One of the most popular and most photographed exhibits at the Monterey Bay Aquarium is the beautiful mesmerizing ballet of sea nettles. The Pacific sea nettle, Chrysaora fuscescens, lives in coastal waters from Alaska to California, to Japan, Kamchatka, the Aleutian Islands, and the Bering Sea. With their long, trailing tentacles these jellies are large: their bells are about 17.7 inches (45 cm) in diameter, mouth-arms from 12 to 15 feet (3.6 to 4.6 m) long. The frilly mouth-arms and tentacles are covered with stinging cells, called nematocysts.
Ranging 2”to 9’ feet, earthworms move miles and miles of earth for us. As children, many of us discovered earthworms while playing in the dirt. We either loved them or thought they were gross—but, their role on our planet is undeniably essential. Earthworms are very important recyclers—a role Charles Darwin recognized. In fact, his last published book in 1881 was about earthworm behavior and ecology.
Earthworms are decomposers: they eat and break down dead plant and animal material in the soil. As they burrow, ingest dirt and poop, they turn the soil and put nutrients back into it.
Boris is a famous missing link in the evolution of chordates: he’s an early tetrapod (tetrapod means “four-legged”) fossil. Paleontologist Jenny Clack was so excited when she uncovered him that she named him Boris. Boris is a missing link because he represents an animal who may have been the first of its kind to make the transition from life in the sea to life on the land. This invasion of the land by vertebrates was a key moment in evolutionary history, leading to colonization of the land by four-limbed animals.
Although it looks like a jellyfish, the gelatinous creature in this photo is a relative of ours: it’s a Chordate called a salp. Salps are pelagic sea squirts – tunicates. What makes these invertebrates Chordates? In our video on Chordates we show how we’re related to these ancient Chordates.
Salps are transparent, barrel-shaped animals that contract their bodies to move by jet propulsion. They feed by straining water through their internal feeding filters, trapping phytoplankton. They may not be familiar animals, but salps live in equatorial, temperate and cold seas; they are most abundant in the Southern Ocean.
Krill are shrimp-like arthropods that make up a large portion of the zooplankton in many regions of the ocean. Krill are near the base of the oceanic food web feeding on phytoplankton. In turn, enormous swarms of krill feed the largest creatures in the ocean: blue and other baleen whales, sea birds, squid, and fish.
Blue whales, the largest animals that ever lived, eat up to four tons of krill a day to fuel their huge bodies. In fact, krill – about two inches long –make up the majority of their diet. Blue and humpback, and other baleen whales, are filter feeders. They take in huge gulps of seawater dense with krill straining out the water though their baleen and then swallowing their catch.
Bivalves, (clams, oysters and mussels), are often on our dinner plates. But when we take a tasty bite, we’re also eating microplastics. These shellfish are filter-feeders, straining plankton from seawater for food. Along with plankton, they’re ingesting microplastic bits.
Scientists have looked in the tissues of several kinds of bivalves to discover the amount and kind of plastic found in these animals. In some places, they’ve found the majority of plastic is overwhelmingly microfibers as these are easily eaten by zooplankton.
Imagine a creature with such a radically different body plan that we, bilateral humans, can’t really fathom how they have been so successful. Sea stars, and other echinoderms, move and feed like no other animals. They are animals that followed a different evolutionary path after evolving from the same bilateral ancestors as us.
Many still call sea stars “starfish”, but they certainly aren’t fish. No head, no tail, all arms –sea stars are just that: stars. Based on five-part radial symmetry (though some sea stars have many more arms), key functions are coordinated in the center of their bodies, then passed down the arms. The sea star has no brain, but a nerve ring in its center, like a relay station that coordinates the movement of its arms. This nervous system relays impulses from light, touch and chemical sensors around its body.
Marine flatworms can dazzle with wild colors and patterns – if you’re lucky enough to see one. They live from the intertidal to tropical coral reefs to deep water. The free-living flatworms (polyclads) have thin, almost leaf-like bodies and move with a gliding motion. Their ancestors were some of the first bilateral animals, and being bilateral gives them a body plan designed for an active life style.
At Shape of Life, we call the flatworm phyla video "First Hunter," and indeed these animals are active carnivorous predators that feed on a wide variety of animals including copepods, isopods, limpets, barnacles, tunicates, and bryozoans.
Where we at Shape of Life live, we know when anchovies are in the neighborhood because when we go down to the ocean, we’ll see hundreds of diving sea birds, jumping sea lions, and if we’re lucky, humpback whales. They’re all here to feed on massive schools of anchovies close to shore. As they swim through the water with their mouths open, anchovies strain out plant and animal plankton. They then are food to all of the animals we see plus so many more, including larger fish and people. In fact, these small schooling fish (@nine inches long) support a large part of the oceanic food web. Some scientists say anchovies are the most important prey—also called forage fish—in the U.S. Pacific Ocean.
Those pin-cushion looking creatures you want to avoid touching or stepping on are sea urchins. There are about 950 species living in all oceans and depth zones, from the intertidal to 16,000 feet deep. Sea urchins are echinoderms, related to sea stars and sea cucumbers. Although that might not seem immediately obvious, sea urchins have five-part symmetry (watch our video on the body plan of these animals: Five part symmetry)