The Pacific coast of North America is strewn with black turban snails and many of these thimble-sized mollusks have triangular chips in their shells. These chips are predatory signs, proof that this turban snail was attacked by a hungry crab at some point in its life. Scientists knew that by studying these scars, they could gain important knowledge about predatory crabs, such as population numbers. In a new study, researchers have shown that they can extend this comparison by up to 120,000 years by looking at the number of scars that modern snails carry and those on snail shells in the fossil record. “It’s really exciting to think that you could walk on the beach and pick up a snail and see this record of an interaction between a predator and its prey,” said Carrie Tyler, a paleontologist at the University of Miami in Florida who does not attend. in the study. Involved. “I find it amazing to go back to the Pleistocene and make this direct comparison.” For the study, Kristina Barclay, a paleo-ecologist at the University of Victoria in British Columbia, compared the scars on black turban snails collected at study sites off the coast of California near Los Angeles and San Diego from Los Angeles. area. Late Pleistocene 120,000 to 80,000 years ago. He found that modern snails have a 10 to 15 percent lower scar rate than their Pleistocene counterparts, most likely due to a reduction in the number of crabs. The predatory scars on Late Pleistocene snails can be compared to the scars on the shells of modern black snails. Courtesy of Kristina Barclay To ensure that the lower scar rate represented a decrease in the crab population, rather than reflecting that crabs became weaker predators over 120,000 years, Barclay also looked at a measure called the size of the attack – or how big it is. snail was when the crab tried to eat it. The scars that destroy the snail shell near its center mean that the crab tried and failed to eat the snail when it was small, and therefore was a weaker predator. Conversely, if the size of the attack was larger at a sample site, it means that the crabs were better predators. Barclay found that the size during the attack remained relatively unchanged despite the long period of time, suggesting that the reduction in scars today was due to a reduction in the number of crabs rather than a change in the effectiveness of crab hunting. The result is consistent with previous estimates and anecdotal reports suggesting that crab populations are declining. “I was very happy to see that this is additional information that could support the story we are already hearing about crabs,” says Barclay. “This study is useful evidence that perhaps we should manage these fishing activities a little better.” Given how easy it is to study the signs of snails, Barclay hopes the method could be used by local science teams or groups of citizens interested in tracking crab populations. “I think this kind of approach is really important and not widely used,” says Tyler. “We have to pay attention to this method, which is really economical [and] which can give us some really important data “. This article is from Hakai Magazine, an online publication on science and society in coastal ecosystems. Read more stories like this at hakaimagazine.com. Similar stories from Hakai Magazine: • The Queen Shell’s Gambit • The Oregon tidal ecosystem is nearing a tipping point Animals California Fossils Mollusks, Worms, Sponges, Starfish Oceans suggested videos
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