Wednesday 29 November 2017

Photograph your specimens through the microscope

I sometimes think of myself as a bit of a Luddite eschewing modern technology (a student laughed at me on a field trip last year for actually using a paper map... I like to think he was sorry when his phone ran out of battery). But when it works I do like it really.

Today I finally got a microscope camera to talk to a computer. I won't bore you with the details because the important thing is that it now works and you can now come and use it. Getting the lighting right seems to be a fine art but I'm getting there. You can zoom in to the important features of your specimens, snap a photo, and then print it out and stick it in your notebook. I used it to identify two freshwater snails and I was very pleased.

They both came from a local pond lined with stone blocks (which apparently used to be where the local gentry washed their carriages - who knows). It didn't look like a very promising environment - it's pretty stagnant with more mud than water! But this actually made it a different sort of habitat to the usual ponds we visit - and so it turned up a species I'd not seen before.

You can see this species is very tightly coiled. It's only about 6mm across, and has 5+ whorls.


But also, it's very thin through - only about 1mm. I managed to hold the shell so you can see its aperture (which is pretty round).


So with these relatively few facts and a look at Collins 'Lakes, Rivers, Streams and Ponds', I identified it as Anisus leucostoma -  the White-lipped ramshorn snail. It doesn't care if the pond it's in dries up a bit: it can resist drought by staying in the mud. There's a similar looking species (Anisus vortex) but it's found in running water (and has an oval aperture) - so can be safely discounted I reckon.

For freshwater and terrestrial species I very much like the drawn illustrations in Janus's 'The Young Specialist Looks at Molluscs' (overlook the daft title) - it shows the shells from different angles (you can get a secondhand copy for about £5, or you're welcome to look at mine). The names can be out of date but that's relatively easily sorted (I might make a list to share).

The other species (in fact the only other thing alive it seemed) was a dextral snail (meaning its aperture is on the right if you hold it upright towards you). You can see the aperture is huge compared to the rest of the shell - it's about 3/4 the height. There's a little dichotomous key to Lymnaea (pond snails) in 'LRSP' - if you follow that (and look at the angle at the top of the aperture) you'll conclude this species is Radix peregra, the romantically-named Wandering snail.


I'm sure with a bit more experience with the lighting (and a bit of fiddling with Photoshop) you could make your photos even clearer. These snails were wet and I probably should have dried them to help with reflections and focusing. But I hope this encourages you that tiny things can be photographed fairly clearly. (You can also have a go down the microscope with your phone, with a steady hand).

Also on the subject of snails, did you know that because their shells are so persistent, they're used by archaeologists and people interested in past climates to work out what environments used to be like? You can see here that freshwater snails have been grouped according to their taste in habitat, so if they're uncovered hundreds of years later you can infer what it must have been like where they were living. My Ramshorn snail is in the (quite rudely titled) 'slum' category. One man's slum is another man's perfectly adequate muddy pond, thankyou. Also, 'catholic' doesn't refer to the snails' religious beliefs, but that they have wide-ranging habitat tastes.

 from Brown (2001) with updated names

So if you're collecting snails - or anything - the moral of the story is to look in a variety of habitats, and then you will find a wider range of species.

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