Question

Then why don't the parents of sea urchins take care of the young? [In fact the adults do in a way. After the embryo has grown large enough and metamorphosed into a young urchin they hide in the spines of the adults, living off of the scraps of food produced from the messy eating of the adults

Answer 1

•After fertilization, the zygote go through cell division and becomes embryo and becomes a blastula.

•In this stage, egg sac break up to reveal a group of cells covered in cilia that help the embryo swim.

•They can't swim well enough and .become part of the plankton and add a protein-rich component.

•The blastulas that aren't eaten continue to develop, starting with digestive systems.

•The embryo starts to elongate, moving into the larval phase, called pluteus, which continues to live with the plankton while he grows spiny structures on one side.

•The pluteus grows large enough to sink to the ocean floor. And start metamorphosis

•He normally has a bud starting to grow and this bud develops small spines and tube feet, continuing to grow.

•The bud grows into a miniature version of an adult sea urchin, disconnects from the now-defunct pluteus skeleton and starts his search for food.

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1.As the young one detached from parent in his embryonic condition and live on planktons . After proper metamorphosis , they again hide in the spine of adult in search of their food and protection from other enemy