Lifestyle and habitat Sand dollar

a sand dollar digging sand on playa novillero beach @ low tide on pacific coast of mexico




cilia on underside of sand dollar on beach @ hilton head island, south carolina

sand dollars live beyond mean low water line on top of or beneath surface of sandy or muddy areas. spines on flattened underside of animal allow burrow or creep through sediment. fine, hair-like cilia cover tiny spines. podia line food grooves move food mouth opening, in center of star-shaped grooves on underside of animal (called oral surface). food consists of crustacean larvae, small copepods, diatoms, algae , detritus.

on ocean bottom, sand dollars found together. due in part preference soft bottom areas, convenient reproduction. sexes separate and, echinoids, gametes released water column , conceived external fertilization. nektonic larvae metamorphose through several stages before skeleton or test begins form, @ point become benthic.

in 2008, biologists learned sand dollar larvae clone mechanism of self-defense. cloning asexual reproductive mechanism, cost borne larva both in resources in development time. larvae have been observed undergo process when food plentiful or temperature conditions optimal. has been suggested cloning may occur make use of tissues lost during metamorphosis. recent research has shown larvae of sand dollars clone when detect predators (by sensing dissolved fish mucus). larvae exposed mucus predatory fish respond threat cloning themselves, doubling numbers while halving size. smaller larvae better able escape detection fish, may more vulnerable predation smaller animals, such pelagic , planktonic larval stages of crustaceans.

sand dollars in mature form have few natural predators, though ocean pouts , sunflower starfish known eat them on occasion.