Image: Creative Commons Taro Taylor/dapete

While it’s only a few centimeters long, this hallucinatory sea slug — Glaucus atlanticus — makes a living doing something few other organisms dare: snacking on the “Blue Fleet”, or collection of stinging, floating filter feeders found at the surface of oceans around the world. These wind-driven organisms (which will all be covered here at some point) include the by-the-wind sailor, blue buttons, the violet snail, and, most famously, Portuguese Men o’War, Physalia physalis.

The man o’ war floats on the surface like a plastic shipping cushion, dangling streamers of nematocyte-bearing and swimmer-irritating tentacles below (remember what those are?). G. atlanticus (also known quite poetically as the sea swallow) roams about the surface, trippy belly up and silvery top down, looking for its prey like pac-man pellets (though whether the sea swallow swims to its quarry or merely relies on bumping into it is still a point of contention among scientists). The sea slug, obviously, is immune to the stings and instead stores the venom at an even higher concentration at the tip of its feathery “cerata” (singular ceras), or body projections, for use in its own defense.

The sea swallow’s psychadellic cum mathematical coloration is allegedly a classic case of “countershading” camoflauge. From above, the blue and white confuses seabirds, while from below, the silvery top/bottom appears as just another section of sea.

Here’s an interestingly-scored home-video* of a day when someone walking along the beach found the wind had driven in scores of these little beauties, and who decided to cast as many back to sea as he could find to continue their vicious (but ecologically useful) bouts of predation. Gold star for the wise use of safety sand.

Sea slugs like the sea swallow are in the Heterobranchia within the gastropods (the snails and slugs), which are themselves nested in the molluks. You can explore this section of the tree of life here.

Kudos to my friend Molly for passing on a note alerting me to this little gem. Thanks Molly!
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*Look for the bonus blue button toward the end!

What mystery of the deep or meditation on life was I pondering so seriously before the dive? Even I can't remember. This photo is kind of growing on me. It reminds me of a Rembrandt. We can call it "The Night Dive". Photo by Jeff Leicher

Don’t I look serious? You’d think I was about to dive at night into 4,000 feet of shark-infested* waters. Actually, I have no idea what I was thinking at that moment, other than probably trying to quiet my mind and prepare myself mentally. As you can see, the lights of Kona are not far behind us, and quite comforting. As recounted in Wonderful Pelagic Things, which I’ve updated with some of these photos to reflect what I saw, dive in I did. Here is some of what we saw (all photos are by Jeff Leicher and/or the crew at Jack’s Diving Locker):

I’m not really sure what this was, although it does look squid-like. I don’t recall seeing this one personally. These photos are a bit deceptive in that in order to capture the animals on film, the camera underexposes the background. In real life, our lights lit the water a vivid blue, not black as it seems here.

Here’s one of the pros with their big expensive camera. This photo helps give you the feel for the sort of equipment needed to film in these conditions, and most definitely not affordable by me.  It should also help give you an idea for the size of most of these creatures relative to us.

Here is one of the ctenophores, or comb jellies, that we encountered. You may recall from my post that just as I started looking at one, it sucked up a tiny pink plankton for dinner. This may or may not be the one — I can’t tell if that thing in its gullet is it, but in my recollection, it was definitely bright pink.

No idea what this is, and I wasn’t fortunate enough to see it personally. Jeff has labeled it as a “quadropus”, presumably the four-tentacled cousin of an octopus, but according to wikipedia, that is a fantasy creature. Any marine biologists out there have any ideas?

This is the fantastic heteropod I missed, with what looks like a small squid or fish in the distance at the tip of its tail. These guys are phenomenally cool ex-mollusks (and I mean that in the same sense as ex-Marines) that have forsaken their snail shells to swim naked and free in the ocean like vicious little hippies. They look for the other pelagic creatures from which to take bites using their saw-like radulas at the tip of a Futurama-esque eye-stalk (but is not — the eyes are at its base). The larval forms still possess coiled mollusk shells, but they lose them when they become adults. They also possess a single “dorsal fin” — which is actually totally inaccurate because it is really ventral (stomach side — they swim “upside-down”) and was originally the mollusc’s foot —  which they undulate and paddle about with. For some reason, when moving, they remind me of Sir Hiss tooling about  in that ridiculous balloon at the tournament in the 1973 Disney “Robin Hood” (see 2:15 here). Some species possess a sucker on their “fin” which the heteropod no doubt uses to hold its prey still while it savages it alive.

And finally, we have the “alien pelagic peanut creature” whose identity I still have not confirmed (Egg mass? Gummy snack?) with a little shrimp hitching a ride. Still have no idea what the heck these are, but they sure look cool.  Any ideas, readers?

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*”shark-infested” intended humorously only. I love sharks as I love all ocean life — just as long as they’re not actively gnawing on/envenomating/ovipositing into me.

http://www.flickr.com/photos/ken-ichi/ / CC BY-NC-SA 2.0 I need the bathtub toy version of this, preferably with squeaker.

I’m back alive from Hawaii (yay!) and working on an account of what happened with my planned pelagic night dive (and whether I worked up the courage to do it! : ) ). In the meantime, enjoy this photo (not mine) of a species of nudibranch that I encountered on one of my dives. It goes by the somewhat undignified name of  the varricose phyllidia, or fried-egg phyllidia (Phyllidia varicosa).

Nudibranchs (an unholy bilingual union of the Latin for “nude” and Greek for “gills” pronounced “nu’-di-brank”) are naked mollusks sometimes called sea slugs, but so are a lot of unrelated things, so wikipedia gives the impression that that is now officially frowned upon. But why even bother calling them sea slugs when nudibranch is so much fun? These organisms are among the most beautiful and psychadelically colored invertebrates on earth. Because they lack shells, they’ve developed other methods for predator deterrence, including the acquisition of several nasty toxins, stinging cells, and tentacle gestures from other organisms. Like poison dart frogs and some poisonous species of snake, caterpillar, and butterfly, being poisonous seems to work best when you are brightly colored enough to help predators remember that they hated eating you (or rather, one of your less fortunate and swiftly regurgitated kin). Here’s how the gastropods, of which nudibranchs are a member, fit into the mollusks.

Other biodiversity highlights of my dives, hikes, and trip to the Hawaii Tropical Botanical Garden included (and none of these photos or video are mine but they amply serve here) several divided flatworms; a conch that pounced on a sea urchin; hard-working sargeant majors guarding their blue egg masses plastered on rocks from hordes of ne’er-do-well marauding fish (watching this free-for-all was one of the best arguments for pregnancy that I have ever seen); a night-hunting yellow-fringed moray eel that pounced and (as per usual, I understand) missed (divers in Hawaii seem perplexed at how moray eels manage to survive); many Hawaiian lichens including shrubby reindeer lichens and pixie cups sprouting from pixie cups near the Kilauea Iki crater; the stunning native ohia trees with their brilliant red-stamened lehua blossoms; some sort of lycopod (very exciting to see in Hawai’i!), gold dust day geckos aplenty; saffron finches; Cook pines; and an explosion of Heliconias, orchids, wild gingers, ti plants (whose leaves composed the famous “grass” skirts of Hawaiians), and “Beware of Falling Mangoes” signs at the botanic gardens. Considering acquisition of “Beware of Falling Mangoes” sign.

More soon!

I also love the way natural patterns are repetitive*. Similar patterns pop up in the oddest places. Look at the Charter Oak on the Connecticut quarter

and you’re looking at the search pattern of a feeding plasmodial slime mold (a giant ameoboid eukaryote), Physarum polycephalum,

http://www.flickr.com/photos/randomtruth/ / CC BY-NC-SA 2.0

which sends out protoplasmic veins in all directions in search of its prey: bacteria, fungal spores, and other microbes.

Does math underlie that too?

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*I also love how this video was for his mom. : )