Effects of hypoxia and hyposalinity on the heart beat of the intertidal limpets Patella granvlaris (prosobranchia) and Siphonaria capensis (pulmonata)

• 1.1. Exposure to hypoxic sea water (p_O2 = 50mm Hg) and hyposalinity (20%.) caused the heart rate of Patella granularis to decline rapidly. This was particularly marked in hypoxia where normal heart rate (50 beats/min) fell initially to between 15–30 beats/min, and later (after 2 hr) cardiac arrest occurred. When oxygen tension and salinity were eventually normalized, heart rate became significantly elevated, above the normal rate.
• 2.2. In Siphonaria capensis, exposure to reduced oxygen tension and salinity usually induced a regular, although often delayed (after 2 hr) bradycardia (< 10 beats/min). No significant cardiac overshoot was observed for this limpet species.
• 3.3. The significance of the different heart beat patterns by the limpet species, which may be linked with respiratory/metabolic responses, is discussed with regard to the respective capacities of the species for colonization of upper-shore pools.

     

The effect of a toxic dinoflagellate (Alexandrium tamarense) on the oxygen uptake of juvenile filter-feeding bivalve molluscs

• 1.1. Oxygen uptake and grazing rates of juvenile bivalve molluscs Mytilus edulis, Mya arenaria, Geukensia demissa, Placopecten magellanicus and Crassostrea virginica were measured following 1 hr exposure to bloom concentrations (10⁶ cells/1) of the toxic dinoflagellate Alexandrium tamarense (GT429) using a non-toxic clone of the same species (PLY 173) as control.
• 2.2. For all bivalves, prefeeding estimates of V̇O₂ were similar to postfeeding values and values recorded 24 hr after exposure to bloom conditions.
• 3.3. V̇O₂ was similar for bivalves fed on both the toxic and non-toxic strains of A. tamarense suggesting that there were no adverse effects on V̇O₂ following 1 hr exposure to toxic GT429.
• 4.4. Bivalves differed in their rates of grazing between toxic GT429 and non-toxic PLY 173. Similar grazing rates were recorded for M. edulis and G. demissa. For P. magellanicus and M. arenaria reduced rates of clearance were recorded in GT429 compared with the non-toxic strain.

     

The dependence of oxygen consumption of the common whelk (Buccinum undatum) on hypoxia,salinity and air exposure

• 1.1. Oxygen consumption of low salinity (20‰) acclimated whelks decreases markedly upon acute exposure to hypoxia (P_WO₂ = 35 Torr), but almost regenerates its original level within 48 hr exposure to the hypoxic condition.
• 2.2. This ability to regain the original level of oxygen consumption is not seen in high salinity (35‰) acclimated whelks.
• 3.3. Oxygen consumption in air at 10°C is more than twice the rate shown by low salinity acclimated whelks in normoxic water (P_WO₂ = 150 Torr).
• 4.4. Q₁₀ for oxygen consumption in air is about 1.0 in the temperature range 10–20°C.

     

Acute toxicity and bioaccumulation of endosulfan in rotifer (Brachionus calyciflorus)

• 1.1. The acute toxicity of endosulfan was determined for the freshwater rotifer Brachionus calyciflorus.
• 2.2. The mean 24 hr lc₅₀ value for endosulfan was 5.15 ppm with a coefficient of variation of 14.7%.
• 3.3. Rotifers were exposed at two sublethal concentrations (1.5–2.0 ppm) of endosulfan for bioaccumulation experiments, for an exposure time of 24, 48, 72 and 96 hr. The rotifers were fed with Nannochloris oculata (5 × 10⁵cell/ml).
• 4.4. The highest accumulation of endosulfan was found 24 hr after the start of the exposure to 1.5 ppm of the toxicant. A steady-state concentration in rotifer was reached between 24–48 hr, followed by a gradual decrease until 96 hr.

     

Oxygen consumption and torpor in the fat-tailed dwarf lemur (Cheirogaleus medius): Rethinking prosimian metabolism

• 1.1. Oxygen consumption was measured in a lemuriform prosimian, Cheirogaleus medius. throughout a 24-hr cycle. The standard metabolic rate was determined to be 0.95 ml O₂ (g · hr)⁻¹ agreeing well with the value predicted by allometric equations, 0.91 ml O₂ (g · hr)⁻¹.
• 2.2. As a group, prosimians are argued to have metabolic levels in agreement with eutherian norms, rather than hypometabolic levels as previously supposed.
• 3.3. Day length is shown to be an important behavioral cue for this species. Its complex yearly and daily torpor cycles are linked to this stimulus.

     

Hypoxia adaptation in the crayfish procambarus clarki

• 1.1. P. elarki is an oxyconformer, with an oxygen uptake rate of 144 ± 4 μl/g wet wt/hr at oxygen tensions above 90% saturation and an uptake rate of 18 ± 3 μl g wet wt/hr at 15 torr.
• 2.2. Between 159 and 40 tort, blood pH decreases slightly from 7.77 ± 0.03 to 7.65 ± .04, and at 15 torr, blood pH drops to 7.36 ± 0.06.
• 3.3. At normoxia, blood lactate levels are low at 0.66 ± 0.01 mM/l blood. After 2 and 5 hr exposure to 15 tort, blood lactate levels increase to 3.29 ± 0.47 and 8.91 ± 0.14 mM/l blood, respectively. Upon return to normoxia, blood lactate levels decrease and are comparable to normoxic controls after 13 hr.
• 4.4. During mild hypoxia, P. elarki maintains adequate oxygen transport by utilizing a high O₂ affinity hemocyanin in conjunction with a low metabolic demand by its tissues.

     

Anaerobic metabolism in sublittoral living Mytilus galloprovincialis in the mediterranean—IV. Role of amino acids in adaptation to low salinities during anaerobiosis and aerobiosis

• 1.1. When Mytilus galloprovincialis were transferred from 38 to 19%. sea water (S), the metabolism became anaerobic for at least 8 hr. After 24 hr the animals were entirely aerobic again.
• 2.2. Upon transfer to 19%. S, the total free amino acid concentration in haemolymph doubled within 4 hr, remaining nearly constant thereafter, up to 48 hr.
• 3.3. In the posterior adductor muscle a strong decrease of alanine and glycine occurred at 48 hr exposure to 19%. S, and a smaller decrease of glutamate; taurine remained relatively constant. When transferred again to 38%. S after 14 days, a strong overcompensation occurred in the concentrations of alanine and proline, and a smaller overcompensation in those of threonine and serine.
• 4.4. In the gill no distinct change in the amino acid pool occurred during 14 days of exposure, with the exception of a decrease in serine. When transferred again to 38%. S, a strong overcompensation occurred in alanine, proline, glycine and serine, and a smaller in glutamate and threonine.
• 5.5. No evidence for anaerobic metabolism in the decrease of the amino acid pool was found.
• 6.6. M. galloprovincialis is less able to adapt to low salinities than the more euryhaline M. edulis.

     

Low metabolic rate in a nocturnal desert lizard,an arbylus switaki murphy (Sauria: Gekkonidae)

• 1.1. Metabolic rates were measured in two xeric-adapted gekkonid lizards, Anarbylus switaki sind Coleonyx variegatus.
• 2.2. Standard metabolic rates (SMR) were 0.074 ml O₂/g hr in A. switaki and were 70% of the value predicted on the basis of mass from regression equations. The SMR of 0.146ml O₂/ghr in C. variegatus is similar to the predicted value for a lizard of this mass.
• 3.3. During intense activity, metabolic rates of 0.378 and 0.804ml O₂/g hr were measured in A. switaki and C. variegatus, respectively.
• 4.4. Various theories to explain reduced SMR in lizards are discussed, and it is concluded that none is entirely satisfactory, and caution should be exercised in interpreting the adaptive significance of reduced SMR.

     

Laboratory studies on the oxygen consumption of the marine teleost,Lichia amia (Linnaeus, 1758)

• 1.1. The oxygen consumption of the marine teleost, Lichia amia was investigated under controlled laboratory conditions.
• 2.2. The routine oxygen consumption showed a strong circadian rhythm with the fish being mainly active during the light period.
• 3.3. The specific mass exponent (dimension: μg O₂/g/hr) is temperature independent and ranges from 0.27–0.29.
• 4.4. Starving the fish results in a mean decrease in active, routine and standard oxygen consumption of 21%, 24% and 20%, respectively.
• 5.5. Feecling led to an increase in the oxygen consumption of the teleosts, with the mean metabolic rate over the 24 hr that followed, being 58% and 50% higher for fish that had been starved for 162hr and 40 hr, respectively.
• 6.6. Apparent SDA showed some variation and ranged from 6.0 to 35.5%.
• 7.7. The results obtained are generally in agreement with those recorded for other teleosts.

     

Ventilatory rate in the butterfish (Pholis gunnellus) as a consequence of temperature and previous emersion

• 1.1. Observation of ventilation in immersed Pholis gunnellus showed a linear relationship between ventilatory rate and temperature between 8 and 20°C.
• 2.2. At 13°C and after 30 min emersion, ventilatory rate was initially lower than prior to emersion, providing evidence of adequate uptake of O₂ for standard metabolism during the emersion period.
• 3.3. This species has a laterally elongate body form with reduced scales and extensive mucus secretion.
• 4.4. During emersion, gaping behaviour probably exposes the gills and extensively vascularised oesophageal regions to air.
• 5.5. These are considered to be morphological and behavioural adaptations by P. gunnellus, to aerial respiration in the intertidal habitats occupied by this species.

     

Oxygen uptake in larval bollworms (Heliothis zea) infected with the fungus Nomuraea rileyi

• 1.1. Healthy 6- to 12-day-old Heliothis zea (bollworm) larvae showed a mean oxygen uptake of 3.1 μl O₂/mg body wt per hr.
• 2.2. Similar larvae infected with the fungus Nomuraea rileyi had a mean uptake of 4.01 μl O₂/mg per hr.
• 3.3. The weights of the two groups of insects did not differ.
• 4.4. T-test showed a significant (P < 0.01) difference in oxygen uptake between healthy and infected larvae.

     

Oxygen debt in reptiles: Relationship between the time required for repayment and metabolic rate

• 1.1. The increase in O₂ consumption in a 5 g lizard (Anolis carolinensis) after feeding and after maximal work was compared with that in a kilogram alligator (Alligator mississippiensis) treated similarly.
• 2.2. The amount of extra O₂ consumed/kg was the same in both. At the peak, there was a 2.6 fold increase in both animals following exhaustive work. Oxygen usage was elevated for 2 hr in the lizard and for 12 hr in the alligator, in inverse proportion to their respective metabolic rates.
• 3.3. Although the extra oxygen consumed was the same. feeding increased metabolic rate at the maximum by 300% in the alligator and by only 40% in the lizard.

     

Sodium balance in adult atlantic salmon (Salmo salar L.) during migration into neutral and acid fresh water

• 1.1. In sea-water, adult salmon (S. salar) exchange an average of 12.6% of total body sodium/hr.
• 2.2. Following transfer to fresh water sodium uptake follows Michaelis-Menton kinetics. F_max = 2.40 mmol Na/1 ECF/hr, K_m = 0.26 mmol Na/1. The uptake system is fully activated immediately following transfer to fresh water.
• 3.3. Post smolts adapted to sea-water for 3 months take up sodium at only one third of the rate of adult fish following return to fresh water.
• 4.4. The concentration of prolactin in the plasma is low in sea-water adapted fish and does not rise during the first 8 hr in fresh water.
• 5.5. At pH 5 sodium uptake is reduced by almost 90%, even in the absence of aluminium, but recovers immediately on return to neutral water.
• 6.6. At pH 5 and 20 μmol Al/1 there is little further effect on sodium uptake but after 6 hr in aluminium the inhibition of sodium uptake continues after return to neutral aluminium fresh water and uptake is only 50% of normal 24 hr later.

     

The effect of hypoxia on carbohydrate metabolism in flounder (Platichthys flesus L.)—I. Utilization of glycogen and accumulation of glycolytic end products in various tissues

• 1.1. Resting oxygen consumption at 10°C did not change from normoxia (150 mm Hg) down to an oxygen tension of 55 mm Hg for the flounder, Platichtys flesus.
• 2.2. Flounders exposed to hypoxia showed increased levels of blood glucose and lactate, dependent on the degree of hypoxia.
• 3.3. Due to hypoxia glycogen was depleted in the liver and swimming muscle but in the heart there was no significant change.
• 4.4. Liver glucose increased after 7 hr of hypoxia. Heart and muscle glucose did not change but the absolute glucose concentration in the heart was five times higher than in the muscle.
• 5.5. There is a transient accumulation of lactate in heart, liver and kidney after 7 hr of hypoxia while lactate accumulation in the swimming muscle is significant only after 21 hr of hypoxia.
• 6.6. Succinate only accumulated in the liver while alanine accumulated in muscle, heart and liver.

     

The effect of salinity on coelomic fluid osmolyte concentration and intracellular water content in Luidia clathrata (Say) (Echinodermata: Asteroidea)

• 1.1. The concentrations (mM) of osmolytes in the coelomic fluid of Luidia clathrata kept at 25‰S seawater (control individuals) were: 345, Na⁺; 10, K⁺; 10, Ca²⁺; 44, Mg²⁺; 387, Cl⁻; 0.67, amino acids; 0.09, NH₄⁺.
• 2.2. When individuals were transferred from 25‰S to 15‰S or 35‰S, the concentrations of inorganic ions in the coelomic fluid usually equilibrated within 24hr and became the same as those in the medium.
• 3.3. The intracellular water content (g intracellular H₂O/g solute-free dry tissue) of the pyloric caeca and tube feet of control individuals throughout the experiment was 2.13 and 5.40, respectively.
• 4.4. In tissues of individuals transferred to 15‰S, the intracellular water content increased by an average 50% in 12 hr but returned to 19% above control levels during 1 week.
• 5.5. In tissues of individuals transferred to 35‰S, the intracellular water content decreased by an average 17% in 12 hr and did not change during 1 week.
• 6.6. Luidia clathrata is an osmoconformer and partial cell volume regulator within the seasonal salinity range it encounters.

     

The flow theory of enzyme kinetics: Role of solid geometry in the control of reaction velocity in live animals

• 1.1. When blood flows, membranes are bombarded with ions etc., whose entry creates an ATP demand proportional to flow rate. Also proportional to flow rate is ATP production from oxidation of substrates [S] from the same blood volume.
• 2.2. O₂ is limiting and reaction velocity at rest (metabolic rate) is determined by flow rate, F, but not by [S].
• 3.3. Since resting blood O₂ A-V difference is about 5 vol%, 11 circulated produces about 0.25 kcal in mammals, birds or warm reptiles.
• 4.4. Where O₂ is not limiting, as in most amino acid deaminations, V = K F[S] with K a constant unrelated to K_m.
• 5.5. At equal blood vol/kg, solid geometry dictates that the average cross-sectional area of major vessels/kg will be an inverse function of body mass. The smaller the animal, the shorter the vessels, the “thicker” the vessels/kg body wt, and at any one blood pressure, the higher the flow/kg/hr. If a man's major vessels were equal in cross-section/kg to those of a shrew, it would take 2241 of blood to fill them.
• 6.6. Growth decreases flow/kg (and therefore metabolic rate), by decreasing vessel cross-section/kg without changing blood pressure or linear velocity of flow.
• 7.7. Surface area/g, body wt to some power, average vessel length/kg, circulation time and average major vessel cross-sectional area are all related mathematically.

     

Factors affecting oxygen consumption in wild-caught yellow-bellied marmots (Marmota flaviventris)

• 1.1. All age groups gained mass during the active season, but mass-gain of adult females was delayed during lactation.
• 2.2. The relationship of body mass to metabolic rate varied widely; when the relationship was significant, R² varied from 10.3 to 72.6%. Body mass affects V_O2 more during lactation than at any other period.
• 3.3. Mean VinO₂ of adult males was higher in June than that of adult, non-lactating females.
• 4.4. V_O2 of reproductive females was significantly higher during lactation than during gestation or postlactation because specific V_O2 varied. Specific V_O2 of non-reproductive females declined over the active season.
• 5.5. Specific V_O2 of all age groups declined between the premolt and postmolt periods. The reduced maintenance costs can contribute 20–46% to daily growth.
• 6.6. Observed V_O2 was lower than the value predicted from intraspecific or interspecific Bm:M regressions.
• 7.7. V_O2 of wild-caught marmots was lower than that of marmots maintained in the laboratory, probably because of dietary differences.
• 8.8. Because basal metabolism is a stage on a food-deprivation curve, we suggest that basal metabolic rate is not an appropriate measure of the metabolic activity of free-ranging animals.

     

The effect of inspired oxygen tension on oxygen uptake and tolerance to anoxia in the water snakes Helicops modestus and Liophis miliaris (Colubridae)

• 1.1. The effect of oxygen tension, p_o2, on oxygen uptake and tolerance to anoxia have been studied by exposure in nitrogen atmosphere and diving in the water snakes Helicops modestus and Liophis miliaris, at 25°C.
• 2.2. The critical P_o2, was the same (70mmHg O₂) for both species, but below that tension H. modestus showed a higher degree of dependence on P_o2.
• 3.3. Anoxia tolerance time was longer (14 min for H. modestus and 4 min for L. miliaris) during forced dive than during exposure to a 100% nitrogen atmosphere. No difference was found in pre- and post-forced dive oxygen uptake values in both species.
• 4.4. The maximum duration of a voluntary dive was shorter than the mean tolerance time to forced dives in L. miliaris. but longer in H. modestus.
• 5.5. H. modestus, the more aquatic species, is significantly more tolerant of complete anoxia (100% N₂ exposure) and submersion.

     

Time-dependent cadmium-neurotoxicity in rat brain synaptosomal plasma membranes

• 1.1. The modulation of lipid dynamics and lipid protein interactions were studied in rat brain synaptosomal plasma membranes (SPM) up to 24 hr after exposure to cadmium (Cd).
• 2.2. The activity of acetylcholinesterase and adenylate cyclase showed a considerable decrease after 6 hr of Cd exposure, followed by a progressive increase up to 24 hr.
• 3.3. SPM chemiluminescence showed a maximum decrease at 12 hr, demonstrating a considerable increase in lipid peroxidation.
• 4.4. SPM of Cd-exposed animals showed a statistical significant increase in fluorescence anisotropy parameter [(r₀/r) — 1]⁻¹ at 18 and 24 hr compared to SPM of the control, indicating a decrease of membrane fluidity.

     

Effect of temperature and salinity on the oxygen consumption of laboratory produced Penaeus californiensis postlarvae

• 1.1. The oxygen consumption by P. californiensis postlarvae (mean wt = 0.38 g) was determined at five different temperatures and four salinities.
• 2.2. The O₂ in each chamber was recorded at 10 min intervals for 1 hr. The time course of oxygen depletion was independent of O₂ concentration down to 1.6 mg/l.
• 3.3. Oxygen consumption increased with temperature from 0.0045 mg/g/min at 19°C, to 0.0142 mg/g/min at 35°C. The thermal coefficient (Q₁₀) indicated a very high sensitivity of the postlarvae to temperature variations at 19–23°C.
• 4.4. The results show that oxygen consumption significantly depends on temperature (P < 0.001) while salinity has only a marginal effect.