Out-of-season spawning of sea urchins in indoor aquaculture settings

Abstract

This study documented a spontaneous out-of-season spawning event of the purple sea urchin Heliocidaris crassispina in an indoor aquaculture laboratory maintained at 24.6 °C with a 12:12 light–dark cycle. On the afternoon of 8 January 2024, 3 days prior to the new moon, three female and four male sea urchins spontaneously spawned for 1.5 hours. This spawning event occurred 2 months earlier than the known spawning period of H. crassispina in Hong Kong. The eggs were successfully fertilised confirming gamete fertility. These findings provided additional insights into the timing and reproductive plasticity of H. crassispina in controlled environments, highlighting the potential of such indoor systems for broodstock conditioning and gamete production in sea urchin aquaculture.