Noun | 1. | ![]() invertebrate - any animal lacking a backbone or notochord; the term is not used as a scientific classification water vascular system - system of fluid-filled tubes used by echinoderms in locomotion and feeding and respiration Echinodermata, phylum Echinodermata - radially symmetrical marine invertebrates including e.g. starfish and sea urchins and sea cucumbers ambulacrum - one of the five areas on the undersurface of an echinoderm on which the tube feet are located brittle star, brittle-star, serpent star - an animal resembling a starfish with fragile whiplike arms radiating from a small central disc basket fish, basket star - any starfish-like animal of the genera Euryale or Astrophyton or Gorgonocephalus having slender complexly branched interlacing arms radiating from a central disc sea urchin - shallow-water echinoderms having soft bodies enclosed in thin spiny globular shells crinoid - primitive echinoderms having five or more feathery arms radiating from a central disk holothurian, sea cucumber - echinoderm having a flexible sausage-shaped body, tentacles surrounding the mouth and tube feet; free-living mud feeders tube foot - tentacular tubular process of most echinoderms (starfish and sea urchins and holothurians) having a sucker at the end and used for e.g. locomotion and respiration |