Have you ever noticed how photographs of underwater scenes have a bluish tint? Sunlight is made up of a rainbow of colors, but when it enters the water the reds and yellows in the light are quickly filtered out. The blues and greens penetrate deeper into the water and give those watery scenes their peculiar cast. Because there is very little red light in the deep sea, most of the animals that live there have never evolved the ability to see the color red. This is why many deep-sea animals are red. In the depths of the ocean, a creature that can’t be seen is safe from many predators.
There is an unusual fish that takes advantage of its fellow sea creatures’ colorblindness. The stoplight loosejaw, a member of the dragonfish family, can see the color red. Not only that, but it has a patch on its face that glows red. It also has a glowing green spot on its face, which is probably used to communicate with other dragonfish. These red and green patches explain the “stoplight” part of this fish’s name. The “loosejaw” comes from this fish’s ability to open its mouth extra wide and swallow large prey. Scientists think that the open structure of the lower jaw allows the fish to close its mouth quickly, making it difficult for prey to escape. Relative to its size, the stoplight loosejaw has one of the widest gapes of any fish, with a lower jaw measuring one-quarter of the fish’s length. It’s not easy for animals that live in the dark waters of the deep sea to find prey. Many of them, including the stoplight loosejaw, have large mouths and sharp fangs that help ensure that their prey cannot escape.
Below about 650 feet (200 meters), very little sunlight penetrates the ocean. Below 3,300 feet (1,000 meters), the only light is that produced by living creatures. Almost all deep-sea creatures can bioluminescence, or make their own light. But the light they produce is usually blue or green. When the stoplight loosejaw switches on its red spotlight, other creatures in the water are illuminated. Being blind to the color red, they don’t realize that they’ve been spotted. Dragonfish are not known as picky eaters. If one of the lit-up animals is a fish, shrimp, or other suitable prey, the stoplight loosejaw quickly grabs it and swallows it.
The stoplight loosejaw's attributes include a red spot, hinged jaws, and needle-like teeth. Illustration by Steve Jenkins
There are two kinds of stoplight loosejaws. The Northern (Malacosteus niger) shown here and the Southern. Together they are found everywhere in the world except the North and South Poles. Wikimedia Commons
Steve Jenkins has written and illustrated more than forty
nonfiction picture books, including the Caldecott Honor–
winning What Do You Do with a Tail Like This? and the
Boston Globe Horn Book honor–winning The Animal Book.
His most recent books are Apex Predators: Top Killers Past
and Present and Who Am I?, an animal guessing game
written with Robin Page.
MLA 8 Citation
Jenkins, Steve. "The Fish That Sees Red." Nonfiction Minute, iNK Think Tank, 6
June 2018, www.nonfictionminute.org/the-nonfiction-minute/
Dorothy Hinshaw Patent
Nature’s Animal Ambassador
Have you heard about the “butterfly effect,” the idea that one small change can bring about big changes over time? This idea is important in the study of ecology, which deals with the interactions of living things and their environments. Each element of an ecosystem has its place. When one element is eliminated, it affects everything else.
The Yellowstone ecosystem centered in Yellowstone National Park provides a great example. Late in the 20th century, biologists were worried about the aspen trees there. Aspens occur in clusters that are actually clones growing up from shared root systems. Some of the Yellowstone clones were hundreds of years old, but the old, dying trees weren’t being replaced by strong young shoots. It looked like they might just die out, and no one was sure why.
When a severe drought in 1988 led to big wildfires in the park, the idea that fire might stimulate aspen growth proved wrong. Perhaps the elimination of wolves from the region in the early 20th century was to blame. Wolves? New trees? How could that be? Without wolves, the behavior of the Yellowstone elk had changed. No predators. No worry. So the elk became lazy, acting like cows, lying around in shaded areas along the rivers and creeks, munching contentedly on the juicy fresh growth of the willows and aspens.
In 1995, after much political battling, wolves were reintroduced into Yellowstone. The wolf population grew and the elk learned to be on the alert. As the wolves’ favorite food, the elk had to change their behavior to survive—no more relaxing by a stream where wolves could easy sneak up and make a meal of them! They had to move around and spend more time in open places where watching for hungry wolves was far easier.
The wolves are changing the Yellowstone landscape in positive ways. The aspens and willows are coming back. Beavers, which had almost disappeared from some parts of the park, are returning. These rodents feed on aspens and willows and use them to build their dams and lodges. Beaver dams create ponds, and the ponds provide homes for hundreds of species of plants and animals, from algae and water striders to ducks and muskrats. The willows and aspen trees around the pond are nesting sites for songbirds and homes for insects and spiders, all thanks to the wolf.
Welcome back, wolves!
Dorothy Hinshaw Patent's book, When the Wolves Returned: Restoring Nature's Balance in Yellowstone, is an IRA/CBC Teachers' Choices book, an ALA Notable Children's Book, A Book Sense Pick, and an Outstanding Science Trade Book for Children, as well as receiving the Orbis Pictus Honor Book Award. Booklist calls it "A great choice for elementary units about science and environmental protection," and Kirkus gave it a starred review. Click here to read the reviews.
Dorothy Hinshaw Patent is a member of iNK's Authors on Call and is available for classroom programs through Field Trip Zoom, a terrific technology that requires only a computer, wifi, and a webcam. Click here to find out more.
MLA 8 Citation
Patent, Dorothy Hinshaw. "Everything Is Connected: The Butterfly Effect and the
Wolf." Nonfiction Minute, iNK Think Tank, 27 Mar. 2018,
For Vicki Cobb's BLOG (nonfiction book reviews, info on education, more), click here: Vicki's Blog
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