Self-recognition (allorecognition) is abundant in the natural world where it regulates diverse behaviors of myriad social interactions, including mating behaviors and predator-prey dynamics. Perhaps the most striking example of self-recognition is found in organisms with the capability to harm or even kill their relatives, whereby it is fundamental to prevent cannibalism of kin. Despite the prevalence of self-recognition behaviors, many examples have only been described in non-model species currently lacking the necessary molecular, neurological, and evolutionary tools required to fully investigate these systems and the associated mechanisms. Furthermore, self-recognition behaviors often act at the interface between neurobiology and immunology, making exploration of the behavioral processes additionally complex.
To overcome these challenges, we explore the self-recognition system evident in the omnivorous roundworm, Pristionchus pacificus. This nematode has evolved teeth-like denticles and is capable of both feeding on bacteria and killing other nematode larvae, including those of its more famous cousin Caenorhabditis elegans. However, while P. pacificus kills other nematode species and strains, remarkably, it does not kill its own progeny; we therefore investigate this self-recognition system which protects the offspring from the predatory parent. Firstly, we are identifying the signals transmitted by P. pacificus to indicate self and prevent attack by their relatives. Secondly, we are elucidating the receptors and circuits behind the killing decision and which distinguish between foreign and self-progeny. Lastly, we are understanding the evolution of these processes by utilising a worldwide representation of P. pacificus from a vast library of strains, many of which display strong killing interactions with each other.