Northernmost record on the planet

Last week the Skye Nature Group went across to Raasay, ostensibly on an earth tongue hunt but recent frosts seem to have knocked them all on the head. So we instead targeted a monad centred on Loch Eadar dà Bhaile and headed off into a lovely patch of Celtic Rainforest, literally dripping with bryophytes and lichens. I'm not sure I saw a single patch of bare bark anywhere in there, just incredible! 

Lots and lots of Wilson's Filmy Fern later, I found a well rotted fallen log partly embedded in the leaflitter. As is my wont, I spun it over and found myself eyeballing a pale Philoscia woodlouse. It was a heart-in-mouth moment as I realised all of my pots were inside a bag, buried somewhere in my rucksack...would it stay still or would it vanish into the leaflitter before I could grab it? Thankfully it remained motionless long enough for me to gently slip a pot over it. Sweet. 

Due to some fairly relentless drizzle, my handlens was covered in raindrops, my camera lens was smeared with raindrops and the glass tube was also soon covered in raindrops. I showed my find to Neil, but his glasses were also covered in raindrops....we agreed to check it out indoors! 

After the walk, we retired to Stephen's kitchen for teas, coffees and chocolate biscuits (I suspect this was the highlight of the day for some folks attending) and Neil unceremoniously dumped the Philoscia onto the table top for a quick photo session. Knowing how quickly these buggers can run, you could say I was just a little on edge! 

Neil's pic of the live animal

Much to my relief, it behaved itself and did not explode across the table, onto the floor and straight out the cat flap never to be seen again. Safely back in its glass tube, I took it home for a closer examination. 

There are just two species of Philoscia known from Britain; the very common Philoscia muscorum and the recently discovered (2017 in fact), long-overlooked Philoscia affinis. For a full account of how Philoscia affinis was discovered to be present in Britain (and it's worth reading the convoluted tale) have a look here.

The females of Philoscia affinis are more or less do-able on colour patterning and head mottling, but not with 100% reliability. It requires a male specimen to conclusively confirm that your specimen is an affinis as opposed to a muscorum. Despite being abundant across much of Britain, up here on Skye muscorum is an uncommon beast, pretty much restricted to warm coastal sites. In three years of turning over rocks, logs and general debris, I've only ever seen a single Philoscia muscorum - beneath a sheet of ply in coastal grassland. However, I've collected three female Philoscia from wet deciduous woodland, all with pale mottled heads and all looking to be affinis, a known woodland species. But I needed a male to confirm.

I wasn't holding out much hope of my fourth possible/probable specimen being a male, the ratios seem to be one male for every nine or so females, so I was suitably stunned to discover a sticky-out 'hook-like' projection on the merus of the seventh pereiopod (halfway down the back leg, in easy lingo). It was a male! I knew one species had a projecting hook and the other a laying down hook - stick your thumb out as if thumbing a lift and then lay it down against your hand to see what I mean - but couldn't recall which way around. I really hoped it was affinis that had the sticking out hook.

Here's a very bad pic of the hook in question

So what you are looking at is the side of the hindleg. The arrowed hook is situated near the base of the merus, which is one of the leg sections of a woodlouse. Here's an image I nicked off the internet to give you a better idea of whereabouts the merus (plural meri) is located.

So you can hopefully see that it's quite a small feature on quite a small part of a small leg on a small animal. No wonder I couldn't see it through my rain-splattered hand lens! Luckily it's easy enough through The Telferscope. I blasted off a few images to Steve Gregory, national recorder for woodlice in Britain, who came back with a big thumbs up (pun intended) and these words:

Excellent! This is by far the most northern known confirmed record of P. affinis on the planet. Isle of Lismore just north of Oban held the previous record. Thanks Seth.

So that's nice...

Philoscia affinis has now been added to the Hebridean fauna. I need to find a male in Uig Wood next, one of my females came from there and would hence be the 'new' northernmost record on the planet. Keith Lugg has accepted the unwritten challenge and intends to find it on Orkney if/when he moves up there. Best of luck Keith, not much in the way of ancient deciduous woodland up there buddy! 

Apologies for the lack of blogging of late, I shall endeavour not to leave it so long until the next one.