Berthellina delicata is common in a variety of Hawaiian habitats, from under rocks in the low intertidal to ledges and caves at night on many reefs. This species was long considered Berthellina citrina, a species apparently restricted to the Red Sea. There have also been suggestions that the yellow form seen below might in fact be another species.
Hawaiian specimens have been found to eat a variety of corals and sponges. One of the more unusual but common dietary items is the orange tube coral Tubastraea coccinea. In the shot immediately below, a specimen has its proboscis extended into the central cup of the coral and is scraping away coral tissue. Just below the Berthellina's head is a cup that has been partially eaten.
Showing the above sighting was not a fluke, below are a couple more photos of Berthellina eating Tubastraea. In the right specimen especially, what appears to be a tiny shell is visible under the skin in the middle of the back.
Berthellina also eats other corals such as Porites sp., as shown in the next photo.
They may have been eating the corals in the next two photos, but since their mouths are not visible, it cannot be confirmed.
These two are definitely eating red sponge.
This one appeared to be eating the white sponge, but this was also not confirmed.
Sea Slugs of Hawaii
Sea Slug Forum
Marshall Islands Sea Slugs
Created 20 April 2009
Updated 14 December 2015
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