Mismatch of Legs

Recently I was sorting through all the specimens which either had no name, or were mixed in with other species so their individual identity was unknown.

I came across this relatively small box of 12 specimens.


As you can imagine, they were piled into the box, with legs and claws everywhere! To say the least it was not suitable for such delicate specimens. They were accompanied by 7 handwritten and pinned labels, so I believe at some point in their history these specimens were probably stored well, but deteriorated as things do over time.

So I searched the collection for each of these labels. I started with the label Portunus depurator. I found 1 record in the existing collection with this name, so got it out (below left) and compared it to these 12 specimens. I found 2 which looked extremely similar to me. I checked literature to find exact characteristics of this species and they matched these two from the pile (below right), so I pinned them in a new box with the handwritten label. I went on to add a reference number and also wrote out the scientific name with author and date and also the family name with author and date. This is useful for anybody looking at the collection as they can see which specimens are of the same family, as well as genus and/or species.


I did the same for each label, extracting specimens from the collection and comparing them to my pile of bodies, looking for similarities in carapace shape, texture, volume, indentation and also looking at the leg and claw size, seeing their shape and size in relation to the carapace.


The next label was Eurynome aspera. As with all the labels in this particular box, I recognised this so knew we had a specimen in our collection. Above right is the specimen which had already been documented, and left is one of the crabs from the mixed box. It was the only one of its kind in the box, and showed massive resemblance to Eurynome aspera so I’m quite happy I’ve found the right guy here!


With the main bodies removed from the box, I was left with a pile of legs. It was quite funny to sort through the legs, because it seemed so bizarre! They luckily had only fallen off 2 species of crab, so were not very difficult to match.


After matching most of the specimens to a label, I was left with these four. I knew straight away that the two you can see on the right, with characteristically “spidery” legs had to be the spider crab, of the species Macropodia rostrata. I think you just get used to handling the crabs so whereas at the beginning of the project I’d have no idea what these were, now I look at them and pick out features.

The left has long thin legs, at least triple the carapace length. The carapace itself is triangular and rough in texture. The front two legs are much thicker than the rest, but are also shorter. I compare these characteristics with existing specimens of Macropodia rostrata in our collection and decide this is the correct one.

As for the left, I found these a little more difficult (and still don’t know for sure what they are!). I am fairly certain they both belong to the genus Liocarcinus, and therefore the Polybiidae family of crabs. I did initially think they were similar to the Xantho genus, but eliminated this as Xantho sp. don’t have paddles. Liocarcinus sp. are swimming crabs, with the characteristically flattened rear legs, to give the crab control in moving when tides are present in a marine environment, but also to aid general swimming.

I have a few species in mind, but need to look into this over the weekend and hopefully I’ll know it by Monday morning!

All in all, I was very happy to have ‘rehomed’ and correctly identified the main body of the assorted box. But this just leaves me determined to identify the Liocarcinus species so that I can feel like I’ve ticked off another box. Any help with this would be greatly appreciated :).

For now, I am going to read up on some literature and then continue sorting the specimens which I have so far not been able to update based on an existing name.

Wish me luck!

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