Philinopsis cyanea ... eating?

April 28, 2005
From: Binyamin Koretz

Dear Bill,

We recently observed a Philinopsis cyanea (of the large red variety reported in message #13457 ) exhibiting the behaviour captured in the accompanying photos.

After the animal had disappeared into the sand, head first, out of curiosity, I  gently touched the sand where I thought he would be. What appears to be a covering of mucus-sealed sand was then ripped open, revealing the slug [Fig 2 - lower left].

In photos 3a through 3d, the front of the slug starts to reappear, first the top of the headshield, and then we see the head bulging forward. I again touched the sand covering the back of the slug, and it felt quite flat - flatter than it should have. This all took about 5 minutes. Unfortunately, we were at the end of a very long dive and I was low on air, so we couldn't stay any longer.

Locality: Eilat, Village Beach, Israel, Red Sea (Gulf of Eilat). Depth: 3 m. Length: 8 cm? 18 April 2005. sand and rubble slope. Photographer: Binyamin and Shulamit Koretz

After reading on your fact sheet about the eversible buccal bulb and the way this species swallows its prey whole, we thought that it was possible that that's what we were witnessing. What do you think?

Best regards,

Koretz, B., 2005 (Apr 28) Philinopsis cyanea ... eating?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Binyamin,
I've looked at your photos carefully, and also the others you sent but I haven't included and I am pretty sure that wjhat you saw is an animal burrowing through the sand. They ahve huge mucus glands around the head which produce a cylinder [or tunnel] of mucus through which they crawl when 'underground' so they don't clog up their gills. What you tore, in your Photo 2 is that mucus skin that the tunnel is made of. In the photo alongside, the blue spot you can see in the middle of the photo is the spot on the posterior tip [or horn] of the headshield, so the bit at the bottom of the photo is the head.

Like all burrowers, catching them feeding is almost impossible. I have watched them engulf various bubble-shells in aquaria, and they do eat bubble-shells which normally live on the surface as well as ones that burrow, but it's difficult. I spent 3 years as a student trying to catch species of Philinopsis and Philine in the act of feeding - a quite soul-destroying activity. Most of our information on their feeding comes from either examination of the stomach contents of preserved animals or from watching captured animals regurgitating the unbroken shells of their prey
Best wishes,
Bill Rudman

Rudman, W.B., 2005 (Apr 28). Comment on Philinopsis cyanea ... eating? by Binyamin Koretz. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


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