Blood gas transport and oxygen consumption in a supralittoral crab, Leptograpsus variegatus (Crustacea: Brachyura)

Abstract

Routine oxygen consumption of Leptograpsus variegatus in air (M_O2=6.12 mass (g)^0.854 µmol h^-1) was elevated from three to six times (depending on body size) following exhausting exercise (M_O2= 42.8 mass^0.608 µmol h^-1). In addition, considerable capacity for anaerobic exercise was apparent and total body L-lactate rose 4.8 times during the exercise period (25-g crab). The respiratory pigment (haemocyanin) had a low affinity under normoxic resting conditions (P₅₀=25 Torr, where 1 Torr = 101 325/760 Pa) but showed a large Bohr effect (Bohr factor = -0.78), a marked temperature sensitivity (ΔH= 67.4 kJ mol^-1), and a large potentiating effect by L-lactate (lactate coefficient = - 0.205). These features are more characteristic of the haemocyanin of aquatic crustaceans than those of terrestrial crustaceans. The affinity of the haemocyanin of L. variegatus was also decreased by elevated P_CO2. Haemocyanin was responsible for 92% of oxygen transport in both resting and exercised crabs. These features are discussed in relation to the degree of adaptation of L. variegatus to a terrestrial lifestyle.