Hyalella azteca

(Saussure, 1858)

scud, freshwater scud

Hyalella azteca is a widespread and abundant amphipod crustacean in North America, reaching 3–8 mm in length. It inhabits fresh and brackish waters across a broad geographic range from Central America to the Arctic tree line. The is a significant food source for waterfowl and serves as a standard test organism in aquatic ecotoxicology and sediment assessments.

Hyalella azteca by (c) Rich Sommer, some rights reserved (CC BY), uploaded by Rich Sommer. Used under a CC-BY license.

IMGP7610-Hyalella azteca with acanthocephalan in body cavity! by Nemataslg. Used under a CC BY-SA 4.0 license.

Pronunciation

How to pronounce Hyalella azteca: /haɪəˈlɛlə æzˈtɛkə/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Distinguished from similar Hyalella by: 1 ≤ antenna 2 in length; single spine on pleosomes 1 and 2; male gnathopods (pereiopods I and II) conspicuously enlarged. The status complicates identification—morphological and genetic divergence occurs among geographically isolated .

Images

Habitat

Permanent freshwater bodies including lakes, rivers, and ponds; extends into tidal freshwater and freshwater barrier lagoons. Found among vegetation and sediments. Tolerates alkaline and brackish conditions but not pH below 6.0. Golf course ponds sometimes support large .

Distribution

Central America, Caribbean, and North America from Mexico to the Arctic tree line. Most abundant amphipod in North American lakes.

Diet

Filamentous and diatoms; organic detritus. Cannot assimilate cellulose or lignin despite their abundance in leaf litter. Assimilates 60%–90% of ingested bacterial .

Life Cycle

Passes through minimum nine instars before sexual maturity. Sexes distinguishable at 6th instar. First mating occurs at 8th instar. Adulthood comprises 15–20 additional instars. Precopulatory pairing: male carries female beneath his surface for several days until she moults, ensuring mating during the post- receptive period.

Behavior

Precopulatory guarding is innate and not dependent on early social experience. Exhibits increased feeding activity as compensatory response to toxic stress.

Ecological Role

Major food source for waterfowl; 97% of female white-winged scoter diet in Saskatchewan and significant component of lesser scaup diet. Standard bioindicator organism for sediment assessment and aquatic ecotoxicology testing.

Human Relevance

Widely used in aquatic and tests due to wide distribution, ease of laboratory culture, and ecological importance in lake sediments. Employed to test bioaccumulation of manufactured nanomaterials, , and metals. Subject of sequencing as part of the i5K initiative.

Similar Taxa

Hyalella texanaDescribed from Edwards Plateau, Texas; formerly considered part of H. azteca
Hyalella montezumaDescribed from Montezuma Well, Arizona; formerly considered part of H. azteca