By Strain, Daniel
Science News , Vol. 179, No. 13
Animals living more than 550 million years ago could have survived inhospitable oceans by associating with dense mounds of cyanobacteria called microbial mats, an international team of researchers argues. Such clumps of oxygen-producing gunk may have supplied the first mobile animals with food to eat and air to breathe, the group reports online May 15 in Nature Geoscience.
Recent fossil finds show that wriggling animals first emerged at least 555 million years ago, when atmospheric oxygen concentrations were about one-tenth what they are today. Yet as creatures moved more, they needed more oxygen. So how early mobile critters, which probably resembled worms or slugs, eked out a living in these choked environments has been a big puzzle for paleontologists, says study coauthor Murray Gingras. "Biomats provided the oxygen that ironically enabled the animals to better exploit biomats as food," he says.
He got his first clue after drilling into a frozen pond in Alberta, Canada. The pond, almost entirely deprived of oxygen, hosted a small number of insect larvae surrounding a layer of photosynthesizing algae. "They were eating the biological material, and they were using it as a scuba tank at the same time," says Gingras, a paleontologist at the University of Alberta in Edmonton.
Alberta's frozen lakes don't look much like ancient oceans, however, so Gingras and his colleagues turned to supersalty lagoons in Venezuela. …