RESUMEN
This work aimed to evaluate the whole-organism and cellular level responses to different combinations of water temperature and salinity of the notothenioid Patagonotothen cornucola at the end of the yolk-sac larval stage. Egg masses of the species were collected in the wild and then maintained at natural water conditions (4 °C and 30 PSU). Newly hatched larvae were placed in aquaria with different combinations of water temperature (4 °C, 12 °C, and 16 °C) and salinity (15 and 30 PSU) during four days before yolk sac absorption. Larvae exposed to 12 °C grew more in length than those exposed to 16 °C, but yolk volume was more reduced in larvae exposed to 16 °C than those exposed to 4 °C and 30 PSU than of 15 PSU. In addition, a higher proportion of larvae exposed to 12 °C and 15 PSU completely absorbed their yolk. Whereas the more tolerant larvae to high temperatures were those exposed to 16 °C and 30 PSU, lipid peroxidation and protein oxidation were highest at natural and at 12 °C and 30 PSU conditions, respectively. The nutritional status (as standardized DNA/RNA index-sRD -) was low in all cases, even at natural conditions (average sRD ~ 1). Our study suggests that, in the context of climate change, the mortality rate of yolk-sac larvae of P. cornucola would not increase due to temperature or salinity stress. However, indirect effects (such as habitat degradation or changes in food availability) would be critical after complete absorption of the yolk.
Asunto(s)
Perciformes , Salinidad , Animales , Peces , Larva , Perciformes/fisiología , Temperatura , Agua , Saco VitelinoRESUMEN
We evaluated the effects of projected, near future ocean acidification (OA) and extreme events of temperature (warming or cooling) on the thermal tolerance of Concholepas concholepas, a coastal benthic keystone species. Three separate trials of an experiment were conducted by exposing juvenile C. concholepas for 1â¯month to one of two contrasting pCO2 levels (~500 and ~1200⯵atm). In addition, each pCO2 level was combined with one of four temperature treatments. The control was 15⯰C, whilst the other temperatures were 10⯰C (Trial 1), 20⯰C (Trial 2) and 25⯰C (Trial 3). At the end of each trial, we assessed Critical Thermal maximum (CTmax) and minimum (CTmin) via self-righting success, calculated partial thermal tolerance polygons, measured somatic growth, determined transcription of Heat Shock Proteins 70 (HSP70) and measured oxygen consumption rates. Regardless of pCO2 level, HSP70 transcript levels were significantly higher in juveniles after exposure to extreme temperatures (10⯰C and 25⯰C) indicating physiological stress. Oxygen consumption rates increased with increasing temperature from 10⯰C to 20⯰C though showed a decrease at 25⯰C. This rate was not affected by pCO2 or the interaction between temperature and pCO2. Juveniles exposed to present-day and near future pCO2 levels at 20⯰C showed similar thermal tolerance polygonal areas; whilst changes in both CTmin and CTmax at 25⯰C and 10⯰C caused narrower and broader areas, respectively. Temperature affected growth, oxygen consumption and HSP70 transcription in small juvenile C. concholepas. Exposure to elevated pCO2 did not affect thermal tolerance, growth or oxygen consumption at temperatures within the thermal range normally experienced by this species in northern Chile (15-20⯰C). At elevated pCO2 conditions, however, exposure to warmer (25⯰C) or colder (10⯰C) temperatures reduced or increased the thermal area, respectively. This study demonstrates the importance of examining the thermal-tolerance edges to better understand how OA and temperature will combine to physiologically challenge inter-tidal organisms.
Asunto(s)
Gastrópodos , Animales , Dióxido de Carbono , Chile , Concentración de Iones de Hidrógeno , Agua de Mar , TemperaturaRESUMEN
The influence of temperature on the aerobic metabolism and the energetic cost of food intake (Specific Dynamic Action; SDA) have been investigated in four species of Sub-Antarctic teleosts. The species were the notothenioids Paranotothenia magellanica, Patagonotothen sima and Harpagifer bispinis and the zoarcid Austrolycus depressiceps. Individuals were captured in the vicinity of Ushuaia Bay. Experimental temperatures were 10, 4 and 2 degrees C, which correspond to summer, winter and extreme winter respectively. Individual respirometry chambers and calorimetric techniques were used. Different food items were provided: crustaceans (isopods and amphipods) and Argentinean hake muscle. Interspecific analysis was done on species fed with isopods. A rapid increase in oxygen consumption was registered after meals, indicating a typical SDA response. The Duration of the SDA was longer at low temperatures. The extra energy spent during the process itself, and when expressed as a percentage of consumed food energy, decreased with decreasing temperature. The SDA Coefficient was higher for H. bispinis that were fed with isopods. We suggest that decreases in temperature diminish the metabolic cost and extend SDA. Energy-saving mechanisms could be an evolutionary advantage to minimize the energetic cost of living at low sub-Antarctic temperatures. A general model of exponential decay is suggested for the duration of SDA and Temperature, based on the present study and compiled from literature data.