Actually, this one was not part of my original Too Cool™ lineup, but it deserves to jump in line.
Courtesy of National Geographic posted by icheesman found through Cracked.com via Mental Floss (link addiction can be cured – please contribute today!) comes a video clip of an utterly fascinating natural phenomenon that I talked about previously: bioluminescence.
There’s a part in there where you can see the shape and the swimming motion of the fish, which is strikingly similar to the effect I saw when I watched the dolphins (who were a bit faster.) Not only that, but see the little shrimp? Yes, you’ve seen them before, or at least, you have if you’ve been poking around the photographic gallery of my site enough.
This video is worth watching several times to see all the details. Catch the water jets of the cuttlefish as it moves around, and of course, don’t miss the stingray. One thing that the video displays very well, but perhaps isn’t described adequately, is that it takes a certain level of disturbance to get the dinoflagellates to fire off. When I witnessed this in Florida, waves splashing against rocks first drew it to my attention, but none of the fish movement within the water produced anything. It was only when the action became desperate that it became visible – I occasionally watched startled fish swim away from me with a streak of color, but otherwise it was dark. Thrashing my hand around certainly showed it, though.
Also, recognize that much of the video is shot at high magnification (the shrimp is probably only 2.5 cm long or so). I never saw individual points of light, and dinoflagellates are not discernible, even in bright light, to the naked eye. What I saw was just a haze of color. Just unreal.
And funny, I never really thought about the bioluminescence as a survival trait, but it makes sense now. Whales will eat them as part of the huge collective term “plankton,” but mostly the predators of such little species are slightly larger species like the grass shrimp and the porcelain crab, which serve as meals for even larger species that would have no interest in the dinoflagellates. In this case, the defensive mechanism seems to be more of a benefit collectively than individually, for two reasons. One, it takes an actual disturbance to light up the dinoflagellates, by which time they may already be eaten. And two, I imagine no small number of them get ingested by accident when something scarfs a shrimp down. Overall, more might survive by the reduction of predators, but the ones that have actually sent the warning, as it were, do so from being at a much higher risk. It works, but less efficiently than many other defensive mechanisms.