One of the aspects that I enjoy most about my job is constantly learning about nature and the interconnected characteristics of critters and their habitats. Last week I was out looking to see what kind of food would be available for early season migrants like blue-winged teal.
Using a dip net I was looking to see what bugs and crustaceans were moving about in the flooded habitat. Some sweeps resulted in a collection of small snails and glass shrimp, while others produced big round predacious diving beetles or a bevy of smaller water boatmen. With each sweep I never knew what would turn up next. Adult bugs weren't the only ones lurking in the water and among the leafy debris. The juicy, protein packed larvae of dragonflies, mayflies, and mosquitoes were also sifted out of the water column and into my net.
On one sweep I pulled up something different. At first glance, it appeared to be a small clam the size of my fingernail. The shell was semi-translucent and kind of papery, but otherwise this capture was rather nondescript...just a small clam, right? What I failed to see upon my initial observation was the small shrimp-like body with feathery legs that was inside the folded shells. This was a clam shrimp, which is a rather remarkable animal in its adaptations to temporarily flooded wetlands, but grossly overlooked species due to its sporadic occurrence, spotty distribution, and unremarkable appearance. I didn't realize the additional features and proper identification until it was pointed out to me a couple days later by a man who has waded through more miles of marsh and swept up thousands of more bugs than myself.
I can't say if these little guys have a Rodney Dangerfield attitude or not, but as I dug up more information on this "new" critter, I found them quite fascinating. Their life cycle takes advantage of when the getting is good and their offspring are able to hunker down when the tough get going. As wetland habitats become flooded their eggs, which have been lying dormant in the soil hatch out. Once rewetted the larval clam shrimp don't mess around. Within a week or two they quickly grow and become sexually mature. From there it takes little time for the females to develop and shed their eggs as they continue to grow and molt. Clam shrimp thrive in wetlands that typically dry out. When this happens the adults die and the eggs become dormant in the soil until the next wet cycle. The hardy eggs can weather the blazing heat or freezing temperatures in this dried out state. If conditions remain wet, the small adult crustaceans can live for several more months swimming about the water column waving their feathery legs back and forth.
This movement helps them go to and fro and also circulates the water, bringing oxygen and food to their mouths. Like other aquatic bugs and crustaceans, these little critters feed on algae, dead plant material, and other microscopic animals in the water. The nutrients consumed by clam shrimp and the host of other aquatic invertebrates continue to move on up the food chain as fish, frogs, shorebirds, waders, and ducks devour these animals once wetlands become seasonally flood.
That brings me to Teal season, which is right around the corner and why I was sweeping a dip net through the marsh in the first place. As you can see from my recent outings, it's literally the little things that make migration possible each fall and spring for millions of birds. Uncovering these dynamics by assessing conditions and learning new critters keeps things interesting and one of the reasons I love my job and the wetlands I have to pleasure to work in.