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General Zoology Handout Lab 8 Exercise 16: Phylum Echinodermata Echinoderms are a deuterostome group. This is an all-marine phylum that is strikingly different from any other animal group. They have radial symmetry like cnidarians. Echinoderms have a dermal endoskeleton of calcareous plates and spines. They have a water-vascular system for locomotion and food gathering. Many echinoderms rely on dermal branchiae (skin gills) to breathe. Class Crinoidea: sea lilies and feather stars; anus on oral surface; five branching arms with pinnules; tentacle-like tube feet for food collecting; no pincher-like pedicellariae. See fossil in rock Class Asteroidea: Star shaped with arms not sharply marked off from the central disc; tube feet, often with suckers, on oral side. Top is referred to as the aboral side; pedicellariae present *** Obtain a starfish from the bucket. Using your manual (Fig. 16-3 & 16-4) familiarize yourself and sketch the following: madreporite, arms, spines, mouth, gonads, pyloic ceca, pyloric stomach, cardiac stomach, anus, ambulacral ridge, tube feet, spine, ring canal, radial canal, lateral canal and ampulla. Class Ophiuroidea: brittle stars and basket stars; star shaped with arms sharply marked off from central disc; tube feet without suckers and not used for locomotion; pedicellariae absent *** Look at the preserved specimens. Class Echinoidea: Sea urchins, heart urchins and sand dollars; disc shaped with no arms; compact skeleton; tube feet with suckers; pedicellariae present *** Look at the sand dollars and the sea urchins in the lab. Sea urchin shell is referred as a test. Mouth is surrounded by chewing mechanism called Aristotle’s Lantern. Class Holothuroidea: Sea cucumbers; no arms; spines absent; anus present; tube feet with suckers; pedicellariae absent *** Look at the sea cucumbers.