While at least one of our reference calls this Neopetrolisthes oshimai, it is generally considered a variety of N. maculatus. We are cautiously figuring these separately only because we see many specimens of both forms at Kwajalein. Nearly all Cryptodendrum adhaesivum and Stichodactyla haddoni anemones host a pair of one form of the crabs or the other, and they also occur on some other large anemones as well. In nearly all cases, they pair up with like forms; that is, the N. maculatus forms pair up separately from the N. sp. 1 forms. Once I notice this, I started watching for mixed pairs, and they were rare. In our many photos, of which these posted are only a few, I could find only one shot showing both forms on the same anemone. This sorting by color seems rather odd if they are indeed the same species. It is not impossible, of course. Perhaps being in certain anemones affects development of color, as it seems to do with the anemonefish Amphiprion tricinctus. However, in the case of the anemonefish, being in certain species of anemones affects development of color; in the Neopetrolisthes crabs, the different forms can be found in any of the host anemones, although from our photos, it seems crabs in Stichodactyla haddoni anemones tend to more often be the N. maculatus form. I don't know if these crabs have yet had their DNA compared, but I think it would be useful. There are many photos below to show variations in host anemones and feeding behavior. Like N. maculatus, it uses net-like filaments on its anterior appendages to capture plankton out of the water.
Closeup of the netlike filaments. You can see find branches between the long filaments.
A pair of like-colored individuals.
We visited a pair on this unique, bright green Cryptodendrum adhaesivum many times.
During a warm spell that led to serious coral bleaching on the reefs around Kwajalein, the green Cryptodendrum adhaesivum above bleached to yellow.
Another bleached Cryptodendrum adhaesivum during a bleaching episode in October, 2016.
Another pair of Neopetrolisthes sp. 1 on a Cryptodendrum adhaesivum.
Juvenile.
Below is the one instance where I could find in our photos a mixed pair of Neopetrolisthes maculatus (right) and N. sp. 1 on the same anemone, in this case a Cryptodendrum adhaesivum.
Created 10 September 2018