Key to Aquatic Macroinvertebrates in Utah - 10+ legs

Key to Macroinvertebrate Life in Ponds and Rivers in Utah

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

Order Picture Description Habitat


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.


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.


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

Can be found in all aquatic environments. 


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.

Can be found in saline waters and temporary ponds near the bottom.


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 posterier end of the abdomen.

In still and rapid moving fresh water 



10-150 mm in length

Decapoda have a carapace, 5 pairs of legs with pinchers on the 2nd pair.

Found in still and fast moving water. 


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.


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. 


Seed shrimp

< 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.

Can be found in all aquatic habitats


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