Weight-specific Oxygen Consumption Rates Research Articles

Adaptive responses in uteroplacental metabolism and fetoplacental nutrient shuttling and sensing during placental insufficiency.

Glucose, lactate, and amino acids are major fetal nutrients. During placental insufficiency-induced intrauterine growth restriction (PI-IUGR), uteroplacental weight-specific oxygen consumption rates are maintained, yet fetal glucose and amino acid supply is decreased and fetal lactate concentrations are increased. We hypothesized that uteroplacental metabolism adapts to PI-IUGR by altering nutrient allocation to maintain oxidative metabolism. Here, we measured nutrient flux rates, with a focus on nutrients shuttled between the placenta and fetus (lactate-pyruvate, glutamine-glutamate, and glycine-serine) in a sheep model of PI-IUGR. PI-IUGR fetuses weighed 40% less and had decreased oxygen, glucose, and amino acid concentrations and increased lactate and pyruvate versus control (CON) fetuses. Uteroplacental weight-specific rates of oxygen, glucose, lactate, and pyruvate uptake were similar. In PI-IUGR, fetal glucose uptake was decreased and pyruvate output was increased. In PI-IUGR placental tissue, pyruvate dehydrogenase (PDH) phosphorylation was decreased and PDH activity was increased. Uteroplacental glutamine output to the fetus and expression of genes regulating glutamine-glutamate metabolism were lower in PI-IUGR. Fetal glycine uptake was lower in PI-IUGR, with no differences in uteroplacental glycine or serine flux. These results suggest increased placental utilization of pyruvate from the fetus, without higher maternal glucose utilization, and lower fetoplacental amino acid shuttling during PI-IUGR. Mechanistically, AMP-activated protein kinase (AMPK) activation was higher and associated with thiobarbituric acid-reactive substances (TBARS) content, a marker of oxidative stress, and PDH activity in the PI-IUGR placenta, supporting a potential link between oxidative stress, AMPK, and pyruvate utilization. These differences in fetoplacental nutrient sensing and shuttling may represent adaptive strategies enabling the placenta to maintain oxidative metabolism.NEW & NOTEWORTHY These results suggest increased placental utilization of pyruvate from the fetus, without higher maternal glucose uptake, and lower amino acid shuttling in the placental insufficiency-induced intrauterine growth restriction (PI-IUGR) placenta. AMPK activation was associated with oxidative stress and PDH activity, supporting a putative link between oxidative stress, AMPK, and pyruvate utilization. These differences in fetoplacental nutrient sensing and shuttling may represent adaptive strategies enabling the placenta to maintain oxidative metabolism at the expense of fetal growth.

Postprandial Ammonia Excretion and Oxygen Consumption Rates in Olive Flounder Paralichthys olivaceus Fed Two Different Feed Types According to Water Temperature Change

Postprandial ammonia excretion and oxygen consumption in olive flounder Paralichthys olivaceus fed two different feed types, moist pellet (MP) and expanded pellet (EP) diets, to satiation were determined at <TEX>$12^{\circ}C$</TEX>, <TEX>$15^{\circ}C$</TEX>, <TEX>$20^{\circ}C$</TEX>, and <TEX>$25^{\circ}C$</TEX> for 48 h. The ammonia excretion and oxygen consumption rates increased with increasing water temperature. However, the postprandial times for the maximum rates of ammonia excretion and oxygen consumption were shortened from 12 h to 6 h after feeding with increasing water temperature. The ammonia excretion and oxygen consumption rates of the fish fed EP were significantly higher (P < 0.05) than those fed MP at 12 h post-feeding both for <TEX>$12^{\circ}C$</TEX> and <TEX>$15^{\circ}C$</TEX>. The highest (P < 0.05) weight-specific ammonia excretion rates at <TEX>$12^{\circ}C$</TEX> were observed in the fish fed EP and MP at <TEX>$12.1mg\;NH_3-N\;kg^{-1}h^{-1}$</TEX> and <TEX>$8.7mg\;NH_3-N\;kg^{-1}h^{-1}$</TEX>, respectively, for 12 h and 9 h after feeding. The highest (P < 0.05) weight-specific oxygen consumption rates at <TEX>$12^{\circ}C$</TEX> were observed in fish fed EP and MP at <TEX>$116.4mg\;kg^{-1}h^{-1}$</TEX> and <TEX>$101.0mg\;kg^{-1}h^{-1}$</TEX>, respectively, for 12 h after feeding. The highest ammonia excretion rates at <TEX>$25^{\circ}C$</TEX> in the fish fed EP and MP increased to <TEX>$16.9mg\;NH_3-N\;kg^{-1}h^{-1}$</TEX> and <TEX>$18.3mg\;NH_3-N\;kg^{-1}h^{-1}$</TEX>, respectively, for 6 h after feeding. The highest (P < 0.05) weight-specific oxygen consumption rates at <TEX>$25^{\circ}C$</TEX> were observed in fish fed EP and MP at <TEX>$184.3mg\;O_2kg^{-1}h^{-1}$</TEX> and <TEX>$197.3mg\;O_2kg^{-1}h^{-1}$</TEX>, respectively. These data are valuable for the design of biofilters and development of effluent treatment technologies for the land-based flounder farms.

English

AbstractVariable crayfish, Cambarus latimanus (LeConte), were collected and acclimated to four temperatures, 15, 20, 25, and 30°C. Following a two-week acclimation period, mean standard metabolic rates (SMR), as determined using oxygen consumption rates, were measured using an intermittent-flow, closed-loop respirometer. For ~10g mean weight C. latimanus, mean weight specific oxygen consumption rates (MO2) at 15, 20, 25, and 30°C were 73.4 ± 0.18, 81.6 ± 0.10, 103 ± 0.11, and 205 ± 0.12 mg O2·kg-1·h-1 (±SE), respectively. Calculated Q10 values of 1.25, 1.61, and 3.92 for the change in metabolic rate from 15 – 20°C, 20 – 25°C, and 25 – 30°C suggest the crayfish were responding normally to temperature increases and were metabolically stressed when temperatures increased above 25°C. Daily caloric energy budgets of 58 (15°C), 65 (20°C), 82 (25°C), and 164 (30°C) calories·day-1 were estimated for crayfishes using SMR data and suggested that crayfish standard (resting) energy requirements nearly tripled when acclimated to 15 versus 30°C. Overall, these data suggest that increased temperatures have substantial effects on C. latimanus energy demands which may reduce potential growth and reproduction.

Oxygen consumption of doliolids (Tunicata, Thaliacea)

The goal of our study was to determine the oxygen consumption of gonozooids of the doliolid Dolioletta gegenbauri at near-environmental conditions. Time-series experiments included three different food concentrations and having the gonozooids suspended during the entire study periods while recording oxygen concentrations in the experimental vessels continuously with integrated planar optodes. Hourly oxygen consumption increased evenly with increasing body weight implying that weight-specific oxygen consumption rates did not change with increasing weight i.e. they were weight-independent. Weight-specific oxygen consumption rates at 218C resulted in average daily metabolic expenditures of 32.0% of body carbon. These rates were in the range of those of salps which had been collected in situ, and of non-feeding ephyrae of Aurelia aurita which were of similar weight as our gonozooids. No significant differences in oxygen consumption rates and metabolic expenditures among zooids feeding at different food levels were observed. Factors probably masking differences in oxygen rates were: (i) ingestion of the animal’s own fecal pellets, (ii) experimental time of 5 h being too short to detect food-related changes in the respiration level and (iii) increase in O2 consumption due to increased motion in small experimental vessels.

Evidence of phenotypic plasticity and local adaption in metabolic rates between components of the Icelandic cod (Gadus morhua L.) stock

Phenotypic plasticity and local adaptations are important considerations in delineating population structure of marine fishes and critical to their conservation and management. We compared the weight-specific oxygen consumption rates (VO2/M) of juvenile cod from the northern and southern components of the Icelandic stock acclimated to 4.0°C, 8.5°C, and 12.6°C and their metabolic response to abrupt temperatures changes within this range. Southern individuals exhibited VO2/M up to 50% higher than their northern counterparts when tested at their acclimation temperature. However, northern fish generally experienced greater changes in VO2/M, three to six-fold increases, relative to that expected at acclimation when moved to higher temperatures. Southern cod showed a greater decrease in VO2/M when exposed to lower temperatures. Our results indicate physiological differences exist between the northern and southern components of the Icelandic cod stock and warrant considering them as two distinct populations.

Effect of body weight and acclimated temperature on the respiration physiology on seawater snail Planaxis sulcatus

This study was designed in Marine Sciences station (Aqaba) during the period September 2000 to October 2001 . The study of the effect of body weight on the metabolic rate revealed the presence of a proportional relationship between the metabolic and body weight and the presence of inverse relationship between the metabolic and body weigh.In snails acclimated to 10 ºC, 20 ºC, and 30 ºC, the Weight specific metabolic rate was influenced by both acclimation as well as experimental temperature. Thus, the oxygen consumption rate increased 1n 10 ºC acclimated snail from 44 µl O2. gˉ¹ . hrˉ ¹ to 105 µl O2. gˉ¹ . hrˉ ¹ As a result of increasing the experimental temperature from 10 ºC to 30. ºC In 20 and 30 ºC acclimated snail, and as a result of increasing the experimental temperature from 10 to 30, the weight specific oxygen consumption rates increased (20 ºC and 30 ºC ) from 40 µl O2. gˉ¹ . hrˉ ¹ to 88 and 35 to 85 µl O2. gˉ¹ . hrˉ ¹ Respectively. Snails acclimated to 10 ºC ,20 ºC and 30 ºC showed Precht s type 3 normal the(partial) compensation in weight specific oxygen consumption rate , since at all experiment temperatures , the highest oxygen consumption rate was observed in 10 ºC Acclimated animals, whereas the lowest rate was observed in 30 ºC acclimated snails.

Effects of temperature on food consumption, growth and oxygen consumption of freshwater prawn Macrobrachium rosenbergii (de Man 1879) postlarvae

Effects of temperature on food consumption, growth and oxygen consumption were estimated for the freshwater prawn Macrobrachium rosenbergii postlarvae at 23 °C, 28 °C and 33 °C in the laboratory. The results showed that the animal's initial body weight had a close linear relationship with food consumption and growth. Food consumption increased directly with temperature. Consumption rates (C; mg day−1 ind−1 ) of the 28 °C and 33 °C groups were much higher than that of the 23 °C group (P < 0.001), and the 33 °C group's consumption rate was higher than that of the 28 °C group (P < 0.05). The relationship of food consumption with temperature and initial body weight (W; mg) could be described as: C = 0.0679W + 0.185t− 3.17. Growth increased significantly with increased temperature. The relationship among specific growth rate, temperature and initial body weight was as follows: SGR = −0.110W + 0.213t + 0.176. However, temperature showed no effect on growth efficiency. Oxygen consumption increased significantly with temperature (P < 0.01). The weight-specific oxygen consumption rates (mg O2 g−1 h−1) at 23 °C, 28 °C and 33 °C were 0.83, 1.16 and 1.49 mg O2 g−1 h−1 for 61.92 mg M. rosenbergii.

Oxygen Consumption Rate and Swimming Efficiency of the Blacknose Shark, Carcharhinus acronotus

Oxygen consumption rates and swimming efficiency of 10 blacknose sharks (4787 cm total length and 0.45-3.51 kg weight), Carcharhinus acronotus, were determined using a closed, circular respirometer. Swimming speed ranged from 20-40 cm sec-1 and averaged 30.8 (? 0.48 SE) cm sec-1. Routine weight specific oxygen consumption rates increased from 278.5 mg 02 kg-' h-1 for a 3.5 kg shark to 486 mg 02 kg-' h-1 for a 0.8 kg shark. The relationship of swimming speed and weight specific oxygen consumption rate for sharks 0.45-0.85 kg was described by the equation log V02 = 0.007 U + 2.38, r2 = 0.31, P = 0.006, where U is swimming speed in cm sec-'. Mean standard metabolic rate, the amount of oxygen consumed at zero activity, was calculated by extrapolating to zero swimming speed and was 239.8 mg 02 kg-l h-1. Total cost of transport (cal g-i km-l), the energy required to travel a given distance at a particular speed, was used as a measure of overall swim efficiency. Highest total cost of transport (1.68 cal g-~ km-') was at 25 cm sec-1 and decreased with increasing speed. Swimming efficiency was optimal at speeds of 3639 cm sec-1. Results suggest blacknose sharks have higher routine oxygen consumption rates and total cost of transport, but the cost of locomotion was similar to other active, tropical sharks. STUDIES on shark oxygen consumption rates

Metabolic responses of Nephrops norvegicus to progressive hypoxia

This work studied some of the metabolic responses of Nephrops norvegicus to a progressive reduction in water oxygen tension (PwO 2) at 12 °C. Experiments were designed to simulate water quality conditions that may occur during the trade of live crustaceans. Oxygen consumption rates and ammonia efflux rates were found to be constant over a wide range of PwO 2 values (20.4–5.9 kPa). A similar result was found for the difference between post-branchial and pre-branchial oxygen concentrations (20.4–2.6 kPa), obtained from a separate experiment. Anaerobic pathways, however, were activated after PwO 2 reached 6.3 kPa, as blood lactate and glucose concentrations increased from 1.24 ± 0.08 and 1.17 ± 0.19 (T 0 values) to 10.55 ± 8.99 and 3.63 ± 0.89 mg · 100 mL −1 respectively. N. norvegicus was able to maintain blood pH levels at relatively constant values despite a drop in water pH levels and the accumulation of lactate observed at low PwO 2. Heart rates also remained stable during PwO 2 reductions, but scaphognathite beat rate increased considerably, probably as an attempt to maintain steady weight-specific oxygen consumption rates. N. norvegicus appeared to be well adapted to cope with progressive hypoxia as may occur during holding and transportation procedures.

Responses of juvenile rainbow trout, under food limitation, to chronic low pH and elevated summer temperatures, alone and in combination

Rainbow trout were exposed (90 days) in synthetic soft water to sublethal low pH (5.2) and a simulated climate warming scenario (+2°C above the control summer temperature range of 16.5–21° C), alone and in combination, under conditions of limited food (∼4% dry body weight day−1). Weight specific oxygen consumption rates (Mo2) were ∼55% of Mo2(max), in contrast to ∼75% of Mo2(max) found in trout fed an unlimited ration. This is likely due to a reduction in food quantity and thus feeding activity. However, the trout exposed to low pH at control temperatures exhibited higher conversion efficiencies and increased growth. In contrast, trout exposed to +2°C had reduced growth rates. No ionoregulatory disturbance occurred in any treatment, suggesting that this ration was sufficient to provide a replacement salt load in the diet. Energy budgets indicated that the limited ration resulted in a lowered optimum temperature for growth, with a greater proportion of the energy intake dissipated for metabolic expenditure, resulting in reduced conversion efficiencies. A fourfold reduction in faecal and unaccounted energy losses indicated higher absorption efficiencies than in satiation‐fed trout.

Ecophysiological interpretation of oxygen consumption rates and enzymatic activities of deep-sea copepods

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 168:95-107 (1998) - doi:10.3354/meps168095 Ecophysiological interpretation of oxygen consumption rates and enzymatic activities of deep-sea copepods Erik V. Thuesen1,*, Charles B. Miller2, James J. Childress1 1Marine Science Institute, University of California, Santa Barbara, California 93106, USA 2College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA *Present address: Evergreen State College, Lab II, Olympia, Washington 98505, USA. E-mail: thuesene@elwha.evergreen.edu ABSTRACT: We measured oxygen consumption rates, the activities of citrate synthase (CS) and lactate dehydrogenase (LDH) and protein contents for over 30 species of deep-sea pelagic Copepoda. The lowest oxygen consumption rates were measured in Euaugaptilus magnus and the highest rates were measured in Paraeuchaeta tonsa. Weight-specific oxygen consumption rates declined significantly with increasing size of the organism. None of the biochemical parameters were particularly good predictors of metabolic rate. Although linear regressions of LDH activity and protein content against oxygen consumption were statistically significant, R2 values for the relationships were very low. CS activity was not significantly correlated with metabolic rate. The highest CS activities were measured in Pleuromamma abdominalis and Calanus pacificus, which were the 2 smallest and shallowest-living species in our investigation. The lowest CS activities were measured in Euaugaptilus antarcticus and Pachyptilus pacificus. Disseta scopularis had the highest LDH activities and Onchocalanus magnus had the lowest LDH activities. Over all specimens, there were statistically significant increases in weight-specific activities of CS and LDH as a function of body mass. There was much greater variation in glycolytic potential as indicated by LDH activity than in CS activities. Epipelagic copepods apparently rely less on glycolytic energy sources than do mesopelagic and bathypelagic copepods. Higher LDH activities of larger Copepoda may indicate a greater dependence on LDH for burst swimming in large species compared with smaller ones or a reliance on glycolytic abilities for sustained swimming during vertical migrations. Our enzyme data do not support the suggestion that high LDH activities are adaptations to the very low oxygen concentrations found in the oxygen minimum layer. Enzymatic ratios were used to interpret lifestyle, and deep-sea copepods fell into 3 metabolic groups, Œmuscular sinkers¹, Œthin-muscled floaters¹ and Œgiants¹, that were related to morphological pattern and behaviour. The effect of hydrostatic pressure on the metabolic rate of an undescribed, but very common, species of Megacalanus was investigated and found to be non-significant. Copepods do not display the depth-related declines in metabolic rates that are found in shrimps, fishes and cephalopods. KEY WORDS: Citrate synthase · Crustacea · Deep sea · Lactate dehydrogenase · Copepoda · Respiration · Zooplankton · Enzyme activity Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 168. Publication date: July 09, 1998 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1998 Inter-Research.

Ontogenetic changes in metabolic activity and biochemical composition in the shrimp, Metapenaeus ensis

The shrimp Metapenaeus ensis (de Haan) were reared from eggs to postlarvae (PL). Biochemical composition, oxygen consumption, and ammonia excretion were quantified at selected developmental stages. The nauplius V–VI, with a lower weight than the egg, also has reduced amount of protein, lipids, carbohydrates and water. The nauplius exhibited higher weight-specific oxygen consumption and ammonia excretion rates than the egg and the protozoeal larva. From protozoea III to 3-day PL, there was a general increase in weight-specific oxygen consumption rate while ammonia excretion rate remained relatively stable with age. A lower oxygen consumption in the 9-day PL was possibly associated with the shift to a benthic mode of life. There was a general rise in oxygen consumption in all feeding stages upon food intake but ammonia excretion rates were unaffected. A lower O:N ratio under starved condition suggested the catabolism of constituent protein, which was the principal biochemical constituent of all stages. There was a general increase in ash and decrease in water, lipid and carbohydrate levels during larval and postlarval development.

Temperature and salinity effects on the intracapsular development, metabolic rates, and survival to hatching of Thais haemastoma canaliculata (Gray) (Prosobranchia:Muricidae) under laboratory conditions

Adult oyster drills Thais haemastoma canaliculata (Gray) were acclimated to 10, 12.5, 15, 20, 25, 30, 35, and 40%. S at 20, 22, 28, and 30°C. Snails deposited capsules when acclimated to 12.5, 15, 20, 25, 30, and 35%. S at 22 and 28° C. The osmolality of the intracapsular fluid was within 13 mOsm (higher/lower) of the ambient culture water in all experimental treatments. Optimal intracapsular survival and development to hatching occurred at 20 and 25%. S at 22 and 28°C. Survival to hatching was higher and development was faster at 28 than 22°C for all salinities ( Q 10 values for hatching = 1.60−2.64). Very high mortality at 12.5%. S and the presence of abnormal veligers at 12.5 and 15%. S limit larval tolerance to above 15%. S. There was a significant ( P < 0.05) temperature and salinity effect and a significant interaction of the two on oxygen consumption rates, ammonium excretion rates, and the oxygen:nitrogen ratio of post-hatching veligers. Weight specific oxygen consumption and ammonium excretion rates, and O:N ratios were higher at 28 than at 22°C for all salinities. Respiration rates and excretion rates varied indirectly with salinity at both 22 and 28°C. O:N ratios were depressed at the lower salinities for both of these temperatures, indicating greater protein catabolism. Data on survival, developmental rates, and O:N ratios indicate that the stenohalinity of larval T. haemastoma canaliculata below 20%. S may contribute to the low salinity distributional limit of this species to greater than 15‰.

Comparative gill characteristics of Munida quadrispina (Decapoda, Galatheidae) from different habitat oxygen conditions

The allometric (bilogarithmic) relationship between dry gill weight and organic body weight was compared for benthic galatheid crabs (Munida quadrispina Benedict, 1902) from a low-oxygen fjord and from a normal oxygen population. In the M. quadrispina from the low-oxygen fjord, the slope (b) of the allometric function of gill weight versus body weight was 1.00. This b value was significantly higher (ANCOVA, p &lt; 0.01) than the corresponding slope for the same function in M. quadrispina from normoxic areas (b = 0.63). However, only the largest crabs from the low-oxygen fjord were living consistently in low-oxygen (&lt;0.15 mL/L) conditions; they also had significantly greater (twice as much) relative gill weight than their normoxic counterparts. This observation agrees with findings from previous studies that only the largest M. quadrispina are able to tolerate severe oxygen depletion. Small M. quadrispina from both the low-oxygen fjord and the normoxic area were always found in oxygen concentrations &gt;2.0 mL/L. There were no significant differences between the relative gill sizes of the small crabs from different areas. It was concluded that gill development in M. quadrispina is affected by long-term habitat oxygen conditions. This factor could be important in comparisons of inter- and intra-specific allometric gill functions and in the study of weight-specific oxygen consumption rates of decapod crustaceans.

Respiratory responses of the tropical millipede Plusioporus setiger (Broelemann, 1902) (Spirostreptida: Spirostreptidae) to normoxic and hypoxic conditions

1. 1. Oxygen consumption and its relationship to declining oxygen tension was examined in the tropical spirotreptid millipede, Plusioporus setiger. 2. 2. At 25°C and normoxia, the allometric equations relating the weight-specific oxygen consumption rates and body weight were V ̇ O 2 = 2.1266 × W −53 for males, and V ̇ O 2 = 2.0915 × W −64 for females, but no significant difference was detected from the b-values. 3. 3. Plusioporus setiger regulated respiration down to 35.40 mmHg O 2 when suddenly exposed to a lowered oxygen tension, or 17.70 mmHg O 2, when examined in a stepwise declining oxygen tension. 4. 4. O 2 dependence indices ( K 1 K 2 ) were relatively low, also expressing regulation, but no relation to size (weight) was recorded. 5. 5. After exposure to hypoxia, P. setiger showed a typical pattern of “under repayment”, on the return to normoxia.

Oxygen consumption in fathead minnows ( Pimephales promelas) following acute exposure to water-borne selenium

. Following determination of a concentration of selenate-Se lethal during 24-hr exposures at 22°C, routine oxygen consumption was measured in fathead minnows ( Pimephales promelas) exposed to various sublethal concentrations of Se for 24 hr. 2. A median lethal concentration for 24-hr exposures (24-hr LC 50) of fathead minnows equalled 82 mg Se/l with 95% fiducial limits of 76–89 mg Se/l. 3. Mean weight-specific oxygen consumption rates of minnows exposed to 0, 15, 40 and 60 mg Se/l for 24-hr ranged from 0.43 to 0.49 mg O 2/g −1/hr −1 and were not significantly different. 4. These results indicate that acute exposure to Se does not affect oxygen consumption; however, observations during respirometry trials suggest that minnows at the highest Se concentration may have physiologically compensated to maintain oxygen consumption rates.

Energetics of Sablefish, Anoplopoma fimbria, under Laboratory Conditions

We measured respiration, growth, ingestion, and excretion rates for sablefish, Anoplopoma fimbria, collected off southern California at a depth of 500 m and maintained in the laboratory. We also measured the water, protein, and lipid content of white skeletal muscle in both laboratory-held and field fish. Sablefish fed a large ration (14% of wet body weight) every 7–10 d showed growth rates two to three times higher than known growth rates for field fish. On a reduced ration (4% of wet body weight) sablefish grew at rates similar to field fish, but white muscle composition varied significantly from field fish. Oxygen consumption rates under constant temperature conditions showed a decrease in the weight-specific oxygen consumption rates with increase in body weight, ranging from routine metabolic rates of 195.8 mg O2∙kg−1∙h−1 for a 0.25-kg fish to 60.8 mg O2∙kg−1∙h−1 for a 2.78-kg fish. Based on measurements of respiration and excretion, sablefish were estimated to have 162 d of energy stored in the body lipids and did not show signs of starvation stress with food deprivation up to 6 mo in the laboratory. Energy allocation shows very slow growth rates, low conversion efficiencies, and low metabolic rates as adjustments made to large, infrequent meals.Key words: physiological responses, benthopelagic fish, growth, metabolic rate, respiration, excretion

The effect of temperature on the respiratory metabolism of selected developmental stages of Emerita brasiliensis schmitt (anomura, hippidae)

1. 1. The rates of oxygen consumption by the first and second zoeae and early post-metamorphic and non-ovigerous, adult female mole crabs. Emerita brasiliensis Schmitt, were measured at 15, 20, 25 and 30°C using Cartesian diver and Warburg respirometers. 2. 2. Weight specific oxygen consumption rates (μ10 2 mg dry wt −1. h −1) decreased from the first zoea through subsequent developmental stages to the adult female. 3. 3. Zoeal metabolism increased steadily from 15 to 25 C, declining sharply at 30 C; rates for the post-metamorphic stage and adult females, in contrast, increased over the entire temperature range used. 4. 4. Metabolic rates of zoeae I and II and the post-metamorphic stage showed highest Q 10 values between 20 and 25°C while the adult female showed a maximum Q 10 value between 15 and 20 C.

Temperature adaptation in sea anemones: Physiological and biochemical variability in geographically separate populations of Metridium senile

Latitudinally separate populations of the sea anemone Metridium senile (L.) are very similar genetically by electrophoretic criteria, yet respond differently to temperature. Anemones from southern and northern California (USA) have different oxygen consumption patterns in response to acclimatory and acute changes in temperature. Northern anemones show a pronounced increase in Q10 at temperatures just above the normal environmental range, but southern anemones do not. The two populations also differed in the extent of metabolic compensation to temperature following several weeks of acclimation. This acclimation regime resulted in changes in the activities of several enzymes of intermediary metabolism, yet the extent and direction of these changes did not display a consistent trend with regard to acclimation temperature or population. The biochemical concomitants of acclimatory and acute temperature effects were studied further by measuring the concentrations of adenylates (ATP, ADP, and AMP) in anemones from the two populations exposed to different temperature regimes. During cold acclimation for several weeks, total adenylate concentrations (AT) increased in both the southern and northern populations, possibly due to metabolic rate compensation, since AT is positively correlated with tissue metabolic rate in many species. Moreover, the extremely low weight-specific oxygen consumption rates of M. senile are probably related to its very low AT values. Acute temperature decreases had no effect on adenylate concentrations and adenylate energy charge (AEC); in contrast, acute temperature increases led to large changes in adenylate concentrations. The effects of starvation on adenylate concentrations are pronounced, and the effect is temperature-dependent. In starved individuals held at 20°C, AEC values fell to 50% of normal values after 8 d, while those held at 10°C maintained normal AEC values.

RESPIRATORY METABOLISM OFMACROBRACHIUM OLFERSII(WIEGMANN) ZOEAE DURING THE MOULTING CYCLE FROM ECLOSION TO FIRST ECDYSIS

The respiratory metabolism of first stage Macrobrachium olfersii (Wiegmann) zoeae was measured at 12 hr intervals with Cartesian diver microrespirometers throughout the 120 hr period from eclosion to first ecdysis. Weight-specific oxygen consumption rates, although slightly higher immediately after hatching, remained constant and did not differ significantly during the first moulting cycle. Larval dry weight decreased from 21.8 to 18.9 µg during this period. There was no evidence of a diurnal metabolic pattern. The moulting cycle was subdivided according to morphological characteristics, based on the degree of cytoplasmic homogeneity, epidermal retraction, and stage of setal development in the telson. Larval metabolism is suggested to be uniform throughout the eclosion—first ecdysis period, in spite of a distinct and divisible moulting cycle.