Created By: Sarah Butler
Sea stars are purely marine animals, even using  sea water instead of blood to pump nutrients throughout their bodies
. Marine scientists have undertaken the difficult task of replacing the beloved starfish’s common name with sea star
because, well, the starfish is not a fish. It’s an echinoderm
, closely related to sea urchins and sand dollars.
There are some 2,000 species of sea star
living in all the world’s oceans, from  tropical habitats to the cold seafloor
. The five-arm varieties are the most common
, hence their name, but species with 10, 20, and even 40 arms exist.
They have bony, calcified skin
, which protects them from most predators
, and many wear striking colors that camouflage them
off potential attackers
. Purely marine animals, there are no freshwater sea stars, and only a few live in brackish water.
Beyond their distinctive shape, sea stars are famous for their ability to regenerate limbs, and in some cases, entire bodies
. They accomplish this by housing most or all of their vital organs in their arms
. Some require the central body to be intact to regenerate, but a few species can grow an entirely new sea star just from a portion of a severed limb.
Most sea stars also have the remarkable ability to consume prey outside their bodies
. Using tiny, suction-cupped tube feet, they pry open clams or oysters
, and their sack-like cardiac stomach emerges from their mouth and oozes inside the shell
. The stomach then envelops the prey to digest it
, and finally withdraws back into the body.
Category: Spring Research Sources | Comments: 0 | Rate: