Field Guide

Zebra mussels are named for their shells, which have alternating light and dark bands. They are a highly invasive nonnative species. Learn how to prevent their spread.

Gilled snails are one of two main groups of aquatic snails in Missouri (the other group is the "lunged" snails). Gilled snails, or prosobranchs, breathe with gills and possess a hard trapdoor-like operculum. They are most common in the Ozarks.

Pulmonate, or lunged snails breathe via a lunglike pulmonary cavity, and they lack the hard trapdoor-like operculum found in gilled snails. Except for in the Ozarks, pulmonate snails predominate in most of the aquatic regions in our state.

Ramshorn snails are easy to identify at a glance, because the shell is a flat, disklike coil. Like other pulmonate aquatic snails, they lack the hard horny “trapdoor” possessed by other types of aquatic snails.

Most people are repulsed by leeches. But once you get past the fact that many species are parasitic bloodsuckers, you will discover that they are fascinating creatures with an important role in nature.

Bryozoans are tiny, filter-feeding invertebrates. They create colonies that can be mossy, branching, or round and jellylike.

Groups of whirligig beetles swim on the water surface in quick, random patterns, searching for food. They have two pairs of eyes — one pair above water, one pair below — to help them quickly and accurately capture their prey.

Like many aquatic insects, these large oval beetles prey voraciously on other aquatic organisms. Excellent swimmers, they fly well, too, and are often attracted to lights.