ABSTRACT: In summer, high temperatures are combined with severe nocturnal hypoxia in the shallow water of Danish fjords. Under these conditions, the prawns Palaemonetes varians (Leach) and Palaemon adspersus (Rathke) are spatially separated, with the former occupying the areas of highest temperature and lowest oxygen tension. If kept together, P. adspersus shows aggressive behaviour towards P. varians. Aerobic/anaerobic respiration and haemocyanin characteristics were measured in laboratory experiments (24°C, 14 ppt). Although the 2 species have similar metabolic rates, P. varians survives severe hypoxia better and has a lower P_c (critical oxygen tension, below which respiration is partly or fully anaerobic) than P. adspersus. Both species accumulate high levels of lactate during anaerobiosis and remove it at similar rates. The haemocyanin concentration and total oxygen carrying capacity (0.78 ± 0.25 mmol l^-1 and 2.25 ± 0.56 vol%) of P. varians was higher than P. adspersus (0.28 ± 0.07 mmol l^-1 and 1.14 ± 0.15 vol%). Haemocyanin oxygen affinity was always higher in P. varians regardless of pH, but the Bohr factor (-1.44 and -1.46) and cooperativity (n₅₀: 2.61 ± 0.20 and 2.82 ± 0.49) were similar for P. varians and P. adspersus, respectively. P. varians is thus better adapted to severe hypoxia than P. adspersus.

KEY WORDS: Aerobic/anaerobic metabolism · Lactate · Oxygen affinity

Published in MEPS Vol. 167 (1998) on June 18
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1998