"Cuckoo for Copepods"

Borrowing a phrase from “Bill Nye, the Science Guy”, my first day back at work could be summed up nicely by going “Cuckoo for Copepods”! We teach a program on Pond life for 5th graders, and one of the coolest lessons is going to the classroom with a micro-projector and letting them see some microscopic crustaceans “Up close and Personal”. Up close indeed, for if you are really lucky, as we were, you will get to see Daphnia reproduce right before your eyes! But more on that later.

About the “cuckoo” part, even though there are reported to be 1,000’s of species of copepods, found the world over, from the ice caps of the Poles to the teeming jungle waterways, just try and find one in your own pond when you have a class to prepare for the next day! Andrea and I spent some back-breaking hours pouring over trays of water we collected from the pond, trying to find these illusive, teeny critters from all the other life swirling around. But finally we were rewarded with enough samples of “Cyclops” copepod to show in class. They get their name from the one eye in the middle of their forehead. And when you are looking for them, you look for a speck that is swimming in a jerky motion, for they use their legs and antennae to move, but they move in opposite directions. Should the occasion arise that you are looking for copepods! The females have sacks of eggs like saddlebags and are easier to spot because of it.

But the darlings of this class we do, are the Daphnia, or water fleas as some call them. Much easier to find; they spiral in circles as they swim, and the coolest thing about them, is they are transparent, so when you magnify them you get to see EVERYTHING! Beating heart that goes at 200X a minute, the gut that has the food that is exiting the body with great regularity to the amusement of the 5th graders, a clearly seen compound eye, and large antennae that they use to spin in a circle like a wild whirligig. But the most exciting thing is that these little reproductive wonders are constantly with child. And I mean constantly.

If you have collected your specimens in a pond, then they are almost guaranteed to be all female. They are able to reproduce by parthenogenesis, meaning loosely; no males need apply. They can have young at the ripe old age of 3 days, and the eggs they produce will take 3-4 days to develop and then they start right at it again, having a new brood every 3-4 days until they die at about 6-8 weeks! Each clutch could have 8-24 young, who look just like Mom and will begin having their young in 3 days, every 3 days until they die! I don’t even want to do the math on that- mind boggling! But such is the life style of anyone who is at the bottom of the food chain, as they are. “Yum-yum”, say all the little damselfly nymphs and hydras and the like.

But again, the coolest of cool things is when this actually happens in a drop of water, under the microscope, for the whole class to see. Which it did for my lucky little devils on Tuesday when I did the class. We could see the young were so ready, filling the Daphnia’s brood chamber without a mm to spare, when blam, they all start exiting out the escape hatch and filling the water, swimming around wildly, looking just like Mom. When no Dad is involved that is what happens after all! Like cloning really. I always lead the class in singing “Happy Birthday dear Daphnia’s” and it is a memorable moment!

Now, if you gather your Daphnia from a vernal pool, you just might find a male, because here is another, “Isn’t nature amazing?” thing. If the Daphnia sense a stressful situation coming on; i.e. the water is disappearing in a vernal pool or there is too much competition for food, they can produce male Daphnia. They will then mate with the female and this union will produce an egg that can sink to the bottom and wait it out. It can survive drought and hatch when times are better. Again, how can anybody say they are bored when there are such things to be learned!

But enough on that. You all have busy lives and I have gone into perhaps more detail then you might have wished. But chock it up to the enthusiasm of being back at work. When Elena is bigger I will delight to show her such wonders, but for now, Cape Cod 5th graders will be the ones to dazzle. And you know, they were.