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"If reefs continue to decline at the current rate during this century, then a few thousand species of decapods are in real danger. They may adapt to a new environment without reefs, migrate to entirely new environments or, more likely, go extinct," says Adiël Klompmaker. (Credit: emmett anderson/Flickr)

corals

Coral reef decline could leave crabs homeless

Modern crustaceans, including shrimp, crab, and lobster, may follow their ancient ancestors into extinction if coral reefs continue to decline.

A new study shows a direct correlation between the number of prehistoric reefs and the number of decapod crustaceans.

The decline of modern reefs due to natural and human-influenced changes also could be detrimental, causing a probable decrease in the biodiversity of crustaceans, which serve as a vital food source for marine animals and people.

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“We estimate that earth’s decapod crustacean species biodiversity plummeted by more than 50 percent during a sharp decline of reefs nearly 150 million years ago, which was marked by the extinction of 80 percent of crabs,” says Adiël Klompmaker, a postdoctoral researchers at the Florida Museum of Natural History at the University of Florida.

“If reefs continue to decline at the current rate during this century, then a few thousand species of decapods are in real danger. They may adapt to a new environment without reefs, migrate to entirely new environments or, more likely, go extinct.”

Some scientists predict as much as 20 percent of the world’s reefs may collapse within 40 years, with a much higher percentage affected by the end of the century due to natural and human-influenced changes such as ocean acidification, diseases, and coral bleaching.

Published in the journal Geology, the study is the first comprehensive examination of the rise of decapod crustaceans in the fossil record.

Researchers created a database of fossils from the Mesozoic Era, 252 million to 66 million years ago, from literature records based on museum specimens worldwide, including 110 families, 378 genera, and 1,298 species.

They examined the patterns of diversity and found an increase in the number of decapod species was influenced by the abundance of reefs, largely due to the role of reefs as a provider of shelter and foraging.

Crab revolution

Researchers call this period the “Mesozoic decapod revolution” because of the 300-fold increase in species diversity compared with the previous period and the appearance and rapid evolution of crabs.

Compiling information about crustaceans on this scale has historically been a challenge for researchers because most decapods possess a fragile and weakly calcified exoskeleton that does not fossilize well.

“Only a scant fraction of decapod crustaceans is preserved in rocks, so their fossil record is limited,” says study co-author Michal Kowalewski, curator of invertebrate paleontology at the Florida Museum.

“But, thanks to efforts of paleontologists many of those rare fossils have been documented all around the world, finally giving us a chance to look at their evolutionary history in a more rigorous, quantitative way.”

“This new work builds a good case for the role of reefs in promoting the evolutionary diversification of crustaceans,” says David Jablonski, a paleontologist in the department of geophysical sciences at the University of Chicago who was not involved in the study.

“We have to take their argument for the flipside of that story very seriously. The positive relation between reefs and crustaceans implies that the damage caused to reefs by human activities—from overfishing to ocean acidification—is likely to have cascading consequences for associated groups, including crustaceans.”

The study could serve as an important springboard for future research, Jablonski says.

“It would be very interesting to extend this analysis into the Cenozoic Era, the 65 million years leading up to the present day. And it would be valuable to look at the spatial structure of the crustacean diversification, for example how closely their diversification was tied to the extensive reefs in the western Pacific and was damped in the eastern Pacific with their much sparser contingent of reefs.”

Researchers from Kent State University were co-authors on the study.

Source: University of Florida

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