Starfish - Asteroidea

We all know these pretty little stars as 'starfish', but recently scientists have begun to correct their name to 'Sea Stars' as the organisms do not come under the kingdom 'fish' but they come under the kingdom 'Echinoderm' closely related to Sea Urchins and Sea Biscuits.

Sea stars are fairly unique in that they're found almost everywhere on the ocean floor from shallow tidal beaches to deep sea.

To cover this massive ocean space, there are at least 2,000 species of Sea Stars. Most having five arms, but some can have 10, 20, even 40.

These critters are sort of magic in a way. If a predator were to break of one arm (or shed it in defence), this arm can not only be re-grown on the body, but if a tiny segment of that arm survives, some species can re-grow a whole new body around that piece. This is because some Stars store their vital organs in their arms rather than central bodies.

Sea Stars aren't all pretty shapes and magic powers though. They have some pretty gruesome table manners. Rather than doing the same as almost every other organism on the planet, (entering food into the mouth then digesting it) they decided to come up with a unique technique for dinner time. The National Geographic has a nice explanation for this: "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."

Another crazy fact, from National Geographic, is that Sea Stars also have no brains and no blood. They have seawater circulating through their bodies rather than blood.
To keep up with the weird theme, some Sea Stars are hermaphrodites, meaning they can produce both sperm and eggs. These are made in an organ called an "ovotestis" coming from "ovary" and "testicle". These then fertilise to become little sea stars. Other species start as males, then as they grow older they become female. If this grown female were to then split into two, the re-growing two would both be male until they reach a certain age again.

These pretty stars aren't all weird adaptations though. Some species are among the most invasive marine organisms. An introduced species from Japan has been destroying coral reefs in Northeast Australia and French Polynesia. They are expected to have been introduced as larvae in off run from Japanese ships.

Currently Sea Stars are unaffected by pollution or human impacts. But scientists believe that high levels of ocean acidification (too much carbon dioxide in the ocean) will stunt the growth of these organism's skeletons. And also some species are unable to survive in water with high temperatures, which may happen with global warming.
But, on the bright side, for now they're a healthy group of marine organisms holding up the food chain whilst being pretty.
That's what we like!