Jellyfish Oocyte Maturation Inducing Hormone And Neuroendocrine Regulation Of Reproduction

Oocyte meiotic maturation is a critical process for all sexually reproducing animals, and its core cytoplasmic regulators are highly conserved between species. In contrast, the few known Maturation Inducing Hormones (MIHs) that act on oocytes to initiate this process have highly variable molecular natures and their evolutionary relationships are poorly understood. Using hydrozoan jellyfish species that spawn in response to opposite light cues we identified from gonad transcriptomes specific amidated tetrapeptides that directly induce maturation of isolated oocytes at nanomolar concentrations. Antibody preabsorption experiments conclusively demonstrated that these PRPamide-related neuropeptides account for endogenous MIH activity. We further showed that they are synthesized by gonad neural cells, are released following dark-light or light-dark transitions, and act on the oocyte surface. Furthermore, they are produced by male as well as female jellyfish and trigger both sperm or egg release, suggesting a role in spawning coordination. We propose an evolutionary link between hydrozoan MIH and the neuropeptide hormones that regulate reproduction upstream of MIH release in bilaterian species.