Life Under Rocks

The days are slowly lengthening, to the point that I just about had time to nip off in search of the Humpback in Loch Dunvegan once more. I blanked, once again. I'm starting to think it may have moved on to fresh hunting grounds. The five Whooper Swans were still on Loch Suardal, it's going to seem strangely empty once they depart (I've managed to get the site added to the national census map for Skye. Crazy that it wasn't listed already) and a young White-tailed Eagle lumbered by, so hardly a wasted journey. Plus Common Dolphins are always entertaining to watch. 

Back at the hotel I noted three Red-throated Divers on the loch outside but still no sign of any Otters as darkness properly fell. I donned my headtorch and hit the garden once more, hoping not to encounter too many New Zealand Flatworms. I found seventeen of them, so I guess I lucked out there!

They're just not a very appealing kind of creature

I heaved over a few biggish rocks that were quite deeply embedded in the soil, which is where most of the flatworms were concentrated. Amongst them was a (sluggishly) active nest of Myrmica ruginodis, a very common red ant here on Skye and my first hymenopteran species of the year. I potted a couple of elongate staphylinids which both turned out to be Lathrobius fulvipenne, the second and third individuals I've had here this year, plus a couple of flat-backed Polydesmus millipedes which I keyed through shortly afterwards. Both were adult, so I was happy they could be identified. Here they are side by side

The larger individual is a female Polydesmus angustus, a common species

The larger was an adult female Polydesmus angustus and readily identifiable as such. The smaller individual was an adult male Polydesmus, but the gonopods didn't match the usual angustus at all. With these it's mostly a case of picture-matching the gonopods to the illustrations in the key, not always particularly straightforward as the shape changes depending on the exact angle you're viewing them from. Essentially there are a pair of longish hooked arms with a secondary smaller pair of arms tucked behind them, plus a few bumps and teeth and whatnot mixed in. It's quite a complicated structure, even in 3D nevermind trying to interpret a 2D illustration. But I got there in the end, finding a perfect match with Polydesmus inconstans, which is a new species for me. Here's the best image I managed through the microscope

It took me a long time to take an acceptable image!

This closely matches part of the gonopods visible in my image above

The angle is a little different, hence the shape doesn't quite line up, but hopefully you can see that my millipede's gonopods match those of the illustration. Polydesmus inconstans, quite widespread in Britain with records from Cornwall to Shetland, and yet it's taken me until now to identify one. I did say there were plenty more myriapod species available for my PSL. This is the second new one for me in the last two weeks, following on from Brachychaeteuma bagnalli. 

The final thing I noticed beneath the same rock was a tiny snail shell, measuring around 2mm diameter and looking faintly glossy and translucent. I popped it into a pot and was soon admiring it beneath the microscope. Using the FSC Key to Land Snails I quickly narrowed it down to the genus Vitrea where it was a toss up between Vitrea crystallina and the very similar Vitrea contracta. Mark Telfer showed me Vitrea crystallina a couple of years back on the Isle of Wight, I've never knowingly seen contracta.

The top image shows some black marks which, after reading this account led me to think it might be Vitrea contracta. But the actual shell morphology fits Vitrea crystallina better, in particular note that the width of the final whorl just above the opening is 1.75x wider than the preceeding whorl at the same position (I measured) which is outside the range of contracta but well within the range of crystallina. I needed to view the shell edge-on to check the profile of the spire and of the aperture, which was easier to do than to photograph. How to balance a 2mm shell on it's edge without it falling over..?

I'm just too good :) 

Note that the spire is exceedingly flat, hardly raised at all. This in itself doesn't necessarily split it from Vitrea contracta which also has an exceedingly flat (in fact even flatter) spire. Comparing with images in the key and images online had me swaying back and forth between the two. Happily the mouth opening itself is just too rounded for contracta, and so I hope that I've correctly identified this as Vitrea crystallina. If you're reading this Mark.....

The yearlist is still coming along quite nicely. I'm up to 474 species so far, so just 26 more to find in the next week or so to hit a personally very pleasing 500 in January. Fingers crossed!