Strange lunch for Navanax

November 15, 2003
From: Bruce Wight

Dear Bill,
Check out the message and photos I received from Walter Marti. Do Navanax feed on Triopha?

"Shot this weekend [October 21, 2003] off of Santa Cruz Island [California, USA], with my video. I didn't stage this, or else I would have taped the strike.

Do you know what the process is? Will the Navanax just chew off a chunk, or will he suffocate the Triopha catalinae and then dine on. It seems that the Navanax has the gills in it's jaws. I filmed the Triopha moving about two feet. It was on top of a large rock and appeared to be running for shelter in the tight recess at the bottom of the rock.

At least now I know what flavor the Navanax likes. I'll work on staging the strike. ... Walter"

Bruce Wight

Wight, B., 2003 (Nov 15) Strange lunch for Navanax. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Bruce [& Walter]
I am afraid the brains and beauty don't always go together and I'm afraid sea slugs have plenty of beauty but not much in the way of brains. The Triopha obviously 'felt' or 'smelled' like food to the Navanax. Unfortunately the Navanax has no way of making a judgement on what size prey is appropriate. As most aglajids lack teeth, and any other biting parts, they cannot eat an object they can't swallow whole. In this case the Triopha may be seriously 'gummed' but it unlikely to suffer any real damage.

I looked at feeding in Melanochlamys cylindrica which is an aglajid which feeds exclusively on polychaete worms which they eat by sucking in like a piece of spaghetti. It was often found intertidally in New Zealand on coralline algal turf and I often wondered why I often found them head down and tail up exposed at low tide until I discovered that sometimes when they were sucking in a worm it half escaped back into its burrow. Unable to bite off the piece it had swallowed, the aglajid was forced to stay anchored against the worm's burrow entrance until the part in its stomach was digested. Similarly when I fed animals in aquaria I would throw in some appropriately sized worms and if by chance two slugs tried to ingest the same worm - one at the head and one at the tail - invariably they would both suck in the worm until the two slug's heads met. They would then sit head to head for up to six hours until they digested the part they each had.

I guess therefore, that it is possible that your Navanax will hang on to the Triopha until the part it has ingested is digested
Best wishes
Bill Rudman

Rudman, W.B., 2003 (Nov 15). Comment on Strange lunch for Navanax by Bruce Wight. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


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