Skeleton shrimp on Tambja affinis

March 27, 2009
From: Vie Panyarachun

Concerning message #22266:

I was just going through my photos and noticed what might be a skeleton shrimp on this nudi which I think is Tambja affinis? Unfortunately I didn't notice the shrimp (?) when I was taking the photograph and didn't get any closer.

Locality: "West of Eden," Island #7, Similan Islands National Park, 12 msw, Thailand, Andaman Sea, 19 February 2009, Reef. Length: Approx. 1 inch. Photographer: Vie Panyarachun.


Panyarachun, V., 2009 (Mar 27) Skeleton shrimp on Tambja affinis. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Vie,

Thanks for this message. It shows another nudibranch being harassed by these caprellid shrimps. In the lower photo you can see many more individuals on the yellow coral on the right of the photo. This again suggests that rather than living on the nudibranchs, the caprellids are living in large numbers on the substrate and unlucky passers-by are likely to get a hitch-hiker.

Apart from the shrimps, your photos are interesting because they show an animal that is apparently at the other extreme of the colour variability of the species. The more 'typical' colour form of this species has dark blue rhinophores, while yours has orange rhinophores with dark blue tips. If you look through the other messages on this species you will see a good coverage of animals showing the change from one colour form to the other. The other interesting thing is that your frontal shots show large lappets (or ledges) on each side of the head [see arrows] which I suspect are sensory structures. There are a variety of such organs in the polycerids which are yet to be investigated, so it is good to get some photos of them showing their 'living' state. Often such organs are described from preserved animals and this is not that useful because usually they are considerably distorted or retracted during preservation.

Best wishes,
Bill Rudman

Rudman, W.B., 2009 (Mar 27). Comment on Skeleton shrimp on Tambja affinis by Vie Panyarachun. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


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