TY - JOUR
T1 - Physiological and biochemical strategies for withstanding emersion in two galaxiid fishes
AU - Urbina, Mauricio A.
AU - Walsh, Patrick J.
AU - Hill, Jonathan V.
AU - Glover, Chris N.
N1 - Funding Information:
The authors thank Peter Gatehouse for access to his property for mudfish collection, and the anonymous reviewers for their thoughtful and constructive comments on earlier versions of this manuscript. This work was supported by grants from the Royal Society of New Zealand (Marsden Grant UOC0711 ) and the Brian Mason Scientific and Technical Trust to CNG. MAU was supported by a Ph.D. scholarship from the Chilean Government, CONICYT . PJW was supported by a Discovery Grant from the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Canada Research Chair Programme (CRC) .
PY - 2014/10
Y1 - 2014/10
N2 - The galaxiid fishes of the Southern hemisphere display variable tolerance to aerial exposure. Brown mudfish (Neochanna apoda), for example, pseudoaestivate, inhabiting moist soil for months at a time, whereas inanga (Galaxias maculatus) emerse under unfavourable water conditions, but only for periods of a few hours. This study sought to identify the physiological and biochemical strategies that determine emersion tolerance in these species. Nitrogenous waste excretion was measured before and after an experimental emersion period (14days for mudfish, 6h for inanga). Both species showed significantly elevated ammonia "washout" upon return to water, but no increase in plasma or muscle ammonia. Post-emersion urea levels were elevated in plasma and muscle in both fish, however the extent of the accumulation did not indicate significant de novo urea production. This was supported by the lack of carbamoyl phosphate synthetase activity in tissues. Consequently, mudfish metabolism was examined to determine whether changes in parameters such as oxygen consumption, carbon dioxide excretion, and/or altered metabolic costs (represented by the key ionoregulatory enzyme Na+, K+-ATPase; NKA) could explain emersion tolerance. Oxygen consumption rates, already very low in immersed mudfish, were largely maintained over the course of emersion. Carbon dioxide excretion decreased during emersion, and a small, but significant, decrease in NKA was noted. These data suggest that the extended emersion capacity of mudfish may result from a generally low metabolic rate that is maintained throughout aerial exposure via cutaneous gas exchange, and which limits the production of potentially toxic nitrogenous waste.
AB - The galaxiid fishes of the Southern hemisphere display variable tolerance to aerial exposure. Brown mudfish (Neochanna apoda), for example, pseudoaestivate, inhabiting moist soil for months at a time, whereas inanga (Galaxias maculatus) emerse under unfavourable water conditions, but only for periods of a few hours. This study sought to identify the physiological and biochemical strategies that determine emersion tolerance in these species. Nitrogenous waste excretion was measured before and after an experimental emersion period (14days for mudfish, 6h for inanga). Both species showed significantly elevated ammonia "washout" upon return to water, but no increase in plasma or muscle ammonia. Post-emersion urea levels were elevated in plasma and muscle in both fish, however the extent of the accumulation did not indicate significant de novo urea production. This was supported by the lack of carbamoyl phosphate synthetase activity in tissues. Consequently, mudfish metabolism was examined to determine whether changes in parameters such as oxygen consumption, carbon dioxide excretion, and/or altered metabolic costs (represented by the key ionoregulatory enzyme Na+, K+-ATPase; NKA) could explain emersion tolerance. Oxygen consumption rates, already very low in immersed mudfish, were largely maintained over the course of emersion. Carbon dioxide excretion decreased during emersion, and a small, but significant, decrease in NKA was noted. These data suggest that the extended emersion capacity of mudfish may result from a generally low metabolic rate that is maintained throughout aerial exposure via cutaneous gas exchange, and which limits the production of potentially toxic nitrogenous waste.
KW - Aerial gas exchange
KW - Aestivation
KW - Ammonia
KW - Galaxiid
KW - Lactate
KW - Lipid metabolism
KW - Mudfish
KW - Nitrogen excretion
KW - Sodium/potassium ATPase
KW - Urea
UR - http://www.scopus.com/inward/record.url?scp=84904874239&partnerID=8YFLogxK
U2 - 10.1016/j.cbpa.2014.07.006
DO - 10.1016/j.cbpa.2014.07.006
M3 - Journal Article
C2 - 25026541
AN - SCOPUS:84904874239
SN - 1095-6433
VL - 176
SP - 49
EP - 58
JO - Comparative Biochemistry and Physiology -Part A : Molecular and Integrative Physiology
JF - Comparative Biochemistry and Physiology -Part A : Molecular and Integrative Physiology
ER -