Sand Dollar

Sand Dollar

Scientific name: Echinarachnius parma

Phylum: Echinodermata

Class : Echinoidea

Description: Sand dollars are flat and round with a 5-petaled pattern of tiny holes (petaloids). They are covered in a fealt-like coating of fine spines which ranges in colour from brownish to tinted purple to red.

Distribution: They are found mostly in sub-tidal to more than 792m deep on sandy bottoms, but also in lower in the inter-tidal zone in bays and on ocean beaches.

Locomotion: Some sand dollars bury themselves completely, but most of them keep part of the body above the surface. Burrowing and crawling are accomplished largely by the action of short movable spines.

Food gathering: Sand dollars are detritus and particulate feeders, commonly eating diatoms. As they plow through sand, a layer of sediment passes over the aboral surface. Small particles are trapped by a mucus coating and are moved by ciliary action to the body edge where podia pass particles to food grooves. What is more, digestion is by way of a simple tube extending from mouth and anus.

Gas exchange: Sand dollars bear highly modified podia on aboral petaloids that serve as the main gas exchange surface.

Reproduction: The sexes are separated, with eggs being fertilized externally. Brooding embryos are held on the petaloids, and there is a free-swimming larval stage.


Sanddollar eparma02 eparma field


OSC Research

Mercier Lab - Research on reproduction, larval development, ecology and growth is carried out on a wide variety of marine invertebrates in this lab.