Opisthobranch of the Week Data
Chromodoris hamiltoni is considered to be uncommon on Okinawa, although the sparse number of collected animals (only two) would indicate the population is quite low. The low numbers are apparently indicative of the collecting bias in my selecting these animals as specimens. Several additional individuals have been photographed but not collected and numerous others have been previously seen but neither photographed nor collected.
Chromodoris hamiltoni is set apart from most members of the large species complex to which it belongs by the presence of its blue ground color and orange gills and rhinophores. The animal nearest to C. hamiltoni in appearance here on Okinawa is C. elisabethina, but one feature of this animal is the presence of a U-shaped black line running around the back of the gill pocket (Rudman, 1982), which C. hamiltoni doesn't possess. Photographs of several specimens of Okinawan C. elisabethina appear to be very difficult to separate from from those of C. hamiltoni and of course the final determination would be made by comparison of radular morphology.