Little Monsters of the Ocean: Metamorphosis under the Waves
CHAPTER 1 Monster Madness What Is Metamorphosis Who is that spiky-headed alien Is he going to stab you with that spike Or whip you with his thorny tail No need to worry about this tyke He’s called a zoea and he’s so tiny you’d need a microscope to see him And he’s not even in control of his own body He just wiggles around in the water spinning in somersaults Why does a zoea look like a monster Maybe that spike scares off hungry critters He needs every bit of defense he can get It’s him against the world And it’s a rough life being little Even though a zoea is always searching for a meal he has a 50 percent chance of starving to death One reason He can hardly swim Zoeae are part of the plankton organisms that drift around in the ocean without control of where they go All they can do is suck water in and hope they slurp up something good 6
7 But finding food isn't the only issue Plankton often become food for other animals Bobbing around in the ocean a zoea is easy prey for a striped bass with a mouth the size of a cave One gulp and swish it's bye bye zoea and a hundred of his buddies A zoea is in the first stage of life At this point our little guy is just a larva He's got more growing to do He'll grow and change and grow and change until he finally becomes a blue crab BOY GIRL BOTH A zoea can be either a male or a female For most marine larvae scientists can't tell what sex they are Some species change from male to female during their lives while others are both female and male In this book the text alternates between male and female pronouns Blue crabs are named for their sky blue claws Adult females have red tipped claws Most blue crabs are right clawed just like right handed people
Time FOR a Change A blue crab starts life as an egg in the bay at the edge of an ocean There the water is shallow and warm just right for little ones His mother scurries around with him on her belly along with one to six million other eggs When he hatches the zoea is just a thorny barb with a lot of growing to do He doesn’t look like Mom or Dad yet That’s because he needs to go through metamorphosis Until he does that however this little guy is at the mercy of the tides After hatching he is washed out to sea by the tides There he’ll spend about a month in the larval stage as a zoea growing growing and growing some more By then the zoea is huge well huge for a zoea about 0 04 inches 1 mm It’s time for him to move up to the next stage a shrimpy-looking ghost called a megalops A female blue crab carries her eggs on her belly As the eggs use up their yellow yolk they turn darker eventually becoming black 8
9 As a megalops his goal is to make it back into the headwaters of the bay where he began his life as an egg The bay offers different kinds of food seagrass with lots of hiding places and not so salty water But he's still just a tiny plankton too small to swim all that way Fortunately now that he has morphed into a megalops he can In the second stage of his life cycle the megalops is swim faster up to easy prey At least ninety three different animals bass jellyfish shrimp and more call young crabs lunch 7 8 inches 20 cm a second Of course that's only one pencil length every second but it might help him avoid a predator It also might help him swim up or down to catch a current And that current could carry him into the bay After his long trip back to the bay he's tired hungry and ready to settle down But he needs to be careful about where he drops down in the muck Otherwise he might get a nip from another crab who has gotten there first About 75 to 97 percent of young crabs become another crabby kid's lunch Yikes If a megalops avoids starving being gobbled up and getting washed away his body will become wide and flat He'll finally look like an adult except he's only 0 08 inches 2 mm wide about the thickness of a nickel That's okay As a juvenile he's good at growing By the time he's one and a half years old he'll be a full grown adult with supersharp claws and all
