Noel's amphipod (Gammarus desperatus) is a federally endangered invertebrate species constrained to localized karst features with reliable sources of clean groundwater. It is a crustacean that depends on gills for respiration,  

• Indicators of whether the species has an FWS focus, has (or had) regulations applied to it (including proposed statuses), and whether the species can be found on a refuge (as sourced from the IRIS database of occurrence data from Refuges).
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• FWS Categories for the species such as fur-bearer, pollinator, etc.
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• Regulatory status changes that have been applied to the species.
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Noel’s amphipods are brown-green in color and flanked with red bands along their thoracic and abdominal segments, often with a red dorsal stripe.

No recorded weight measurements for Noel's amphipod are available at this time. 

Noel's amphipod sounds have not been identified or recorded. 

Noel's amphipods have the shape of tiny shrimp. They are laterally-flattened and covered in bristles, with long, kidney-shaped eyes. Noel’s amphipod males are generally larger than females.

Measurements
Males typically range from 9.45 to 14.8 millimeters (0.37 to 0.58 inches) in length.
Females typically range from 8.5 to 12.6 millimeters (0.34 to 0.50 inches) in length. 

Noel’s amphipods that measure smaller than 8.5 millimeters in length have been observed with regularity during monitoring efforts at Bitter Lake National Wildlife Refuge.

Most amphipods complete their life cycle in one year or less.

The breeding season for most amphipods is dependent on water temperature and commonly occurs from February through October. Typically one brood is produced, however some species have been recorded having produced a series of broods over their breeding season.

Gammarus males and females pair for one to seven days, feeding and swimming together prior to copulation. Copulation and sperm transfer lasts less than one minute. An average of 15 to 50 fertilized eggs are retained in the female’s brood pouch, also called a marsupium, where they are incubated for one to three weeks. Young remain in the marsupium for another one to eight days before being released into the aquatic environment, where they develop independently. 

A marsh at Bitter Lake National Wildlife Refuge may contain two sympatric Gammarus species from two different Chihuahuan Desert lineages. One species is Noel's amphipod, and the second is undescribed and may be most closely related to a Gammarus lacustris type.

The sinkhole and cavern karst topography that are abundant in the desert grasslands of the Roswell Artesian Basin has provided isolated limestone and gypsum springs, seeps and wetlands where Noel's amphipods have evolved. Typical aquatic habitat characteristic of gammarid amphipods are cool, shallow, well-oxygenated water that is fresh to moderately saline, permanently flowing with slow to moderate velocity, with specific acidity thresholds of pH generally between 6 and 8. Vegetation associated with Noel's amphipod habitat ranges from dense beds of emergent macrophytes, or aquatic plants, to clear, spring-fed flows with vegetated banks and submerged aquatic vegetation.

Amphipods are omnivorous, feeding on a variety of plant material, animal matter and detritus. Beds of submerged aquatic plants are frequent shelter for Noel's amphipod, where they likely consume a diet of algae, diatoms, bacteria and fungi. Young amphipods depend on microbial foods, such as algae and bacteria associated with aquatic plants.

Freshwater amphipods rely primarily on gills for respiration. They are typically nocturnal, light-sensitive and strongly oriented to their substrate. They use various appendages to clutch, push, stabilize, crawl and swim. Cannibalism is common in gammarid amphipod populations with high densities and limited food supplies.