Our days are short this time of year, with dusk coming fast on the heels of our afternoon snacks. Night has often blanketed us in darkness by the time dinner hits our tables. As we finish homework and spend the evening with family and friends, we are drawn to the cheer of lights of all kinds, from candles and lanterns to flashing toys and night lights.
Outside, though, wild living things have their own purposes for lighting up the dark – without flame or electricity – and have adapted remarkable natural ways of doing so.
Most people are familiar with fireflies, or lightning bugs, flashing in the summer sky. These insects “talk” to each other with pulses of light known as bioluminescence. A chemical reaction in their abdomens, similar to that in a glow stick or glow necklace, helps fireflies of the same species to flash their own special signals back and forth to find a mate.
So, could this be the warm glow of insect romance? Not quite. Scientists call bioluminescence “cold light” because the very efficient reaction makes almost no heat.
LIGHT IN THE FRIDGE
Despite the popularity of fireflies, nearly all of nature’s glowing animals live in the sea. Some of them use their lights to find food. In the Indian and Pacific oceans, the pinecone (or pineapple) fish, a pale yellow fish with tough scales outlined in a pinecone pattern, uses luminous spots beneath its lower lip to attract zooplankton, its tiny swimming dinner.
In the deep, dark sea where food is hard to find, some species of anglerfish use natural “light bulbs” to attract their meals. The anglerfish has a long spine sticking up from the middle of its head like a fishing rod. The tip of this fishing rod features a glowing, fleshy bulb. Swishing its light back and forth as a lure, the predator attracts curious animals right into its gaping jaws.
Both anglerfish and pinecone fish need help to light up, though. Their glow comes from bioluminescent bacteria, which they store inside “bulbs” and other specialized body parts. These live-in guests receive shelter and nutrients from the fish while helping their hosts catch prey.
Never-ending battles between predators and prey drive much of the light-up undersea action. Sailors report electric blue swirls of light trailing behind boats at night. Divers moving around underwater stir up this same display.
These bright swirls are caused by tiny plankton called dinoflagellates. Scientists think the light acts as a burglar alarm for the plankton. Dinoflagellates glow in response to movements of small fish (burglars) feeding on them. These sudden bright swirls might attract hungry bigger predators (police), which take care of the burglars with a few chomps.
Orange sea pens also seem to have adapted the burglar-alarm defense. The fluffy relatives of jellies live here in Puget Sound. Orange sea pens anchor to the sea floor and resemble large, swaying orange feathers like a fancy quill pen. When something touches a sea pen, it reacts with yellow-green waves of bioluminescence up and down its body.
Some hunting sea stars, such as ochre stars and sunflower stars, eat orange sea pens. When a sunflower star touches one sea pen, it can trigger the whole colony of sea pens to light up. If this bright burglar alarm lures in predators that eat sea stars, it can protect the entire colony like a neighborhood watch.
Marine animals glow in many other ways that researchers are only beginning to understand. But, as we flip our switches and plug in our night-lights this winter, we can take comfort knowing we are only one of many species with good reason to light up the dark.
HELP CARE FOR THEM
Properly dispose of waste products and household chemicals, such as bleach, cleaners, motor oil and batteries. For details and drop-off locations in Pierce County, visit co.pierce.wa.us/index.aspx?NID=1544.
Avoid fertilizers and pesticides. Use only organic lawn-care products and incorporate native plants, which require much less care, into your landscape.
Wash your car at commercial carwash facilities, which are better equipped to dispose of the soaps, oils and other runoff.
Save energy by using efficient light-emitting diodes, or LED, lights. These last longer and use less energy than incandescent bulbs. LEARN MORE
THE DETAILS: Look for bioluminescent plankton and other interesting marine life in local waters at an upcoming Pier Peer event sponsored by Metro Parks Tacoma and Foss Waterway Seaport. Adults and children ages 8 and older are invited to see and touch ocean creatures brought to the surface by local divers.
WHEN: Upcoming Pier Peer events are scheduled for Saturday, Feb. 2, Feb. 23 and March 2.
For details and to register: Go to metroparkstacoma.org/ tacomanaturecenter.