Phylum Hemichordata, Acorn Worms

Phylum Chordata, Subphylum Hemichordata

Acorn Worms

Acorn worms are related to the vertebrates since they possess a notochord but there are no vertebral bones. There is a collar-like structure at the head which makes them easy to distinguish from other worm phyla. They are burrowing forms that leave coils of sand at the surface. A food source for many mollusks and fishes.

HAWAII

Ptychodera flava

Kaneohe Bay, Oahu, 10 feet
Paiko, Oahu, 1 foot	Makua, Oahu, 30 feet
Kaneohe Bay, Oahu, 3 feet

YELLOW ACORN WORM

A common buried species on sand flats. Expels coil of sand as it feeds. Preyed upon by fishes, cones, and auger shells. Attains at least 8 inches. A much larger form occurs in deep water but may not be the same species. Hawaii, Indian Ocean to the Galapagos.