Freshwater macroinvertebrates are a diverse group of animals, ranging from worms and leeches to crustaceans and insects. You can encounter them when fishing, hiking, or bird watching, and you don’t have to study them intensively to appreciate them.

Freshwater sponges are much smaller and less spectacular than their saltwater relatives. They are often confused with aquatic plants, algae or fungal growth because of their simple construction. In fact, until the eighteenth century, sponges were not recognised as animals.

This group of animals is united by the simplicity of their shapes. They all have simple digestive systems, some have a single opening, like the flatworms (including the temnocephalans), while others like the gordian worms have none at all.

Freshwater oligochaet worms are plain-looking animals. They can look like ordinary earthworms but more often they are much thinner and shorter. They are all segmented, and if you use a microscope you can observe short bristles and hairs on each segment.

Arachnids have eight legs and highly fused body segments. Instead of having a head, prothorax, mesothorax, metathorax and abdomen, these have been simplified to a cephalothorax and an abdomen in spiders and a single body segment in mites.

Primitive crustaceans tend to have more legs than those that have evolved more recently. Syncarids, brine shrimp and tadpole shrimp all have numerous pairs of legs and closely resemble their geologically ancient ancestors found as fossils around the world.

Springtails look like tiny insects and were once regarded as a primitive insect group. However, these soft-bodied invertebrates have now been placed in a separate class.

Larger, terrestrial members of this order of insects hold their abdomens with a distinctly scorpion-like posture and this is where they get their name.

This order includes some of the strangest aquatic insects. They are usually quite rare but very distinctive.

The dipterans are a very diverse group of insects that occur in most, if not all of the inland waters of temperate Australia. They can be found in a range of environmental conditions, thriving in septic tanks and wilderness areas alike.

Although the term ‘bugs’ is often used as a nickname for all insects, true bugs are hemipterans, belonging to the suborder Heteroptera. There are around 270 aquatic or semi-aquatic species in Australian inland waters—many people will have heard of backswimmers, water striders or waterboatmen.

Stoneflies are a small, relatively primitive, group of insects. The nymphs are sensitive to water quality and are abundant in alpine streams.