Journey of Life - Seas of Life 13
Steve travels back 3.8 billion years to when life began. Journeying round the oceans, he explores life's first laboratory and discovers how the incredible variety of sea creatures arose, from the first microbes to hagfish and dolphins.
...so there's always a lag period when making buoyancy changes, for a fast-swimming fish that's too slow.
So speedsters like the bonito have abandoned swim bladders completely. But with nothing to stop themselves sinking they have got to pay the penalty and keep swimming all the time.
Not all boney fish like life in the fast lane. Others have turned to a more sedentary life. Take this weirdo for example. It's a frogfish, and it's come up with a novel use for its bones. That's no wiggly worm but a flashy lure operated by a modified fin bone. But all these damselfish see is a juicy mouthful.
Not only is the frogfish a master of deception, he is also perfectly camouflaged. This shrimp is unlikely to see it until he moves, and by then it's too late. No matter how quick its reaction is, they just can't be quick enough, because the frogfish's jaws move faster than muscle. How? Well, that's down to bones again. It's a trap-jaw, pre-set under full tension. When triggered, the trap snaps open increasing the mouth volume ten times sucking the prey inside.
But when it comes to bone structure, these small fry are the most extreme of all. For the first two weeks of their lives, they look like any other baby-fish. Then something begins to go awry: the face distorts and one eye starts to shift, moving across to meet the other on the opposite side of the head. It's the beginning of a bizarre transformation. The makeover takes less than a week and the results are fixed for life.
This flatfish is now perfectly adapted to life on the seabed. Its bony shape and coloring mean it can keep a low profile, handy for hiding from predators or creeping upon prey.
But if you don't have what it takes to hide out on the ocean floor, safety in numbers is your best bet. Living in a shoal is a great way to minimize the chances of being eaten. Throughout their evolutionary history, shoals of bony fish have come under fire from all sides. |
