Berthella martensi from Thailand

December 8, 2003
From: Mark Atwell & Dana Rayfield

Dear Bill,

We came across this 12cm monster Berthella martensi at Lucy's Reef off Phuket in Thailand a couple of weeks ago.

We didn't know what it was at the time, partly due to it being inactive (pity!). As you can see it was 'resting' vertically on some well-weathered reef at about 18-20m a few 10's of meters from a sandy plain.

Note the white/cream coloured areas between the segments.

Mark Atwell & Dana Rayfield

Atwell, M. & Rayfield, D., 2003 (Dec 8) Berthella martensi from Thailand. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Mark & Dana,
Thanks for the photo. Richard Willan (1984) records a specimen reaching 73mm when fully extended as the largest known specimen, so your animal, 120mm long when not extended is about twice the reported length for this species. I'm afraid I can't see the 'white/cream coloured areas between the segments' that you mention. There is a translucent white object on the lower right but I'm not sure what it is. It could be the end of the gill, which sits on the right side under the mantle but I'm can't be sure

• Willan, R.C. (1984) The Pleurobranchidae (Opisthobranchia: Notaspidea) of the Marshall Islands, Central-West Pacific Ocean. The Veliger, 27(1): 37-53.

Best wishes
Bill Rudman

Rudman, W.B., 2003 (Dec 8). Comment on Berthella martensi from Thailand by Mark Atwell & Dana Rayfield. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


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