Ectoparasitism is the phenomenon in which a parasite lives externally on a host. An ectoparasite usually has a mouth that can suck and pierce. It also often has organs that attach it to its host. Until recently, scientists have been dismayed by the scarcity of fossil ectoparasites.
The fossil of the fly larva Qiyia jurassica has been found among the rubble of China’s Daohugou rock beds, and described by Jun Chen from Linyi University in China and other international scientists in the journal eLife. All five specimens discovered were determined to have lived during the Middle Jurassic Period, about 165 million years ago. They comprise a tiny fraction of the 300,000 fossilized insects housed at two institutions devoted to nature in Nanjing.
Flies have independently evolved blood-sucking ability multiple times in history. They exist in three families of living Tabano-morpha, an unraked group of the order Diptera.
Qiyia is derived from the Chinese word for bizarre, because the insect fossils were quite distinctive. This is related to its likely status as being the “earliest known aquatic ectoparasitic insect.” Yet it certainly had the “efficient protein-digesting enzymes and salivary glands” characterizing all ectoparasitic fly larvae. These specifics allowed an easy shift to blood-sucking as an adult.
One of the aspects of this insect’s life that scientists could infer from its excellent preservation is that it did not travel far. This fly lived in an area without much energy – the Daohugou paleolake. No fish live in the Daohugou, however, there was a plethora of salamanders living in this area at the time of Qiyia jurassica. These salamanders lived in water throughout their entire lifespan. They had skin to which Qiyia jurassica could very well have attachedand infiltrated. The two are furthermore well-matched in size – the salamanders were approximately 500 mm and 150 mm long. Conclusively, the fly probably fed on the blood of these salamanders.
Adult water snipe flies also eat the blood of amphibians. Scientists assert that Qiyia jurassica had similar adaptations to today’s water snipe flies (family Athericidae). Nonetheless, its description fits no modern species.
The fossil ectoparasite was approximately 21 mm long. Its head was located on the thorax. It possessed the ability to greatly recede when necessary. An important part of any parasite is the sucker, or mouth. This was located near its head; it could extend a whole 2 mm! Suckers were not only used to fasten to hosts, but to abiotic material in the rapid water in which they these flies lived. Six ridges were additionally discovered sprouting from the center of its piercing-sucking mouth, detailed with tiny spines. This suggests that the slight head had restricted mobility. Far from being a disadvantage, researchers say that it made for capable attachment to, penetration of, and finally sucking of, the host’s blood. The sole extant (living) insect larvae that has similar suckers are not only miniscule in comparison, but have no ridges on the abdomen. Other aquatic parasitic organisms, such as the lamprey and leech, have similarly powerful suckers. An alternative form of aquatic parasitism involves burrowing into the body of the host, one such parasite being the anchor worm.
Mandibles, located near the mouth, were approximately half a millimeter long; they were used to eat or defend. Legs were found on the ridges of it’s thoracic sucker. These legs were surprisingly strong. They allowed for greater friction and suction, which increased the ability to move side to side and stay still. Scientists liken them to the “grooves in modern octopus suckers,” as well as ribs in suction cups.
The thorax was composed of three fused parts and was somewhat bloated, although less so than its abdomen. The abdomen consisted of eight sections, and was covered in stiff bristles. Researchers theorize that the bristles allowed the insect to move and stop itself underwater. It also had ten small projections on the end, similar to the urogomphi (horns at the tip of the abdomen) found in living water beetles; the abundance of these projections, according to scientists, means that they were used for breathing. There were also seven small prolegs on the abdomen. Prolegs are fleshy stubs found on the underside of most fly larvae. Its prolegs, and stiff hairs, or bristles, also functioned as adhering mechanisms. This allowed the parasite to stick to a host without killing it too rapidly.
Such an “extreme morphological specialization of fly larvae” represents a paradigm in the understanding of diversity in ancient insects.
Source: Chen, J., Wang, B., Engel, M. S., Wappler, T., Jarzembowski, E. A., Zhang, H., … & Rust, J. (2014). Extreme adaptations for aquatic ectoparasitism in a Jurassic fly larva. eLife, 3, e02844.
The Paleontological Research Institution, Ithaca, New York, is pleased to sponsor Paleontology content for This View of Life. Founded in 1932, PRI has outstanding programs in research, collections, and publications, and is a national leader in development of informal Earth science education resources for educators and the general public.
