Adaptations of a deep sea scavenger: High ammonia tolerance and active NH4+ excretion by the Pacific hagfish (Eptatretus stoutii)

摘要: Abstract The Pacific hagfish ( Eptatretus stoutii ) has an exceptional ability to both withstand and recover from exposure high external ammonia (HEA). This tolerance is likely due the feeding behavior of this scavenger, which feeds on intermittent food falls carrion (e.g. fish, large marine mammals) during time it may be exposed concentrations total T Amm  = NH 3  + NH 4 + while burrowed inside decomposing carcass. Here we 20 mmol L − 1 for periods up 48 h then let animals in ammonia-free seawater. During HEA period, plasma increased 100-fold over 5000 μmol L excretion J amm was transiently inhibited. increase resulted NH influx down massive inwardly directed Δ P NH3 gradients, also led a short-lived metabolic alkalosis. Plasma [ ] stabilized after 24–48 h, possibly through reduction permeability across body surface, lowered influx. Ammonia balance subsequently maintained re-establishment against . Calculations Nernst potential strongly indicated that taking place electrochemical gradient. Recovery water characterized by washout, restoration near control concentrations. clearance accompanied residual acidosis, offset ammonia-induced alkalosis seen early stages exposure. We conclude involves secondary active transport , mediated Na /NH (H exchange.