All metazoan animals synthesize in large quantities a tiny number of highly conserved, specialized proteins as provisions of nutrients to their progeny. These include vitellogenins (Vtg), the precursors of yolk proteins (YP) that are deposited in the eggs of nearly all oviparous animals (Sun & Zhang, 2015). In viviparous mammals, which have no Vtg genes (Zhou et al., 2021), this functional role is taken up in a sense by casein, the major protein component of milk.Interestingly, unlike casein proteins, Vtgs are not merely nutrients