Drilled shells show extinction's lasting effects

December 23, 2004

Give a marine snail an easy life, and it will take its time drilling into a clam. Put it under competitive stress, and it will look for a faster route. Those changes, scarred into fossils, show that an unknown catastrophe nearly two million years ago changed the competitive balance in the Western Atlantic and the ecosystem has yet to fully recover, according to research published this week in the journal Science.

In the seagrass meadows of the Gulf of Mexico, Chicoreus and Phyllonotus marine snails feed on Chione clams by slowly drilling a hole through the shell wall. That process can take a week, while the snails risk losing their prey to another snail or being attacked themselves by fish, crabs or other predators.

High levels of competition should favor faster feeding, said Geerat Vermeij, professor of geology at UC Davis and an author on the paper. The snails can get a quicker meal by drilling through the thinnest part at the shell's edge -- but risk getting their feeding proboscis nipped off by the closing shell.

The pattern of drill holes in fossil shells can give insight into what life in the ocean was like millions of years ago and how it compares to today.

In the laboratory, Gregory Dietl, a postdoctoral researcher at the University of North Carolina who is now at Yale University, UC Davis graduate student Gregory Herbert (now at the University of South Florida) and Vermeij found that when modern-day snails had to compete for food with other snails, they began edge-drilling their prey. When they were separated, they went back to slow wall drilling.

"They have the same gene pool, but you can elicit different behaviors depending on the competitive environment," Vermeij said.

A severe but regional extinction event at the end of the Pliocene Epoch 1.7 million years ago seems to have tilted the balance from high competition to low competition, according to the researchers. At that time, up to 70 percent of marine species in the Western Atlantic Ocean disappeared, with some parts of the world affected to a lesser extent and others unscathed.

The researchers looked at thousands of fossil clam shells from before and after the extinction and compared them with modern shells. Edge-drilled shells are abundant up to 1.7 million years ago, and then disappear entirely. None of the modern shells they looked at show edge-drilled holes.

The results show that competition intensity has not returned to pre-extinction levels even though a long time has passed since the event, Vermeij said.

The cause of the Pliocene extinction remains unknown. The work is published in the Dec. 24 issue of Science.
-end-


University of California - Davis

Related Competition Articles from Brightsurf:

Cell competition in the thymus is crucial in a healthy organism
The study published in Cell Reports demonstrates that the development of T lymphocytes lays on the coordination of signals followed by cells in order to ensure the maintenance of a healthy organism.

How sexual competition and choice could protect species from extinction
New research shows that removing sexual competition and choice through enforced monogamy creates populations that are less resilient to environmental stress, such as climate change.

Aging and nutrients competition determine changes in microbiota
Two studies with surprising discoveries: in the elderly, the bacterium E. coli evolves in a way that can become potentially pathogenic and increase the risk of disease and, according to data obtained in another study, the metabolism of the same bacterium present in the microbiota evolves differently if it is alone or accompanied by other bacteria.

Is human cooperativity an outcome of competition between cultural groups?
A study by ASU researchers looks at how culture may have fueled our capacity to cooperate with strangers.

Location and competition
Those of us who drive regularly are keenly aware of gas prices and their daily fluctuations.

Political competition is hurting our charitable giving
As the midterm election heats up and the fallout of the Supreme Court nomination rings across the political divide, a new study presents a unique angle of American politics: how party affiliation affects charitable donations.

For wineries, competition boosts profits from sustainability
An international study of small- to medium-sized wineries and vineyards finds that the more sustainability practices a winery has in place, the better its financial performance -- and the effect is enhanced when a winery perceives significant pressure from competitors.

Outside competition breeds more trust among coworkers: Study
Working in a competitive industry fosters a greater level of trust amongst workers, finds a new study from the University of British Columbia, Princeton University and Aix-Marseille University, published today in Science: Advances.

Step aside Superman, steel is no competition for this new material
When it comes to materials, there is no question as to who wins the strongman competition.

Competition between males improves resilience against climate change
Animal species with males who compete intensively for mates might be more resilient to the effects of climate change, according to research by Queen Mary University of London.

Read More: Competition News and Competition Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.