The oxygen content of air-equilibrated haemolymph from three species of hyperiid amphipods, Hyperoche medusarum, Parathemisto sp. and Hyperia galba was similar to that of air-equilibrated sea-water. The concentration of haemolymph protein was low in each case. Both features, taken together with the fact that we were unable to detect the presence of copper in the haemolymph in any of the species examined, suggests that hyperiids, unlike gammaridean amphipods, do not possess the respiratory pigment haemocyanin.

All the information available on the O2-binding properties of amphipod haemolymph has been derived from members of the amphipod sub-order Gammaridea. In common with many other crustaceans (Truchot, 1992), O2 carriage in gammarid haemolymph is facilitated by the presence of the copper-containing respiratory protein, haemocyanin (Spicer, 1994). Unfortunately no comparable data exist for the other major amphipod sub-orders, the Hyperiidea, the Caprellidea and the Ingolfiellidea. Consequently we have examined haemolymph from three species of hyperiid amphipod, Hyperoche medusarum (Miiller, 1777) and Parathemisto sp., from the west coast of Vancouver Island, Canada, and Hyperia galba (Montagu, 1813) from the Clyde Sea area, Scotland.