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Photo#169949
isopod -

isopod - "rock louse" - Ligia pallasii
Port Townsend, Jefferson County, Washington, USA
February 16, 2008
Found under a rock at Point Wilson

Images of this individual: tag all
isopod - isopod -

Ligia oceanica?? *eek*
Hi Andrew/Ferenc,

Somehow this specimen does looks disconcertingly like Ligia oceanica - it seems to have some features that do not comply with L. pallasii too well. I *cough*"know"*cough* pallasii from images and descriptions only, but still, I can't help thinking that it might rather be L. oceanica (which I do know fairly well).

Disconcerting indeed, as Ligia oceanica is thought to be present (introduced from Europe) on a few scattered spots on the east coast only. It would indeed be a minor miracle to find it on the west coast.

Andrew, do you still have any other images of the animal (or similar ones from the same area), or does the original of this one allow you to make a bigger crop of some areas? Especially better close-ups of the tail end, the head structure and antennae could be helpful.

Or do you live in the area and could you find this species again?

Mostly what should be examined is the exact shape of the telson (terminal plate) and the length of antennae and uropods (tail appendages).

Meantime I'll try and find out if images of European specimen are allowed on bugguide, and if so upload some images for comparison.

Interesting puzzle :o)
Cheers, Arp

 
have another look
I have tightened the crop on the main photo, plus added a detail of the hind section.

 
Wow, that was fast :o)
Hi Andrew, thanks for the extra image/cropping. The (de)tail(ed) shot rules out L. oceanica, which is probably a good thing - too much excitement and all that ;o) Within the set of known species on the west coast that certainly leaves pallasii as the best fit, so all's well - even if it's still a tad uncanny how this specimen is different from much of the other info and images I've found for the species. Makes me wonder if pallasii has strong sexual dimorphism or something.

Anyway, if not anything else this exercise has shown me that most of the drawings and descriptions in the (oldish) literature I've dug up are quite useless I'm afraid, making the images on bugguide all the more valuable.

Thanks for the help, I'm sure the (de)tail image will be handy at some point for a species account or such :o)

Cheers, Arp

Moved
Moved from Ligia.

Dear Andrew, This isopod bel
Dear Andrew,
This isopod belongs to the family Ligiidae and genus Ligia. One widely distributed common species is known as Ligia oceanica, but I can't give specific identification from the picture.

Ligia, however, is a group of isopods that live on seashores under permanently humid conditions.
Best wishes, F.

 
not oceanica
Thanks for the genus identification. Further exploration on the internet reveals that oceanica can be ruled out by range (it is limited to Europe and the US east coast). Ligia pallasii is the only one I can find whose range includes the Pacific Northwest (where it was found).

 
Thanks to both of you:-)
Thanks Andrew for the great image! Thanks, Ferenc for the identification and information. We truly appreciate your expertise on the isopods.

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