Little Killers: The Ferocious Lives of Puny Predators
Hangin Out Chaetognaths spend a lot of time hanging suspended in the water Their horizontal fins help keep them from sinking very rapidly When they do sink or detect prey they dart forward using rapid muscle contractions in their bodies Chaetognaths have superb tools to help them ambush and seize their prey Their bodies are see through making them almost impossible to spot especially in the dim regions where they prefer to hunt Tiny hairs on their skin help them detect the smallest water movements allowing them to target their prey Perhaps most impressive are the chaetognath’s mouthparts Hooks or spines surround the mouth and are used for grasping prey while needle-sharp teeth inside its mouth help the animal pierce and swallow prey Many chaetognaths can even inject poison into their victims An arrow worm’s see through body and slim profile help it sneak up on prey and escape the notice of other predators 6
Chaetognaths first appeared on Earth at least five hundred million years ago Since then their bodies have changed very little a sign that they are very well adapted to living where and how they do Because of this scientists consider them one of Earth’s most successful predators But chaetognaths also are some of Earth’s smallest predators While a few deep water species can grow to 4 or 5 inches 10 to 12 cm long most are shorter than a pencil eraser Chaetognaths however are far from Earth’s only puny-sized predators Fisherman’s Foe Besides eating copepods chaetognaths are major predators of small fish and fish larvae They may even control or limit some fish populations around the world TINY KILLERS When most of us hear the word predator we imagine lions sneaking through tall grass after zebras or great white sharks tearing seals to shreds That’s no surprise Large predators from wolves to polar bears to orcas are some of Earth’s most impressive animals But the vast majority of Earth’s predators aren’t humongous lion or whale sized creatures Many such as spiders and ladybird beetles are so small that you can easily overlook them while taking your dog for a walk Others such as chaetognaths are so little you often need a microscope to see them Some chaetognaths can eat up to a third of their weight each day What makes these little killers so successful MICRO ADVANTAGES Like larger predators small predators come equipped with an arsenal of weapons to help them catch and subdue their prey These weapons such as the teeth hooks and transparent body of a chaetognath are perfectly adapted to each predator’s size habitat and way of life Little killers also have a couple of advantages over other predators 7
While a sample of creek water might look clear or empty it may contain thousands of living organisms including a host of tiny predators 8
Mood Lighting Scientists have discovered two species of arrow worms that are bioluminescent they make their own light When a predator approaches the arrow worms release a spray of light-producing chemicals behind them confusing the predator and allowing the arrow worms to get away One is that small predators have a lot more places to live The world is only big enough to hold a limited number of lions sharks and wolves but almost unlimited spaces exist for their tinier counterparts Small predators can live in cracks between sand grains in muddy sediments on leaves and flowers and even on other larger animals Predators can live in so many places that scientists haven’t come close to identifying all of the different kinds of little predators on our planet A second great advantage for puny predators is the abundance of prey For every small predator there may be hundreds or thousands of other miniscule animals to eat If you search a flower bed you might find thousands of aphids for every ladybird beetle that you see In one Egyptian lake scientists counted more than 120 copepods in each gallon 3.8 L of water With odds like these is it any wonder that thousands perhaps millions of kinds of tiny predators populate our planet Let’s turn the page and eat I mean meet some more of them starting with some of the smallest 9
