title: Acute toxicity of ammonia and its effects on the haemolymph osmolality, ammonia-N, pH and ionic composition of early juvenile mud crabs, Scylla serrata (Forskål).
abstract: The current study was conducted to determine the LC(50) value of ammonia-N as well as the effects of acute exposure to elevated ammonia on the haemolymph osmolality, ionic composition, ammonia-N and pH levels of early juvenile mud crabs, Scylla serrata. The results show that early S. serrata juveniles have a high 96-h LC(50) value of 95.35 mg/L ammonia-N (6.81 mg/L NH(3)-N) or 6.80 mmol/L total ammonia-N (0.486 mmol/L NH(3)-N). Following a 96-h exposure, the haemolymph osmolality and K(+) levels of the surviving crabs remained unaltered (p>0.05) at all ammonia-N concentrations, while the haemolymph Na(+) and Ca(2+) were significantly lower (p<0.05) for the crabs exposed to 5.710 and 7.138 mmol/L ammonia-N. While the haemolymph ammonia-N levels of the crabs significantly increased (p<0.01) with increasing external ammonia-N concentrations, the haemolymph ammonia-N of the crabs remained below the external ammonia-N concentrations. The haemolymph pH of the crabs significantly increased between 0.714 and 4.283 mmol/L total ammonia-N. However, at 5.710 mmol/L total ammonia-N the haemolymph pH dropped and was not significantly different (p>0.05) from that of the control crabs which coincided with significantly lower (p<0.05) haemolymph Na(+) and Ca(2+) levels. These physiological responses may explain the high ammonia tolerance of early S. serrata juveniles.
authors.affiliation: School of Marine and Tropical Biology, James Cook University, Townsville, Qld 4811, Australia. Nicholas.Romano@jcu.edu.au
authors.forename: Nicholas
authors.initials: N
authors.lastname: Romano
authors.forename: Chaoshu
authors.initials: C
authors.lastname: Zeng
mesh_terms: D000222:Adaptation, Physiological; D000641:Ammonia / Q000633:toxicity*; D000818:Animals; D003386:Brachyura / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006458:Hemolymph / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007928:Lethal Dose 50; D009584:Nitrogen / Q000378:metabolism; D009994:Osmolar Concentration; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D013997:Time Factors; D014882:Water-Electrolyte Balance / Q000187:drug effects*
chemical_list: D000641:Ammonia; D012964:Sodium; D009584:Nitrogen; D011188:Potassium; D002118:Calcium