The crabs were observed and pictures were taken on oceanic shore and in mangroves of the Iriomote Island (Southern Ryukyu, Japan).
The crab may be Uca triangularis, although the view is not good for discerning the outline of the carapace. The form of the fingers and the color pattern on the pereiopods suggests U. triangularis. I am no help on the hermit. Your identification is reasonable. Rod
Only by these images is a little difficult to identify the crustaceans , it would be necessary to check more closely , I suggest you take them to a specialist in crustaceans Brachyura , the last image I believe it is a Ocypodidae crab, the other images are well identified . the especiemes are very interesting
Uca jocelynae does have a far narrower front than this specimen here.
The second crab is indeed Sesarmops intermedium (de Haan, 1835).
O. ceratophthalma should be correct too, the only other Ocypodid with horned eyes in Japan is O. mortoni as far as i can see. https://en.wikipedia.org/wiki/Ocypode might be in this case a good starting point but everything should carefully be verified by scientific papers in the end.
The Gecarcinid should be C. carnifex although more pictures would be better to rule out Discoplax hirtipes and D. rotundum which occur on Ryukyu too.
The last Ocypodid is either a young specimen of O. ceratophthalmus or O. mortoni (which does not yet posess the horns on the eyes) or O. stimpsoni.
Cheers, Ollie
Thank you for these valuable details and links. Actually, I am conservation biologist working mainly on threatened trees and thus interested in mangrove forests. I am preparing this winer a lecture about this interesting ecosystem for the Natural History Museum in Fribourg (Switzerland) - and would like to show the extraordinary diversity (also the animal diversity) of the Ryukyu Islands. All the best, Greg
Please Look upon the book of the Emperor of Japan about Japanese Brachyra !
Good luck. Remember that male Brachyuran are finely identified by the penis sexual appendices.
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