Mollusks are very efficient in the use of their body parts. They never settle for one function when an organ could serve two or six purposes at once.
A good example of this is the mantle, a membranous projection of a mollusk body wall. The mantle encloses and protects the animal’s internal organs, leaving room for an open internal space called the mantle cavity. The cavity is positioned differently in different mollusk groups and is filled with air or water—whatever is in the outside environment of the animal. It can serve as a space to exchange carbon dioxide for oxygen from that air or water (respiration, in either case), a chamber through which to pump water and filter out food particles, a sampling area for sensory organs to test the air or water, a threshold through which to dump waste products, or a safe place to keep eggs while they mature. Some groups use it for all five.
The mantle also secretes the shell, in those mollusks that have one. In many gastropods and cephalopods, the mantle is brightly colored and important for communication. In giant clams, the outer mantle tissue is colonized by symbiotic algae that provide their host with food energy in exchange for shelter. Since in bivalves the mantle is the tissue closest to the outside world, it’s the best place to put sensory organs, like eyes or sensory tentacles, or both. In many bivalves and snails, and in cephalopods, part of the mantle is modified into a siphon, which can be used to pump water through the mantle cavity for respiration, feeding and/or jet propulsion.
Freshwater and marine mollusks have gills (called ctenidia) for respiration, located in the mantle cavity. In most bivalves, these are enlarged and serve to trap food particles as well…
images: Common Octopus by Elaine Soulanille; Helix pomatia by Azchael | Wiki; Aplachophorans by Chris Allen; Sea Angel by Roy Hopcroft | Arctic Ocean Diversity; Limpet by BioImages; Glaucus atlanticus byWang, TC, WJ, Chen & Robert; Chiton by Don Loarie; Giant Clam by Ria Tan
Although they may seem to be fixed to the rock, common limpets (Patella vulgata), a mollusk, actually move around to graze on algae during moist conditions or when they are submerged by the tide. They return to the same spot by following the mucus trail that they deposit.
They look like heroic survivors of a brutal mugging, where they got stamped on and shot in the head and the assailants got away with most of its shell which is probably now on its way to China because the Chinese economy has a high demand for snail shell building materials and that’s increasing the price which means unscrupulous bastards are mugging and stamping and shooting.
But they just happen to be really weird snails!
Elephant Snails are a kind of Keyhole Limpet, which are snails that usually have cone-shaped shells with a little hole on top for breathing out. Elephant Snails are different in that their shell just has a little notch on one end…
Genomes of limpet, leech, and worm put spotlight on lophotrochozoans.
by JADE BOYD
A new report in the journal Nature unveils three of the first genomes from a vast, understudied swath of the animal kingdom that includes as many as one-quarter of Earth’s marine species. By publishing the genomes of a leech, an ocean-dwelling worm and a kind of sea snail creature called a limpet, scientists from Rice University, the University of California-Berkeley and the Department of Energy’s Joint Genome Institute (JGI) have more than doubled the number of genomes from a diverse group of animals called lophotrochozoans (pronounced: LOH-foh-troh-coh-zoh-uhns).
Lophotrochozoans are a diverse group of animals that includes mollusks – such as snails, clams and octopuses — and annelids — such as leeches and earthworms. Like humans and all other animals, lophotrochozoans can trace their evolutionary history to the earliest multicellular creatures. But the lophotrochozoan branch of the evolutionary tree diverged more than 500 million years ago from the branch that produced humans.
Almost all published genomes are from the animal kingdom’s most-studied clades: deuterostomes, which includes humans and other vertebrates, and ecdysozoans, which includes insects. Only two lophotrochozoan genomes have been previously mapped, and both are for parasitic worms, which aren’t representative of most species in the clade…
Newly Discovered Volcanic Sea Vents Crawling with Creatures
by Ker Than
Smoke-like columns of mineral-rich water rise from a hydrothermal vent—one of ten active volcanic vents recently discovered in the Gulf of California, the long, narrow body of water between Baja California and mainland Mexico.
The vents are the first to be found in the region despite many years of searching. Scientists had suspected active vents existed in the gulf, due to the region’s volcanic activity, but until now they’d been hard to track down.
The new “black smokers” were found using sonar-equipped robotic submarines, which were deployed during the last leg of a three-month expedition by California’s Monterey Bay Aquarium Research Institute (MBARI). The team has been using sonar vehicles to successfully locate new vents in the northeastern Pacific since 2006.
On the latest excursion, sonar maps of the seafloor revealed the tell-tale structures of vent chimneys, showing the team just where to send its remotely operated vehicles (ROVs)…