Hemolymph Lactate Concentrations Research Articles

Physiological stress and recovery kinetics in trawl escapees of the Antarctic krill Euphausia superba Dana, 1850 (Euphausiacea)

Abstract When caught in a trawl, some individuals interacting with the fishing gear may escape, but such interactions may lead to physiological trauma that causes direct delayed mortality and/or increased vulnerability to predation. Understanding fishery-induced stress levels and the recovery period of escapees is therefore crucial for predicting total fishing-induced mortality. Hemolymph lactate concentration is commonly used as an index of physiological stress in many crustacean species, and the clearing time of lactate back to normal levels indicates the ability to recover from stress. We measured the hemolymph lactate concentration in three groups of Antarctic krill (Euphausia superbaDana, 1850): Group 1, trawl escapees collected during fishing; Group 2, specimens subjected to simulated mesh penetration; and Group 3, an onboard acclimated control group. Individuals that had escaped the trawl during fishing had the highest concentrations of hemolymph lactate (mean > 6 mmol–l). Exposure to mesh penetration was in itself not stressful, as hemolymph lactate concentrations did not differ significantly between Group 2 and the control Group (mean 0.8 mmol–lversus 0.7 mmol–l, respectively). Additional stress factors during the capture and handling process likely added to the elevated lactate levels observed in Group 1. For the trawl escapees, the lactate clearance time during stress recovery was modeled as a function of exponential decay. Hemolymph lactate levels did not differ significantly among the three groups after 200 min, which suggested that Antarctic krill recovered from fishery-induced stress within this time period.

Bioenergetic status and oxidative stress during escape response until exhaustion in whiteleg shrimp Litopenaeus vannamei

The escape response in some decapod crustaceans through tail-flipping represents an excellent model of short-term, exhausting muscular activity to understand the role of energy depletion and oxidative stress in muscle fatigue. In this study indicators of oxidative stress and changes in energy metabolism were measured during escape response until fatigue in whiteleg shrimp Litopenaeus vannamei. The escape response of individual shrimp was elicited in a tank by prodding the shrimp with a stick until exhaustion (no further response). A control group consisted of undisturbed shrimp, and a third group was allowed to recover. Arginine phosphate (ArgP) and adenylic energy charge (AEC) were measured by reverse phase HPLC, while fuels, reserves, antioxidant enzyme activities (superoxide dismutase, catalase, glutathione peroxidase-GPx), thiobarbituric acid reactive substances, and protein carbonyl content were analyzed by spectrophotometric methods. Shrimp reached fatigue after 31 tail-flips, which decreased abdominal muscle ArgP by 75% and AEC by 18%. Hemolymph lactate levels increased 5 times and muscle GPx activity by 2.7 times. After 1h of recovery, ArgP and AEC base levels were re-established, while hemolymph lactate concentration and GPx activity were still increased, and glucose hemolymph content increased 1.8 times. The drastic decrease in ArgP levels prevents a drop of AEC to a critical level, in accordance with a situation of non-lethal stress. Although no significant changes were observed in muscle glycogen or lactate concentrations, the increase in hemolymph lactate levels indicates an important contribution of muscle glycolysis to prevent a more pronounced decrease in ATP and AEC. The increase in GPx activity in abdominal muscle suggests an increase in reactive oxygen species production during intensive muscular activity, which was adequately neutralized, for no signs of oxidative damage occurred, as indicated by the lack of lipid and protein oxidation. These responses suggest adequate energy efficiency and prevention of oxidative damage during the escape response, in accordance with the adaptative value of such behavior to avoid instantaneous danger, with a capacity of rapid recovery.

Physiological responses to emersion in the intertidal green crab, Carcinus maenas (L.)

The green shore crab, Carcinus maenas, undergoes on average 6 h periods of emersion during each low-tide cycle during the summer months. Under those conditions, the crab is cut off from its normal water environment and is exposed to potential stress from a suite of environmental and physiological changes: dehydration, compromised gas exchange and resultant internal hypoxia and hypercapnia, thermal stress, and ammonia toxicity. This study examined the comprehensive responses of the green crab in water and to a 6 h emersion period laboratory simulation of a tidal cycle followed by a 1 h re-immersion period, measuring indicators of dehydration, hemolymph osmolality, oxygen uptake, hemolymph acid–base status, heart and ventilatory rate, and hemolymph ammonia and ammonia excretion. Green crabs showed physiological responses of varying magnitude to 6 h of emersion. Individuals were found in the field exclusively under rocks and large clumps of seaweed where temperatures were approximately half those of exposed surfaces and relative humidity was about twice as high as ambient air. During emersion, crabs lost less than 5% of their wet weight, and hemolymph osmolality did not increase significantly. Oxygen uptake continued in air at about 50% of the control, aquatic values; and the gills continued to be ventilated by the scaphognathite, albeit at lower rates. Hemolymph lactate concentrations increased, indicating a shift to a greater reliance on anaerobic metabolism to support energetic needs. A slight acidosis developed in the hemolymph after 1 h of emersion, but it did not increase thereafter. Ammonia concentrations in the hemolymph were unchanged, as ammonia was volatilized by the gills and excreted into the air as NH3 gas. These results show that the green crab copes with emersion by seeking refuge in microhabitats that mitigate the changes in the physical parameters of intertidal emersion. Physiologically, desiccation is avoided, cardio-respiratory processes are maintained at reduced levels, and hemolymph acid–base balance is minimally affected. Ammonia toxicity appears to be avoided by a shift to excreting NH3 gas directly or indirectly to air.

Effects of walking on ventilatory and cardiac function in intact and cardiac-impaired lobsters.

Decapod crustaceans with normal heart function respond to the increased oxygen delivery requirements during walking with a step increase in heart and ventilation rate. In American lobsters, ventilation rate increased by the same amount during exercise at two walking speeds (2.4 and 8 m min(-1)); however, ventilation volume was significantly greater at the fastest walking speed (280 mL min(-1)) compared to animals at rest or walking at the slower speed (180 mL min(-1)). The heart responded in a similar manner to locomotion. Heart rate was elevated to the same level at the two different walking speeds, but cardiac stroke volume was greater, implying increased cardiac output, at the faster walking speed. The communication and compensation between the cardiac and ventilatory systems was revealed when the function of one was impaired. Ventilatory rate was significantly elevated when cardiac output was impaired by sectioning two of the alary ligaments and/or the regulatory nerves to the heart. When cardiac output was more severely impaired, ventilation rate was greater. Despite ventilatory compensation, anaerobic metabolism made a greater contribution to energy production with impaired heart function. Hemolymph lactate concentration was three to five times greater in impaired animals than controls. It is known that the ventilatory and cardiac systems of lobsters are coregulated. These data demonstrate that the performance of one system can respond to compensate for impaired function in the other.

Effect of variation in photoperiod and light intensity on oxygen consumption, lactate concentration and behavior in crayfish Procambarus clarkii and Procambarus digueti.

The effects of light intensity and duration on metabolic and behavioral parameters of two species of crayfish, Procambarus clarkii and Procambarus digueti, were studied. Sixty animals of each species were submitted to high irradiance conditions of two different photoperiod lengths, one normal light/dark (LD) 12:12 and one extreme LD 20:4 for 2 weeks. Hemolymph, lactate and oxygen consumption were determined throughout the experimental period. Simultaneously in 18 additional animals of each species, motor activity was individually recorded under the same control and experimental conditions. Both species showed a decrease in oxygen uptake and an increase in hemolymph lactate concentration. The statistical significance of this finding was higher for LD 20:4. This extreme condition evoked a significant decrease of motor activity in P. clarkii and a high mortality rate in P. digueti. P. digueti did not survive after the experiment, whereas P. clarkii survived and adapted to the laboratory conditions. Changes in metabolic and behavioral parameters could indicate different adaptation abilities in these species.

Effect of hypoxia on hemolymph lactate and behavior of the blue crab Callinectes sapidus rathbun in the laboratory and field

1. 1. Hemolymph lactate concentrations were monitored in blue crabs ( Callinectes sapidus Rathbun) during hypoxic exposures and subsequent normoxic recoveries. 2. 2. High hemolymph lactate levels resulting from hypoxia were associated with marked behavioral abnormalities which were predicatable indicators of eventual mortality. 3. 3. Elevated lactate levels returned to pre-hypoxic levels after 7–8 hr of normoxic recovery.

Patterns of energy metabolism in the stone crab, Menippe mercenaria, during severe hypoxia and subsequent recovery.

Specimens of the stone crab, Menippe mercenaria, survived severe hypoxia (PO2 less than 8mm Hg) for at least 12 hr at 28-30 degrees C. During the time course of 12 hr of hypoxia, hemolymph L-lactate levels rose to 30-50 mumoles/g wet wt. There was a slight elevation of L-alanine levels, whereas succinate was found in only trace quantities in the hemolymph. Pronounced metabolic changes took place in the heart, cheliped closer, and leg socket muscles during severe hypoxia. L-lactate accumulated to levels ranging from 16-20 mumoles/g wet wt. There were pronounced changes in high-energy phosphate levels in the cheliped closer and leg socket muscles. Taking into account expected intra- and extracellular water content, the calculated intracellular lactate content in the three muscles investigated is substantially less than the hemolymph lactate concentrations. Part of this reverse concentration gradient may be accounted for by the reduction in lactate activity due to cation-lactate complex formation. Hemolymph calcium and magnesium concentrations rose considerably during severe hypoxia. During recovery from severe hypoxia, approximately 50% of the accumulated lactate in the hemolymph was cleared in 6 hr. Hemolymph lactate and alanine levels returned to near control levels after 24 hr of recovery. This study shows that the stone crab, M. mercenaria, survives severe hypoxia by a reliance on glycogen fermentation to lactate. This species is capable of tolerating high levels of accumulated lactate.

Acid-base regulation during exercise and recovery in the blue crab, Callinectes sapidus

During swimming activity Callinectes sapidus incurred a severe hemolymph acidosis due to elevated levels of P CO 2 and lactate. Although hemolymph lactate concentration rose steadily during 1 h of exercise, hemolymph pH was maximally depressed within the first 15 min. A discrepancy between the quantities of lactate and H + released from the tissues into the hemolymph is explained by a large apparent efflux of H + into the ambient seawater, presumably via a branchial ion exchange process. Ammonia excretion increased 6 fold during exercise, but it is not clear if this contributed to the excretion of H +. The total quantity of H + excreted into the environment during exercise and recovery far exceeded that which could be attributed to hemolymph lactic acid, indicating that some of the excreted H + must have originated from other sources, such lactic acid which dissociated intracellularly, with the lactate anions remaining in the cells. Because lactate anions increase hemocyanin O 2 affinity when unopposed by the Bohr shift, the excretion of a large portion of the metabolic H + load, leaving lactate behind in the hemolymph, has important consequences for the regulation of O 2 transport during swimming.

Oxygen uptake and the potentiating effects of increased hemolymph lactate on oxygen transport during exercise in the blue crab,Callinectes sapidus

At the onset of moderate swimming activity,Callinectes sapidus rapidly increased branchial ventilation, heart rate, and oxygen uptake, reaching steady state values in 2–3 min, with a half-time of 30 sec. Although O2 extraction efficiency decreased slightly (50% to 43%) upon reaching steady state, O2 uptake was increased 2.6 fold over resting (routine) levels. HemolymphP O 2 did not change during sustained (30–60 min) exercise, but a marked decrease in pH (7.60 to 7.10), associated with a 14-fold increase in hemolymph lactate concentration, caused decreases in both pre-and postbranchial O2 content due to a large hemocyanin Bohr shift. The effect of the Bohr shift on O2 binding, however, was minimized by an increase in hemocyanin O2 affinity induced by lactate ions; the influence of lactate on hemocyaninP 50 was shown to be the same in vivo and in vitro. As a result of the interaction between the Bohr and lactate effects, only slight increases were observed in the a-v O2 difference (13%) and the quantitative role of hemocyanin in oxygen transport (11%) during exercise. The increase in O2 delivery was therefore attributed primarily to a 2.3 fold increase in cardiac output (Fick estimate), resulting from increases in both heart rate (1.61 X) and stroke volume (1.42X). During exercise hemocyanin remained 21% oxygenated upon leaving the tissues, thus maintaining a substantial ‘venous O2 reserve’ which could be utilized to fuel more strenuous levels of exercise at least partly by aerobic pathways. The high hemolymph lactate levels, however, indicate that anaerobic metabolism makes a significant contribution to energy production even during moderate exercise. These results are similar to the respiratory and circulatory responses reported for other decapod crustaceans and fish during mild exercise.C. sapidus, however, appears to be highly resistant to fatigue, which correlates with its welldeveloped locomotor capabilities.