External Anatomy Of Starfish

Arms or rays. Most starfish have five arms however some have more or less.

Bay Nature Sea Star Bodies Are Wildly Different From Our Own

In this article we will discuss about asterias starfish 1.

External anatomy of starfish. Most species have five arms or rays radiating from a central disk although several species have six or more arms. These are the five extensions that you see projecting from the middle of the starfish. Others eg blood stars have spines so small that their skin appears smooth.

Asteris arm microscopic xs. Close up of madreporite and stone canal. Dorsal view of a dissected starfish showing pyloric cecum and pyloric ducts.

Using your diagram sheets and the pictures below to locate the following structures and note their functions. A 2014 analysis of 219 genes from all classes of echinoderms gives the following phylogenetic tree. Sea stars are composed of a central disc from which arms sprout in radial symmetry.

Some sea stars like the crown of thorns starfish have large spines. Sea stars are invertebrates and organisms with no head but tube feet and arms where they can sense as well as see. These five arms or more can regenerate them as long as the central disk is not affected.

Respiratory and excretory system 12. Water vascular system 9. Starfish are deuterostome animals like the chordates.

Others eg blood stars have spines so small that their skin appears smooth. The times at which the clades diverged is shown under the labels in millions of years ago mya. Ventral view of starfish showing external anatomy.

Dorsal view of a dissected starfish showing gonads and ampullae. Habit and habitat of asterias 3. They have radial symmetry and an oral surface as well as aboral with the arms and disk covered with spikes.

Place the starfish on your dissection tray with its aboral surface facing upward. History of asterias 2. Start studying starfish anatomy externalinternal.

External anatomy starfish express pentamerism that is pentaradial symmetry. Learn vocabulary terms and more with flashcards games and other study tools. Dissection showing where cardiac stomach opens into the mouth.

In fact some starfish can have different numbers of arms even within one species.

Starfish Anatomy Worksheet Google Search Starfish Sea