Nudibranchs in the sand

I thought fellow critterphiles might be able to interested to see some more antics of nudis in the sand ...

The first shot is a bit of a mystery ... its Hypselodoris bennetti ... but is it getting dragged into the sand ??? ...

My theory was that it had been predated by a lurking predator ... but I wasn't destructive and didn't dig it up

That is a big mystery - congratulations.

I have never seen this before. I would suggest it is indeed being eaten. Maybe by a worm of some kind.

Wow, this really is a unique shot. You will send it to the Sea Slug Forum, I hope?

Actually there are two mysteries here. The first of course is what's eating the bennetti. I doubt it's a worm -very few of them will touch a nudi. A camoflagued crab or a fish would probably come out of the sand to ambush & eat its prey. There would be tentacles if the predator was an anemone or an octopus. I suspect it's another sand-dwelling opisthobranch, happily hidden while sucking down dinner. The second mystery is what's the Hypselodoris doing on a sand bottom! These guys are sponge eaters & spend their short lives in search of more sponge and mates. For them that means staying on hard bottoms. Do you think it was cruising between bommies?

This was one time when it would have been perfectly okay for you to be "destructive". So little is known about predators on branchs that finding the identity of the predator would have been a valuable bit of info. So get out there & find another one!

Cheers, Leslie

It will go to the forum, but I will wait until Bill is back so maybe it doesn't get lost in the backlog

At the time I thought it might be the work of an Armina cygnea lurking like this one ...

... as there were many of them on this particular dive ... but apparently they eat sea pens. There are the much smaller Navanax at this sight, but they would to small to drag a Bennett's through the sand !?!

This site is called the Scallop beds. It consists of sponge "trees" scattered on a sandy bottom. Nudi's are often on the move over the sand and there is a lot of diversity. Many are species that wouldn't typically be known as sand dwellers.

I'm off to dive there tonight so fingers crossed I might find something unusual :>

cheers

Lndr

Armina cygnea on the surface ...

It certainly wouldn't have been an Armina - you're right, they specialize on sea pens or other cnidarians. There are lots of branchs that eat other branchs and some are sand dwellers. Navanax, Philinopsis, & Chelidonura will eat other slugs as well as bubble shells. Binyamin (bkeilat) has posted a fantastic feeding sequence of a Gymnodoris cf citrina eating a Gymnodoris sp2

http://www.digitaldiver.net/yabbse/index.p...;threadid=16364

Travelling between the sponge trees? That makes sense. Good luck with tonight's dive!

Cool! I love to see life in all its Darwinian glory!

I hesitate to use the lur**** word, 'cause that has now been disclosed to be one of the magic words that will bring NSA to your door (or worse, to your favorite predator), but nemerteans are classic lur**** predators and one would happily swallow a nudi whole this way, even one much bigger diameter than itself. There was a great picture of one in action on Bill Rudman's (I think) site last year. It's about equally as likely as a subterranean opisthobranch.

--Jon

Quite true, and I apologize for leaving your beloved nemerteans off the list of suspects! For those who haven't seen it, the Sea Slug Forum post Jon refers to shows an Aplysia parvula being engulfed by a Lineus fuscoviridis in 4 shots: http://www.seaslugforum.net/display.cfm?id=13659