Sexing the Horseshoe Crab

crab1crab2 Never know what I will be learning, do I? In recent years, a decline in the population of horseshoe crabs (not really crabs) has occurred as a consequence of coastal habitat destruction in Japan and overharvesting along the east coast of North America. Hence they are being counted and tagged. These incredible plate-sized creatures, encrusted with other shells, can be lifted easily – but carefully for their sake – examined for health, sex, and then given a piece of plastic to carry around as well as all the other stuff on their shells.

Sexing a horseshoe crab? Easy when you know how!

Looking underneath [click for a bigger picture] the claws are all double except for the end pair on this crab  – at the right hand side in the photo. They are called ‘boxing glove’ shape, and enable the crab to grab and hold on to the female shell. So this one is a male. Females have all double claws, no grabber. Now you know too!

Other information, they have no nerves in the shell, so inserting the tag does not harm; there is a special little awl designed to make the insertion without danger of cracking.

We tagged four this morning at Andy’s Way. Wading into the water, walking along with eyes peeled to see if that brown patch is yet another rock or seaweed clump, or, the magnificent prehistoric creature, the horseshoe crab. At 3/400million years they were around before dinosaurs!

Thank you Ocean View Foundation and Project Limulus

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5 thoughts on “Sexing the Horseshoe Crab

    1. I am a volunteer – one of the others asked about this – especially as the tags are quite big. It is odd as obviously those in charge are very concerned about conservation etc. and I know they hate plastic bags balloons and all that sort of stuff. For example, there are some terrific documentaries The Ocean View Foundation has been showing us this winter.

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