Phylum Echiura anterior flattened proboscis (=prostomium) (Spoon Worms) can be extended and retracted 140 species posterior cylindrical trunk sausage shaped worms Proboscis 1 cm to 50 cm has ciliated groove giving it a spoon-like all marine appearance most live in shallow waters; a few deep water forms proboscis is very mobile !many burrow in sand or mud sweeps on mud to find organic debris !other live in rock and coral crevaces can extend up to 10 times its retracted length eg. Bonellia is 7 cm (~3.5”) long and can extend its !a few live inside dead sand dollars, mollusc proboscis 1.5 meters (4.5’) shells, or annelid tubes no tentacles they enter shells when young and get too large to leave Trunk generally are deposit feeders trunk is gray, reddish brown, or rose Body Form body has several sets of setae cylindrical and somewhat sausage shaped !hooked, anterior setae used for digging resemble sipunculans in size and general habits burrows body in two parts: !setae at posterior end for anchorage Anials: Phylum Echiura; Ziser Lecture Notes, 2012.10 1 Anials: Phylum Echiura; Ziser Lecture Notes, 2012.10 2 Reproduction & Development ! circles of setae around posterior end for anchorage and burrow maintenance dioecious Feeding and Digestion show sexual dimorphism; most are deposit feeders males often much smaller collect small particles of detritus gametes shed into water digestive system is extremely long and coiled external fertilization mouth is at base of prostomium produces trochophore larva anus is at posterior end of trunk metamorphosis to wormlike adult Circulation Human Impacts simple closed circulatory system in arctic spoon worms were once eaten by eskimos Excretion excretion by nephridia Nervous System simple nervous system circumenteric nerve ring ventral nerve cord Anials: Phylum Echiura; Ziser Lecture Notes, 2012.10 3 Anials: Phylum Echiura; Ziser Lecture Notes, 2012.10 4 .