Gill area relationships in an ecological series of gammaridean amphipods (Crustacea)

Abstract

From scale drawings of over 1200 gills, total gill area has been determined by computer for the following ecological series of amphipods: Gammarus locusta (L.) (aquatic, marine), G.pulex (L.) (aquatic, freshwater), G. duebeni Liljeborg (high shore, brackish water), Echinogammarus pirloti (Sexton & Spooner) (high shore, fluctuating salinity), and Orchestia gammarellus (Pallas) (semi-terrestrial). Gill area/body dry weight relationships are established for each species and are shown to differ significantly from one another. For a given body weight Gammarus pulex possesses the largest gill area, followed by G. locusta then G. duebeni, Echinogammarus pirloti and Orchestia gammarellus. The anterior gills (G2-5) are equivalent in area (≈20% per pair) in the gammarids with G6 and 7 declining in area. In Orchestia, G2 and G6 each make up ≈25% of the total gill area. Gills 3, 4, and 5 are relatively small and G7 is missing altogether. A reduction in gill area, to reduce desiccation, is thus related to the acquisition of terrestrial habits; an increase in gill area may, however, be promoted in reduced salinities as a means of facilitating ion uptake.