Biology Is Weird — The Stars of the Sea.
I think the title is pretty explanatory, which is rather unlike me but there’s a first time for everything. And in case it’s not explanatory enough for you; this edition is about a certain star-shaped marine animal who despite its misleading name isn’t actually a fish. I’m sure you’ve guessed it but let me spell it out anyway. We’re talking about starfish.
We all remember SpongeBob’s pink friend and his rather questionable behavior. Well, there’s actually an explanation for his slow, erratic and illogical reasoning. Starfish do not have brains. So dear ol’ Patrick was just doing his best. They do have eyes, however, these eyes are on the ends of each limb. Freaky.
Starfish don’t have blood either. Which is why you shouldn’t take them out of water for longer than 5 minutes. Instead of blood, starfish have seawater running through their…veins? The seawater is pumped through the animals’ circulatory system through a trapdoor on its surface called a madreporite. What’s more? The seawater also flows into the tiny tube-feet on the bottom? back? underside? of its body. These tubes are what help the starfish to move across the seabed, and muscles in these tubes help it to fold and curve its arms.
In a savage twist of fate, starfish are carnivorous, besides a select few species that are herbivores, omnivores or detritivores. So, how do these star-shaped wonders eat? Well, they pounce on their prey with their underside and trap them with the tiny tube feet that cover its surface. These tubes then pry open the shell of the mollusk wide enough for the starfish to literally puke its guts into it. The starfish ejects one of its stomachs, the cardiac stomach, into the shell of its prey, which then digests the animal and gets sucked back into the star. The food is then transferred to the pyloric stomach for further processing. Yes, it is as disgusting and gory as it sounds. Even worse? Some starfish species eat other starfish.
Despite their petrifying and disturbing method of feeding, starfish are also prey to animals like sharks, manta rays, octopi, dolphins and other starfish as mentioned before. And their little tube feet, as many as they are, are not built for high speed chases but they don’t give up without a fight. Armed with a strong, heavily calcified upper layer, they make it tough for hunters to feast on them. Some even go the extra mile to have numerous spiny structures covering this layer.
Now, for the part you’ve all been waiting for. Drum roll, please. Yes, starfish can regenerate their limbs. It is not a myth.
A starfish caught in a trap or by a predator will sacrifice a limb or two to save its life, confident in the knowledge that it can simply regrow them. Some starfish species can regenerate a whole body from a severed limb and can use this as a means of reproduction. If you cut some starfish in half, you will get two separate stars. Just like that. Despite this, starfish choose to reproduce sexually rather than asexually. I’m guessing it’s because it actually hurts to lose a limb, even if you can regrow it. Why cut off your body parts for the sake of propagation when you can release sperm/egg cells into the water for nature to do her thing?
And seeing as there are about 2000 different species of starfish, you can’t really expect all of them to be 5-pointed perfection, can you? There are starfish with more then 5 limbs, some reaching up to 30. And others with weird shapes, but as long as they meet most of the internal and structural requirements of stardom, they get to bear the name.
That is it for today. I’m sure you can see, it is not easy to be a star. I hope you learned something or at least smiled once. Thank you for coming to my Ted talk.
