E. pusillus has separate sexes and fertilization takes place externally. The breeding season is in the summer months. The larvae are pelagic. They are characterized by a body skeleton forming a basket-like structure (Mortensen, 1927; Fish & Fish, 1989). E. pusillus is a deposit-feeding clypeasteroid. lts gut content includes sediment, remains of plants and bottom material (detritus), and infauna, especially foraminiferans. E. pusillus is eaten by fish, especially by dab and haddock (Mortensen, 1927; De Ridder & Lawrence, 1982; Fish & Fish, 1989).