Life at the Bottom

The riverbed is made of a fine, fertile silt with a few stones and pebbles. Plants such as curled pondweed provide oxygen and shelter for invertebrates. Some caddisfly larvae make protective damselflycases out of pieces of leaf, but other species make cases out of bits of stick, sand grains, or tiny shells; others make no case at all. The damselfly nymph (larva) lives for up to 2 years underwater and then climbs up a water plant into the air, emerging from its case as a winged adult. Caddisflies and damselflies are carnivorous insects, leeches are worms which suck the blood from vertebrates and the freshwater shrimp are scavenging crustaceans, eating decaying plant and animal material on the bottom.

Make a list of other invertebrates you may find at the bottom of the river or amongst submerged plants.