Northwest Dive Club

I took the following pics at Sunnyside today. They are of a BUNCH of Striped Nudibranchs devouring an Orange Sea Pen. It reminded me of a pride of lions feeding on a downed gazelle or even a bunch of sharks on something in open ocean. I wonder whether these guys are attracted to a smell? ...something else? There were plenty of them around, but I still wonder how they ALL got on this hapless Orange Sea Pen? Very interesting!

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These are on the "top" of the pen.
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Amazing shots Tom! I've never seen behavior like that before. Crazy. Janna, what gives?!!

wow; that is a cool find - glad you got some photos! i saw my first striped nudi a couple of weeks ago at possession point. i didn't know what it was called when i found it (well; not officially), but when i looked it up it said its favorite food was orange sea pens. it didn't say they hunted them in packs, though!

thelawgoddess wrote:wow; that is a cool find - glad you got some photos! i saw my first striped nudi a couple of weeks ago at possession point. i didn't know what it was called when i found it (well; not officially), but when i looked it up it said its favorite food was orange sea pens. it didn't say they hunted them in packs, though!

They hunt in packs so they can flank it when it tries to escape...

Thinking about it, Tom - remember how many we saw off Fox Island... and remember the sea pen forests? (light bulb turns on... "ding!")

I knew that their primary prey were Orange Sea Pens... I think I actually found a picture online of one "rearing up" to attack one, much like the pictures I've seen of Giant Nudibranchs attacking their favorite prey, the tube dwelling anemone. It's pretty amazing actually.

As Sounder mentioned, when we dove Fox Island West Wall we crossed a very large field of Orange Sea Pens, and the Striped Nudi's were everywhere there. I just never saw this many of them feeding on one poor hapless Sea Pen!

Again, I wonder if when one starts in on a Sea Pen if they "give off" something akin to an odor / pheromone / whatever that attracts other like minded hungry nudi's...

This was pretty cool to see! I was fortunate to get pics as my camera lens had fogged because I allowed it to heat up in the truck before we splashed. It was only clear enough to take pics about the last 20% of the dive.

Here's a better shot of the beautiful prey of the Striped Nudibranch, the Orange Sea Pen.
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We took those on the above referenced dive at Fox Is West Wall. Here's a link to the pics from that day of diving.

The pics from yesterday's dive are here, but as I mentioned I had camera fogging issues so there are only a couple and they aren't the best quality.

Wow, what a find Tom!

Tom Nic wrote:We took those on the above referenced dive at Fox Is West Wall. Here's a link to the pics from that day of diving.

The pics from yesterday's dive are here, but as I mentioned I had camera fogging issues so there are only a couple and they aren't the best quality.

i love these two:

the spotted tail and handful of dollars are cool! (i have yet to see one dollar!)

Thanks LG!

The Wolfie was a younger one... the way his tail is wrapped around is really cool. That was on the 1st dive of the day at DIW. The Sea Pens and Striped Nudi's were at Fox Is West Wall. I've only dove Fox Is West Wall once, but I am told it is a great place for sanddollars!

Tom Nic wrote:I've only dove Fox Is West Wall once, but I am told it is a great place for sanddollars!

aparently! i haven't done either of those dives - looks like i need to get down there some time!

How come some of the nudi's in the pictures are half buried in the sand?

My guess is that they move through the sand pretty comfortably. Most of the ones I've seen of that species have sand on them and / or they are half buried. They may burrow down them come up...

The ones below are probably mating...
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In the pic in the original post I count at least 12 of them on the Sea Pen, plus a couple on the fringes, and most of them have sand on them.

But don't let Tom take your sand dollars and try to put them in your pocket... the man doesn't know his own strength! :naka: Well, I guess if you want sand change (get it? crumbled sand dollars make sand change?! sorry.)

ha, ha.

i went and looked at the pictures i have of a striped nudi - he's got sand on him, too!

Hi Tom,

Sunnyside is THE place to see Striped Nudis pile onto Orange Sea Pens - that's very common there and you got to see it - nice shots! I have quite a few in my collection too that are similar, taken at the same location.

I don't know the exact method of attraction there - but they must emit something that tells the other Striped nudis that they're onto something delicious!

- Janna

divernick wrote:How come some of the nudi's in the pictures are half buried in the sand?

It's probably the full bellies from feasting on Sea Pens....

-Valerie