Physiology, behavior, habitat, and morphology are used to determine the degree of adaptation to life on land
for amphipod species and systemization within the four functional groups of the family talitridae. Talorchestia
longicornis is a semi-terrestrial amphipod found in the supratidal zone of estuaries. The present study investigates
the physiological adaptations of this species to life on land through measurements of osmoregulation
and respiration. Over the salinity range of 1–40‰, T. longicornis regulated its hemolymph hyperosmotically at
low salinities and hypoosmotically at high salinities. The isosmotic point was about 27‰. Analogously, hemolymph
chloride levels were well regulated being hyperionic at low salinities and hypoionic at high salinities.
This species is capable of respiration in both air and water. Slopes (b values) of the relationship between
weight and oxygen uptake rates ranged from 0.316 to 0.590. Oxygen uptake rates were higher in air than
water and at night versus day. Q10 values were slightly below 2.0 for respiration in air for amphipods, irrespective
of weight. These physiological adaptations, along with its behaviors, habitat, and morphology,
place T. longicornis within the Group III sandhoppers of the Talitridae.