Research conducted by an Oregon State University scientist, George Poinar Jr., has shed light on a unique parasitic relationship between tiny worms known as nematodes and pseudoscorpions. The findings, published in Historical Biology, reveal that millions of years ago, nematodes were living inside and feeding on the outer protective layer of pseudoscorpions. This discovery is unusual as no other invertebrate-associated nematodes have been known to exhibit this specific behavior.
Pseudoscorpions, a type of arachnid that are smaller than scorpions and lack a stinger and tail, are a highly diverse lineage found in various habitats worldwide. They are known to be associated with a wide range of parasitic organisms, including nematodes. Nematodes, on the other hand, are among the most abundant animals on the planet, with some species living freely in water, soil, and the Earth’s crust while others parasitize plants and animals.
The fossil nematodes studied by Poinar exhibited well-developed spear-type structures known as stylets, which are used by the nematodes to pierce cells and extract food from the pseudoscorpion’s integument. Despite some limitations in observing certain characteristics of the nematodes, Poinar placed them in a collective group genus called Vetus, which was established for fossil nematodes that could not be linked to any known extant family. The age estimates of the Baltic amber in which the fossils were found vary widely, ranging from 23 million to 55 million years ago.
The uniqueness of the parasitic relationship between these nematodes and pseudoscorpions has sparked interest among researchers, and Poinar hopes that this study will prompt further investigation into the systematic placement of these nematodes. The discovery of these fossil nematodes in Baltic amber highlights the unusual nature of their parasitic associations and raises questions about the evolution of such behaviors. Further research is needed to uncover more details about these ancient relationships and the ecological implications they may have had in the past.