Download General Zoology Handout

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.