Respiration, ventilation and circulation under hypoxia in the glacial relict Saduria (Mesidotea) entomon

Abstract

The glacial relict Saduria (Mesidotea) entornon (L.) (Crustacea: Isopoda) lives buried in sandy/muddy bottoms in the Baltic. During hypoxia Saduria remains buried until oxygen tension (P,Oz) has decreased to < 5 Torr (8°C; 7 % S). Respiration rate (MO2) for buried Saduria was lower than for other crustaceans of similar size. Saduria is able to maintain a stable MO2 with decreasing P,Oz down to < 5 to 10 Torr, i.e. in practice over the entire P , 0 2 range. After exposure to severe hypoxia for many hours a respiratory overshoot was sometimes found. Only small amounts of haemolymph lactate had accumulated at P,02 = < 5 Torr; up to 30mg 100ml-' after 144 h exposure. The presence of anaerobic endproducts other than lactate is suggested. Patterns of heartbeat frequency (fh) and gill ventilation (6) changed considerably, but gradually, with time in buried Saduria. Normoxic fh varied from 0 to 120 beats min-' in a cyclic sequence lasting 5 to 6 min. f, varied in a similar way although with different rates. At P,Oz = < 10 Torr the acute ventilatory response was a high stroke frequency, but after some hours the ventilatory pattern changed to the same cyclic sequence as at higher P,,02, f, retained the same cyclic sequence in hypoxia as in normoxia but without cardiac arrests. Cardiac output remained constant over the entire P, O: ! range but ventilatory efficiency increased with decreasing P,02. Respiratory independence is governed by changes in ventilatory pump flow and in behaviour in order to facilitate the transfer of oxygen from the often hypoxic Baltic bottom water to respiratory tissues.

The influence of defined ante-mortem stressors on the early post-mortem biochemical processes in the abdominal muscle of the Norway lobster,Nephrops norvegicus(Linnaeus, 1758)

“…In Nephrops norvegicus it was shown that not only anoxia (through aerial exposure) but also the hypoxic conditions (10Á30% O 2 saturation) in the bottom water of certain fishing grounds cause significant glycogen depletion, thus indicating anaerobic fermentation (Baden et al 1994). Interestingly, some animals like Saduria entomon (Linnaeus, 1758) can also maintain their oxygen demand (aerobic ATP production) for some time by adaptation of ventilation and haemolymph circulation frequencies, before ultimately switching to anaerobic pathways (Hagerman & Szaniawska 1988).…”

Haemolymph nitrogen compounds and ammonia efflux rates under anoxia in the brackish water isopod Saduria entomon

“…Leonardsson et al 1987, Hagerman & Szaniawska 1988, 1990, 1991, 1992, Haahtela 1990, Vismann 1991. These studies have revealed S. entomon to be a most adaptable species with an exceptional tolerance of anoxia and hydrogen sulphide concentrations.…”

“…Although the respiratory responses of Saduria entomon have been studied intensively (Hagerman & Szaniawska 1988, 1990, 1991, 1992, the origin and fate of the nitrogenous end products of this species are not well known. The purpose of the present study was thus to investigate ammonia efflux rates and haemolymph nitrogen compounds under anoxia in S. entomon.…”

Anaerobic metabolic strategy of the glacial relict isopod Saduria (Mesidotea) entomon

“…Anaerobic metabolism, starting when oxygen extraction can no longer be maintained, results in only a slight increase in haemolymph lactate with time in Saduria entomon (Hagerman & Szaniawska 1988). This is surprising as lactate is normally the only endproduct of anaerobic glycolysis in crustaceans (de Zwaan & Putzer 1985).…”

“…It is a very eurybiontic species showing extremely high tolerances to anoxia and salinity variations, whilst temperatures above 12 to 15 "C are lethal (Hagerman & Szaniawska unpubl.). The metabolic rate is low with a high efficiency of oxygen extraction making it possible to maintain a stable MOz respiratory rate down to 5 or 10 Torr (Hagerman & Szaniawska 1988). Even at low p,02 S. entomon seems to be active, undertaking digging and feeding.…”