Lousy with Success: Genetics Reveal Fossil Lice as Evolutionary Champions [Slide Show]
Lice lineages began to split and diversify during the late Cretaceous, when dinosaurs, birds and early mammals probably were on the resilient parasites' menus
![Lousy with Success: Genetics Reveal Fossil Lice as Evolutionary Champions [Slide Show]](https://www.scientificamerican.com/sciam/cache/file/2EC59B26-CFDD-450C-B97ADD151D2E94AC.jpg?w=590&h=393)
Lousy with Success: Genetics Reveal Fossil Lice as Evolutionary Champions [Slide Show]
- MIND CONTROL: Not all prehistoric parasites simply made homes in their hosts. A particular kind of fungus took over the minds of its victims in order to continue its life cycle, and still does today. Ophiocordyceps is a fungal parasite that causes ants to climb high into the forest canopy and clamp down hard on leaves just before dying, after which the fungus bursts out of the corpses to rain spores on new live victims below. Thanks to distinctive marks left on a fossil leaf by ants under the influence of such a parasite, in 2010 entomologists David Hughes of The Pennsylvania State University, Torsten Wappler from the University of Bonn and Conrad Labandeira of the University of Maryland, College Park, were able to demonstrate that Ophiocordyceps-like fungi have been creating zombie ants for over 48 million years. Conrad Labandeira
- TYRANNICAL TRICHOMONAS A Tyrannosaurus rex whose fossilized frame is now affectionately known as "Sue" may have been one of the biggest and baddest carnivorous dinosaurs of all time, but she may have met her doom because of parasitic microorganisms. Smooth-walled lesions in Sue's lower jaw—as well as the jaws of many other tyrannosaur specimens—are consistent with damage the microscopic protist Trichomonas gallinae creates today in the jaws of some modern birds (which themselves are living dinosaurs, evolutionarily speaking). Although not immediately fatal, the ulcers and lesions the microorganism created would have prevented Sue from feeding properly—the great predator may have even starved to death. Further evidence that tyrannosaurs bit each other on the face and cannibalized the corpses of their own kind suggests that this devastating parasite could have spread easily from one tyrant to another. Chris Glen/PLoS One
- CLUES IN DINO-DUNG: The gastrointestinal tract of one carnivorous dinosaur was home to at least three types of prehistoric parasite. The fossilized dung of this early Cretaceous theropod found in Belgium bears evidence, in fact, of varieties that still afflict organisms today—cysts of the protozoan Entamoeba, eggs from nematode roundworms, and eggs from trematode flatworms. How these parasites affected their hosts is unknown, but their discovery, made in 2006 by entomologist George Poinar and paleontologist Arthur Boucot, both of Oregon State University, opens up the possibility that other little surprises may await scientists who take a closer look at fossil feces in the future. George Poinar
- NUTRIENT THIEVES: Platyceratid snails were such sneaky parasites that, until recently, paleontologists were unsure whether they were truly parasites or not. Researchers typically find the fossil gastropods on the stalks of frond-shaped cousins of sea stars called crinoids. For decades the reason why the snails attached themselves to the crinoids was a mystery, but then in 2002 University of Michigan at Ann Arbor paleontologist Tomasz Baumiller and Forest Gahn of Brigham Young University–Idaho recognized that all the host crinoids had stunted growth. The snails were stealing nutrients directly from the crinoids, with each snail species becoming adapted to suck resources from particular hosts. In this image the snail Platyceras is attached to the crinoid Corocrinus calypso. Joe Koniecki and Tomasz Baumiller
- A BEAUTIFUL DEFENSE: Around the same time that early fish were playing host to a variety of arthropods and worms, archaic, coil-shelled cephalopods called ammonoids also had some unwelcome houseguests. Tiny trematode worms made themselves comfortable in the cephalopods' shells, but the ammonoids had a unique defense. The irritation that the worms caused the bodies of the soft-bodied hosts spurred shell growth, encasing the invaders inside prehistoric pearls. In turn, these pearls left depressions and imprints on internal casts of ammonoid shells, like those in the shell of Sellanarcestes (pictured). Kenneth De Baets
- PARASITE EXPLOSION: Some of the oldest signs of parasites found among vertebrates date back to the Devonian period between 400 million and 360 million years ago. Fossils recovered from Estonia, Latvia and western Russia show that early, armored fish were beset by a variety of tiny nibblers. Although the bodies of the parasites have not been found, they left distinctive boreholes and other marks in the bony body armor of fish like the jawless Psammolepis, the heavily-armored Bothriolepis and, one of our own very distant cousins, the lobe-finned fish Eusthenodon. The patterns of damage are similar to those left by living trematode flatworms and some parasitic arthropods called copepods (like the modern species Lepeophtheirus pectoralis pictured above), meaning that many types of parasitical invertebrates had the jump on fishy hosts very early on. Hans Hillawaert/Wikipedia
