Marine biology: Sea stars (starfish).

This diagram is from Wiki -Asterias diagram 1 Pyloric stomach 2 Intestine 3 Rectal gland 4 Stone canal 5 Madreporite 6 Pyloric duct 7 Pyloric cecum 8 Cardiac stomach 9 Gonad 10 Ambulacral plates 11 Ampullae

image from Pinterest

~Sea stars, commonly called Starfish are not really fish at all.  Fish have gills, scales, and fins and sea stars do
not.  Sea stars also move differently than fish do.  Sea stars have tiny tube feet which helps them move.  They belong in the phylum Echinodermata which  simply means spiny skin. 

~This phylum includes sea urchins, sea cucumbers, and sand dollars.  Sea stars can vary in colors including blue, red, yellow, orange, and purple, and they can also vary in shapes and sizes.  

sunflower starfish-image from the web

~For the most part, sea stars have five arm-like limbs that extend outward making them resemble a star.  There are, however, a few sea stars that have more limbs like the twently-rayed sunflower star.  These sunflower starfish can have up to 40 limbs.  Youtube video of a sunflower starfish.

~Did you know if a sea star loses a limb, it can regenerate?  Yep, if one breaks off another will grow in its place.  This is helpful if the sea star is being threatened by a predator.  The majority of their organs are also in their arms.  

~Sea stars do not have blood.  Instead sea stars have a water vascular system which allows them to pump sea water through its sieve plate into its tube feet.

~sea stars have two stomachs.
~a cardiac stomach eats the food outside of the sea star's body and the food is then transferred to the pyloric stomach.
~sea stars eat bivalves such as clams and mussels. They also eat snails, barnacles, and small fish.
~sea stars have microscopic eyes at the end of each limb.
~sea stars can change their gender, when it is time to lay eggs, a male sea star can turn into a female sea star and lay eggs to increase their population.  A sea star can lay up to one million eggs at a time.
~sea stars are brainless-(some humans are too so not big deal).
~if a sea star gets cut, each piece can become a new sea star.

~a few different types of sea stars:
*Common starfish
*Horned starfish
*Blue starfish
*Ochre starfish
*Carpet starfish
*Eleven-armed starfish
*Chocolate chip starfish
*Comb starfish

~We attempted this dissection with the sea star in our kit, and I have to say, these little guys are a lot different than I had imagined them to be on the inside.
Our dissection pics.

The specimen-stinks!

The instructions said to cut one of the limbs off and open it up. 

Another shot of the amputated limb.

This is a shot after the limb amputation.  This is the underside of the sea star cut open.

I have to say again, this dissection was interesting.  I was expecting something completely different.  The insides of the sea star were soft and the internal structure looked very complex.  Interesting!

Marine bio
Sea star dissection help.
Animal planet