Fig. 2

Graphical representation of the standalone system used for egg incubation. a The opaque conocylindrical PVC tank has a water inlet at the top (blue arrow), which creates a circular current and delivers seawater at an exchange rate of 3 L min^− 1. A mechanical filter (1 mm mesh size) is placed at the bottom of the tank in the water outflow. An O. vulgaris egg string is attached to a glass rod and placed on the lateral side of the tank, where it moves constantly by a gentle current generated by the water inflow. The blue arrows indicate the water flow (from top to bottom) and the red horizontal bars indicate the water level. b The standalone system consists of 10 conocylindrical tanks placed on top of a reservoir. Artificial seawater is aerated by the strong water flow pouring into the biological filter in the reservoir and is sterilized by an external UV filter (details provided in Methods section). The total volume in the system is 100 L.