In the late period of the sea urchin eight wrist larvae, the sea urchin primordia is fully developed. Once the first five tubes are out of the body, this is an urgent signal that the larvae will become abnormal. At this time, the larvae should be migrated to the benthic diatom-attached tile. In the metamorphosis pool, the sea urchin larvae soon settled and the metamorphosis was completed in less than a day. After the metamorphosis, the juvenile sea urchins are adsorbed on the attachment base and feed on the above benthic diatoms. After that, they live for life.
The newly metamorphosed juvenile sea urchins have a shell diameter of only about 350 microns. At this time, benthic diatoms are sufficient to eat these tiny sea urchins. The original pond for the metamorphosis of sea urchin larvae is actually a bait cultivation pond for juvenile sea urchins. It should be noted that juvenile sea urchins are very sensitive to urea in seawater, and 5 ppm urea can cause a large number of juvenile sea urchins to die. The difference in the growth rate among individuals of juvenile sea urchin is very large. One month after metamorphosis, the large shell diameter reaches 3 mm and the small one is less than 1 mm. When the juvenile sea urchin shell diameter reaches 3-5 mm, other multicellular algae can be eaten. At this time, the juvenile sea urchin has fully developed to the stage of young sea urchins.
The newly metamorphosed juvenile sea urchins have a shell diameter of only about 350 microns. At this time, benthic diatoms are sufficient to eat these tiny sea urchins. The original pond for the metamorphosis of sea urchin larvae is actually a bait cultivation pond for juvenile sea urchins. It should be noted that juvenile sea urchins are very sensitive to urea in seawater, and 5 ppm urea can cause a large number of juvenile sea urchins to die. The difference in the growth rate among individuals of juvenile sea urchin is very large. One month after metamorphosis, the large shell diameter reaches 3 mm and the small one is less than 1 mm. When the juvenile sea urchin shell diameter reaches 3-5 mm, other multicellular algae can be eaten. At this time, the juvenile sea urchin has fully developed to the stage of young sea urchins.