Mass aggregation saves the day

Whilst going throught the Crustacean collection here at the museum, I have come across a rather interesting species, scientific name Leptomithrax gaimardii, common name the giant spider crab. I like to look into the species that I am describing to gather some history about them, but also to make sure I’ve got the right name for the specimen. For instance this specimen isn’t very giant, which leaves me wondering whether this specimen is just very young- or we’ve got the wrong name! Ours is around 5cm length carapace, when giant spider crabs reach 15cm… hmmm!

When having a look at the species background, I came across a blog post by the Museum Victoria (also where the above photo was sourced) in melbourne. It was discussing the mass aggregation of spider crabs in the Port Phillip Bay just befofe they are due to malt for winter.

I got hooked on this article, and that’s when I realised it was definitely a suitable thing to post on here!

Basically, there are hundreds of these large orange crabs which all come into the bay. It was suspected this could be for mating, but it has been found to most likely be that they are creating protection for themselves during malt season- safety in numbers!

When they climb out of their old shell (above photo by Museum Victoria), they are so brightly orange in colour that they are extremely vulnerable to predators. Rather than moping around on their own like usual, they congregate to ensure the probability of being eaten or predated upon is largely reduced- just like with herding behaviour in mammals. Pretty cool!

Definitely puts a spring in my step every time I pull one of these cool specimens out of the draw, and see it has a whole load of ecological, habitual and historical features which leave me in awe! Whether or not they are linked to this particular species, it is still so interesting, and leaves me wondering why I didn’t come and volunteer at Manchester Museum earlier…

2 Replies to “Mass aggregation saves the day”

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