Is brood care in Nephrops norvegicus during hypoxia adaptive or a waste of energy?

Abstract

Summary 1We examined if the lobster Nephrops norvegicus exhibits active brood care and if oxygen shortage modifies such behaviour. Furthermore, adult caring behaviour was related to embryonic tolerance and cardiac response of developing embryos. 2Brood care behaviour was measured as irrigation (pleopod activity) in ovigerous and non-ovigerous females when exposed to normoxia and acute hypoxia. Survival and heart rate was analysed in embryos when exposed to acute and chronic progressive hypoxia. 3Females carrying eggs in late developmental stages exhibited brood irrigation in normoxic conditions (> 90% oxygen saturation) and the behaviour was also initiated in females with early eggs when exposed to hypoxia (30% oxygen saturation). 4Both early and late embryos survived acute exposure to 5–95% oxygen saturation Early embryos also survived chronic progressive exposure down to 5% oxygen saturation, while late embryos displayed premature hatching (< 16% oxygen saturation) and decreased survival rate (< 7% oxygen saturation). Late embryos exhibited a linear bradycardia when exposed to < 30% oxygen saturation Heartbeat pausing (intermittence) was frequent at high oxygen concentrations, whereas double heartbeats mainly occurred at < 20% oxygen saturation.