Field Guide

Aquatic Invertebrates

Showing 1 - 10 of 14 results
Photo of a gray-speckled crayfish.
Gray-Speckled Crayfish
Faxonius palmeri (formerly Orconectes palmeri)
The gray-speckled crayfish is gray with numerous greenish-black speckles and blotches. A pair of large blotches are present near the back of the head, and another pair occur where the carapace joins the abdomen. In Missouri, it is found only in the southeastern section.
pond mussel
Freshwater Mussels
Bivalve molluscs in order Unionoida
Secretive and seldom seen, freshwater mussels are extraordinarily diverse in Missouri. We have nearly 70 species within our borders. Many are declining, and several are endangered.
Photo of several prosobranch pond snails crawling on a rock.
Gilled Aquatic Snails (Prosobranch Pond Snails)
Over 20 Missouri species in former subclass Prosobranchia
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.
Photo of pulmonate snail crawling on rock
Lunged Aquatic Snails (Pulmonate Pond Snails)
Over 30 Missouri species in former subclass Pulmonata
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.
Photo of a ramshorn snail on a wet rock.
Ramshorn Snails
Gyraulus, Helisoma, Menetus, Micromenetus, Planorbula spp.
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.
Hydras
Various species in the genus Hydra
We’ve all seen aquariums and pictures of tropical saltwater invertebrates such as corals, jellyfish and anemones—but did you know that there are similar creatures living in the freshwater habitats of Missouri?
Gray, speckled, translucent gelatinous blob cut in half to show structure
Bryozoans (Moss Animals)
Freshwater species in the phylum Bryozoa
Bryozoans are tiny, filter-feeding invertebrates. They create colonies that can be mossy, branching, or round and jellylike.
Photo of a stonefly naiad clinging to a rock underwater
Stonefly Larvae
There are hundreds of species in North America
Stonefly larvae are aquatic and somewhat resemble the larvae of mayflies and damselflies. Their presence usually indicates good water quality.
Photo of caddisfly larva with case made of detritus
Caddisfly Larvae
About 1,500 species in North America north of Mexico
The aquatic larvae of caddisflies are famous for building portable, protective cases out of local materials, including grains of sand, bits of leaves and twigs, and other debris. The adults are mothlike.
Photo of a horsehair worm in an aquarium
Horsehair Worms
About 350 species scientifically described.
Adult horsehair worms can be nearly 3 feet long and live in water. They are practically featureless, smooth, aquatic worms that writhe into knots and curls.
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About Aquatic Invertebrates in Missouri

Missouri's streams, lakes, and other aquatic habitats hold thousands of kinds of invertebrates — worms, freshwater mussels, snails, crayfish, insects, and other animals without backbones. These creatures are vital links in the aquatic food chain, and their presence and numbers tell us a lot about water quality.