Our last museum stop of this New York trip was at the American Museum of Natural History. Although we always enjoy browsing through the museum’s galleries, this stop was particularly focused on a particular exhibit called “Creatures of Life.” The display explained that at least 50 different species have independently developed some form of their own light-emitting capabilities. It profiled and explained the nature of creatures that produce light and the very different ways this light is used by each species.
The exhibit explains the nature and the chemistry of three different forms of light:
- Fluorescence, the immediate emission of longer-wavelength light by a substance that has absorbed lower-wavelength light;
- Phosphorescent , the slower, longer-term emission of light from a substance that had been “charged” by light that was absorbed previously.
- Luminescence, the emission of “cold” light by a substance not resulting from a process other than heat, primarily a chemical reaction in the case of animal-based “bioluminescence.”
It showed models of and examined the uses of each of these three in the tiny number of terrestrial fungi and animals (fireflies, a few types of bacteria, a couple species of millipedes and glow worm larvae) that produced light and then provided an overview of the large number of light-producing aquatic creatures. Although we have seen the glow worm larvae in caves of the south island of New Zealand, we had never been aware of the examples in our own back yard, such as Oregon Blue Mountains fungi, Ozark Mountains larvae and Sequoia National Park millipedes.
It then explained and showed examples of the role of florescence in simple shallow water coral and anemone, provided an interesting explanation of the phosphorescent bacteria in a small bay in Puerto Rico’s Vieques Island, the ways in which small flashlight fish have developed pouches that contain and control the use of luminescent bacteria for use in attracting mates and how certain species of jellyfish use bright flashes of luminescent light to startle produce bright flashes to startle predators.
The vast majority of, and the most fascinating uses of animal light, however, are from the pitch black ocean depths. It showed the ways in which certain types of cucumbers a cucumbers use light to hide themselves from predators and how the ominous looking angler fish uses luminescent lures to attract prey and another form of luminescence to evade predators. It showed examples of one fish that is able to produce a very rare red light to find tiny shrimp in this totally dark environment and, most interesting of all, how small primitive sea creatures called zooids come together into huge, 40-50 meter organisms called Siphonophora. The individual zooids than morph to perform specialized functions (such as stinging tentacles, digestive system and so forth) within the larger organism. They are one of only two known specifies to produce red (most produce blue, green or white) luminescent light to lure and then paralyze and digest fish.
A few organisms even have multiple means of creating their own light, such as by using their own chemical-based luminescent light to fuel their own phosphorescence.
Although the exhibit, by its very nature, had to display models, rather than living organisms, it was fascinating.