Abstract
Although thiobiotic meiofauna live under anoxia, they have higher levels of the oxygen-detoxifying enzymes catalase and superoxide dismutase (SOD) than oxybiotic species. Microoxyphilic oxybios have lower enzyme activities than other oxybiotic species. All meiofauna have lower activities than oxybiotic macrofauna. Catalase and SOD activities increased in direct proportion to sulfide tolerance in thiobios and to ambient oxygen concentration in oxybios. All meiofaunal species studied, including oxybios, are usually exposed to lower O2 concentrations than burrow-dwelling macrofauna and so have lower catalase and SOD activities. Enzyme activities in thiobios must be related to sulfide concentration and sulfide metabolism because simple oxygen exposure is an unlikely explanation. Thiobiotic catalase is insensitive to both azide and 3-amino-1,2,4-triazole, similar to a sulfide-insensitive bacterial enzyme called pseudocatalase. Catalase and SOD activities are inversely proportional to light sensitivity in three planarian species, suggesting a photo-protective role for these enzymes in these species.
Published Version
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