Freshwater Amphipoda of North America

An effort to record the rich inland amphipod fauna of North America. With ~300+ species North American freshwater systems boast an impressive richness of amphipods. This project aims to raise interest in our amphipods and assist in identification.

Amphipods are super interesting organisms but they are often very small in size (averaging at lengths of ~10mm) and outwardly similar in form and coloration, making identification difficult. Identification literature is often pretty technical, and sometimes reliant on microscopic/dissected characters. However, generally a clear macro picture or a picture through a microscope/land lens can be pretty readily IDed to at least genus. Taxonomically important characters include the 3rd Uropods, Antennae, Gnathopods, and sometimes the eyes. Photographs clearly showing the 3rd uropods (the last pair of appendages in the "tail fan") from a dorsal view can almost always be IDed to genus, and clear photos of the other characters can be useful in IDing to species when possible.

The amphipod fauna of North America consists of ~15 families, the most common of which are Hyalellidae, Gammaridae & Crangonyctidae.
Gammarids and Hyalellids are mostly epigean and easily observed. ~14-15 gammarids occur in north america, being most common in the east.
Hyalellidae is a family endemic to the 'New World' with a majority of species occurring in the Neotropics, ~10 described species occur in North America, the majority are rare and restricted in range. However, the "widespread" species Hyalella azteca is very common and thought to occur throughout North America, however recent molecular studies have determined that Hyalella azteca is likely a complex of several species, and its occurrence at all in North America may be dubious.
Crangonyctidae is a family that is at its most diverse in North America, with genera like Crangonyx, Stygobromus, & Bactrurus occurring almost nowhere else. It is also the most diverse family with ~200 described and many undescribed species. Most crangonyctids are stygobitic, occurring in subterranean systems, and rarely encountered. Some species are at least partially epigean and can be easily observed.
The other 12 families are rarely encountered, a majority of which being stygobitic or euryhaline. The Anisogammaridae of the Pacific Northwest and the Pontoporeiidae of the Great Lakes are notable exceptions.

Any and all freshwater/euryhaline and terrestrial observations are welcomed! less ↑