Asellidae

Latreille, 1802

Freshwater Isopods

Genus Guides

4

Asellidae is a large of freshwater isopod crustaceans primarily distributed in North America and Europe. Members inhabit both surface waters (epigean) and subterranean aquatic systems (hypogean), including caves, springs, wells, and lakes. The family exhibits significant morphological diversity, particularly in male genital pleopods used for identification. Many species show troglomorphic adaptations in cave , including depigmentation and reduction. Some species have expanded their ranges through human-mediated , including ballast water transport and aquarium trade.

Caecidotea tomalensis by no rights reserved, uploaded by Scott Loarie. Used under a CC0 license.Caecidotea tomalensis by no rights reserved, uploaded by Scott Loarie. Used under a CC0 license.Caecidotea tomalensis by no rights reserved, uploaded by Scott Loarie. Used under a CC0 license.

Pronunciation

How to pronounce Asellidae: /əˈsɛlɪdiː/

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

Images

Habitat

Freshwater aquatic including surface streams, springs, lakes, and wells; subterranean aquatic habitats including caves, groundwater systems, and phreatic zones. Some inhabit specialized environments such as saline crater-lakes (e.g., Caecidotea williamsi in Alchichica, Mexico at 8.5 g l⁻¹ salinity, pH 9.0) and tufa crevices. Water temperature ranges observed from 14.5°C to 20°C in studied . Depth distribution extends to at least 30 m in some lacustrine habitats, with anoxic layers limiting deeper occurrence in some systems.

Distribution

North America and Europe; disjunct distribution patterns include East Asian ( Nipponasellus in Russian Far East and Japanese archipelago). Specific documented ranges include: Interior Highlands of south-central USA (Ozark and Ouachita provinces), Interior Low Plateaus and Appalachians of eastern USA, Trans-Mexican Volcanic Belt of Jalisco, Mexico, Dinarides region (SW Slovenia, NE Italy), Lake Ohrid (Balkan region), and Nordic countries. Some exhibit strict endemicity to ancient lake systems or karst regions.

Behavior

Cryptic use documented: some inhabit empty trichopteran cases embedded in tufa crevices. Troglomorphic exhibit reduced pigmentation and blindness. Secondary between cave and surface populations observed in some systems (e.g., Postojna Caves). Some specimens observed with heavy coverage of epizooic ciliates on thoracic and abdominal segments of and pleopods.

Human Relevance

Range expansion of common aided by human activities; Proasellus coxalis and P. meridianus increasing ranges in Northern Europe through shipping ballast water and possible aquarium trade (fish transport in microaquaria). Risk of trans-oceanic freshwater species transfer through ballast water. Anthropogenic desiccation threatens in restricted such as Alchichica crater-lake.

Sources and further reading