The metabolic response to hypoxia and emersion of aestivating fishes (Lepidogalaxias salamandroides and Galaxiella nigrostriata) and a non-aestivating fish (Bostockia porosa) from south-western Australia

We measured the metabolic rate of three fishes (Lepidogalaxias salamandroid es, Galaxiella nigrostriata, Bostockia porosa) that are endemic to the sout h-west of Western Australia. The first two species have been reported to ae stivate, the third does not aestivate when the ponds dry up in late summer. For normoxic conditions, the metabolic rates of B. porosa and G. nigrostri ata in water (0.48 mL g(-1) h(-1) and 0.44 mL g(-1) h(-1) respectively), ar e significantly higher than in air (0.21 mL g(-1) h(-1) and 0.08 mL g(-1) h (-1) respectively) but for the more benthic and terrestrially mobile L. sal amandroides there was no significant difference between (V) over dot O-2 in water (0.29 mL g(-1) h(-1)) and air (0.18 mL g(-1) h(-1)). Progressive hyp oxia (12, 5 and 2% O-2) decreased the metabolic rate of G. nigrostriata and B. porosa in both water and air but there was a reduction in metabolic rat e for L. salamandroides only in water. The metabolic physiology of L. salam androides in water and air is consistent with the capacity to aestivate in moist soil, but the different metabolic response of G. nigrostriata suggest s that it adopts a different strategy to L. salamandroides to survive when the ponds dry up in summer. The metabolism of G. nigrostriata in air and wa ter declines with progressive hypoxia (from 12 to 5 to 2% O-2) B. porosa do es not appear to be able to cope metabolically when out of water or under h ypoxic conditions, and therefore would not be able to aestivate.