title: Acute exposure to high environmental ammonia (HEA) triggers the emersion response in the green shore crab.
abstract: The physiological effects of high environmental ammonia (HEA) exposure have been well documented in many aquatic species. In particular, it has recently been demonstrated that exposure to ammonia in fish leads to a similar hyperventilatory response as observed during exposure to hypoxia. In littoral crabs, such as the green crab (Carcinus maenas), exposure to severe hypoxia triggers an emersion response whereby crabs escape hypoxia to breathe air. We hypothesized that exposure to HEA in green crabs would lead to a similar behavioural response which is specific to ammonia. Using an experimental arena containing a rock bed onto which crabs could emerse, we established that exposure to HEA (4mmol/l NH4HCO3) for 15min triggers emersion in crabs. In experiments utilizing NaHCO3controls and NH4HCO3injections, we further determined that emersion was triggered specifically by external ammonia and was independent of secondary acid-base or respiratory disturbances caused by HEA. We then hypothesized that emersion from HEA provides a physiological benefit, similar to emersion from hypoxia. Exposure to 15min of HEA without emersion (no rock bed present) caused significant increases in arterial haemolymph total ammonia (Tamm), pH, and [HCO3-].When emersion was allowed, arterial haemolymph Tammand [HCO3-] increased, but no alkalosis developed. Moreover, emersion decreased haemolymph partial pressure of NH3relative to crabs which could not emerse. Overall, we demonstrate a novel behavioural response to HEA exposure in crabs which we propose may share similar mechanistic pathways with the emersion response triggered by hypoxia.
authors.affiliation: Department of Biology, University of Ottawa, Ottawa K1N 6N5, ON, Canada; Department of Zoology, University of British Columbia, Vancouver V6T 1Z4, BC, Canada; Bamfield Marine Sciences Centre, Bamfield V0R 1B0, BC, Canada. Electronic address: azimmer@uottawa.ca.
authors.forename: Alex M
authors.initials: AM
authors.lastname: Zimmer
authors.affiliation: Department of Zoology, University of British Columbia, Vancouver V6T 1Z4, BC, Canada; Bamfield Marine Sciences Centre, Bamfield V0R 1B0, BC, Canada.
authors.forename: Chris M
authors.initials: CM
authors.lastname: Wood
mesh_terms: D000641:Ammonia / Q000633:toxicity*; D000818:Animals; D003445:Crustacea / Q000502:physiology*; D004781:Environmental Exposure; D006801:Humans
chemical_list: D000641:Ammonia
keywords: Acid-base balance; Air exposure; Ammonia sensing; Behaviour; Carcinus maenas