I bring in buckets of pond water (my favorite ponds to get samples from are at the Landis Arboretum in Esperance, NY – but you can find any of these creatures in most ponds throughout the Northeast). I explain how an aquatic ecologist tries to understand how pond organisms live, thrive and survive. I explain some of the equipment that an aquatic ecologist might use to investigate the pond environment. The students get to use my “uncamouflage” equipment (see my upcoming Aquatic Ecology Field Kit write-up coming soon) to capture and observe the many small creatures of the pond.
After a short time of capturing pond life we settled in for my final overview. I have taken some of the smallest samples and placed them in a special slides (available from Carolina Biological Supply Co., called “deep well slides”) that are used with old style slide projectors. I call these slides, "special aquariums" that can be used to magnify the pond animals, taking something that might be a quarter of an inch large and making it look about 30 or 40 times larger. We have the chance to look at the same enlarged creature and learn about "who is who, what they do, how they grow and where they go".
Here are a few of the creatures we recently found. All of these creatures are in the pond now as winter approaches. They will live under the ice through the winter and will be ready to continue on with their life cycle when the warm weather melts the ice on the pond next spring.
The scud or side swimmer is a kind of freshwater shrimp. They belong to a group of arthropods called amphipoda. They are scavenger, eating dead plant and animal material. They then are eaten by a lot of larger pond animals and thus are important parts of the food chain.
They often are easy to see but hard to catch. They are easy to see because they spend a lot of time swimming rapidly around in the water. They are hard to catch because as soon as they stop in a bunch of pond plants or detritus they disappear with they good camouflage.
One of my favorite creatures to show students is the phantom midge or gnat. It's called a phantom because it has a transparent (see-through) body. What a great adaptation for living in the water, to have a body that is see-through. Many times you don't notice that there is a midge larva in view. You see a few pieces of what looks like dirt floating in the water and then you see them wiggle around and notice the outline of a larva's body. Those little specks of dirt are the float bladders inside the midge that help it sink or float. You can also see it's digestive system.
The phantom midges or gnats are hunters. They use their antennae to catch small aquatic organisms and pull them to their mouths so that they can eat them. Here in this picture you can see these antennae. They look like a hook on top of the larva's head.
This past sample had hundreds of mayfly nymphs, most of them just about a quarter of an inch long. I suspect that most of these had hatched from eggs just before the cold weather arrived. They will live in the pond along with the other creatures we were capturing through the winter and be among the first of the pond insects to grow up and leave the pond next spring.Mayfly nymphs are hunters in the pond. They will eat other small pond creatures like daphnia and copepods, along with aquatic worms and other insects.
When they are ready to leave the pond they will climb up out of the water on to a rock, or log, or dock, or something sticking out of the water and shed their exoskeleton one last time. This time their new exoskeleton will have something none of their past exoskeletons have had, wings!
When they leave the pond, though, they will have no digestive system. That means that the adult mayfly will not live long, but it leaves extra room for eggs in the females. They quickly find mates and lay eggs in the water for their species to continue on.
Here is a damselfly nymph. They are hunters while they live in the water. As they eat and grow they become to large for their exoskeletons and shed. Sometimes we are lucky and find the cast off exoskeleton they leave behind when they do.
When they are ready to leave the water they do the same as mayflies and climb up on to a dry area and shed their exoskeleton that also has new wings. They pump up their wings so that they are fully extended. The wings dry off and harden and off flies the damselfly to be a winged hunter chasing down and catching flying insects. One of their favorite insects to eat are mosquitoes.
I always leave the leach as the last of the critter to look at. What most people know about leaches if fiction from movies that they see, or folk tales that they've heard. Scientists are interested in the facts, not fiction. Here are some of the facts about leaches.
Most of the leeches that we find in a pond do not suck blood. They are either hunters or scavengers. All leeches have a suction cup tail that can grasp on to an animal like a duck or turtle. When the animal travels to another pond the leach takes a ride and can end up in a new pond far from where it started.
Blood sucking leeches get a bad rap. When they bite you usually don't feel it (not like deer flies or horse flies), after they bite it usually doesn't swell up or itch (not like mosquito or black fly bites) and to my knowledge there are no diseases passed on by leaches - not like a lot of other biting organisms like ticks [Lyme disease] or mosquitoes [West Nile virus or malaria]. They are important parts of the food chain, eating small animals or scavenging and then being food for larger animals like fish and if you eat the fish that you catch in a pond food in turn part of the food chain that ends in you.
