I picked up this specimen from the banks of the Taff in Cardiff (llandaff area) on Saturday morning:
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| Arcitalitrus dorrieni? |
I think it is a specimen of
Arcitalitrus dorrieni, the dark colour (which was much blacker when the specimen was fresh) and the habitat (wet, humus-rich soils with leaf litter under trees) point to it being that species. I understand there are no terrestrial amphipods native to the UK.
A. dorrieni was introduced from Australia with the first specimen taken from Tresco in the winter of 1924/5 and may have been introduced on multiple occasions. It is now becoming more common throughout southern and south west England, south Wales and sporadically around the coast.
It's abundance was striking; significant numbers seemed to be lurking under every handful of leaf litter, stone or log. Also striking was the fact that in 20 minutes of so of searching, I didn't find a single carabid or Staphylinid beetle, in fact the only predator I found was a single Linyphiid spider. It makes me wonder what impact it has on the native soil fauna!
More info here:
http://www.brc.ac.uk/gbnn_admin/index.php?q=node/192 and here:
https://www.brc.ac.uk/downloads/Presentations/2012_TonyBarber_Amphipod.pdf.
Interesting post Adam. When we moved to Llandaff North in 2007 a friend who lives locally showed us a large population of this species (presumably the same species anyway) in leaf litter at the end of his garden. He only lives about 100m from us but we've never seen them in our garden despite having suitable-looking habitat. He lives on the other side of Gabalfa Avenue and a big roundabout, so perhaps all the tarmac is too much of a barrier to them.
ReplyDeleteI've never seen them up here and I do a lot of dibbling about in leaf litter, while working. I'll keep a closer watch for them, How large are they? Tiny if the comparison to that beech leaf is anything to go by.
ReplyDeleteHaving looked again at the map George, the area where I found them is south of the A48 so probably more Gabalfa than Llandaff to be honest, possibly quite close to your friend. I've got NGR ST 165 783 on the specimen label if you want to have a look. Apparently they have very limited tolerance of dessication and are confined to areas with significant leaf litter (woodland I guess that would be!) so a road may be a significant barrier.
ReplyDeleteThey look just like dark sand-hoppers Mark, pretty unmistakeable in fact, although you could be forgiven for mistaking the smaller ones for larger collembola as they jump in a similar way. At their largest they are about 10mm long, though the specimen in the photo was smaller at about 7mm. I'm not surprised you haven't seen them up your way as they apparently have poor tolerance of low temperatures, and temps below 0 degrees gives 100% mortality. The last winter with it's mild temperatures and constant rain must have been perfect for them though which I guess is why they are now out in plague proportions!
That's about 1km from where I saw them (ST153788). The lack of freeze tolerance perhaps means that the population near me has been lost anyway, as I saw them before the cold winters of 2009 and 2010. I'll have to ask Mike if he still sees them.
ReplyDelete