Monday, 5 December 2016

Aquatic Centipedes?

Today dawned bright and beautiful, not a cloud in the sky and not a breath of wind to stir the treetops. Despite this the air temperature remained pretty low and a thick frost blanketed the ground. Perfect for a quick shomble through a new part of my square. I whacked on a few dozen layers and staggered off into the unknown. 

There's a side road just before Uig Woods which leads to a few residences along the sea front. I ambled my way along this road for maybe half a mile or so before turning back - wouldn't want to accidentally wander out of the square! I really need to get myself a handheld GPS one of these days. 

The glass-like state of the sea afforded me excellent views across the bay. I could see a flock of 30-40 Eider out by the pier (and hence outside NG3963) but happily 2 males were inside my boundary so that's Eider on the list. Also on the water were 12 Wigeon, 10 Mallard, 2 Red-breasted Mergansers and a lone Great Northern Diver which was busily spending 90% of its time underwater, doubtless catching fish in the placid sea conditions. Divers hunt fish by sight, so if the water is too turbid they resort to crabbing by touch on the bottom. Fish use their lateral line to navigate in murky conditions so aren't hampered in the least by poor visibility, hence can easily evade a big blundering bird. Crabs are just shit out of luck when it comes to escape/evasion manoeuvres.

Still on the beach I did a bit of stone-turning. There aren't any rockpools here, something that greatly disappoints me, so hand searching through the cobbles and rocks is my only option. Put it this way, half an hour of turning rocks revealed 2 Beadlet Anemones, a Common Limpet, 3 Green Shore Crabs, a Common Mussel and lots of Edible Periwinkles. That was about it, crap! Oh, and millions of hoppers that I'll (probably...) try and do one day soon. Strewn around the beach were thousands of bivalve shells, mussels, razor shells, cockles and otter shells being the majority. No worm casts that I could see which seems odd. Maybe they don't like the volcanic sand? A determined closer look added the flat periwinkle Littorina obtusa and a clump of shaggy bryozoan which was microscopically confirmed as Cradoscrupocellaria reptans with its lovely antler-shaped scutum. One final shoreline sighting of note - I was in the Channelled Wrack zone of the beach (upper part but still completely covered by water at high tide) so you can probably imagine my surprise when I spun a large rock and found myself looking at a big wriggling knot of centipedes! Huh, aquatic centipedes??? I was initially a bit confounded, just one individual I could put down as a wandering animal who had unwittingly doomed itself by foraging too far down the beach. But dozens?!?!? Clearly this was their habitat, I needed to do some investigating. (At this moment I haven't microscopically checked them but suspect either Strigamia maritima or the aptly named Hydroschendyla submarina).

EDIT: They are indeed Strigamia maritima, a species already known from Skye and one I've seen before in Cornwall. Hydroschendyla submarina only occurs in the far south-west, typically in rock crevices.

So are they aquatic? Really good at holding their breath? Or is it just a mass suicide pact? 
The wrack-covered rocks in the foreground is the habitat they were in. Crazy shenanigans.
My square includes all of this water and the near woodland to the right of the dwellings. 
River Conon running into the bay. See those same dwellings? This is to the right of the previous image. 
Scrub and reeds just a smidge inland from the last pic. The river runs right-left at the foot of the Alder copse.

So, a tad overdue perhaps, but now you have an idea of what a part of the mighty NG3963 looks like! Next time I shall endeavour to show you both halves of Uig Wood. Or maybe the area upslope of the hotel if I head that way instead.

As a footnote, various other additions to the square's Pan-species List included the plants Common Ragwort, Meadow Buttercup, Viviparous Sheep's-fescue, the easy-to-recognise-so-I'll-have-a-go bryophytes Polytrichum juniperum, Plagiomnium undulatum and Lophocolea bidentata plus the microfungus Phomopsis subordinaria on dead Ribwort Plantain stems (supposedly very rare in Britain but I've seen it on Scilly, at Southampton and now here on Skye this past few months. I think it's just massively under-recorded, not rare at all!) 

Back at our accomodation that night, I spied a short-legged harvestman on the wall amongst the Dicranopalpus ramosus (although technically even a giraffe looks fairly short-legged compared to ramosus...) Using the FSC Harvestman Synopsis it keyed through fairly painlessly to Oligolophus hanseni, which has been recorded from Skye before, although not from Uig. This was a lifer for me and my 14th species of harvestman.  I've updated the PSL Running Total Page accordingly.
 

2 comments:

  1. S.maritima isn't aquatic - it's usually top of the shore and can't cope with more salinity - at least that's what I read somewhere recently!

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  2. Hi Ali, yup I realise that we don't have aquatic centipedes, I meant that a bit tongue in cheek. Same as I doubt it was an attempted mass suicide pact. However, they really were in the wrack zone (uppermost part admittedly) so I can only assume that they either survive trapped in an air pocket whilst the stone they were under is submerged (and it would be fully submerged), or that they quickly scamper further up the beach when their feet start getting wet? Despite turning lots of stones/boulders I only found centipedes beneath one rock. What was so special about that particular rock? I've seen Lagoon Snails (Paludinella litorina) beneath rocks that are submerged at high tide, and these aren't aquatic either. Maybe there's more to the underside of certain rocks than we think? Fine substrate may be the key, more air pockets? Might be worthy of further investigation, I think.

    Thanks for commenting Ali, it really is very gratifying to know I'm not the only one reading this, I shall get back to you about those centipedes! :)

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