Opisthobranch of the Week Data
Haminoea sp. 2 is considered to be very rare in the waters of Okinawa's main island as I have seen and collected only three individuals. The above featured animal was collected from a mixed live~dead stony coral reef during a mid-day SCUBA excursion under conditions of a high spring tide. I've added a second page with an image of the additional collected specimens. The two individuals (ca. 3 & 5mm) were found together.
Paula Mikkelsen (2004) points out some of the challenges* associated w/ studying the shelled cephalaspids:
* Taken from an on-line resource of the American Museum of Natural History, Division of Invertebrate Zoology.Shelled Opisthobranchs (Cephalaspidea)
Opisthobranch gastropods comprise a large and diverse group of marine snails and slugs, including some of the most beautiful and most specialized forms. The most recognizable to non-specialists are perhaps the sea slugs, or nudibranchs, and the pelagic sea butterflies, or pteropods. Morphologically intermediate between the more traditional snails and the shell-less nudibranchs are the "bubble-snails," belonging to the Order Cephalaspidea. Challenges to studying the relationships among these snails are: (1) species descriptions based almost exclusively on shells, which are themselves reduced (i.e., relatively featureless, paper-thin) compared to those of other gastropods; (2) high phylogenetic importance of characters from soft-body morphology, necessitating live observation, gross dissection, and histology; (3) reduction and loss of many morphological features, such as the shell, operculum, radular teeth, jaws, and stomach chamber; and (4) high incidence of parallelism and/or convergence in characters, especially those related to the burrowing habit. Phylogenetic analyses from these studies have confirmed the "rampant parallelism" suspected in cephalaspid morphology, but have nevertheless identified useful characters to suggest new classifications and re-defined clades.
In addition to the above featured animal, I've previously presented on these pages the following three members of the genus from Okinawan waters: