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Montagu's / Furrowed crabs

Observed: 20th August 2012 By: Nick UptonNick Upton’s reputation in InvertebratesNick Upton’s reputation in InvertebratesNick Upton’s reputation in InvertebratesNick Upton’s reputation in Invertebrates
Montagu's / Furrowed crab (Lophozozymus incisus = Xantho hydrophilus) in rockpool amog mix of red and green algae, near Falmouth, Cornwall, UK, August.
Montagu's / Furrowed crab (Lophozozymus incisus = Xantho hydrophilus) in defensive posture among boulders low on the shore, near Falmouth, Cornwall, UK, August.
Description:

I found several of these medium sized (6cm wide carapace) crabs of quite variable colour recently in Cornwall with a smoother outline to the carapace than shore crabs and big "muscular" looking claws. I think they have to be Montagu's crabs aka Furrowed crabs. Their latest scientific name is Lophozozymus incisus but also known until recently as Xantho hydrophilus or X. incisus (NBN has it as that). Mostly far SW and west coast of UK.

Identifications
  •  
    Likely ID
    Montagu's / Furrowed Crab (Lophozozymus incisus)
    Confidence: I'm as sure as I can be.
Species interactions

No interactions present.

Comments

nightfly's picture

Very nice Nick, havent seen

Very nice Nick, havent seen this one before. They are quite big. Impressive crab.

Cathal.

Nick Upton's picture

Thanks

They were new to me too, but I was looking out for them and found lots - commoner than shore crabs in some areas I visited. Some Cornish locals call them "bodybuilder crabs" as they look like they're on steroids!

Nick Upton, naturalist and photographer.

Nick Upton's picture

Dominant crab on some shores

I've recently been to the site where I photographed this distinctive crab last year, near Falmouth, on some exceptionally low tides and was struck by how dominant this species is there, especially low on the shore. Looking under 50 or so boulders (only exposed on exceptional low spring tides) I found several hundred of these of all sizes up to 10cm or so across the carapace. That size was matched by a few velvet crabs and outdone by some edibles. I found virtually no Shore crabs, Carcinus maenas (some small ones under holders and one large one emerged in high shore rockpool). I wonder if Montagu's crab outcompetes them where conditions favour it. Looking at NBN gateway (under the old name Xantho incisus) it may a warm water/gulf stream specialist. Strictly SW and Western UK coasts or is it a habitat thing - very rocky, not muddy shores…or a combo of the 2. Clearly it's very unfamiliar to most as no ID confirmations have been added, but there is no doubt in my mind on the ID. Perhaps ProjectM1 followers will take some interest!

Nick Upton, naturalist and photographer.