A field versus laboratory study of blood oxygen status in normoxic crabs at different temperatures

Abstract

The blood oxygen status of two species of active crabs (Carcinus maenas and Necora puber) was studied in the field and compared with the results of previous laboratory experiments performed on a wide spectrum of physiologically different water-breathers. The aim was to determine whether, as in the laboratory, the functioning of the O 2 supply system in the field could be based on maintaining the arterial [Formula: see text] in the low range, 1–3 kPa. The O 2 partial pressures and concentrations in the arterial and venous blood, arterial blood pH, and blood respiratory pigment concentration were measured in normoxic water at various temperatures ranging from 10 to 20 °C and in various seasons. In the field, [Formula: see text] values in normoxic C. maenas and N. puber were in the low range, 1–3 kPa, independently of temperature, season, and blood haemocyanin concentration. It is concluded that in the field as in the laboratory, [Formula: see text] values mainly in the low range provide a head pressure sufficient to meet O 2 needs. The changes that appear to occur in other respiratory variables are discussed in relation to field versus laboratory conditions and temperature differences. The consequences for analysing problems of hypoxaemia in hypoxic waters or situations are discussed.