scholarly journals Energetically Defining the Thermal Limits of the Snow Crab

1989 ◽  
Vol 145 (1) ◽  
pp. 371-393 ◽  
Author(s):  
TIMOTHY P. FOYLE ◽  
RONALD K. O'DOR ◽  
ROBERT W. ELNER
Keyword(s):  
Food Consumption ◽  
Cold Water ◽  
Caloric Intake ◽  
Oxygen Demand ◽  
Energy Budgets ◽  
Snow Crab ◽  
Temperature Sensitive ◽  
Growth Equation ◽  
Temperature Changes ◽  
Lactate Levels

The snow crab, Chionoecetes opilio, is a cold-water species found naturally at temperatures below 5°C. Its physiology and energetics were examined to understand the metabolic limitations that restrict the snow crab to these temperatures. The species is not confined to cold water because of a limited respiratory system. Routine oxygen demand can be met even at lethal temperatures of 18°C (56 mg O2kg−1h−1, with a Q10 of 2.2). Blood lactate levels remain below 1.5 mmol l−1 and actually decline slightly with temperature. Energy budgets, which were constructed from an examination of oxygen uptake, activity and food consumption in morphometrically mature male animals between 0 and 18°C, indicate that the snow crab is energetically restricted to cold water. Rising metabolic costs overtake caloric intake around 7°C. This is probably due to digestive metabolism which is temperature-sensitive. Food consumption increases up to 6°C but then falls. Crabs stop feeding above 12°C. Although the growth equation is positive between 1 and 7°C, it becomes slightly negative below 1°C. This observation is unexpected since snow crabs are commonly found between 0 and 1°C. Slight temperature changes in the natural environment may, therefore, regulate growth and reproduction in this species.

scholarly journals Size-at-maturity shift in a male-only fishery: factors affecting molt-type outcomes in Newfoundland and Labrador snow crab (Chionoecetes opilio)

2020 ◽  
Author(s):  
Darrell R J Mullowney ◽  
Krista D Baker
Keyword(s):  
Population Density ◽  
Newfoundland And Labrador ◽  
Cold Water ◽  
Large Male ◽  
Snow Crab ◽  
Size At Maturity ◽  
Chionoecetes Opilio ◽  
Factors Affecting ◽  
Male Density ◽  
Process Factors

Abstract A sex-asymmetric downward shift in size-at-terminal-molt has recently occurred in males in some portions of the Newfoundland and Labrador (NL) snow crab stock range, a first known occurrence for such processes in snow crab (Chionoecetes opilio) stocks. This study examines plausible factors promoting the shift in size-at-terminal-molt [synonymous with size-at-maturity (SaM)] including individual size, temperature, population density, and sex ratio. Analyses highlight expanse of cold water and large male density as being significant predictors of molt-type outcomes. A confluence of cold conditions and low density of large males promoted the SaM shift. In turn, the low male density was associated with recently elevated fishery exploitation rates under quota-controlled management. It remains unknown the extent to which the reduction in terminal size reflects a phenotypic vs. genotypic process. Factors affecting skip-molting in male snow crab are investigated, and we find that skip-molting occurs most frequently under extreme cold and high population density conditions. Potential complications arising from altered growth dynamics are discussed. Overall, the results advance knowledge on intraspecific competition processes within snow crab populations and inform fisheries management systems that male-only harvest strategies do not provide full protection from biological harm to aquatic resources through fishing.

scholarly journals Smart Hydrogel Bilayers Prepared by Irradiation

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1753
Author(s):  
Weixian Huo ◽  
Heng An ◽  
Shuquan Chang ◽  
Shengsheng Yang ◽  
Yin Huang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Gamma Radiation ◽  
Antibacterial Properties ◽  
Cross Linking ◽  
Temperature Sensitive ◽  
Temperature Changes ◽  
Smart Hydrogel ◽  
Isopropyl Acrylamide ◽  
Hydrogel Synthesis ◽  
Potential Applications

Environment-responsive hydrogel actuators have attracted tremendous attention due to their intriguing properties. Gamma radiation has been considered as a green cross-linking process for hydrogel synthesis, as toxic cross-linking agents and initiators were not required. In this work, chitosan/agar/P(N-isopropyl acrylamide-co-acrylamide) (CS/agar/P(NIPAM-co-AM)) and CS/agar/Montmorillonite (MMT)/PNIPAM temperature-sensitive hydrogel bilayers were synthesized via gamma radiation at room temperature. The mechanical properties and temperature sensitivity of hydrogels under different agar content and irradiation doses were explored. The enhancement of the mechanical properties of the composite hydrogel can be attributed to the presence of agar and MMT. Due to the different temperature sensitivities provided by the two layers of hydrogel, they can move autonomously and act as a flexible gripper as the temperature changes. Thanks to the antibacterial properties of the hydrogel, their storage time and service life may be improved. The as prepared hydrogel bilayers have potential applications in control devices, soft robots, artificial muscles and other fields.

scholarly journals Impact of Global Warming on Dissolved Oxygen and BOD Assimilative Capacity of the World’s Rivers: Modeling Analysis

Water ◽  
2021 ◽  
Vol 13 (17) ◽  
pp. 2408
Author(s):  
Steven C. Chapra ◽  
Luis A. Camacho ◽  
Graham B. McBride
Keyword(s):  
Dissolved Oxygen ◽  
Natural Waters ◽  
Cold Water ◽  
Oxygen Demand ◽  
Oxygen Depletion ◽  
Assimilative Capacity ◽  
Mountainous Regions ◽  
Modeling Analysis ◽  
Lower Oxygen ◽  
The Impact

For rivers and streams, the impact of rising water temperature on biochemical oxygen demand (BOD) assimilative capacity depends on the interplay of two independent factors: the waterbody’s dissolved oxygen (DO) saturation and its self-purification rate (i.e., the balance between BOD oxidation and reaeration). Although both processes increase with rising water temperatures, oxygen depletion due to BOD oxidation increases faster than reaeration. The net result is that rising temperatures will decrease the ability of the world’s natural waters to assimilate oxygen-demanding wastes beyond the damage due to reduced saturation alone. This effect should be worse for nitrogenous BOD than for carbonaceous BOD because of the former’s higher sensitivity to rising water temperatures. Focusing on streams and rivers, the classic Streeter–Phelps model was used to determine the magnitude of the maximum or “critical” DO deficit that can be calculated analytically as a function of the mixing-point BOD concentration, DO saturation, and the self-purification rate. The results indicate that high-velocity streams will be the most sensitive to rising temperatures. This is significant because such systems typically occur in mountainous regions where they are also subject to lower oxygen saturation due to decreased oxygen partial pressure. Further, they are dominated by salmonids and other cold-water fish that require higher oxygen levels than warm-water species. Due to their high reaeration rates, such systems typically exhibit high self-purification constants and consequently have higher assimilation capacities than slower moving lowland rivers. For slow-moving rivers, the total sustainable mixing-point concentration for CBOD is primarily dictated by saturation reductions. For faster flowing streams, the sensitivity of the total sustainable load is more equally dependent on temperature-induced reductions in both saturation and self-purification.

Temperature Sensitivity of Intracellular and Extracellular Soil Enzyme Activities

2021 ◽  
Author(s):  
Adetunji Alex Adekanmbi ◽  
Laurence Dale ◽  
Liz Shaw ◽  
Tom Sizmur
Keyword(s):  
Enzyme Activity ◽  
Soil Temperature ◽  
Temperature Sensitivity ◽  
Extracellular Enzymes ◽  
Extracellular Enzyme ◽  
Daily Maximum ◽  
Temperature Sensitive ◽  
Intracellular Enzyme ◽  
Temperature Changes ◽  
Som Decomposition

<p>Predicting the pattern of soil organic matter (SOM) decomposition as a feedback to climate change, via release of CO<sub>2</sub>, is extremely complex and has received much attention. However, investigations often do not differentiate between the extracellular and intracellular processes involved and work is needed to identify their relative temperature sensitivities. Samples were collected from a grassland soil at Sonning, UK with average daily maximum and minimum soil temperature of 15 °C and 5 °C. We measured potential activities of β-glucosidase (BG) and chitinase (NAG) (extracellular enzymes) and glucose-induced CO<sub>2 </sub>respiration (intracellular enzymes) at a range of assay temperatures (5 °C, 15 °C, 26 °C, 37<sup>  </sup>°C, and 45 °C). The temperature coefficient Q<sub>10</sub> (the increase in enzyme activity that occurs after a 10 °C increase in soil temperature) was calculated to assess the temperature sensitivity of intracellular and extracellular enzymes activities. Between 5 °C and 15 °C intracellular and extracellular enzyme activities had equal temperature sensitivity, but between 15 °C and 26°C intracellular enzyme activity was more temperature sensitive than extracellular enzyme activity and between 26 °C and 37 °C extracellular enzyme activity was more temperature sensitive than intracellular enzyme activity. This result implies that extracellular depolymerisation of higher molecular weight organic compounds is more sensitive to temperature changes at higher temperatures (e.g. changes to daily maximum summer temperature) but the intracellular respiration of the generated monomers is more sensitive to temperature changes at moderate temperatures (e.g. changes to daily mean summer temperature). We therefore conclude that the extracellular and intracellular steps of SOM mineralisation are not equally sensitive to changes in soil temperature. The finding is important because we have observed greater increases in average daily minimum temperatures than average daily mean or maximum temperatures due to increased cloud cover and sulphate aerosol emission. Accounting for this asymmetrical global warming may reduce the importance of extracellular depolymerisation and increase the importance of intracellular catalytic activities as the rate limiting step of SOM decomposition.</p>

Activity-related constraints on overwintering young-of-the-year striped bass (Morone saxatilis)

2001 ◽  
Vol 79 (1) ◽  
pp. 129-136 ◽  
Author(s):  
Thomas P Hurst ◽  
David O Conover
Keyword(s):  
Food Consumption ◽  
Striped Bass ◽  
Morone Saxatilis ◽  
Metabolic Cost ◽  
Hudson River ◽  
Energetic Cost ◽  
Energy Budgets ◽  
Swimming Velocity ◽  
Thermal Dependence ◽  
Young Of The Year

The importance of activity to overwintering fishes has received little attention. Activity imposes two constraints: maximum swimming speed limits habitats that can be occupied for short periods of time, while the metabolic cost of swimming limits the habitats that are suitable for long-term residence. We measured the energetic consequences of activity and maximum swimming speeds of young-of-the-year striped bass (Morone saxatilis), a species that overwinters in tidal estuaries. The energetic cost of swimming was determined from energy changes in unfed fish forced to swim at various speeds, while energy changes in fed fish provided a measure of their ability to offset swimming costs through feeding. In high-velocity treatments, mortality was size-dependent and appeared to be related to fatigue rather than to depletion of energy reserves. The energetic cost of swimming increased with swimming velocity, but fish increased food consumption and thereby met their metabolic needs. In a second experiment the thermal dependence of swimming capacity in winter-acclimated striped bass was measured. Swimming speeds increased with temperature, from 2.7 body lengths (BL)/s at 2°C to 4.8 BL/s at 8 and 11°C, but were considerably below observed flow velocities in the Hudson River, suggesting a need for behavioral or physical refuge from tidal currents. These results indicate the flexibility of energy budgets of overwintering fishes, allowing energetic stress to be minimized by reducing activity or elevating food-consumption rates when sufficient prey are available.

Ventilatory and treadmill endurance during acute semistarvation

1986 ◽  
Vol 60 (6) ◽  
pp. 1823-1827 ◽  
Author(s):  
P. R. Bender ◽  
B. J. Martin
Keyword(s):  
Muscle Strength ◽  
Metabolic Rate ◽  
Caloric Restriction ◽  
Basal Metabolic Rate ◽  
Treadmill Exercise ◽  
Caloric Intake ◽  
Blood Levels ◽  
Disease States ◽  
Lactate Levels ◽  
Beta Hydroxybutyrate

Little is known about respiratory muscle function in acute undernutrition, although an inadequate caloric intake is common in numerous disease states. Twelve young-adult, healthy female volunteers performed two familiarization experiments and were then studied after 7 days of consuming 40% of normal daily caloric intake as well as after 1 wk of normal caloric intake. In each experiment subjects performed tests of resting pulmonary function, inspiratory muscle strength, and ventilatory endurance, the last of which involved two 60-s and two 6-min isocapnic maximum voluntary ventilation maneuvers. Subjects then walked to exhaustion in 8–20 min on a treadmill. The caloric restriction did not affect performance of any breathing test but did lower endurance time in severe treadmill exercise (P less than 0.05). Basal metabolic rate was lowered, resting blood levels of free fatty acids and beta-hydroxybutyrate elevated, and glucose lowered following the caloric restriction (P less than 0.05). Blood lactate levels were lower during and after exercise following caloric restriction (P less than 0.05). We conclude that ventilatory muscle strength and endurance are fully preserved in caloric restriction severe enough to cause mild ketoacidosis and hypoglycemia, lowered basal metabolic rate, and decreased endurance in severe treadmill exercise.

A Niche Definition for Lake Trout (Salvelinus namaycush) and Its Use to Identify Populations at Risk

1994 ◽  
Vol 51 (11) ◽  
pp. 2513-2519 ◽  
Author(s):  
Phil A. Ryan ◽  
Terry R. Marshall
Keyword(s):  
Oxygen Content ◽  
Lake Trout ◽  
Cold Water ◽  
Natural Populations ◽  
Oxygen Demand ◽  
Oxygen Depletion ◽  
Salvelinus Namaycush ◽  
Phosphorus Concentration ◽  
Suitable Habitat ◽  
Populations At Risk

Lake trout (Salvelinus namaycush) populations require cold water with high dissolved oxygen content for survival. We developed models that predict the availability of such habitat, using lake mean depth, which describes both the thermal regime and the initial oxygen reserves, and using a measure of primary productivity, which defines the subsequent oxygen demand of the sediments and water column. Measures of primary production include either phosphorus concentration, chlorophyll a concentration, or Secchi disk transparency. The models are presented as a series of seasonal oxygen depletion isopleths that predict the extent to which the oxygen content of thermally suitable habitat is lost during the period of thermal stratification. The presence or absence of native lake trout in lakes of northwestern Ontario superimposed on these graphs indicated that natural populations seldom occur in lakes in which the seasonal oxygen depletion exceeds 40%. This isopleth is a niche boundary in its representation of adverse temperature and oxygen conditions for lake trout. The delineation of this boundary permits the identification of lakes where lake trout populations could be seriously affected by cultural eutrophication, overfishing, or climate warming.

A generic model to estimate food consumption: linking von Bertalanffy’s growth model with Beverton and Holt’s and Ivlev’s concepts of net conversion efficiency

2009 ◽  
Vol 66 (4) ◽  
pp. 683-700 ◽  
Author(s):  
Axel Temming ◽  
Jens P. Herrmann
Keyword(s):  
Food Consumption ◽  
Growth Model ◽  
Conversion Efficiency ◽  
Gadus Morhua ◽  
Generic Model ◽  
Similar Degree ◽  
Growth Equation ◽  
Von Bertalanffy ◽  
Gastric Evacuation ◽  
Consumption Rates

In this paper, a mathematical derivation is presented that links von Bertalanffy’s growth model with the concept of net conversion efficiency of Beverton and Holt, aiming at the development of an equation that can calculate food consumption rates of wild populations from parameters of the von Bertalanffy growth equation and an estimate of the net food conversion efficiency of Beverton and Holt. The derivation is based on Pauly’s version of the generalized von Bertalanffy equation, which allows the allometric exponent of the anabolism term to differ from 2/3, as in the standard von Bertalanffy equation. As a side product, a general model is formulated that describes the gross growth conversion efficiency (K1 of Ivlev) as a function of weight of the organism. The new equations for the estimation of food consumption are applied in two case studies, North Sea cod ( Gadus morhua ) and whiting ( Merlangius merlangus ), for which a variety of consumption estimates is available from conventional gastric evacuation-based methods. The new method produces results that show a similar degree of variability as was observed in various applications of the gastric evacuation method.

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