Abstract:
The order Amphipoda are commonly known as beach-hoppers, sand-hoppers, side-swimmers, scuds, or land hoppers. Previously, they consisted of four suborders with distinct habitats, namely: Gammaridea (benthic in marine to freshwater environments); Caprellidea (marine skeleton shrimps); Hyperiidea (marine pelagic parasites of gelatinous zooplankton); and Ingolfiellidea (mainly living in interstices of aquatic gravel and sediments). However, they were recently re-classified into six suborders: Amphilochidea, Colomastigidea, Hyperiidea, Hyperiopsidea, Pseudingolfiellidea, and Senticaudata (includes species formerly part of Gammaridea and Caprellidea). There are almost 10,000 described species of 221 families, 444 subfamilies, and 1664 genera of Amphipoda. Around 300 terrestrial, 1900 freshwater, and 7800 marine species exist, and most are benthic. In the sea, Amphipoda inhabit coastal, tropical, polar, deep-sea, and hydrothermal vents. Eighteen fossil species have been discovered, and all are Gammaridae and Pontogammaridae, which are mostly from the freshwater environment.