worms haven't been preserved in the best of ways so might be damaged at that scale anyway. Tricky.

So, while Smith happens to be doing her internship thing at the NHM, she decided to find some Otostrongylus circumlitus in the collections and take some photos to compare the mystery worms with, because if something is going to be correctly identified anywhere, you'd hope it would be in the NHM collections. Last week, the parasite curator gave us a little jar of O. circumlitus and Smith searched through looking for males. It turns out that this group of nematodes does have one identifiable feature: the male tail. It's a sort of fan/sucker thing used for mating, like a tiny frilly collar on the very end of the worm. Once she'd found a couple of males, they went into a little dish of creosote (of all things: https://en.wikipedia.org/wiki/Creosote), which would eventually turn them translucent so that we could see them in detail.

We went back to have a look this afternoon. The creosote had certainly worked. Smith did the neat trick of taking photos through the microscope eyepiece. Here's one worm's head with all of the weird bunchy tissues and bits:

And here's the tail with a side-on view of the transparent frilly collar thing:

Fortunately, there are people (and books) that know what these tiny wibbly jelly tail prong bits mean. The photos have all been sent off to the US to compare to the mystery worms. We'll see if anything comes of it.