Water Oxygen Tension Research Articles

Early Developmental Arrest During Immersion of Eggs of a Tropical Fresh-Water Turtle, Chelodina-Rugosa (Testudinata, Chelidae), From Northern Australia

Freshly laid. eggs of Chelodina rugosa survived for up to 12 weeks when immersed in water and subsequently underwent successful incubation and normal hatching. Embryonic development was arrested during immersion, remained arrested in an atmosphere of nitrogen, and recommenced when eggs were exposed to air. The hypoxic conditions during immersion appear to extend the arrest typical of turtle embryos during their period in the oviducts. Freshly laid eggs of the temperate-zone C. longicollis died when immersed for longer than one week and eggs of both species died when immersed after post-laying embryonic development had commenced. These results, supported by anecdoctal and experimental evidence, suggest that C. rugosa lays its eggs in saturated or flooded ground in the late wet or early dry monsoonal season. Embryonic development presumably remains arrested until water levels drop and oxygen tensions in the nest rise by diffusion through the drying soil. Partly developed embryos in nests that are flooded after laying would perish. In contrast, C. longicollis of temperate Australia nests only in relatively dry substrates, and its eggs appear not be have evolved the capacity to withstand immersion.

Effects of anoxia, hyperoxia, and salinity on neurons in the leech Nephelopsis obscura (Erpobdellidae): RNA redistribution by fluorescence histochemistry

The histochemical distribution of cytoplasmic RNA in ganglion cells of the freshwater leech Nephelopsis obscura has been studied using the fluorochrome acridine orange as a marker of nucleic acids. Two series of experiments, employing 50 adult animals, involved changes in oxygen tension in the water and changes in salinity. Normal leech neurons exhibit finely granular orange fluorescence uniformly distributed throughout the cytoplasm, with a perinuclear ring of especially strong fluorescence. After exposure to anoxic (0% O 2), hypoxic (20% O 2), or hyperoxic (200% O 2) conditions at 20°C for 1–15 days, the orange cytoplasmic fluorescence is no longer uniformly istributed; the redistribution is generally toward the periphery, leaving the perinuclear zone without RNA fluorescence, but irregular zones of cytoplasm devoid of RNA also occur not as a gradient. Leeches exposed to salinity of, or greater than, 2.5 ppt for 15 days exhibit similar changes. These alterations are confirmed by electron microscopy. Seasonal fluctuations in oxygen tension and salinity of lake water affect the distribution and abundance of organisms. The acridine orange method provides one measure of stress to the nervous system in freshwater invertebrates that might be applicable to ecological studies as well as to metabolic studies of individual animals.

The Transition Between Branchial Pumping and Ram Ventilation in Fishes: Energetic Consequences and Dependence on Water Oxygen Tension

ABSTRACT Ram ventilation has been demonstrated in rainbow trout, Salmo gairdneri. The swimming speed eliciting the transition in mode of ventila-tion increased with declining ambient water oxygen tension . The mode of ventilation of fish swimming at a constant speed could be altered by controlled variations in . Oxygen consumption decreased by 10·2% when rainbow trout, swimming at a constant speed, shifted from active to ram ventilation. This difference can be ascribed to a lowering of the energetic cost of active ventilation as well as improved drag characteristics. Water velocity required for the transition from active to ram ventila-tion in the resting sharksucker, Echeneis naucrates, increased with decreas-ing . The results show that water oxygen tension is an important stimulus for setting the ventilatory mode in rainbow trout and sharksucker.

The influence of hypoxia on the blood regulation of the brackish water shrimp Palaemonetes varians Leach

During periods of hypoxia in hypotonic media, Palaemonetes varians Leach showed an unimpaired regulation of blood chloride until some minutes before death. Heart rate showed no clear dependence on the water oxygen tension (P wO 2) and postbranchial haemolymph oxygen tensions slowly decreased during progressive hypopoxia from a normoxic level of ≈ 30 mm Hg until the animals turned opaque some minutes before they died. Blood pH increased in hypoxia, from 7.6 in normoxia to > 8 in P wO 2 10 mm Hg. Taken together, these data have been taken to indicate that the oxygen consumption rate at the critical point (MO 2 P cr) of this species is very low (P wO 2 = < 10 mm Hg) compared with other brackish water natantians studied. The ecological significance of this to the species is considered.

Ketonic rancidity in coconut due to xerophilic fungi

A type of deterioration called ketonic rancidity occurred in coconut after inoculation with four xerophilic fungi, Eurotium amstelodami, E. chevalieri, E. herbariorum and Penicillium citrinum. The fungi were incubated at low water activity and oxygen tension. A homologous series of aliphatic methyl ketones and secondary alcohols C 5C 11 were isolated and identified in the rancid samples after fungal growth. Evidence is presented that odd numbered methyl ketones (C 5C 11) are derived from even numbered short chain fatty acids with one more carbon atoms than the ketones via a modified β-oxidation of the parent fatty acid. Heptan-2-one and heptan-2-ol are the main reaction products except in the case of E. herbariorum where even numbered hexan-2-one, hexan-2-ol, octan-2-one and octan-2-ol were produced. Other moulds grown on coconut under similar conditions— Aspergillus flavus Link and Chrysosporium farinicola (Burnside) Skou ( C. fastidium Pitt)—did not cause ketonic deterioration.

Physiological and biochemical properties and population studies in the M lactate dehydrogenase polymorphism of Discoglossus pictus (Amphibia, Anura)

1. 1. M LDH polymorphism has been previously described in Discoglossus pictus. 2. 2. Gene frequency at the LdM locus varied significantly in two isolated areas which differed markedly in water oxygen tension. 3. 3. Sex distribution, relative activity of the LDH isozymes, percentage of total H and M subunits and enzyme kinetics did not differ among the distinct LDH phenotypes. 4. 4. Under decreasing oxygen conditions, mean time to death, LT 50 and oxygen consumption were similar in tadpoles of the three LDH phenotypes (fast, intermediate and slow). 5. 5. Our results are compatible with a neutral role for this LDH polymorphism.

Respiratory rate, haemolymph oxygen tension and haemocyanin level in the shrimp Palaemon adspersus: Rathke

The marine shrimp Palaemon adspersus Rathke, frequenting Zostera meadows, shows an oxygen consumption rate (MO 2) that is independent of water oxygen tension (P wO 2) as PO 2 decreases to a critical point (P cr) near 70 mm Hg. This respiratory independence is associated with maintenance of a relatively constant “arterial” (post-branchial) haemolymph tension (P aO 2) at 70–80 mm Hg. At lower P wO 2 values, both MO 2 and P aO 2 fall, reflecting, in contrast to the above independence, a direct dependence of MO 2 on internal PO 2. Haemolymph copper measurements demonstrate relatively high haemocyanin concentrations and oxygen-carrying capacities, but MO 2 levels reflect an insignificant rôle for the pigment as an oxygen store. The data are discussed as regards adaptations for aerobic metabolism.

Oxygen uptake in the lingcod, Ophiodon elongatus, during progressive hypoxia

Oxygen uptake [Formula: see text] in the resting lingcod was 22.8 ± 0.6 mL O2∙h−1∙kg−1. During progressive environmental hypoxia lingcod maintained or elevated their [Formula: see text] provided the water oxygen tension was greater than 45 mmHg. Increased [Formula: see text] (up to fourfold) during moderate hypoxia was associated with activity.

Tide-related changes of volatile fatty acids in the blood of the lugworm, Arenicola marina (L.)

The intertidal lugworm, Arenicola marina, develops a respiratory and metabolic blood acidosis when the oxygen availability is reduced during emersion time at low tide. Measurement of volatile fatty acids in prebranchial blood sampled in the field showed that blood acetate and propionate concentrations increased with length of emersion time. Experimentally confined lugworms excreted acid by-products into the medium when water oxygen tension dropped below 50 Torr (1 Torr = 133.322 Pa) or when oxyhemoglobin concentration fell below 0.45 mmol L−1. A metabolism oriented toward easily excreted end-products may be considered as adaptive in view of the energy yield and the possibility of minimizing metabolic acidosis.

Localization of receptors causing hypoxic bradycardia in trout (Salmo gairdneri)

Receptors causing the cardiac response to environmental hypoxia have been located in rainbow trout (Salmo gairdneri). Intact, unrestrained trout, acclimated to7or 16 °C. showed a marked increase in ventilation and bradycardia when exposed to hypoxia at their acclimation temperature, In experiments designed to locate the site of receptors causing hypoxic bradycardia, the buccal cavity of a fish was divided into two chambers by a tongue depressor, allowing oxygen tension of water flowing over each set of gills lo be varied independently. Irrigating one set of gills with hypoxic water [Formula: see text] while flowing hyperoxic water [Formula: see text] over the other caused heart rate to fall from 42.2 ± 0.6 (± SEM) to 26.4 ± 0.5 (± SEM) beats/min after 1 min of hypoxic water flow. Dorsal aortic [Formula: see text] was always above that recorded when both sets of gills were flushed with normoxic water [Formula: see text]. Bilateral ligation of the efferent pseudobranch artery and the pseudobranch nerve (cranial nerve IX) had no effect on the cardiac response to irrigation of one set of gills by hypoxic water. Physical removal of, or section of the nerve supply (cranial nerves IX and X) to, the first gill arch eliminated hypoxic bradycardia. The biological advantage of hypoxic bradycardia is discussed and it is suggested that gill arch receptors may function to monitor and maintain oxygen tension of blood leaving the gills.

Some responses of the electric ray (Torpedo marmorata) to low ambient oxygen tensions.

I. Blood samples were taken during prolonged hypoxia experiments in which the inspired water oxygen tension was less than 10 mmHg. The oxygen tension of the post-branchial blood was about 5 mmHg and its pH shows a significant lowering from normoxic levels. 2. The decrease in blood pH is correlated with increases in levels of lactate and pyruvate. The lactate/pyruvate ratio increases during hypoxia. 3. An increase in blood succinate was also found, and strongly suggests the accumulation of multiple anaerobic end-products within the tissues. 4. Recovery of normoxic levels of succinate takes place almost immediately following the restart of ventilation whereas the decrease in lactate concentration is slower. 5. It is concluded that these adaptations may be related to the habitat of the fish at low tide in pools where the Po2 may fall very markedly.

The cardiac responses to shell opening and closure in the bivalve Arctica islandica (L.)

Shell closure in Arctica islandica is followed by an exponential decrease in the oxygen tension of the mantle cavity water and is accompanied by an initial increase in heart rate which is followed at lower oxygen tensions by a bradycardia. Prior to shell opening there is a slight increase in heart rate before any movement of the shell valves can be detected. However, once the shell opens and pumping activity recommences there is a rapid increase in heart rate, often to levels above normal. Perfusion of the mantle cavity with water of high and low oxygen tension resulted in the cardiac responses normally associated with shell opening and closure. Recordings of the PO2 of the blood in the ventricle, made simultaneously with cardiac recordings, showed that the changes in heart rate were recorded only after the PO2 of the blood had changed. These experiments suggest that changes in the PO2 of the mantle cavity water may be primarily responsible for the cardiac responses to shell closure in Arctica.

The responses of three species of bivalve mollusc to declining oxygen tension at reduced salinity

1. 1. Geloina ceylonica and Anadara granosa experience hypoxic conditions and can regulate their oxygen consumption at reduced oxygen tension in water of full sanity. 2. 2. These two species, and Mytilus edulis, can also regulate oxygen consumption at reduced oxygen tension in diluted sea water. Their capacity to regulate is reduced under these conditions, although only in Anadara is this reduction very marked. 3. 3. At reduced salinity, oxygen consumption by Mytilus is inhibited at first, but recovers within 48 hr. The ability to regulate oxygen uptake at reduced oxygen tension is not lost during the acclimation period. 4. 4. At 23·5% 0 S perfusion index increases with reduced PO 2, but at 16·3% 0 S perfusion index does not change as PO 2 is reduced to 60 mm Hg.

Gas Exchange in Rainbow Trout (Salmo gairdneri) with Varying Blood Oxygen Capacity

The effects of large changes in hemoglobin concentration were studied in rainbow trout in fresh water between 8 and 14 C. Anemia was produced by injecting phenylhydrazine hydrochloride or by replacing blood with either saline or plasma.No significant changes were observed in the rate of oxygen consumption, arterial or venous oxygen tensions, ventilation volume, inspired and expired water oxygen tensions, or dorsal aortic blood pressure. The primary compensatory mechanism invoked was an increase in the cardiac output, which was accomplished almost entirely by increases in stroke volume. Although the viscosity of the blood was reduced, there must also be large changes in the peripheral resistance to blood flow, since greatly increased cardiac output was achieved without significant increase in blood pressure.The change in blood oxygen capacity and increase in cardiac output caused significant lowering of the ventilation–perfusion ratio, but the capacity–rate ratio of water to blood varied only a little. A small rise occurred at low hematocrit values, due to small changes in a number of parameters.The experiments illustrate what happens when blood oxygen capacity is reduced, but do not elucidate the mechanism for control of stroke output of the heart. They also indicate that a species' hemoglobin level is maintained at a level that allows cardiac output to vary over an optimal range of its efficiency curve.

The respiratory function of teleostean gills

1. 1. Histological methods revealed that blood entering the gill filament may reach the efferent artery (1) through the lamellae, (2) through a central, lymphatic compartment and (3) directly from the afferent to efferent artery at the tip of the filament. 2. 2. In gill filaments immersed in saline, blood was shown to pass through the lamellae in the presence of adrenaline, and through the other vascular paths in the presence of acetylcholine. 3. 3. Inravascular injection of adrenaline caused a marked increase in the degree of blood oxygenation in the eel. 4. 4. The arterial oxygen tension was much higher in active than in resting eels, whereas the oxygen tension of efferent water was higher in resting than in active eels. The average difference in oxygen tension between blood and water was the same in resting and active eels. 5. 5. The expected oxygen uptake, as calculated from the anatomical dimensions of the gills and the measured blood-to-water oxygen tension difference, corresponded to the oxygen uptake which has been measured for active eels. 6. 6. It is concluded that the vascular arrangement of the gills of the eel permits variations in blood oxygenation, and thereby in oxygen uptake, by directing a varying proportion of the blood to circulate the respiratory lamellae while the rest is shunted through the alternate non-respiratory path of the central cavity. 7. 7. A double, intercommunicating vascular system, more or less similar to that of the eel, was demonstrated in all the other ten teleost species investigated, and we suggestthat it is common to all teleosts.

The influence of water and light upon the pigmentary system in the common frog Rana temporaria.

ABSTRACT A significant influence of water in relation to colour change in Rana temporaria has been established. Its action on the melanophores in relation to background shows it exerts an independent influence. Thus (a) with a black illuminated environment, water accentuates the background response, (b) with a white illuminated environment there is antagonism, (c) in darkness the presence of water induces extreme expansion, and drying induces contraction, but only after prolonged periods. Immersion on a white illuminated background causes immediate expansion, and prolonged drying even upon a black background induces contraction. During the breeding cycle, the males fail to darken when immersed upon a white illuminated background. This particular seasonal effect is not shown by the females. It was further shown that the water response is independent of the primary response. The greater the degree of immersion, the greater the degree of expansion maintained upon a white illuminated background, so that the area of contact is significant, and it is highly probable that skin receptors are concerned. The lower oxygen tension of water as compared with that of the atmosphere was not a significant factor in the expansion of the melanophores due to immersion.

MODIFICATION OF THE RATE OF OXYGEN CONSUMPTION BY CHANGES IN OXYGEN CONCENTRATION IN SOLUTIONS OF DIFFERENT OSMOTIC PRESSURE

In tap water the rate of oxygen consumption of Planaria dorotocephala is independent of the oxygen concentration of the water between 3.53 cc. and 13.84 cc. per liter. In so far as the methods coincide, this confirms the results of Hyman (1929). In Ringer's solution after four hours' exposure Planaria lose approximately 16 per cent of their total weight, or approximately 20 per cent of their total water content. In Ringer's the rate of oxygen consumption is sharply dependent on the oxygen concentration of the solution between 3.79 cc. and approximately 14 cc. per liter. Above this concentration the rate of oxygen consumption tends to become constant. In distilled water the animals imbibe water; irregular data indicate that during the first four or five hours of exposure the weight increases on the average 15 per cent, which represents an increase in water content of approximately 11 per cent. The rate of oxygen consumption in distilled water is lower than normal and constant in oxygen concentrations between 2.65 cc. and 5.35 cc. per liter. Above this concentration the rate of oxygen consumption increases as the oxygen tension increases, rising above the normal at approximately 9 cc. per liter, and continues to increase as the oxygen concentration increases, up to 15 cc. per liter, the maximum employed. Planaria dorotocephala contain approximately 78 per cent free water, as shown by weight loss on desiccation over sulphuric acid. The facts indicate that two conditions may be involved in the regulation of the rate of oxygen utilization in relation to oxygen tension in natural water: Concentration of water within the organism, thus controlling the concentration of the oxidative enzymes; boundary regulation of the admission of oxygen. In this animal, size (surface-volume) and the degree of development of its circulatory and respiratory mechanisms do not appear to be important. In abnormally high oxygen tensions in distilled water the rate of oxygen consumption is higher and the rate of disintegration is lower than in distilled water with oxygen tension at saturation at 20°.