Wildlife: Find aquatic invertebrates on stream bottoms

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In just a few weeks temperatures will get uncomfortably warm. A great source of thermal relief is a spring-fed stream where one can wallow on a hot summer day. Such days are great opportunities to study aquatic invertebrates.

On the water's surface you'll find predaceous water striders and frantically active whirligig beetles searching relentlessly for prey. Where the water is clear, you may see crayfish patrolling the streambed. And where the water is still, look for tiny freshwater sponges and jellyfish.

But most freshwater invertebrates stay hidden beneath large flat rocks that cover clear stream bottoms. Flowing waters are home to a surprising variety of filter-feeding clams and mussels that range in size from less than an inch to 10 inches.

Gravel stream bottoms are home to myriad species of snails and larval aquatic insects. Flip large flat rocks, let the current clear the sediment and you'll observe an impressive diversity of aquatic life.

The flat-bodied creatures that cling tenaciously to the undersides of submerged rocks are stonefly and mayfly larvae. From the tip of the stonefly larva abdomen, you'll notice two tail-like filaments. Larval mayflies have three such tails. The presence of stone flies and mayflies indicate clean water. Fishing these spots should be productive.

My favorite aquatic insects are caddis fly larvae. If you notice a bundle of tiny pebbles or twigs moving across the stream bottom, watch it closely. Pick one up -- you'll discover it's home to an insect. On one end there's a head and thorax, complete with legs. The soft tissues of the abdomen are protected by the case that surrounds it.

Caddis fly larvae build their own house and carry it on their back. The weight of the case helps anchor the larva in moving water, and it's excellent camouflage when the larva rests. The materials used to make such cases include grains of sand, tiny pebbles and sometimes plant material. Some of the pebble-users actually build a spiral case that can easily pass for a snail.

No one hates hot steamy weather more than I, but it presents a great opportunity to get wet, stay cool and learn a little natural history.

Biologist, author, and broadcaster Scott Shalaway can be heard 8-10 a.m. Saturdays on 1370 WVLY-AM (Wheeling) and online at www.wvly.net. He can be reached at www.drshalaway.com, sshalaway@aol.com and 2222 Fish Ridge Road, Cameron, W.Va., 26033.


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