The echinoderm with long spines
belongs to the class Echinoidea which includes sea urchins, heart urchins, cake
urchins and sand dollars. This spine serves as their protective mechanism from
predators. The spines are joined to the skeleton and muscles surround it. The muscles
enable them to swivel its spines from predators.
Embryonic stem cells can become all cell types of the body because they are pluripotent. Adult stem cells are thought to be limited to differentiating into different cell types of their tissue of origin. Embryonic stem cells can be grown relatively easily in culture.
The relationship between the two species is a symbiotic relationship.
