A Comparison of the Respiratory Function of the Haemocyamns of Vertically Migrating and Non-migrating Pelagic, Deep-sea Oplophorh) Shrimps

The effects of temperature and pH on haemocyanin oxygen-binding were compared for three species of diurnally vertically migrating and two species of non-migrating, pelagic oplophorid shrimps from the deep sea off the Hawaiian island of Oahu. The effects of L-lactate were also measured for three of these species. Haemocyanin concentrations were higher in the haemolymphs of oplophorids that migrate vertically (39.4, 46.8 and 57.6mg ml") than in those of non-migrators (26.0 and 36.4 mg ml"). Moderately high Bohr effects were found for vertically migrating and non-migrating oplophorids at all temperatures examined (5-25°C, =-0.46 to -0.80, and -0.55 to -0.88, respectively). The vertically migrating species had temperature-sensitive haemocyanins (A//=-23.1 to -41.2kJmol~) across the normal temperature range (5-25°C) encountered during diurnal vertical migration. This results in haemocyanins that have relatively high affinities (P50=0.80-1.06 kPa at pH 7.8,5 °C) at the low temperatures and low O2 partial pressures (approximately 2.66kPa O2 at 5°C) found at depth, and low affinities (P5o=4.00-4.66kPa at pH7.5, 25°C) at the higher temperatures and higher O2 partial pressures (approximately 13.33-17.50 kPa at 25°C) found in the near-surface waters. In contrast, the non-migrating species, which live within a narrower temperature range (3-6°C) and at a constant, low partial pressure of O2 (2.66-4.00 kPa), have haemocyanins with a high affinity for oxygen (P50=0.67-0.93 kPa at pH7.8, 5°C) and lower sensitivity to temperature (AH=-4.2 to -21.6kJ mol"). The effects of temperature on the haemocyanin oxygen-affinities of the vertical migrators appear to be highly adaptive, enabling these haemocyanins to be functional across the entire depth (and thus, temperature and oxygen partial pressure) range encountered.