RT Journal Article SR Electronic T1 A gonad-expressed opsin mediates light-induced spawning in the jellyfish Clytia JF bioRxiv FD Cold Spring Harbor Laboratory SP 140210 DO 10.1101/140210 A1 Gonzalo Quiroga Artigas A1 Pascal Lapébie A1 Lucas Leclère A1 Noriyo Takeda A1 Ryusaku Deguchi A1 Gáspár Jékely A1 Tsuyoshi Momose A1 Evelyn Houliston YR 2017 UL http://biorxiv.org/content/early/2017/12/03/140210.abstract AB Across the animal kingdom, environmental light cues are widely involved in regulating gamete release, but the molecular and cellular bases of the photoresponsive mechanisms are poorly understood. In hydrozoan jellyfish, spawning is triggered by dark-light or light-dark transitions acting on the gonad, and is mediated by oocyte maturation-inducing neuropeptide hormones (MIHs) released from the ectoderm. We determined in Clytia hemisphaerica that blue-cyan light triggers spawning in isolated gonads. A candidate opsin (Opsin9) was found co-expressed with MIH within specialised ectodermal cells. Opsin9 knockout jellyfish generated by CRISPR/Cas9 failed to undergo oocyte maturation and spawning, a phenotype reversible by synthetic MIH. Gamete maturation and release in Clytia is thus regulated by gonadal photosensory-neurosecretory cells that secrete MIH in response to light via Opsin9. Similar cells in ancestral eumetazoans may have allowed tissue-level photo-regulation of diverse behaviours, a feature elaborated in cnidarians in parallel with expansion of the opsin gene family.