Starfish. Also known as sea stars. We see them all over the place. They're a ubiquitous ocean species, with around 1,800 living species occurring in all the world's oceans, and even at depths greater than 6,000 meters. In fact, they're so common, we may too often overlook exactly how strange and amazing they really are. So let's take a moment to have our minds blown by the freaky, gorgeous starfish.
Have you ever picked up a starfish? Or attempted to pick one up off a rock? If you have held one, you'll notice how weird they feel. Rock hard on the top, and the wiggly tube feet on the bottom are a trip on the palm of your hand.
The starfish can go from soft (enabling it to squeeze into small spaces) to rigid (how it feels when you try to pick it up) in a split second. In fact, their entire anatomy is surprisingly complex, including their nervous system.
The underside of the starfish has a couple important features. First, its many tube feet serve to grasp on to things with amazing force. They work on a hydraulic water vascular system to help the starfish move around. While starfish seem quite slow (and admittedly, many species are) some species can move at quite a pace, even over 9 feet in one minute.
The tube feet are also used to grasp and deal with food.
Secondly, the underside is where their mouth is located. They can swallow their prey whole and down it goes in a short esophagus to a cardiac stomach, and then on to a second pyloric stomach. But they don't have to swallow... when dealing with prey larger than its mouth, many species of starfish can also spit out their stomachs to engulf the food and begin to digest it before pulling everything back into its body. Aaammazing!
And the colors and shapes they come in... Wow!! Just have a look at the diversity:
Starfish species don't all come with five arms. Some have, let's count, one two three four... a gazillion arms. Okay not a gazillion, but a lot. Several species have 10 to 15 arms, and a few other species can have up to 50.
They're masters at using those arms for so many purposes, including hiding:
Many species are famed for being able to grow back lost limbs, which is good if they survive a close encounter with a predator:
And yes, some species can even create new starfish from their arms, shedding one arm that will regrow four more! Some other species can split their bodies and regenerate the rest of each body, with one starfish becoming two.
The next time you come across a starfish, take a moment to really look at it. Think about what a wonder of evolution this creature is, and how strange and brilliant their anatomy. Starfish truly are mind-blowing!
What makes you say "WHOA!"? Tell us on on Twitter with #natureblowsmymind. We may feature your mind blowing suggestion later in the series!