Aquatic Macroinvertebrates with 4+ Legs

Crustacea

Organisms with 10 or more legs belong to the class Crustacea (with the exception of Podocopida which belongs to the class Ostracoda). There are 8 orders of Crustacea  and 1 order of Ostracoda found in Utah.

Family	Picture	Description	Habitat
Amphipoda (Scud or Side Swimmers)		5-25 mm in length. Amiphoda have laterally flattened bodies which forces them to swim on their side. They can be opaque, green, white, brown, or yellow in color.	Can be found in all aquatic habitats. They are scavengers and detritivores of bottom sediments
Anostraca (fairy shrimp, brine shrimp, or sea monkeys)		7-50 mm in length. Anastroca have cylindrical body with a distinct head and stalked eyes. They have 11 or 17 pairs of swimming legs. No carapace.	Found in ephemeral ponds and pools in desert habitats and the Great Salt Lake.
Cladocera (water fleas)		0.2-3 mm in length. Cladocera have laterally flattened bodies with a carapace, with visible antennae, and 5-6 pairs of legs.	All aquatic environments.
Conchostraca (clam shrimp)		2-16 mm in length. Conchostraca are laterally flattened and covered with a clam shell-like carapace. They have 10-32 pairs of legs.	Saline waters and temporary ponds near the bottom.
Copepoda		1-2 mm in length. Copepods have cylindrical, segmented bodies with appendages on the head and thorax. They have 6 pairs of legs and 2 tail like structures on the posterior end of the abdomen.	Still and rapid moving fresh water
Decapoda (Crayfish)		10-150 mm in length. Decapoda have a carapace, 5 pairs of legs with pinchers on the 2nd pair.	Still and fast moving water
Isopoda (Sow bug)		5-20 mm length. Isopoda have dorsoventrally flattened body and 7 pairs of legs. They are opaque to light brown in color. When disturbed they will roll up into a ball like pill bugs.	Often found in cold springs and regulated rivers. Some species can be found in waters with organic waste.
Notostraca (Tadpole shrimp)		10-75 mm in length. Notostraca have a shield-like carapace and 35-71 pairs of legs on their abdomen & 2 well developed tails.	Found in ponds & emphemeral habitats mostly in the desert and higher elevations.
Podocopida (Seed shrimp)		Less than 1 mm in length. Ostracoda have been described as tiny bivalves with legs. Their body is encased within a single or bivalve carapace.  They have a single antenna and may have a rostrum.	All aquatic habitats

Family	Picture	Description	Habitat
Hydrachnidae (water mite)		Hydrachnidae are very small and brightly colored. Many are red, but can be green, yellow, and blue. These organisms also have pedipalps that can appear to be a 5th pair of legs. Less than 2mm.	Found in all types of freshwater habitats including rivers, streams, lakes, ponds, wetlands, and springs.