May 26, 2016 by Julie Cohen
Vampires are real, and they've
been around for millions of years. At least, the amoebae variety has. So
suggests new research from UC Santa Barbara paleobiologist Susannah Porter.
Using a scanning
electron microscope to examine minute fossils, Porter found
perfectly circular drill holes that may have been formed by an ancient relation
of Vampyrellidae amoebae. These single-celled creatures perforate the walls of
their prey and reach inside to consume its cell contents. Porter's findings
appear in the Proceedings of the Royal Society B.
"To my knowledge these holes
are the earliest direct evidence of predation on eukaryotes," said Porter,
an associate professor in UCSB's Department of Earth Science. Eukaryotes are
organisms whose cells contain a nucleus and other organelles such as
mitochondria.
"We have a great record of
predation on animals going back 550 million years," she continued,
"starting with the very first mineralized shells, which show evidence of
drillholes. We had nothing like that for early life—for the time before animals
appear. These holes potentially provide a way of looking at predator-prey
interactions in very deep time in ancient microbial ecosystems."
Porter examined fossils from the
Chuar Group in the Grand Canyon—once an ancient seabed—that are between 782 and
742 million years old. The holes are about one micrometer (one thousandth of a
millimeter) in diameter and occur in seven of the species she identified. The
holes are not common in any single one species; in fact, they appear in not
more than 10 percent of the specimens.
"I also found evidence of
specificity in hole sizes, so different species show different characteristic
hole sizes, which is consistent with what we know about modern vampire amoebae
and their food preferences," Porter said. "Different species of
amoebae make differently sized holes. The Vampyrellid amoebae make a great
modern analog, but because vampirelike feeding behavior is known in a number of
different unrelated amoebae, it makes it difficult to pin down exactly who the
predator was."
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