Friday mystery object #365 answer

Last week I gave you this little critter to have a go at identifying:

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This particular shrimpy specimen arrived as an enquiry, after it was found in some Irish drinking water.

Prawn cocktails may be a thing, but most of us don’t think of shrimps (or shrimp-like decapod crustaceans) as an ideal addition to a beverage.

According to WHO these critters aren’t actually a health problem if they get into the water supply in temperate regions, where they don’t carry significant parasites or pathogens – but it’s a different story in the tropics.

Knowing which species this is could help in working out how it might have entered the water supply. I’m not an expert on crustaceans by any means, but there are useful keys out there [links to pdf] for working out this kind of information and I’m very fortunate in having to hand the expertise of my predecessor at the Dead Zoo, Mark Holmes, who specialises in crustaceans and is still often at the Museum doing research. Of course, I also have all of you lovely people!

My first thought on seeing this was that it was one of the Gammeridae, based mainly on my exposure to many photos of Gammarus shrimps infected by microsporidian parasites that change them from males into females (which is some fascinating biology). I was therefore delighted when so many of you put forth suggestions in that same area.

By working through the key of Irish shrimp I narrowed it down to Gammarus pulex (Linnaeus, 1758), which was also suggested on Twitter by @RobertsZivtins and @DianeBarlee. It could be G. tigrinus or perhaps G. lacustris – or of course a species not previously recorded from Ireland that doesn’t appear on the key.

However, I got it fresh and there were no stripes and the uropods and telson (taily-bit) looks more pulexy to my eye.

I am now eagerly waiting to hear what Mark thinks – I will update this post as soon as I do!

I have now checked with Mark and he identified this as G. lacustris so it looks like the taily bit isn’t pulexy after all. Thanks Mark!

Friday mystery object #365

After 10 years of posting photos from the museums I’ve worked in, I’ve finally posted enough mystery objects to have one a day for a whole year. As long as it’s not a Leap Year of course.

So here’s the 365th Friday mystery object:

Any idea what this mysterious wee beastie might be? N.B. it is a genuine enquiry, so no need to drop cryptic clues – I’m just keen to see if anyone agrees with what I’ve identified it as.

Have fun!

Friday mystery object #363 answer

Last week I gave you this crusty critter to identify:

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It’s not the easiest mystery object, since there are around 850 species of crab, and several converge on similar forms. However, the triangular body and spindly legs meant that everyone recognised this as a species of spider crab in the Superfamily Majoidea.

Beyond that it gets harder, although there are resources out there to help. The Marine Species Identification Portal has a useful key for species that occur in the North Sea. I know that’s not always useful in these instances, but as it turns out, this particular species has a range across the East Atlantic and into the Mediterranean, including populations in the North Sea.

This little crab is Pisa armata (Latreille, 1803), which is one of several spider crabs that camouflage themselves with sessile animals and algae from their local environment, earning them the name Decorator Crabs.

Decorator crab covered in stinging hydroid polyps, which defend the crab while benefiting from food scraps and greater mobility. Image by Nick Hobgood, 2006

Decorator crab covered in stinging hydroid polyps, which defend the crab while benefiting from food scraps and greater mobility. Image by Nick Hobgood, 2006

Bit of an obscure one for you, but Diane Barlee did figure it out on Twitter, so it was manageable. Watch out for more mysteries next week!