We’ve all seen earthworms and think we know all about them. But do we? We think they’re good for our gardens, and that’s true. They aerate the soil and provide nutrients. But what’s good for the garden isn’t good for most forests in North America. That’s because earthworms are an invasive species. When the ice sheets moved across the continent more than 10,000 years ago, they wiped out native earthworms. Today, most earthworms north of Pennsylvania are non-native. They arrived with the European explorers.
photo source: http://www.gbif.org/species/116785650#images
Most of us have seen sea anemones on the rocky shores. But, the pom-pom anemone (Liponema brevicornis) lives unattached on muddy seafloors at depths of 330-3,300 feet. It feeds on food particles drifting by. They have been found near hydrothermal vents and cold seeps as well as near whale carcasses.
The pom-pom anemone can be puffed up like in the top picture, or can flatten out more like a rolled tube. Scientists have seen the anemones in this shape being blown by currents on the sea floor like a tumbleweed. Another common name for this animal is the tumbleweed anemone. (But, we prefer Pom-Pom).
Photo from National Oceanic and Atmospheric Administration
How can a sponge catch prey when it just sits on the bottom of the ocean pumping water? It seems that even the sponge’s simple body plan has evolved a way to trap animals and then eat them. Talk about Adaptability!
Many marine worms (Annelids) live in the waters of the deep sea. One, named the green bomber worm lives as deep as 3,000 meters (1.9 miles) beneath the surface. It’s dark that deep in the ocean with only the occasional light from deep sea creatures, called bioluminescence.
The green bomber worm, Swima bombiviridis, is a segmented worm that releases tiny fluid filled sacs that glow in the dark. The sacs are modified gill parts near its head. Researchers think that, when threatened by a predator, the worm drops this glowing “bomb” to distract the predator. The researchers observed worms swimming backwards after dropping the “bomb.”
Corals are cnidarians, in the same large family as anemones. There are more than a thousand coral species worldwide, but the best known are the stony corals, like staghorns, which make skeletons of calcium carbonate. What looks like one organism is actually a colony made of tiny coral polyps that look like tiny anemones. Inside each polyp live plant-like cells called zooxanthellae that produce food from sunlight, supplying energy to the coral. In turn, the coral polyp supplies the zooxanthellae with nutrients from the ocean and shelter. It’s these zooxanthellae that are sensitive to the increase in ocean temperatures.
The giant Pacific octopus is the largest octopus, with arms up to 16 feet long and weighing as much as 100 pounds. Ranging from Japan to Alaska to Baja California, this octopus lives in shallow coastal waters to depths of 5,000 feet. Each of the octopus’ eight arms is covered with as many as 200 suckers that are sensitive to touch and taste. And it’s a smarty pants, too: octopuses are big-brained invertebrates.
Watch an octopus catching a crab here: http://shapeoflife.org/video/behavior/molluscs-octopus-catching-crab
The purple sea urchin that lives in the west coast of the United States is an echinoderm with tube feet and long spines and a mouth with strong jaws. It’s a voracious herbivore that can have a devastating influence on its environment if not held in check by predation.
Arthropods grow in a very different way than you and I do. Blue crabs, like all arthropods, shed their exoskeletons to grow. For crabs, that means shedding their shells and growing a new one, a process called molting. Watch a blue crab molting: http://shapeoflife.org/video/behavior/arthropods-blue-crab-molting