Almost everyone knows what an earthworm is, but these very familiar animals are just one variation on a very rich theme that is at its most fabulously varied in the oceans. The mind-boggling appearances and lifestyles of the marine segmented worms are perfectly exemplified by this week’s animal.
Looking like an intricately folded napkin or a collection of another animal’s soft parts, parchment-tube worms are wonderfully odd. It’s actually very difficult to make out what’s what with these creatures. They don’t really have a discernible head and other easily recognized morphological landmarks are few and far between. Completely adapted to a life in marine sand and mud, the U-shaped burrow they construct—roughly the same size and shape as a banana—is essentially an extension of the worm’s body and integral to how they feed, akin to a spider and its web.
The extremely fragile parchment worm lives in a banana-shaped burrow in marine sediment, which is essentially an extension of its own body. Photo by: © Arthur Anker – https://www.flickr.com/photos/artour_a/.
Out of sight, down in the sand, the body of these worms is soft, pale and very fragile, but it works beautifully in conjunction with its burrow to filter particles of edible matter from the water. By rhythmically beating some of its appendages the body of a parchment-tube worm works like a pump to drive water, laden with edible morsels, through the burrow. To actually trap the good stuff the worm has a very neat trick. Some of its winglet-like appendages form a structure reminiscent of a tiny basket-ball hoop that secretes a mucus bag, the end of which is gripped by a small, cup-like structure. As the water is pumped through the burrow, the mucus bag grows increasingly heavy with edible matter until the little cup rolls up the bag and its contents into a ball. The food cup then stretches forward to deposit the nourishing bounty into a ciliated groove, along which it is shuffled towards the animal’s waiting mouth.
Sediment dwelling segmented worms, like the parchment-tube worms, are of enormous ecological significance. They are so abundant that, collectively, they filter huge quantities of sea water to extract edible matter and churn vast amounts of marine sediment – key processes in the cycling of nutrients and energy.
In this image of a parchment-tube worm you can see the fan-like appendages that rhythmically beat to pump water through the burrow. Photo by: © Arthur Anker – https://www.flickr.com/photos/artour_a/.
Dr. Ross Piper is a zoologist and author and has recently presented on the BBC/Smithsonian TV production, Wild Burma: Nature’s Lost Kingdom, soon to be shown in the USA. You can read an interview with Ross Piper here: Animal Earth: exploring the hidden biodiversity of our planet.
(02/11/2014) The Critically Endangered European eel makes one of the most astounding migrations in the wild kingdom. After spending most of its life in Europe’s freshwater rivers, the eel embarks on an undersea odyssey, traveling 6,000 kilometers (3,720 miles) to the Sargasso Sea where it will spawn and die. The long-journeying eels larva than make their way back to Europe over nearly a year. Yet by tracking adult European eels (Anguilla anguilla) with electronic data loggers, scientists have discovered that some eels never make it to their spawning ground, but instead are swallowed-up in the depths by leviathans.
(02/11/2014) Biologists recently documented one of nature’s least-known, big events. On the banks of the Purus River in the Brazilian Amazon, researchers witnessed the mass-hatching of an estimated 210,000 giant South American river turtles (Podocnemis expansa). The giant South American river turtle, or Arrau, is the world’s largest side-necked turtle and can grow up to 80 centimeters long (nearly three feet).
(02/10/2014) Almost nothing is known about the little dodo, a large, archaic, pigeon-like bird found only on the islands of Samoa. Worse still, this truly bizarre bird is on the verge of extinction, following the fate of its much more famous relative, the dodo bird. Recently, conservationists estimated that fewer than 200 survived on the island and maybe far fewer; frustratingly, sightings of the bird have been almost non-existent in recent years. But conservation efforts were buoyed this December when researchers stumbled on a juvenile little dodo hanging out in a tree. Not only was this an important sighting of a nearly-extinct species, but even more so it proved the species is still successfully breeding. In other words: there is still time to save the species from extinction so long as conservationists are able to raise the funds needed.
(02/05/2014) The genus Bombus consists of over 250 species of large, nectar-loving bumblebees. Their bright coloration serves as a warning to predators that they are unwelcome prey and their bodies are covered in a fine coat of hair – known as pile – which gives them their characteristically fuzzy look. Bumblebees display a remarkably capable flight performance despite being encumbered with oversized bodies supported by relatively diminutive wings.
(01/30/2014) The range of habitats that animals have come to occupy is nothing short of staggering. Take the dicyemids for example. They are among the simplest animals on the planet, with a tiny, worm-like adult body that consists of between 10 and 40 cells. They have no organs, body cavities or even guts—a structural simplicity which is a consequence of where and how they live. The only place you will find adult dicyemids is inside the bodies of cephalopods, typically octopuses and cuttlefish where large numbers of them cling to the inner wall of the mollusc’s kidney.
(01/27/2014) Sea anemones are supposed to sit on the bottom of the ocean, using their basal disc (or adhesive foot) to rest on a coral reef orsand. So, imagine the surprise of geologists in Antarctica when they discovered a mass of sea anemones hanging upside from the underside of the Ross Ice Shelf like a village of wispy ghosts. The researchers weren’t even there to discover new life, but to learn about south pole currents through the Antarctic Geological Drilling (ANDRILL) Program via a remotely-operated undersea robot.
(01/17/2014) Nematodes are typically small animals that to the naked eye look very much alike; however, these creatures are fantastically diverse —on a par with the arthropods in terms of species diversity. At face value, nematodes lack the charisma of larger animals, so there are very few biologists who have made it their life’s work to understand them. Those who do have been rewarded with a glimpse of the incredible diversity of these animals, an example of which is the complex menagerie of nematodes that dwell in the guts of large, tropical millipedes.
(01/10/2014) Biofluorescence is widespread among marine fish species, indicating its importance in communication and avoiding detection, finds a new study published in the journal PLOS ONE. The research shows that biofluorescence — a phenomenon where organisms absorb light, transform it, and emit it as a different color — is more common in the animal kingdom than previously known.
(01/10/2014) Rove beetles are among the most diverse animals on the planet, with around 56,000 species currently described. Amongst this multitude of species is a dazzling array of adaptations perhaps best illustrated by the genus Stenus. These beetles, with their bulbous eyes and slender bodies are often found near water running swiftly over the wet ground and clambering among the vegetation.