Meeting Abstract
Molecular and geochemical data suggest that the first animals evolved during a period of climate instability and limited ocean oxygenation. The hypothesis that sea sponges—the simplest living animals—predate a uniformly oxygenated ocean has gained support; there is growing evidence for “sponge” biomarkers ~650Mya, and some sponges can survive in extremely oxygen-poor environments. Much less is known about pelagic animals such as jellyfish and ctenophores, which appear to have evolved within a similar window of time as sponges. Here I present ongoing work on the jellyfish Aurelia, which provides new insight into the ways early animals might have survived on an inhospitable Earth. Firstly, molecular clocks and gene expression data derived from the Aurelia genome support the hypothesis that jellyfish diversified long before the Cambrian. Secondly, by studying growth and tissue regeneration in Aurelia, my colleagues and I have discovered a high level of developmental plasticity, which is primarily dictated by the amount of nutrition the animal can obtain. Some of these developmental strategies utilize extremely low levels of oxygen consumption. The results from this work suggest that pelagic, gelatinous animals may have been an important part of Neoproterozoic ecology. Additionally, this work shows how metabolic and respiratory information from early-branching animals could prove useful for calibrating both molecular clocks and geochemical proxies of Earth’s biosphere.
