External Anatomy Of Starfish

A 2014 analysis of 219 genes from all classes of echinoderms gives the following phylogenetic tree. External anatomy starfish express pentamerism that is pentaradial symmetry.

Starfish Wikipedia

Others eg blood stars have spines so small that their skin appears smooth.

External anatomy of starfish. Most starfish have five arms however some have more or less. The times at which the clades diverged is shown under the labels in millions of years ago mya. Learn vocabulary terms and more with flashcards games and other study tools.

Dissection showing where cardiac stomach opens into the mouth. Start studying starfish anatomy externalinternal. Arms or rays.

Ventral view of starfish showing external anatomy. Sea stars are invertebrates and organisms with no head but tube feet and arms where they can sense as well as see. Close up of madreporite and stone canal.

In this article we will discuss about asterias starfish 1. Place the starfish on your dissection tray with its aboral surface facing upward. Using your diagram sheets and the pictures below to locate the following structures and note their functions.

Respiratory and excretory system 12. Asteris arm microscopic xs. Dorsal view of a dissected starfish showing pyloric cecum and pyloric ducts.

In fact some starfish can have different numbers of arms even within one species. Water vascular system 9. These are the five extensions that you see projecting from the middle of the starfish.

Habit and habitat of asterias 3. These five arms or more can regenerate them as long as the central disk is not affected. Most species have five arms or rays radiating from a central disk although several species have six or more arms.

Starfish are deuterostome animals like the chordates. Others eg blood stars have spines so small that their skin appears smooth. History of asterias 2.

Dorsal view of a dissected starfish showing gonads and ampullae. They have radial symmetry and an oral surface as well as aboral with the arms and disk covered with spikes. Some sea stars like the crown of thorns starfish have large spines.

Sea stars are composed of a central disc from which arms sprout in radial symmetry.

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