This species can usually be distinguished from the frequent Proasellus meridianus by the pattern of pigmentation of the head, with two pale spots at the back separated by a central dark pigmented area. However, head pigmentation can vary and the two are frequently confused. The shape of the male first pereopod (leg) is diagnostic.
Distribution and Habitat
A. aquaticus is abundant throughout the British Isles, occurring in a wide variety of water-bodies, including small urban garden ponds, ditches, lakes, canals and rivers.
It can be found among water plants, under stones and submerged bits of dead wood, among the roots of riparian trees and on the stonework of bridges. It is tolerant of organically polluted waters, high salinities, low pH and high metal concentrations.
This summary is based on the detailed account in Gregory (2009).