An examination of gill area relationships in an ecological series of talitrid amphipods from Tasmania (Amphipoda: Talitridae)

Abstract

Total gill area and gill distribution was studied in 8 species of Tasmanian terrestrial amphipods. Gill area/dry body weight relationships were established for each species and compared with published data for other amphipods to identify possible evolutionary and ecological trends among Bousfield's four talitrid groupings (1984). Species in only one genus, Mysticotalitrus, showed allometric changes in the relationship between total gill area and body size, but gill areas differed between most species. Although gill areas of group IVa landhoppers were close to those of the palustral species, gills 2 and 6 in the former species were significantly enlarged. Gill area decreased with habitat dryness. Comparisons with published data on sandhoppers and beachfleas confirm previous suggestions that sandhoppers are specialized species with greatly reduced gills, and that beachfleas also show very reduced gill areas. Group IVa landhoppers gave gill areas in the range typical of aquatic and palustral species, while the Group IVb species had a gill area comparable with beachfleas. The relative development of gills 2 and 6 suggests that natural selection has affected more than simply total gill area in landhoppers. The function of landhopper gills is discussed in terms of gas exchange, ion and water uptake, water transport and marsupial egg retention.

Keywords :

• Talitridae
• landhoppers
• gill areas
• land colonization
• evolution
• Tasmania