In fossil shark poop, Brazilian scientists found the oldest parasite ever found in a vertebrate. It seems that tapeworms have been looking for vertebrate organs since the Permian.
In São Gabriel, in the south of Brazil, a group of scientists made a remarkable discovery. In an area of 100 by 30 meters they dug up 500 coprolites, or fossilized turds. The turds come from the Permian. In one of the feces, the research team saw the eggs of a tapeworm species, in addition to fish scales and pieces of bone. The latter is very special, never before have such ancient remains of a parasite been found. One of the eggs shows the advanced development of a larva. The turd is estimated to be 270 million years old.
Cartilage fish
The unusual coprolite is five centimeters long, two centimeters in diameter and has the typical shape of the excrement of a cartilaginous fish, in this case a shark. Based on these eggs, the researchers cannot say which tapeworm species it is, but the shape and size are strongly reminiscent of the Tetraphyllidea, an order that contains 540 species.
Cartilaginous fish have different types of parasites in their spiral intestines. Tapeworm species in particular often seek out the organs of a shark or ray. When one of the segments of the worm's body is full of eggs, it breaks down in its host's stomach or intestines. This is where the eggs mature and hatch. They leave the body of their host through the excrement.
The hosts of a tapeworm
Tapeworms need different hosts to complete their development. The first is often an invertebrate. If a second host, such as a frog, fish or reptile, eats the first, development continues. By the time a third, and final, host eats the second, the tapeworms reach the adult stage. The turd studied contained fish scales and bones, indicating that the second host was probably a fish.
The conditions in which the droppings were left were ideal for the spread of parasites. 270 million years ago, the site was probably a freshwater pool where fish were crowded together during a dry period. The scientists base this on the fact that many different coprolites were found in a small area and on the discovery that there was virtually no oxygen at the bottom of the pool. The latter can be seen because the coprolites contain pyrite. Moreover, the turds could not have been preserved so well if there had been a lot of oxygen present.