Sunday, 8 January 2017

Splishin' and a-splashin'

I targeted the River Conon today to see if I could find anything special under stones and rocks. Last week it was in full spate, or at least the highest I've seen it since moving here. It was still fairly rapid today but nothing like it has been (no trees or dead sheep whizzing downstream for starters). My favoured stretch is about 200 metres east of the A87. There's a nice little backwater channel only a few inches deep and littered with nice sized submerged stones and cobbles. Here's a habitat shot of part of the section I was working, very shallow and sheltered as you can see. 

This was a minor torrent last week!
It didn't take much effort to find River Limpet (Ancylus fluviatilis), probably every second or third pebble had one attached! I was especially on the look out for freshwater triclads and again it didn't take too long to find some. I've only found Polycelis felina in this river but today I added a second species, Crenobia alpina which was a lifer for me. This is my 10th British platyhelminth and it's very pleasing to have achieved double-figures at last! 

This was the first Polycelis felina I encountered today.
Then this! My first ever Crenobia alpina (with a River Limpet thrown in for good measure)
I quickly popped them into a pot (well, the lid of a pot to be precise) and took lots of pics in the vague hope that one my be sharp. No such luck! This was about the best of a bad bunch

Crenobia alpina is the grey one on the left, Polycelis felina the reddish one on the right.
It's not clear from the pic, but Crenobia has awl-shaped tentacles and one pair of whitish eyes set quite far back on the centre of its head. Polycelis has more pointed tentacles and a long series of tiny black eyes that run up one side of the head, across the front end and back down the other side. My Key to the Freshwater Triclads of Britain & Ireland suggests that Crenobia is outcompeted by Polycelis, yet clearly both occur together here. Though mostly Polycelis to be fair. Crenobia isn't thought to occur in waters that regularly exceed 15 degrees in the summertime. That could be a determining factor along this lower stretch of the River Conon. I expect the water stays cooler higher up the valley where Crenobia probably replaces Polycelis. How many more times can I write the words Crenobia or Polycelis in this paragraph I wonder? None.

I found a handful of snails on the submerged rocks too, I initially thought they were Physa but the body mantle clearly didn't flare out to cover part of the shell as it does in Physa. I always find that a bit creepy, reminds me of the face-huggers from Alien...

Back indoors I took the following three pics. The freshwater snails were all Wandering Snails (Radix [Lymnaea] peregra) which I've recorded before, though not from Skye. The land snail is the same one I keep finding under boulders, namely Oxychilus cellarius. Plus there's a slightly better image of Crenobia alpina, taken through my microscope. Still very unsatisfactory though. I let them all go in the burn that runs by just outside my room. 

Wandering Snail (Radix peregra) - common in Britain whether in a pond, river or torrential mountain stream!
Crenobia alpina - cold mountain streams are the preferred habitat.
Oxychilus cellarius - note the brown-spotted upper edge of the mantle, diagnostic of this species.
The only other thing I found of note were these two Nemastoma bimaculatum, unbelievably the first arachnids I have identified this year! Another poor pic, they were moving quite rapidly! 

Nemastoma bimaculatum - a pair on the underside of a rock I'd just lifted.
So there you have it, an entire post without a single lichen image. You lucky, lucky people!

No comments:

Post a Comment