Build me up to break me down: Frothed spawn in the sandpaper frog, Lechriodus fletcheri, is formed by female parents and later broken down by their offspring

Several genera of anuran amphibians deposit their eggs within mucous secretions that have been aerated by the parents to produce a foam or bubble spawn body. This is a dynamic medium for embryo development given that is gradually breaks down over time, and one that has been hypothesised to serve a variety of purposes including protecting embryos from external stresses. In this study, I provide additional details of bubble spawn production in the sandpaper frog, Lechriodus fletcheri. Field and laboratory observations showed that females aerate spawn while in inguinal amplexus, using flanged fingers to transport air bubbles into the mucous. While the frothed spawn is initially resistant to breakup, it gradually loses bubbles and flattens out into a film. This temporal shift in structure is likely to be adaptive, as the resultant increase in surface area allows embryos to come in direct contact with the open water, which may accommodate their increased oxygen demands or facilitate hatching. I provide evidence that this process is controlled by the residing embryos, given that spawn in their absence does not breakdown, highlighting the ability of offspring to modify their immediate environment even before hatching to ensure conditions remain suitable for their changing needs.