Anaerobic metabolism of the common cockle Cardium edule

Changes in the level of the adenylates (ATP, ADP, AMP), arginine phosphate, arginine, octopine, D-lactate, succinate, and aspartate were determined in the foot of Cardium edule, after 12 h of anoxia and after aerobic recovery for up to 12 h. Control levels of the adenylates, the calculated energy charge and the arginine phosphate content were restored after about 1 h of recovery. On the other hand, the recovery of the D-lactate, succinate, and aspartate pools was a slow process, taking place over about 12h.     

The functions of octopine dehydrogenase and D-lactate dehydrogenase in the pedal retractor muscle of thedog whelk Nassarius coronatus (Gastropoda: Nassariidae)

The pedal retractor muscle of Nassarius coronatus, unlike most mollusc muscles, contains high activities of both octopine dehydrogenase (159 IU g^-1 wet wt muscle) and D-lactate dehydrogenase (40 IU g^-1 wet wt muscle). Pedal retractor muscles show accumulation of octopine (increase of 4.7 mol g^-1 wet wt muscle), and a fall in arginine phosphate concentration (decrease of 4.1 mol g^-1 wet wt musscle) after exercise. During recovery from exercise, octopine returns to resting levels after about 120 min, D-lactate accumulates (5.1 mol g^-1 wet wt muscle), and arginine phosphate returns to resting levels within 30 min. D-lactate (2.0 mol g^-1 wet wt muscle) accumulates during long-term exposure to air. The results show that octopine dehydrogenase and D-lactate dehydrogenase can function to catalyze the terminal step of glycolysis during muscle anoxia associated with these different physiological states.     

Reproductive investment reduces recuperation from exhaustive escape activity in the tropical scallop Euvola zizac

In scallops, mobilization of reserves from the adductor muscle to support maintenance and reproductive activity may impinge upon a major role of the adductor muscle, the movement of the valves during swimming and escape responses. The tropical scallop Euvola ziczac (Linnaeus 1758) invests energy reserves to different degrees during its two periods of reproduction each year. We evaluated the impact of reproductive investment on the escape responses (clapping capacity and recovery after exhaustive exercise) of E. ziczac sampled at different reproductive stages (immature, mature, spawned) during the two reproductive periods in 1997. We compared the escape response capacities with the levels of muscle energetic reserves (glycogen, proteins, and arginine phosphate) and muscle metabolic capacities [activity of the glycolytic enzymes: glycogen phosphorylase (GP), pyruvate kinase (PK), phosphofructokinase (PFK), octopine dehydrogenase (ODH), arginine kinase (AK), and the mitochondrial enzyme, citrate synthase (CS)]. Gonad size, gamete volume fraction, and levels of gonadal protein and lipid were greater for mature scallops during the first than during the second reproduction. Numbers of claps during escape responses (49–57) and levels of muscle arginine phosphate remained similar throughout the different reproductive stages in both reproductive periods. In contrast, recovery was slowed during gonadal maturation in both reproductive periods and during spawning in the first reproduction. Scallops generally took more time to regain their initial clapping capacity during the first (25–40 min) than during the second reproduction (20–30 min). Muscle glycogen decreased markedly during both gonadal maturation and spawning in both reproductions; whereas, muscle proteins decreased only in the first reproduction. The levels of most enzymes decreased during gonadal maturation in both reproductions, and also after spawning, particularly during the first reproduction. We concluded that gonadal maturation and spawning did not decrease clapping capacity of E. ziczac, but decreased its capacity to recover from exhaustive exercise most likely due to decreased levels of energetic reserves and a reduced metabolic capacity of the adductor muscle. Moreover, these effects were probably stronger during the first cycle because of the greater reproductive investment coincident with decreased food availability. Received: 28 April 2000 / Accepted: 21 September 2000     

Biochemical adaptations of the mudskipper Boleophthalmus boddaerti to a lack of oxygen

Specimens of the mudskipper Boleophthalmus boddaerti, collected along the estuarine canal at Pasir Ris, Singapore between April 1987 and December 1989, were examined in the laboratory. After being exposed to environmental hypoxia for 6 h, no accumulation of lactate, alanine or succinate was observed in the muscle tissue of B. boddaerti. In addition, the blood lactate content and muscle creatine phosphate (CrP), adenosine triphosphate (ATP) and glycogen contents were not significantly different from those of the control. During normoxic recovery, oxygen debt repayment was only a small fraction of the oxygen deficit incurred during the 6 h of hypoxic exposure. Therefore, it would appear that B. boddaerti coped with environmental hypoxia by undergoing metabolic rate reduction. After anoxic exposure, the CrP, ATP and adenosine diphosphate (ADP) contents in the muscle tissue of B. boddaerti were significantly lower than the corresponding control values. Lactate accumulated in the blood and muscle tissue of the anoxic fish though the muscle energy charge and glycogen content remained constant. Hence, B. boddaerti was able to cope with such a period of anoxia without increasing its glycolytic rate. Succinate, which was not detected in the muscle tissue of the control and hypoxia-exposed fish, accumulated in significant quantities in the muscle tissue of B. boddaerti exposed to environmental anoxia and functional hypoxia. In the case of functional hypoxia, there was a significant decrease in the muscle glycogen content, and the muscle lactate content increased 17.3-fold, indicating that glycolysis was activated to provide the source of energy during muscular exercise.     

Functional and environmental anaerobiosis in the razor-clam Ensis directus (Mollusca: Bivalvia)

In Ensis directus (Conrad) metabolic changes accompanying muscular activity and experimental anoxia were investigated. Octopine dehydrogenase, strombine dehydrogenase, alanopine dehydrogenase and lactic dehydrogenase were shown to be present in different parts of the body, but the activity of ODH always exceeded that of the other enzymes by far. Muscular activity connected with escape digging or evoked by electrical stimulation resulted in a decrease of stored phosphagen and in an accumulation of octopine. During recovery the normal concentrations of energy-rich phosphates were restored quickly, whereas octopine was removed more slowly. In experimental anoxia only minor quantities of L-and D-alanine, succinate, propionate, and acetate were formed. Quantitatively the most important endproduct was strombine, which rose linearly with the duration of anoxic incubation.     

Purification and characterisation of octopine dehydrogenase from the marine nemertean Cerebratulus lacteus (Anopla: Heteronemerta): comparison with scallop octopine dehydrogenase

Octopine dehydrogenase from the nemertean Cerebratulus lacteus was purified over 1000-fold to almost homogeneity. The enzyme does not bind to arginine Sepharose 4B. It has a monomeric structure with a relative molecular mass of 40000. Two isoenzymes were identified with isoelectric points of 5.6 and 5.4, whereas the purified isoenzymes of Pecten jacobaeus adductor mucles (which bind to arginine Sepharose 4B) had lower IEP's of 4.9 and 4.7. Apparent K_m's of the nemertean ODH for arginine and pyruvate are dependent on the respective co-substrate concentration. This phenomenon may result in activation of ODH and, thus, production of octopine in locomotory highly active individuals while attacking food, especially when this takes place in a hypoxic habitat, such as decaying mud near the high-water mark. The apparent K_m's for octopine (0.22 mM) and NAD⁺ (14 M) are low. Octopine is a substrate inhibitor for the reverse reaction above 2 mM, and a product inhibitor of the forward reaction by 50% at 1.2 mM. Therefore, only small amounts of octopine are likely to accumulate in vivo. Amino acid substrate specificity is limited to guanidino amino acids. We believe that the amino acid substrate specificity is not an evolutionary modification, but rather that it is narrowed to guanidino amino acids (or even specificity to arginine) in those species where ODH has a physiological function in maintaining redox balance during exercise. The specificity for keto acids is dependent on chain length, (-ketobutyrate>-ketocapronate); a second carboxyl group inactivates the enzyme.     

Changes in protein-bound and free amino acids in the muscle of the tiger prawn Penaeus esculentus during starvation

Using the starvation technique, changes in protein and free amino acids were examined in Penaeus esculentus Haswell collected from Moreton Bay, Australia, by trawling in 1985. Prawns of 17.7±0.26 g wet weight were held at 25°C until 2 d after moulting. Groups of seven or eight were then starved fro 5, 10, or 15 d, with appropriate control groups. At the end of each period, ecreted amino acids were collected for 24 h and whole-muscle amino acids and free amino acids (FAA) g^-1 in each prawn were analysed. Concentrations of whole-muscle amino acids showed only minor changes with starvation, but concentrations of many of the FAA changed significantly. Total FAA averaged 1 182±45 mol g^-1 dry weight. Individual FAA, in order of abundance, were glycine, arginine, proline, taurine, threonine, hydroxyproline, alanine, glutamic acid, valine, aspartic acid and lysine; the remaining FAA each contributed <0.2% of the total. Only taurine and alanine did not show significant changes with starvation. Concentrations of glycine, arginine, hydroxyproline, glutamic and aspartic acid increased, while those of proline, threonine, valine and lysine decreased with starvation, that of proline approaching zero after 15 d starvation. Excreted amino acid-nitrogen represented <2% of excreted ammonianitrogen ornithine being the most abundant (35%), followed by leucine (22%) and lysine (17%). The relative abundance of excreted amino acids did not correspond with those of the FAA. It is suggested that, as starvation progresses, the muscle protein is progressively hydrolysed, but with the remaining muscle maintaining its amino acid composition. The liberated amino acids enter the FAA pool and become available for energy production. Proline may have an important role as an energy source, but the ability to synthesise proline may be limited, and thus the artificial food of penaeid prawns may be improved by its addition.     

Effects of anoxia on the activities of pyruvate kinase and phosphoenolpyruvate carboxykinase,and the production of lactate and succinate in the intertidal pulmonate Onchidium tumidium

Onchidium tumidium, an intertidal pulmonate, has evolved to depend mainly on the formation of succinate, rather than lactate and opines, to survive in anoxia. For our study O. tumidum were collected from the mud flats of the mangrove swamp at Mandai, Singapore between 1988 and 1991. After 24 h of anoxic exposure, the lactate and succinate contents of the anoxic individuals were approximately 10 and 150 times, respectively, the corresponding values of the normoxic individuals. Alanine and acetate accumulations also occurred during anoxia, though to a much lesser extent. No propionate or octopine was detected. The depletion in aspartate content in O. tumidium could not account for the amount of succinate accumulated during anoxia. The succinate formed might have originated from glycogen involving the flow of carbon through the phosphoenolpyruvate (PEP) branch point of glycolysis. In support of such a hypothesis, results indicate that there was a decrease in the affinity of pyruvate kinase from O. tumidium exposed to 24h of anoxia to PEP to facilitate succinate formation through phosphoenolpyruvate carboxykinase (PEPCK). In comparison, the affinity of PEPCK from O. tumidium exposed to anoxia to PEP was apparently unaltered.     

Sub-lethal effect of chlorpyrifos on protein metabolism of the food fish Clarias batrachus and monitoring of recovery

The effect of sub-lethal concentrations of chlorpyrifos on protein metabolism in physiological important tissues, namely gills, kidney, liver, and muscle of the freshwater fish, Clarias batrachus, was studied. Fish were exposed to 1/20th and 1/10th of 96?h LC₅₀ concentrations for 7, 14, 21, and 28 days. After 28 days of exposure, fish were released into fresh water and kept in the same for 21 days in order to study the recovery. Fish were sacrificed at the stipulated periods and gills, kidney, liver, and muscle tissues were used for the estimation of total protein, amino acids, ammonia, urea, glutamine, protease, transaminases, and phosphatases. Total protein, amino acid, and ammonia contents were decreased in all tissues for 28 days and recovery was observed during the recovery period. Urea and glutamine levels were elevated, except in kidneys, and recovered at the end of the recovery period. The activities of protease, alanine, and aspartate aminotransferases, and acid and alkaline phosphatases were elevated in the tissues for 28 days exposure at both concentrations. Recovery of these enzymes activities was noticed during depuration.     

Survival of the intertidal pulmonate Onchidium tumidium during short term and long term anoxic stress

Onchidium tumidium showed a triphasic response to anoxia. Twelve hours of anoxic exposure had no effect on the glycogen content in O. tumidium. However, there were significant increases in the alanine, lactate and succinate contents in the anoxic individuals. These were accompanied by a significant decrease in the ATP content. These results suggest that O. tumidium survived the first 12 h of anoxic exposure without increasing the glycolytic flux to compensate for the lower efficiency of ATP production through anaerobic pathways. Indeed, the fructose-2,6-bisphosphate (F-2,6-P₂) content and the percentage of phosphofruc-tokinase (PFK) associated with the subcellular particles remain unchanged in O. tumidium exposed to 12 h of anoxia. Hence, a reduction in the metabolic rate of these individuals might have occurred during such a period of anoxia. In contrast, in between 12 and 24 h of anoxic exposure, the glycogen content O. tumidium decreased significantly, and levelled off thereafter. A significant increase in the percentage of PFK associated with the subcellular particles was observed in individuals exposed to 24 h of anoxia. In addition, the F-2,6-P₂ content of these anoxic individuals increased significantly. Taken together, these two mechanisms could activate PFK and lead to a greater glycolytic flux. Beyond 24 h of anoxic exposure, survival of O. tumidium must have required considerable suppression of metabolism as accumulation of end products and depletions of glycogen and ATP had reached constant levels.     

Cyclic AMP-dependent protein kinase: role in anoxia and freezing tolerance of the marine periwinkle Littorina littorea

A key regulatory mechanism underlying the switch between aerobic and anaerobic metabolism amongst anoxia-tolerant marine molluscs is reversible protein phosphorylation. To assess the role of cAMP-dependent protein kinase (PKA) in aerobic–anaerobic transitions, the effects of anoxia on the activity and subcellular distribution of PKA were assessed in foot and hepatopancreas of the marine periwinkle, Littorina littorea. Exposure to N₂ gas at 5 °C caused a rapid decline in the percentage of total enzyme present as the free catalytic subunit (PKAc) in both tissues; the percentage of PKAc fell from ∼30% in controls to 3% after 1 h anoxia and remained low over 72 h. Total PKA also fell by 30% after 72 h anoxia in hepatopancreas but rebounded during aerobic recovery. Freezing at −8 °C elicited parallel results for both percentage of PKAc and total PKA, suggesting that PKA responses to freezing were stimulated by the ischemia that develops when hemolymph freezes. Anoxia also led to a shift in PKA subcellular distribution in hepatopancreas (but not in foot), the percentage of total PKA activity associated with the nuclear fraction dropping from 25% in controls to 8% in 12 h anoxic snails with opposite changes in the cytosolic fraction. The catalytic subunit (PKAc) of foot PKA was purified to a final specific activity of 63.5 nmol phosphate transferred per minute per milligram protein. Enzyme properties included a molecular weight of 33 to 35 kDa, an activation energy from Arrhenius plots of 65.1 ± 4.8 kJ mol⁻¹, and substrate affinity constants of 151 ± 6 μM for the phosphate acceptor, Kemptide, and 72 ± 9 μM for Mg.ATP. Activity was strongly reduced by mammalian PKA inhibitors (H-89, PKA-I), by neutral chloride salts (I₅₀ values 165 to 210 mM) and by NaF (I₅₀ 62 mM). Reduced PKA activity under anoxic or freezing conditions would facilitate the observed suppression of the activities of numerous enzymes that are typically PKA-activated and thereby contribute to the overall anoxia-induced metabolic rate depression. Received: 19 November 1997 / Accepted: 30 September 1998     

Acclimatization to intertidal conditions modifies the physiological response to prolonged air exposure inMytilus edulis

Both the tolerance of air exposure and the metabolic means by which mussles,Mytilus edulis, face air exposure can be modified by intertidal acclimatization. Short-term intertidal acclimatization enhanced the tolerance of air exposure most in early summer. Prevention of air breathing increased the mortality of wild and non-acclimatized cultured (i.e., control) mussels, but only slightly enhanced that of intertidally acclimatized mussels, suggesting their increased dependence upon anaerobic metabolism. In June, anaerobic end products accumulated in the adductor muscle of cultured but not of wild mussels. Intertidal acclimatization shifted the pattern and rates of metabolite accumulation. Control mussels accumulated succinate and alanine in the adductor muscle while intertidally acclimatized mussels accumulated strombine + alanopine, albeit at far lower levels. Pyruvate kinase (PK) from adductor muscle of intertidally acclimatized mussels was gradually activated during prolonged air exposure, while that of control and wild mussels was more inhibited. In July and August, during prolonged air exposure, the PK from the most viable mussles generally was the most inhibited. Prevention of air breathing did not markedly change the time course of PK inhibition during air exposure. Cultured mussels used in the present study were obtained from growers in Québec, and wild mussels were collected from the Baie des Chaleurs (Québec, PQ) in 1988.     

Effect of sexual maturation on the tissue biochemical composition of<Emphasis Type="Italic"> Octopus vulgaris</Emphasis> and<Emphasis Type="Italic"> O</Emphasis>.<Emphasis Type="Italic"> defilippi</Emphasis> (Mollusca: Cephalopoda)

Changes in the protein, lipid, glycogen, cholesterol and energy contents, total amino acid and fatty acid profiles of Octopus vulgaris and O. defilippi tissues (gonad, digestive gland and muscle) during sexual maturation (spermatogenesis and oogenesis) were investigated. Both species showed an increase of amino acids and protein content in the gonad throughout sexual maturation (namely in oogenesis), but allocation of these nitrogen compounds from the digestive gland and muscle was not evident. The major essential amino acids in the three tissues were leucine, lysine and arginine. The major non-essential amino acids were glutamic acid, aspartic acid and alanine. With respect to carbon compounds, a significant increasing trend (P<0.05) in the lipid and fatty acid contents in the three tissues was observed, and, consequently, there was also little evidence of accumulated lipid storage reserves being used for egg production. It seems that for egg production both Octopus species use energy directly from food, rather than from stored products. This direct acquisition model contrasts with the previous model for Octopus vulgaris proposed by ODor and Wells (1978: J Exp Biol 77:15–31). Most of saturated fatty acid content of the three tissues was presented as 16:0 and 18:0, monounsaturated fatty acid content as 18:1 and 20:1 and polyunsaturated fatty acid content as arachidonic acid (20:4n-6), eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3). Though cholesterol is an important precursor of steroid hormones, this sterol content exhibited variations that do not seem to be related with the maturation process. Moreover, significant differences (P<0.05) were obtained between genders, suggesting that perhaps there is a greater physiological demand for cholesterol during spermatogenesis than oogenesis. If the component sterols of octopus are of a dietary origin, considerable variation in the cholesterol content between species might be expected on the basis of the sterol composition of their prey. The glycogen reserves increased significantly in the gonad and decreased significantly (P<0.05) in the digestive gland and muscle of O. vulgaris (these trends were not evident in O. defilippi). Glycogen may play an important role in the maturation process and embryogenesis of these organisms, because carbohydrates are precursors of metabolic intermediates in the production of energy. It was evident that sexual maturation had a significant effect upon the gonad energy content, but the non-significant energy variation (P>0.05) in the digestive gland and muscle revealed no evidence that storage reserves are transferred from tissue to tissue. The biochemical composition of digestive gland and muscle may not be influenced by sexual maturation, but rather by other biotic factors, such as feeding activity, food availability, spawning and brooding.Communicated by S.A. Poulet, Roscoff     

Some aspects of nitrogen metabolism in Mytilus edulis: effects of aerial exposure

The effects of starvation and emersion on the ammonia effluxes of Mytilus edulis L. were studied. Both fed and starved groups showed similar patterns of efflux during re-immersion, indicating no compensation for starvation during anaerobic catabolism; this is taken as evidence that carbohydrate or lipid is the predominant energy source at the outset of anaerobiosis. Instead of an overshoot of ammonia excreted during the 4 h following re-immersion, all groups showed significantly reduced efflux rates independent of emersion duration. Such results suggest some conversion of ammonia during the recovery period, as no significant drop in haemolymph ammonia occurred at this time. The level of ammonia accumulation in haemolymph and mantle cavity fluid decreased exponentially with emersion duration, implying the stabilisation, at a low rate, of ammonia production after a relatively long period of emersion (16 to 24 h). Oxygen levels of the mantle cavity fluid dropped rapidly during emersion but never attained anoxia over 24 h of emersion, which may indicate some oxygen uptake by emersed mussels. It has been concluded that the behaviour and physiological responses shown by M. edulis to emersion appear to reflect a need for respiratory gas exchange more than a response to desiccation – presumably in the interest of energy-conservation. The reductions in ammonia efflux rate during emersion and, to a certain extent, immediately after re-immersion have also been considered here to be energy-saving strategies that illustrate the importance of ammonia in restoring normal levels of some amino acids following re-immersion. Received: 26 August 1997 / Accepted: 27 May 1999     

Changes in the level of transaminases in Indian major carp, Labeo rohita exposed to sublethal concentration of tannery and distillery effluents

The activity of alanine aminotransferase (ALAT) and aspartate aminotransferase (AAT) of different tissues of fingerlings of Labeo rohita under the influence of two effluents has been studied. The alanine aminotransferase activity was increased over the control in different exposed periods of tannery and distillery effluent treatments. The alanine aminotransferase in the liver showed increased activity at different periods than that of the muscle, kidney, gill and brain (p < 0.001) (60.09%) over the control during the 40 days exposure in both the effluents treatments. The increased activity of alanine aminotransferase was highly significant (p > 0.001) in all the tissue in tannery and distillery effluents treatments. Similarly aspartate aminotransferase activity was increased over the control in all the treated tissues from 10 to 40 days exposure. But this increase, was not significant in the muscle tissue in distillery and tannery treatements after 10 days exposure. From 10 to 40 days, the activity was increased but a maxmum elevation was observed during 40 days, where the elevation was more in the liver, which was followed by muscle, kidney, gill, brain (brain < gill < kidney < muscle < liver).     

Effects of turbidity on calcification rate,protein concentration and the free amino acid pool of the coral Acropora cervicornis

Calcification rate in the coral Acropora cervicornis was reduced significantly when exposed for 24 h to 100-ppm kaolin, but was unchanged in corals exposed to 50-ppm kaolin. Calcification rate returned to control levels during a 48-h recovery period. Most free amino acids (FAA) in the FAA pool decreased significantly in corals exposed to 100-ppm kaolin, but were unchanged in corals exposed to 50-ppm kaolin. After a 48-h recovery period, the FAA pool remained considerably below control levels in the 100-ppm exposed corals and dropped below control levels in the 50-ppm exposed corals. Calcification rate dropped less and later during the exposure period in the growing tip than in sections further down the stalk. The reduction in FAA pool size was considerably larger in the growing tip than further down the stalk. Soluble protein concentration remained unchanged during both exposure and recovery. The data are consistent with the interpretation that turbidity not only causes a decrease in photosynthetic rate and the synthesis of small molecules, but also causes a large increase in the utilization of stored organic molecules for such metabolically costly processes as mucus production and sediment removal.     

Free amino acids as energy substrate in developing eggs and larvae of the cod Gadus morhua

The content of free amino acids (FAA) in the cod (Gadus morhua L.) egg is about 200 nmol at spawning, decreasing by about 100 nmol/egg during the egg stage and about 75 nmol/larva during the yolksac larval stage. Together, alanine, leucine, serine, isoleucine, lysine, and valine account for about 75% of the decrease. Ammonium accumulates gradually during the egg stage and is quickly excreted after hatching. The body protein content is maintained during the egg and yolksac larval stages. The measured oxygen uptake of the cod embryo during the egg and yolksac larval stages accounts for about 85% of the oxygen necessary to catabolize the FAA disappearing during this period. Ammonia excretion of the cod embryo, as taken from literature data, is similar to the expected ammonia production from catabolism of the FAA. Our data suggest that FAA are a major substrate for aerobic energy production in cod eggs and yolksac larvae. The implication of this finding for the production of a favourable first-feed for cod and other cultivated marine fish larvae, and for the selection of high quality eggs of marine fishes, is stressed.     

Metabolic adaptation of Zostera marina (eelgrass) to diurnal periods of root anoxia

The temperate seagrass Zostera marina L. is common in coastal marine habitats characterized by the presence of reducing sediments. The roots of this seagrass grow in these anoxic sediments, yet eelgrass is highly productive. Through photosynthesis-dependent oxygen transport from leaves to roots, aerobic respiration is supported in eelgrass roots only during daylight; consequently, roots are subjected to diurnal periods of anoxia. Under anoxic root conditions, the amino acids alanine and -amino butyric acid accumulate within a few hours to account for 70% of the total amino acid pool, while glutamate and glutamine decline. Little ethanol is produced, and the pool size of the organic acid malate changes little or declines slowly. Upon the resumption of shoot photosynthesis and oxygen transport to the roots, the accumulated -amino butyric acid declines rapidly, glutamate and glutamine pools increase, and alanine declines over a 16-h period. These adaptive metabolic responses by eelgrass to diurnal root anoxia must contribute to the successful exploitation of shallow-water marine sediments that have excluded nearly all vascular plant groups. A metabolic scheme is presented that accounts for the observed changes in organic and amino acid pool sizes in response to anoxia.     

Copper sulphate (CuSO4) toxicity on tissue phosphatases activity and carbohydrates turnover in Achatina fulica

A time course study on the sublethal toxicity of CuSO4 on tissue carbohydrate metabolites level and their phosphatases activity in Achatina fulica revealed differential response. The levels of total carbohydrates and glycogen in the body mass muscle, foot muscle and hemolymph revealed their involvement in the endogenous derivation of energy during stress. The same metabolites in digestive gland revealed its importance to reproduction and development. The lactate accumulated in all the tissues implied the mechanism of CuSO4 toxicosis in the metabolic acidosis. The decrease of pyruvate in foot muscle, body mass muscle and hemolymph inferred the preponderance of glycolysis in energy derivation. In contrast, the pyruvate concentration in digestive gland revealed its differential response in the stress metabolic sequence of changes, as a unique tissue. The lactate/pyruvate ratio and the calcium content in tissues constitute direct evidences for the snails adaptation to toxic stress.     

Relation of habitat to glycogen concentration and glycogen synthetase in polychaetes

The glycogen content of whole body or muscle of 14 species of polychaetes was determined, and the activity, co-factor requirements, and substrate affinity of glycogen synthetase from muscles of 4 of the species were measured. Species average glycogen concentrations were positively correlated with the risk of anoxia each species faced in the field. Total activity of glycogen synthetase was not correlated with glycogen concentration in muscle, but polychaetes most likely to experience anoxia had the highest proportion of the enzyme in the active (co-factor independent = I) form; moreover, in such species, the glycogen synthetase had the highest affinity for substrate. It was concluded that evolutionary adaptation to oxygen-poor habitats occurs through qualitative changes in enzyme properties rather than through quantitative changes in enzyme production.