Courtesy of Reuben Clements

Friday, January 11th, 2008--

Researchers working in Malaysia have unearthed a new species of snail with what they describe as a "bewildering" shell. Named Opisthostoma vermiculum (vermiculum meaning "wormy"), the shell of this newly-discovered gastropod breaks several accepted shell rules. The find was reported in the journal Biology Letters this week.

Shells in the gastropod family, which includes snails and slugs, have some standard characteristics. The shells are usually cone-shaped and right-handed; they spiral along a single axis and expand logarithmically, researchers say.

The shell of O. vermiculum, which was uncovered in a limestone quarry in Malaysia by Reuben Clements and colleagues, is puzzling. "At first we thought it was a mutant," says Clements, a species conservation manager for the World Wide Fund for Nature-Malaysia and the lead author on the paper. After inspecting 38 shells with similar characteristics, the researchers determined that this was no mutant, but a new species with a consistent, if unusual, shell design.

O. vermiculum's shell has four different axes of rotation. Previously, the maximum number of shell axes was three, and the norm is a single axis, researchers say. A snail makes a shell with multiple axes by turning inside its shell during shell formation, Clements says. Another notable feature is that O. vermiculum's shell--which is only a millimeter in length--coils and uncoils, attaching and reattaching its coils several times. Shells that uncoil have been found before, but shells that uncoil and reattach have never been seen.

The blueprints for shell design are encoded in an organism's genes and because the shell is the snail's interface with the outside world, shell morphology is likely subject to strong natural selection, experts say. Presumably O. vermiculum's strange shell is an adaptation, Clements says. But the researchers have only found the shells, not the organisms that live in them (although Clements suspects O. vermiculum is a living species because the shells are shiny--a sign of freshness). Without observing a live specimen it's not clear exactly why such an unusual shape would benefit a snail. "This is an example of how little we know regarding the relationship between form and function," Clements says.

One hypothesis is that uncoiled shells with multiple axes makes an organism appear larger than it is. But this snail is so small, shell shape is not likely to be much a defense mechanism, Clements says, adding, "We didn't want to make any wild conjectures until we find the live individual."

--Flora Lichtman

Sources

Reuben Clements
Species Conservation Manager World Wide Fund for Nature-Malaysia Selangor, Malaysia

Tools:

Elsewhere on sciencefriday.com

• 

  Lousey Death
  Pink salmon populations are careening towards collapse--but this time fishing isn't the cause.

• 

  Super-Sized Scorpion
  Ancient claw indicates sea scorpions were over eight feet long.

• 

  Giant Penguin Fossils Found In Peru
  Researchers describe fossil giant penguins.

• 

  Deep-Sea Biodiversity
  Thirty-thousand species under the sea: the amazing diversity of bacteria at hydrothermal vents.

• 

  A New Species, or Just Small Humans?
  The discovery of unusual skeletal remains on the islands of Palau suggests that the so-called 'hobbits' found several years ago in Indonesia may have been dwarf humans, not a separate species.

• 

  Video: Attack of the Ladybugs

• 

  Video: Michael Novacek on Toothy Dino Discovery

Explore More

• Biology
• Flora and Fauna
• Animals