Sand dollars reproduce sexually and asexually. Female sand dollars distribute eggs into the ocean water as males hover nearby. The male sand dollar expels sperm over the eggs to fertilize them. The fertilized eggs float out to sea, develop into larvae and eventually settle at the bottom of the sea where they continue their life cycle.
Sand dollars are marine invertebrates that belong to the echinoderm family. This family also includes brittle stars, sea urchins and sea cucumbers. Spiny echinoderms, such as starfish and urchins, can reproduce asexually by rejuvenating, or reproducing damaged limbs and spines. Since sand dollars are rounded animals with no spiny arms, they can rejuvenate damage done to their body structure asexually. Male and female sand dollars are identical with no distinguishable markings to identify their sex.
Researchers at the US National Library of Medicine report that larvae of the sand dollar Dendraster excentricus clone when predators are nearby. This means that sand dollar larvae have the ability to reproduce asexually when threatened in an attempt to protect and propagate their species. Cloned larvae are much smaller in size than their original counterparts, making them difficult for predators to detect. In order for larvae to clone, their environmental conditions must be favorable for growth and reproduction.