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This is where I post various musings about wildlife and ecology, observations of interesting species (often invertebrates)
and bits of research that grab my attention. As well as blogging, I undertake professional ecological & wildlife surveys
covering invertebrates, plants, birds, reptiles, amphibians and some mammals, plus habitat assessment and management
advice
. I don't work on planning applications/for developers. The pages on the right will tell you more about my work,
main interests and key projects, and you can follow my academic work here.

Monday, 1 April 2013

The Lawn Shrimp cometh

I quite often receive invertebrates in the post, but they are usually leaf beetles (Chrysomelidae) sent to me for identification/verification in my capacity as organiser of the UK's Chrysomelid Recording Scheme - like here for example. However, a couple of days ago I came home to find something quite different awaiting me on the doormat - a crustacean looking like a small shrimp, or to be more precise an amphipod of the family Talitridae (a group usually associated with seashore habitats rather than inland terrestrial ones).

In this case, it had already been identified as Arcitalitrus dorrieni, the 'landhopper', 'woodhopper' or 'lawn shrimp' by the finder/sender, Dennis Trunecka of the Southampton Natural History Society. This is an interesting find as it is Australian in origin (New South Wales & Southern Queensland), with the first UK record being from the Scilly Isles in 1924. Since then, it has been found in a number of sites across southern England, and also in Ireland, the Channel Isles, west Wales and western Scotland (coastal when north of southern England). However, it is not entirely clear how widely it has established itself in the last couple of decades, although individuals can move tens of metres per day as well as being moved over longer distances by the plant trade etc. (Cowling et al. 2004).

Arcitalitrus dorrieni found in woodland leaf litter in Hampshire. The seven segments of the peraeon and the three segments of the pleon are indicated. Length (head to rear of body in this curved position) approx. 6.5mm.
It is most often found under stones and dead wood or among damp material (detritus, debris, leaf litter) in gardens, damp scrub and woodland. It most likely arrived (and to some extent spread) in the UK through the transport of plants/soil to and between plant nurseries and garden centres. It is uncertain whether this non-native species has a significant ecological impact in the UK, although it is possible that it competes with (and maybe replaces) native detritivores in woodlands. In some locations, it can be found in high densities - up to approximately 2,500 per square metre in Dicksonia antartica litter on the Scilly Isles (Richardson 1980). It certainly can be a significant detritivore, consuming 24.7% of annual litter fall in a coniferous woodland in Ireland (O'Hanlon & Bolger 1999) - more than any of the native macrofaunal species.

Identification is fairly straightforward, especially given the small number of possible confusion species. Orchestia cavimana  is an introduced semi-terrestrial Mediterranean amphipod (Konopacka et al. 2009) but much paler in colour - A. dorrieni is variably dark, and orange when dead as here, though pale if preserved). However, there is another introduced terrestrial amphipod, A. sylvaticus, although this is much rarer in the UK. Using the key in Peart & Lowry (2006), the two species can be separated by looking at the epimera (the three segments of the pleon, singular 'epimeron'). In A. dorrieni, the 2nd epimeron is longer than the 3rd while in A. sylvaticus they are more-or-less equal. In the top photo, this is unclear as the rear edge of eipermon 3 is obscured by one of the legs, but with some legs (re)moved, it is clear that this is A. dorrieni. There are other features which might be required to separate further species but these do not (yet) occur in the UK, although it is possible they could be imported with plants.

A. dorrieni - from the green lines, it is clear that epimeron 2 is longer than epimeron 3.
The head bears numerous appendages including two pairs of antennae (typical of crustaceans) and a complex array of mouthparts - I won't go into the details here but there are plenty of resources online and in print providing introductions to crustacean anatomy. The lateral compression is clear (flattened side-to-side) and is generally a good way of separating amphipods from isopods (e.g. woodlice which are flattened top-to-bottom i.e. dorso-ventrally). The antennae are inserted in front of the eye which is black and not especially well developed, being covered by a transparent plate. This is likely to be an adaptation to its life within/under leaf-litter and under damp material where vision is less likely to be useful than senses such as touch - note the long antennae and various bristles.

A. dorrieni showing its lateral compression.
Head of A. dorrieni (side view)
Mouth and mouthparts of A. dorrieni (ventral view)
So, an interesting find and thanks to Dennis for passing it on to me for closer scrutiny. As ever, finds such as this are useful in determining the distribution (and in this case, spread) of species, so it is worth keeping an eye out - especially in case a third Arcitalitrus finds its way here.

References

Cowling, J.E., Spicer, J.I., Weeks, J.M. & Gaston, K.J. (2004). Current status of an amphipod invader, Arcitalitrus dorrieni (Hunt, 1925) in Britain. Journal of Natural History 38: 1665-1675. 
Konopacka, A., Grabowski, M., BÄ…cela-Spychalska, K. & Rewicz, T. (2009). Orchestia cavimana Heller, 1865 (Amphipoda: Talitridae) enters freshwater inland habitats in the Vistula River, Poland. Aquatic Invasions 4(4): 689-691.
O'Hanlon, R.P. & Bolger, T. (1999). The importance of Arcitalitrus dorrieni (Hunt) (Crustacea: Amphipoda: Talitridae) in coniferous litter breakdown. Applied Soil Ecology 11: 29-33.
Peart, R. & Lowry, J.K. (2006). The amphipod genus Arcitalitrus (Crustacea: Amphipoda: Talitridae) of New South Wales forests, with descriptions of six new species. Records of the Australian Museum 58: 97-118.
Richardson, A.M.M. (1980). Notes on the occurrence of Talitrus dorrieni Hunt (Crustacea: Amphipoda: Talitridae) in south-west England. Journal of Natural History 14: 751-757.


17 comments:

  1. I saw my first one of these a couple of weeks ago, in my garden under an old bin. Never seen one before in my life (45+) so out of curiosity I searched online to find out what it was. I searched for ages to no avail - it was only when I stopped searching for insects/bugs and started searching for prawns/shrimps that I found them. FYI, I'm in mid Kent, UK.

    Good article, thanks Dave.

    Shaun Dunmall
    sdunmall@gmail.com

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  2. Incredibly numerous in the woodsy garden I work in near Heathfield, E. Sussex. Not sure which of the two spp though. I've never seen them on chalky soils though so never came across them when I was a kid in Brighton (and I was an avid bug hunter - if they'd been there I'd have seen them). Do they prefer lime free soils?

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    1. Hi. I live in Hangleton Brighton and have just pulled one of these off of my very soggy cat. Freaked out, thought it was a giant flea. Wish I hadn't have smushed it so quick now

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  3. Found one in the house up on Bodmin moor in cornwall today!

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  4. Finding large numbers of these dead in the house at the moment (in Hastings) due to the wet weather I presume.

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  6. Just moved into a new house in Hastings and the previous owners had astro turf in the courtyard. Had to remove it as it was retaining the rain water. Literally 100's of these came jumping about, and now hiding under planters. Hopefully their numbers will decrease now that there are less places to hide, otherwise it's out with the hoover

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  7. We have just moved into a converted nunnery in Hastings and the cellar has masses of these creatures, but they are always dead. I sweep up the dead bodies, but a couple of days later there are more on the floor. Should I worry that they are eating the wooden beams etc in the cellar, or are they just there because it's damp ?

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  8. I've found lots of these in the last week (all dead) in our house near the coast just outside St Austell.

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  9. I found one yesterday evening in my house, it was already dead. Never seen them before.
    I'm in Paignton, Devon. UK
    Kelly x

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  10. My email is kellykent1609@hotmail.co.uk

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  11. I have just found hundreds of these under a fence panel that had been on the ground for a couple of months. Very similar to fleas in the way they jump. We are near Beaulieu in Hampshire.

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  12. I've found quite a lot of these dead on my carpet in the mornings for the last 10 days or so. Off putting as they're the same colour as the carpet, but at least they've all been dead up until tonight when I've found around 6 jumping about. They do die off fairly fast, but I'm not too keen on having them in my living room dead or alive! The seem to be getting in round the sliding patio door, any suggestions as to how to deter them or kill them off outside? I'm on the Isle of Arran off the west coast of Scotland, and it's been very wet today and there's definitely more about after it's been wet. Considering that wet is fairly normal here, I'm not looking forward to sharing my house with them on a regular basis! Is there anything that will put them off coming inside?

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  13. I think these are what I've just found on our bedroom carpet. Was a bit freaked out and hoovered them all up but if I see any more I'll get some pictures! I found out what they were after determining they looked nothing like carpet beetles and Googling 'prawn like bug'. They were shrimp coloured and not moving, so all dead I guess.

    The bedroom is on the ground floor and has old doors leading to a small garden terrace. It is a damp room in an old damp house (!) near the sea. We're in Swansea. From all that, and everyone else's comments, it seems feasible that they could indeed be lawn shrimp.

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  14. I think these are what I've just found on our bedroom carpet. Was a bit freaked out and hoovered them all up but if I see any more I'll get some pictures! I found out what they were after determining they looked nothing like carpet beetles and Googling 'prawn like bug'. They were shrimp coloured and not moving, so all dead I guess.

    The bedroom is on the ground floor and has old doors leading to a small garden terrace. It is a damp room in an old damp house (!) near the sea. We're in Swansea. From all that, and everyone else's comments, it seems feasible that they could indeed be lawn shrimp.

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  15. I have these in my garden in Cardiff, and in the shared back alley, so I imagine all properties in the neighbourhood have them. I first noticed them in the alley about 8 years ago, but now they are most definitely in the garden.

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  16. Found one of these in my garden in Lyme Regis and had to Google what it was.

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