Echinoderms, meaning “spiny skin”, are radial symmetric marine animals. They are found at all depths—both shallow and deep water. They play important roles in their ecosystems. Despite appearances, they do not have skeletons. The “spiny skin” is, in fact, skin covering a spiny endoskeleton (internal skeleton).
How do echinoderms move? How do they feed themselves?
Echinoderms have a water vascular system responsible for gas exchange, movement, and feeding. This system is an internal network of fluid-filled canals. Depending on the species, they have various ways of getting food into their water vascular systems. Some are filter feeders, while others (such as starfish) are predatory. They use this system in place of gills, heart, and a closed circulatory system. Although they do not have brains, they do have nerve nets responsible for receiving and processing sensory information.
What about their reproduction? They reproduce sexually—with sperms and eggs. Some species provide brainless parental care.
Here’s a super-short quick snippet about starfish:
Echinoderms are found worldwide, and play important roles in their environments. Primarily, they are strong links in the food chain. For example, they control the growth of algae on coral reefs (making it easier for the reefs to filter-feed), and they serve as food for other organisms (otters, for example).
Starfish Dissection
You can do this dissection at home! Here’s a very inexpensive starfish dissection guide and starfish specimen and simple dissection to
ols!
That is a sunflower sea star. Yes, they do eat other sea stars as well as sea urchins, clams, snails, abalone, sea cucumbers.
isnt the starfish in the middle video called a sunfish and it eats starfish???
That’s a sea urchin 🙂
what was the long spiny thing in the first video?
Starfish aren’t fish, right? Or are they?
Nope. These animals have five-axis symmetrical as adults, a water-vascular system, and an endoskeleton. Think starfish, sea urchins, sea cucumbers, and sea lilies.
Echinoderms don’t have eyes right?
Euell
Wow! Starfish have to be the coolest fish!
Until I went to the aquarium and touched one, I thought starfish were slimy!
Tamar
The video of the starfish and sea urchins reminded me of this awesome thing I found out about: this type of starfish called the crowned starfish, I think, destroys coral, therefore removing a type of sea urchin’s habitat. The sea urchins then actually then attack the starfish! This is actually vital to the world wide ecosystem, since the reef that this happened at was the Great Barrier Reef. They did a better job at removing the starfish than theses divers with knives did. Huzzah for urchins!