Opisthobranch of the Week is Micromelo undata

Micromelo undata
Tablamu, Phangnga Province, Western Thailand
Photo courtesy of Lawrence Neal
Depth 8 meters

Micromelo undata ,(Bruguiere, 1792)

Micromelo undata - variously known as Micromelo undatus, Micromelo undatum or Micromelo guamensis, take your pick - is a gorgeous bubble shell found in warm waters around the world, but which is, nonetheless, seldom seen by scuba divers. With blue or turquoise green lines on a speckled white body and a small shell with chocolate brown to blackish undulating lines, the species is something of a diamond in the rough, standing out in the rocky or sandy habitats that it favours.

M. undata is believed to feed on polychaete worms present in sand and under rocks, possibly sequestering toxins from its prey for its own defensive purposes in the manner of many opisthobranchs rather than relying on a shell for protection.

Here on the west coast of Thailand, the blue colour form of this species can occasionally be found in shallow rocky and sandy environments, in less than eight meters of water. Individuals move along the sandy substrate quite rapidly, occasionally pausing and burrowing headfirst down into the sand for a few moments, presumably in search of prey, before continuing on their way. Crawling individuals are often seen dragging coiled white or transparent egg masses along behind them.

The specimen shown was about 30 mm in length.

Lawrence Neal
Bangkok, Thailand
July 2012

Lawrence at Tulamben, Bali, Indonesia with
Agung Volcano in background

Lawrence is a newspaper journalist based in Bangkok, Thailand. He escapes the office as often as he can to go diving in the rich waters of the Indo-Pacific but his regular dive sites are just down the road at Pattaya. The vis is usually pretty appalling and the diversity nothing like as rich as hotspots like Lembeh or Anilao, but, in his words, "that's what makes it challenging and fun".

Lawrence uses a Nikon D200 in a Nexus housing with a housed Nikon SB800 Speedlight, Inon Z240s or some combination thereof. At Pattaya his lens of choice is the 60 mm macro, "the water is much too murky for anything longer".

Send Lawrence mail at lorenzo_n@yahoo.com