I found this citation in the Wikipedia page on "Ouroboros"
> Soto-Andrade, Jorge, Sebastia Jaramillo, Claudio Gutierrez, and Juan-Carlos Letelier. "Ouroboros Avatars: A Mathematical Exploration of Self-reference and Metabolic Closure". "One of the most important characteristics observed in metabolic networks is that they produce themselves. This intuition, already advanced by the theories of Autopoiesis and (M,R)-systems, can be mathematically framed in a weird-looking equation, full of implications and potentialities: f(f) = f. This equation (here referred to as Ouroboros equation), arises in apparently dissimilar contexts, like
Robert Rosen's synthetic view of metabolism, hyper set theory and,
importantly, untyped lambda calculus. ... We envision that the ideas behind this equation, a unique kind of mathematical concept, initially found in biology, would play an important role in the development of a true systemic theoretical biology."