Abstract

The physiological capacities of the chthamaloid cirripede Jehlius cirratus were evaluated under hypoxic and anoxic conditions. J. cirratus is the dominant species in the upper intertidal zone (3-6.5 m above the lowest tidal level) in southern Chile; local tidal amplitudes of 7 m on the average produce cyclic periods of food scarcity and long periods of hypoxia and anoxia, involving survival risk. J. cirratus demonstrated a high capacity for aerial respiration, with no difference between periods of emersion of 1 h and 3 h, but differing at different temperatures: it was higher at 20°C than at 10°C. Aerial respiration capacity ranged between 74.5% and 89.5% of total respiration in submersion. No significant oxygen debt was observed after maintaining the specimens in emersion for 3 h and 6 h. J. cirratus had a high survival rate in emersion at 16°C (LP50 = 25.0 days ± 4.5) and in anoxic submersion (LP50 = 8.4 days ± 3.8) and a high tolerance to desiccation, with low rates of water loss during prolonged emersion, even under high temperature conditions. These results show that J. cirratus possesses a high capacity for adaptation to emersion and desiccation. This explains their dominance in the upper intertidal zone in southern Chile, where there are large variations between tides.