Gammaridea and Caprellidea (Crustacea — Amphipoda) of the Portuguese south-western continental shelf: taxonomy and distributional ecology

Amphipods from the Portuguese south and south-western continental shelf were studied with regard to the species inventory, distribution, and ecology. This study allowed the identification of 113 species, belonging to 52 genera; of these species 28 are recorded for the first time along the Portuguese coast. Two species, Ampelisca heterodactyla Schellenberg, 1925, and A. latifrons Schellenberg, 1925, are redescribed. The latter is different from the Ampelisca named latifrons by Ledoyer in 1972 and 1982. The absolute frequencies and abundances of the species, and their distribution in terms of bathymetry and type of substrate are also analysed. The most frequent and abundant species also presented wide ranges of vertical distribution. In addition, these species are preferentially found in medium or fine sand bottoms. The granulometric structure of the habitats might, therefore, be the most important factor conditioning the development of amphipod populations. The group of the most frequent and abundant species was dominated by Ampelisca. Thus, at least in the shelf sediments, the species of this genus might have a key role as food for many secondary consumers, especially demersal fishes.