Clytia sp. IZ-D, a newly identifed jellyfish species from Izushima Island, on the Pacific coast of Japan. Life-cycle diagram (top left) and images of each stage (top ight; a–f) of Clytia sp. IZ-D, which is morphologically very similar to the model species Clytia hemisphaerica. Magenta arrows in the gonozoid cartoon (c) indicate individual medusa buds. Arrows in the mature female medusa photo (e) point to the four gonads in the subumbrella. Bottom: Illustration of spawning regulation in Clytia sp. IZ-D. This species spawns every evening, unlike the closely related C. hemispharica, which spawns in the morning. Surprisingly, in both cases, it is sunrise, not sunset, that provides the temporal cue for spawning. In Clytia sp. IZ-D at 21°C, spawning occurs 14 hours after sunrise, regardless of sunset timing. A further surprise is that a 20-hour spawning rhythm is maintained even under constant light. Such autonomous circadian gamete release has not previously been reported in cnidarians (jellyfish, corals, or sea anemones). Future molecular studies using this Clytia species are expected to shed light on the mechanisms underlying light-controlled reproduction in marine organisms. Illustration by Ruka Kitsui.
#Jellyfish rely on light cues to help time their #gamete release. @momotsuyo.bsky.social &co reveal an additional autonomous #circadian mechanism that synchronizes gamete release, entrained to a 24-hr period by dark-to-light transition @plosbiology.org 🧪 plos.io/4btAwpY
