Paula C. Dentzien-Dias

ScienceShot: A 270-Million-Year-Old Tapeworm Infection

As a lifestyle, parasitism obviously works. Long before our human ancestors crawled down from the trees, freeloading bloodsuckers were already making themselves at home within the guts and veins of primitive vertebrates. These tenacious little pests arrived on the scene at least 270 million years ago—140 million years earlier than previous records of intestinal parasites—according to new evidence uncovered by chance in the fossil record. While examining fossilized shark feces (main picture) collected from southern Brazil, researchers noticed a strange cluster of oval-shaped objects. Taking a closer look, they realized they had found a tapeworm egg case bearing an uncanny resemblance to those produced by modern pests today. The eggs featured operculums (indicated by the blue arrows in inset), or small teapot lid-like flaps characteristic of tapeworm eggs, which helped the researchers identify the finding. Such discoveries, they write in PLOS ONE, are exceptionally rare; the older the fossil, the less chance of finding signs of the tiny, fragile parasites that may have once colonized it. The "amazing" new specimen contains 93 tiny eggs, they write, each measuring about the same width as a human hair. Some of the eggs appear swollen, suggesting that they still contain the makings of ancient tapeworm babies. One of the eggs even holds what appears to be a developing larva. The egg case ranks as the earliest known evidence of tapeworm parasitism in vertebrates, indicating that this particular parasite has been plaguing fellow animals since the days of the massive supercontinent Pangaea. And more likely than not, it will stick around for millennia to come.

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