THE ANAEROBIC ENDPRODUCT LACTATE HAS A BEHAVIORAL AND METABOLIC SIGNALING FUNCTION IN THE SHORE CRAB CARCINUS-MAENAS

This study presents the first evidence that, in invertebrates, the ana erobic endproduct lactate has an alarm signal function and induces met abolic and behavioural responses as in the anuran Bufo marinus. In sup port of this function, behavioural hypothermia was demonstrated in the shore crab Carcinus maenas. The animals moved to a cooler environment when exposed to hypoxic conditions. A decrease in preferred temperatu re of the same magnitude was also found when normoxic animals were inj ected with an iso-osmotic lactate solution resulting in a haemolymph c oncentration of approximately 12 mmoll(-1). Under normoxic (P-o2=>18kP a) and moderately hypoxic conditions (P-o2=12kPa), injection of this l actate solution also caused a significant increase in the rate of oxyg en consumption (100 and 50% respectively). The increase in the rate of oxygen consumption was smaller and delayed, but lasted longer, under hypoxic conditions compared with normoxic conditions, Low but signific ant correlations between levels of lactate and levels of adrenaline, o ctopamine and tryptophan suggest the involvement of biogenic amines in the mediation of the signal.