Haemolymph Lactate Research Articles

Temperature acclimation and response to acute thermal stress in the adults of the snow crab Chionoecetes opilio Fabricius, 1788 (Decapoda: Brachyura: Oregoniidae)

ABSTRACT Ectothermic marine animals vary widely in their tolerance to temperature changes, and polar stenothermal species seem to have poor ability to compensate for a rise in water temperature. The sub-Arctic snow crab (Chionoecetes opilioFabricius, 1788) lives in the northwestern Atlantic Ocean and northern Pacific Ocean at temperatures ranging from about −1.5 °C to 4 °C. Since the metabolic costs overtake caloric intake above 7 °C, the snow crab appears to be energetically restricted to cold water. We investigated thermal stress responses in adult male crabs exposed to a sudden temperature increase to 9.5 °C for 24 hr after four weeks of acclimation at 2.5 °C or 5.5 °C. Heart-rate loggers implanted in a limited number of crabs showed 60% increase in cardiac activity during the thermal stress. Surplus oxygen supply in all crabs was inferred by the low hemolymph lactate and unchanged glucose levels, but only the crabs acclimated at 5.5 °C were still active at the elevated temperature. Low heat shock and oxidative stress responses were suggested by the missing upregulation of the genes encoding four heat shock proteins (Hsp70a, Hsc71, Hsp90a2, Hsp60) and the antioxidative enzymes superoxide dismutase and catalase. The trend towards inverse temperature-dependent on the expression of the hsp genes may be related to increased protein damage at low temperatures, or possible trade-offs between costs and benefits of producing heat shock proteins at elevated temperature. Although adult snow crabs seem to be able to cope with short-term heat stress, the tolerance to chronic elevated temperatures should be further examined using a larger number of individuals.

Implications of dietary phosphorus sources on zootechnical performance and stress response of the pacific white shrimp Litopenaeus vannamei

The phosphorous (P) is an essential element for several functions, including the synthesis of high energy compounds in cells like adenosine triphosphate (ATP) and arginine phosphate (ArgP). The dietary requirements of P could change according to physiological and environmental conditions, particularly if organisms are exposed to stress conditions. As the P availability could be related to its chemical form in the diet, the present study analyzed the influence of different P sources (KH2PO4, NaH2PO4, NH4H2PO4, Na5P3O10), on the stress response of the Pacific white shrimp Litopenaeus vannamei. Final weight was 8.5% higher (p < 0.01) in shrimp fed on tripolyphosphate (Na5P3O10) diet compared with the monophosphate diets. Weight gain and specific growth also trend to increase, whereas feed conversion ratio trend to decrease with this polyphosphate source, although not significantly. Stress response of shrimp exposed to handling followed by hypoxia was characterized by an overall increase of lactate and glucose levels in hemolymph, as well as a decrease in Adenylate Energy Charge (AEC) and ArgP in the muscle. No effect of dietary P sources was observed on baseline biochemical composition and overall indicators of stress response, except for higher carbohydrate levels in hepatopancreas and RNAm expression of arginine kinase (AK) in muscle with the NaH2PO4 diet, suggesting a potentially better energy status with this diet.

Adenosine modulates heart rate and tissue glycogen of the giant freshwater prawn Macrobrachium rosenbergii (De Man, 1879)

Transport of live crustaceans to market induces a variety of stressors, increases rates of mortality and results in a metabolic imbalance between adenosine triphosphate (ATP) supply and demand. Re-aligning ATP demands with impaired supply during transport should prolong survival. Adenosine acts as a “retaliatory” metabolite and has the potential to induce metabolic depression amid periods of energetic stress. Consequently, in this study, the effect on the metabolic markers, heart rate (HR), tail muscle glucose/ glycogen and haemolymph lactate from administering a range of adenosine concentrations (0.25, 2.5 and 25 mM; n = 6, 5 & 5 respectively) to the giant freshwater prawn (Macrobrachium rosenbergii) by injection was assessed over 3 h. Equivalent water volumes (vehicle) were injected into control animals (n = 5). Adenosine at 2.5 and 25 mM decreased heart rate 20–25 % from baseline for several hours. Free glucose and tail muscle glycogen decreased following treatment with adenosine at 2.5 mM, while haemolymph lactate remained unchanged across treatments. There were zero mortalities across all four treatments. This study shows that adenosine safely depresses the heart rate of M. rosenbergii and may mitigate the stresses associated with live transport.

Differences in Agonistic Behavior and Energy Metabolism between Male and Female Swimming Crab Portunus trituberculatus Based on the Analysis of Boldness.

Simple SummaryBoldness is a widely studied personality trait that is positively related to an individual’s willingness to fight. To explore the agonistic behavior between female and male crabs with different degrees of boldness, we quantified the boldness of females and males using a behavior observation system and used the experimentally determined boldness and classification. The results showed that boldness affected the agonistic behavior between female and male swimming crabs, the fighting willingness and capacity of male crabs is higher than that of female individuals and is higher in bold crabs than in shy individuals. Energy reserves and metabolic rates may be one of the factors affecting the agonistic behavior in crabs and that the agonistic behavior resulted in significant changes in key energy metabolites.Individual differences in metabolism and agonistic behavior have been a key research area in evolution and ecology recently. In this study, we investigated the boldness of swimming crabs Portunus trituberculatus and explored the agonistic behavior between female and male crabs, specifically examining competitions between bold females vs. bold males (BF–BM), bold females vs. shy males (BF–SM), shy females vs. shy males (SF–SM), and shy females vs. bold males (SF_BM) and its relationship with energy metabolism. The main results revealed the following: There was no significant difference in boldness between females and males, while there were more bold individuals than shy in both females and males. Bold individuals initiated significantly more fights than shy individuals, and male initiators won significantly more fights than female initiators. The duration and intensity of fight between bold individuals was significantly higher than fights between shy individuals. For males, the concentration of glucose in the hemolymph was significantly higher in shy crabs than bold crabs, while there was no significant difference between shy and bold individuals in females. After fighting, the concentration of glycogen in claws was lower than that before fighting, and the concentrations of glucose and lactate in hemolymph were significantly higher after fighting than before. We found that the fighting willingness and ability were higher in male crabs than females and higher in bold crabs than shy. Fighting ability varied between sexes and was influenced by boldness and energy state.

What Forms, Maintains, and Changes the Boldness of Swimming Crabs (Portunus trituberculatus)?

Simple SummaryThe formation and maintenance mechanism of personality is a hot topic in personality research. The boldness of the swimming crab (Portunus trituberculatus) has the greatest influence on its behavior, but the physiological factors leading to the stability of and difference in boldness are not yet clear. In this study, the factors affecting the formation and maintenance of and change in the boldness of swimming crabs are investigated from the perspectives of behavior, physiology, and neurotransmitters. The results show that the differences in boldness among crabs remain consistent for a long time and are closely related to the body’s energy and neurotransmitter metabolism.Boldness of personality is an important theme in animal behavior and has significant ecological and evolutionary consequences. Studies on boldness in crustaceans typically focus on their behavior, while relatively few studies have focused on the formation and maintenance of and change in boldness, such as energy metabolism and neurotransmission. In this study, we measured the boldness of swimming crabs (Portunus trituberculatus) and analyzed the relationship between boldness and oxygen consumption rate, energy concentration, and the relative expression of energy-metabolism-related and 5-HT genes in mRNA. The results showed that boldness remained stable across repeated tests but changed under dangerous conditions. Swimming crabs could be divided into bold and shy individuals. Bold individuals consumed oxygen at a significantly higher rate than shy individuals. Lactate and glucose concentrations in hemolymph were significantly lower in bold individuals than in shy individuals, and mRNA relative expression of Na+/K+-ATPase and 5-HT genes was significantly higher in bold than in shy individuals. Preliminary results indicate that energy metabolism and neurotransmitters may underlie the formation and maintenance of personality characteristics of swimming crabs. Swimming crabs also exhibit behavioral flexibility in order to cope with risks. This may be an adaptation to their complex environments.

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 &amp;gt; 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.

Effect of different amount of food and female resource on competitive strategy and agonistic behavior of swimming crab (Portunus trituberculatus)

Obtaining limited resources is an important motivator behind competition in animals. In pond cultures of swimming crabs (Portunus trituberculatus) common resources that cause conflict are food and mates. To explore the effects of different levels of food stimulus (clam extract; CG, control group: 0; LCH, little clam homogenate: 5 mL; ACH, abundant clam homogenate: 25 mL) and mate stimulus (female-conditioned water FCW; SW, seawater: 85 L seawater; LFW, low concentration FCW: 21 L FCW + 64 L seawater; HFW, high concentration FCW: 85 L FCW) on competitive strategies and agonistic behaviors of male crabs, we built an agonistic behavior recording system. We analyzed behavior, changes of oxygen consumption rate (OCR), and the concentrations of glycogen, glucose, and lactate in chelipeds and hemolymph after fighting. The main results revealed the following: (1) With increased perceived availability of food, the frequency of contact and key behaviors was significantly higher in the CG and LCH group than the ACH group. Fight duration in the LCH group was significantly longer than in the ACH group. The fight intensity and OCR of the LCH group were significantly higher than CG and ACH group. The concentration of lactate in hemolymph and glucose in chelipeds of the LCH group were significantly higher than the ACH group. The concentration of glycogen in cheliped muscle of the LCH and ACH group was significantly higher than the CG. (2) The increased concentration of FCW in the HFW group caused the duration of fights and the frequency of contact behaviors to be higher than in the SW group. In the HFW group the key behaviors occurred significantly more than in the SW and LFW groups. Fight intensity was also higher in the HFW group than the other two groups, and the LFW group had higher fight intensity than the SW group. The OCR of LFW and HFW groups were significantly higher than the SW group. The lactate concentrations in hemolymph and chelipeds in the LFW group were significantly higher than those in the SW and LFW groups. The glycogen concentrations in the chelipeds of the LFW and HFW groups were significantly higher than in the SW group. These results showed that the crabs adopt different competitive strategies, either to fight or yield, depending on type and availability of resources. These strategies are associated with costs such as physical risk and energy expenditure. In pond cultures of swimming crabs, increasing the density of food and isolating females from males during the breeding season may help to reduce appendage mutilation or death caused by fighting, thereby increasing aquaculture efficiency.

Effects of a mixture of glyphosate, 17α-ethynylestradiol and amyl salicylate on cellular and biochemical parameters of the mussel Mytilus galloprovincialis

In this study the effects of a mixture of glyphosate (herbicide), 17a-ethinylestradiol (synthetic estrogen) and amyl salicylate (fragrance) to the mussel Mytilus galloprovincialis were evaluated. Mussels were exposed for 7 days to two realistic concentrations of the mixture (10 and 100 ng/L) and the effects on total haemocyte counts, haemocyte diameter and volume, haemocyte proliferation, haemolymph lactate dehydrogenase activity and haemocyte lysate lysozyme activity were measured. In addition, superoxide dismutase, catalase, acetylcholinesterase, glutathione-S-transferase and glutathione reductase activities were measured in gills and digestive gland. The survival-in-air test was also performed. Results demonstrated that the mixture affected both cellular and biochemical biomarkers, but not tolerance to aerial exposure of M. galloprovincialis. The negative effects recorded in this study suggested that more efforts should be done to assess the ecotoxicological risks posed by contaminant mixture to aquatic invertebrates.

Biomarkers of homeostasis, allostasis, and allostatic overload in decapod crustaceans of distinct habitats and osmoregulatory strategies: an empirical approach

The term "allostasis", meaning the assumption that homeostasis may not be as static as the term implies, has been vastly employed for mammals, and other vertebrates, for which the degree of internal stability is maximal, according to their higher complexity. We have here investigated how these states of homeostasis, allostasis, and allostatic overload could be diagnosed in decapod crustaceans, upon acute salinity challenges. Decapods of distinct lineages and habitats have been submitted to 3 salinity levels for 6 and 12 h. The first salinity was the habitat salinity (control), considered as the one that allows the homeostatic condition. The next salinity represented a mild challenge, that would potentially lead to allostasis, and the third salinity was intended to represent an overload, albeit not lethal. Species used were: the marine crab Hepatus pudibundus (Hp, osmoconformer, salinities 33, 25, and 20‰), the marine/estuarine swimming crab Callinectes danae (Cd, weak regulator, salinities 30, 20, and 10‰), and the diadromous freshwater prawn Macrobrachium acanthurus (Ma, strong regulator, salinities <0.5, 15, and 30‰). These 3 species follow a sequence of growing regulatory capacity (Hp<Cd<Ma), and euryhalinity (Hp<Ma<Cd). The biomarker of allostatic overload in Hp was the dramatic build-up of hemolymph lactate in 10‰; Cd was so euryhaline that had its homeostasis barely disturbed by the treatments, and the overload biomarker for Ma was low reduced muscle hydration in 30‰. The concept of allostasis can be successfully applied to comparative osmoregulation of decapods, with potential implications in areas of applied physiology such as aquaculture.

Ecotoxicological hazard of a mixture of glyphosate and aminomethylphosphonic acid to the mussel Mytilus galloprovincialis (Lamarck 1819)

Assessment of the effects of chemical mixtures is a very important objective of the ecotoxicological risk assessment. This study was aimed at evaluating for the first time the effects of a mixture of glyphosate and its main breakdown product aminomethylphosphonic acid (AMPA) on various biomarkers in the mussel Mytilus galloprovincialis. Mussels were exposed for 7, 14 and 21 days to either 100 µg/L of glyphosate, 100 µg/L of AMPA or a mixture of both (100 + 100 µg/L). Various haemocyte parameters, such as total haemocyte counts, haemocyte diameter and volume, haemocyte proliferation, haemolymph lactate dehydrogenase activity and haemocyte lysate acid phosphatase activities were measured. In addition, the effects of exposure on the activity of antioxidant enzymes, acetylcholinesterase and glutathione-S-transferase were evaluated in gills and digestive gland from mussels. On the whole, this study demonstrated that the variables considered in the experimental plan, namely treatment, exposure time and their interaction, affect significantly biomarker responses in M. galloprovincialis. The effects of the mixture were comparable to those of the individual compounds, whereas their synergistic effects were occasionally observed, under the experimental conditions tested at least.

Lower-intensity net-chasing training facilitates the survival and growth of the Chinese shrimp Fenneropenaeus chinensis reared at high stocking densities

Low survival and growth are the major problems in intensive culture of the Chinese shrimp Fenneropenaeus chinensis. We used net-chasing training to simulate predator-like threat to improve the survival and growth of F. chinensis reared at high stocking densities (up to 240 individuals m−2). The shrimps were trained three times a day under four chased intensities, control, 25%-, 50%- and 100%-exhausted, reared at densities of 240 individuals m−2 in each intensity. After 40 days, the biochemistry (lactate concentration, enzyme activities of anaerobic and aerobic metabolism), behavioural indicators (tail-flipping speeds; time spent on stationary, walking and swimming), survival and growth were determined. The net-chasing training increased tail-flipping speeds due to the increased activities of phosphofructokinase, pyruvate kinase and lactate dehydrogenase in abdominal muscles. The shrimps spent less time on swimming and more time on stationary after chasing training. The survival rates were 54.44% in the control group, but ranging from 88.89% to 90.56% in the 25%-, 50%-, and 100%-exhausted groups. Most of dead shrimps lost their pleopods, periodpods and (or) uropods. The 50%- and 100%-exhausted chasing reduced the total food consumption due to high levels of hemolymph lactate, resulting in low growth rates in these groups. The shrimps showed elevated growth rates with no reduced ingestion in the 25%-exhausted group. We conclude that net-chasing increased the tail-flipping ability and suppressed the cannibalistic behaviour, increasing the survival of F. chinensis reared at the high densities. The low-intensity (25%-exhausted) chasing increased the growth rates due to shrimp having more energy available allocating for somatic growth.

Glyphosate affects haemocyte parameters in the clam Ruditapes philippinarum

This study was aimed at evaluating the effects of glyphosate on haemocyte parameters of the clam Ruditapes philippinarum. Clams were exposed for 7 days to differing glyphosate concentrations (10, 100 and 1000 μg/L) and various haemocyte parameters were measured, such as total haemocyte count (THC), haemocyte diameter and volume, haemocyte proliferation, haemolymph lactate dehydrogenase activity, haemocyte lysate lysozyme and acid phosphatase activities. Glyphosate reduced significantly THC values, while increased both diameter and volume of haemocytes. Exposure to the highest herbicide concentration increased significantly haemocyte proliferation. No significant effects on haemolymph lactate dehydrogenase and haemocyte lysate lysozyme activities were observed, whereas haemocyte lysate acid phosphatase activity resulted significantly increased in clams exposed at 100 and 1000 μg/L. On the whole, this study demonstrated that glyphosate influenced significantly haemocyte parameters in R. philippinarum.

Changes in hemolymph lactate and ammonia in the hermit crabPagurus samuelis(Stimpson, 1857) (Decapoda: Anomura: Paguridae) during shallow burial

Increased sedimentation in intertidal areas may stem from anthropogenic sources such as coastal development and natural processes, including discharges by rivers, landslides, and floods. Furthermore, global climate change could eventually lead to environmental hypoxia altering the composition of intertidal communities when hypoxia events surpass the physiological tolerance of intertidal organisms. We measured hemolymph lactate and ammonia (NH3 and NH4+) in the hermit crab Pagurus samuelis (Stimpson, 1857) subjected to shallow burial events and found high lactate and ammonia, indicating a switch to anaerobic respiration. The likelihood of hermit crabs dying during burial increased 31% for every 10 mM increase in lactate. Lactate levels were generally raised by increasing temperature, burial depth, or burial duration. At 20 ºC and 30 ºC, more lactate was detected at 3 cm and 6 cm burial depths than in the control (0 cm). Lactate concentrations were higher at 3 cm burial depth after 6 h than after 2 h. Lactate concentrations were higher at 20 ºC and 30 ºC than at 5 ºC at both 3 cm and 6 cm. A 10 µg ml–1 rise in ammonia concentration was associated with increased probability of death by 21%. Ammonia concentrations were higher at 3 cm than at 6 cm, indicating a shift in ammonia production or excretion at 6 cm. Burial time did not impact ammonia production. Large numbers of hermit crabs survived up to 24 h following lactate (92.9%) and ammonium salt (83.3%) injections. These results provide evidence that neither lactate nor ammonia buildup are principal causes of death following shallow burial.

Effects of aminomethylphosphonic acid, the main breakdown product of glyphosate, on cellular and biochemical parameters of the mussel Mytilus galloprovincialis

The effects of the breakdown products of herbicides on aquatic species are largely unknown. In a recent study, we evaluated the effects of glyphosate on the mussel Mytilus galloprovincialis. This study was designed to evaluate for the first time the impact of aminomethylphosphonic acid (AMPA) - the main breakdown product of glyphosate - on cellular and biochemical parameters of the mussel Mytilus galloprovincialis. Bivalves were exposed for 7, 14 and 21 days to 1, 10 and 100 μg/L of AMPA and various biomarkers were measured in haemolymph (total haemocyte counts, haemocyte diameter and volume, haemolymph pH, haemocyte proliferation, haemolymph lactate dehydrogenase activity, haemocyte lysate lysozyme and acid phosphatase activities), as well as in gills and digestive gland (superoxide dismutase, catalase, glutathione S-transferase and acetylcholinesterase activities). AMPA concentrations in seawater samples from the experimental tanks were also measured in order to correlate the biomarker responses of mussels with their exposure to the actual concentrations of AMPA. The MANOVA analysis demonstrated that the experimental variables considered (exposure dose, exposure duration, and their interaction) affected significantly biomarker responses. Nevertheless, the two-way ANOVA analysis revealed significant effects of AMPA on most of the biomarkers measured. The overall results of this study demonstrated that AMPA can affect cellular and biochemical parameters in mussels, similarly to glyphosate.

Interactive effects of hypoxia and dissolved nutrients on the physiology and biochemistry of the freshwater crayfish Paranephrops zealandicus

A key contributing factor to the decline of the at-risk freshwater crayfish Paranephrops zealandicus is the presence of hypoxia associated with eutrophication. However, there is little information regarding the effects that dissolved nutrients have on the physiological and biochemical mechanisms that this and other freshwater crayfish use to cope with lowered dissolved oxygen. In the present study, P. zealandicus were exposed to an abrupt hypoxia (1.3kPa) in the absence or presence of either ammonia (30mgL–1 total ammonia; 0.04mgL–1 as un-ionised ammonia) or nitrite (20mgL–1) over a 6-h exposure using semi-closed box respirometry. Respiratory (oxygen consumption, haemolymph oxygen partial pressure), cardiac (heart rate) and biochemical (haemolymph acid–base status, glucose and lactate; tissue glucose and lactate) end points were measured. In hypoxia alone, haemolymph oxygen partial pressure, glucose and pH fell, whereas haemolymph lactate increased. The only significant effects of nutrients on hypoxic responses were a further decline in haemolymph oxygen partial pressure and an enhanced hypoglycaemia in the presence of nitrite. These effects may be linked to a nitrite-mediated improvement in tissue perfusion. Overall, these data indicate little additional effect of the presence of nutrients on the responses of P. zealandicus to hypoxia.

Ecotoxicological risk assessment for the herbicide glyphosate to non-target aquatic species: A case study with the mussel Mytilus galloprovincialis.

Glyphosate (GLY) is one of the most used herbicide worldwide. Considering that information concerning the impact of GLY on bivalves is scarce, in this study we evaluated for the first time the effects of environmentally realistic concentrations of GLY (10, 100 and 1000μg/L) to the mussel Mytilus galloprovincialis. Mussels were exposed for 7, 14 and 21 days and several biomarkers were measured in haemocytes/haemolymph (total haemocyte counts, haemocyte diameter and volume, haemolymph pH, haemolymph lactate dehydrogenase activity, haemocyte lysate lysozyme and acid phosphatase activities), as well as in gills and digestive gland (antioxidant enzyme and acetylcholinesterase activities). The concentrations of GLY and its main metabolite aminomethylphosphonic acid in the experimental tanks were also measured. The MANOVA analysis demonstrated that the experimental variables considered (exposure concentration, exposure duration, and their interaction) affected significantly biomarker responses. In addition, the two-way ANOVA analysis indicated that GLY was able to affect most of the cellular parameters measured, whereas antioxidant enzyme activities resulted to be influenced moderately. Interestingly, exposure to GLY reduced significantly acetylcholinesterase activity in gills. Although preliminary, the results of this study demonstrated that GLY can affect both cellular and biochemical parameters in mussels, highlighting a potential risk for aquatic invertebrates.

Oxygen consumption remains stable while ammonia excretion is reduced upon short time exposure to high salinity in Macrobrachium acanthurus (Caridae: Palaemonidae), a recent freshwater colonizer

ABSTRACT Palaemonid shrimps occur in the tropical and temperate regions of South America and the Indo-Pacific, in brackish/freshwater habitats, and marine coastal areas. They form a clade that recently (i.e., ~30 mya) invaded freshwater, and one included genus, Macrobrachium Bate, 1868, is especially successful in limnic habitats. Adult Macrobrachium acanthurus (Wiegmann, 1836) dwell in coastal freshwaters, have diadromous habit, and need brackish water to develop. Thus, they are widely recognized as euryhaline. Here we test how this species responds to a short-term exposure to increased salinity. We hypothesized that abrupt exposure to high salinity would result in reduced gill ventilation/perfusion and decreased oxygen consumption. Shrimps were subjected to control (0 psu) and experimental salinities (10, 20, 30 psu), for four and eight hours (n = 8 in each group). The water in the experimental containers was saturated with oxygen before the beginning of the experiment; aeration was interrupted before placing the shrimp in the experimental container. Dissolved oxygen (DO), ammonia concentration, and pH were measured from the aquaria water, at the start and end of each experiment. After exposure, the shrimp’s hemolymph was sampled for lactate and osmolality assays. Muscle tissue was sampled for hydration content (Muscle Water Content, MWC). Oxygen consumption was not reduced and hemolymph lactate did not increase with increased salinity. The pH of the water decreased with time, under all conditions. Ammonia excretion decreased with increased salinity. Hemolymph osmolality and MWC remained stable at 10 and 20 psu, but osmolality increased (~50%) and MWC decreased (~4%) at 30 psu. The expected reduction in oxygen consumption was not observed. This shrimp is able to tolerate significant changes in water salt concentrations for a few hours by keeping its metabolism in aerobic mode, and putatively shutting down branchial salt uptake to avoid massive salt load, thus remaining strongly hyposmotic. Aerobic metabolism may be involved in the maintainance of cell volume, concomitant with reduced protein/aminoacid catabolism upon increase in salinity. More studies should be conducted to broaden our knowledge on palaemonid hyporegulation.

The euryhaline crabUca tangerishowed metabolic differences to sex and environmental salinity

This study constitutes a first attempt to investigate sex differences in osmoregulatory capacity and metabolic responses in relation to hyper- and hypo-osmoregulation in the intertidal euryhaline crabUca tangeri. Adult male and female specimens from Cadiz Bay, Spain (36°23′–37′N 6°8′–15′W), were acclimated to three different environmental salinities (12, 33 and 55 psu) during 7 days, and several parameters were assessed in haemolymph (osmolality, glucose, amino acids, triglycerides and lactate) as well as in metabolic key organs (hepatopancreas, anterior and posterior gills: glycogen, free glucose, amino acids and triglycerides). Specimens from both sex exhibited high and similar hyper- and hypo-osmoregulatory capacities. However, metabolite levels were differentially affected upon acclimation to low and high salinity in several metabolic organs and haemolymph of male and females: (i) glycogen in gills, (ii) free glucose in gills and hepatopancreas, (iii) amino acids in hepatopancreas, (iv) triglycerides in haemolymph, hepatopancreas and posterior gills, and (v) lactate in haemolymph. The results suggest the occurrence of differential metabolic adjustments upon hyper- and hypo-osmoregulation related to sex in the intertidal euryhaline crabU. tangeri.

Effects of stocking density on the individual growth and differentiation of the oriental river prawn Macrobrachium nipponense (de Haan, 1849) (Caridea: Palaemonidae)

We evaluated the effect of stocking density on the concentrations of oxy-hemocyanin and lactate in hemolymph, the antioxidant ability of the hepatopancreas, and the biochemical composition in large and small individuals of the prawn Macrobrachium nipponense (de Haan, 1849) cultured in a cage system. Juveniles (0.24 g initial weight) were stocked in 15 cages with stocking densities of 40, 80, 120, 160, and 200 individuals/m2 for 8 weeks. The results demonstrated that final mean weight, weight gain, gross feed conversion ratio, and survival rate were significantly lower in stocking densities of 160 and 200 individuals/m2 (P<0.05) than in other treatment groups, not through water quality deterioration or food competition, but through the role of density as an environmental stress factor. The coefficient of variation (CV) of body weight increased as the stocking density increased, and the CV in the 160 and 200 individuals/m2 groups were over 70%. The values of hemolymph oxy-hemocyanin and lactate concentration, superoxide dismutase (SOD), catalase (CAT) activities, malondialdehyde (MDA) content, and heat-shock protein 70 (HSP70) mRNA expressions of hepatopancreas in small individuals were significantly higher than those of the large ones in high stocking densities of 160 and 200 individuals/m2. This study provides evidence that crowding stress can stimulate the physiological response of the small individuals raising their oxy-hemocyanin and lactate level in the hemolymph and decreasing antioxidant ability on hepatopancreas, which ultimately lead to suppress growth performance of the small individuals.

Hypothermal effects on survival, energy homeostasis and expression of energy-related genes of swimming crabs Portunus trituberculatus during air exposure

Previously, dry or semi-dry approach under the hypothermal condition is proved to be an alternative method in transport of live swimming crabs Portunus trituberculatus. However, we wondered whether this method can improve crab survival when temperature is kept as cool as possible. In this study, we hypothesized that there is a thermal threshold below which dry or semi-dry approach (air exposure) could cause crab physiological disruption and therefore aggravate their mortality. To test the above hypothesis, crabs (23°C) were exposed to air at temperatures ranging from 4 to 16°C. Results showed that crabs had a worse survival and vigor at temperatures below 12°C. Then we tested crab energy metabolism to explore the possible reason. It was shown that total adenine nucleotide and adenylate energy charge in gills were remarkably reduced by air exposure of below 12°C. This increased the need for crabs to re-balance energy metabolism, which was indicated by the upregulation of AMPKα and HIF-1α. Meanwhile, there was a significant increase of the expression of Na+/K+-ATPase, V-type ATPase and HSP90 at temperatures below 12°C, while all treatments shared a similar level of hemocyanin, urate and lactate in hemolymph and expression of cytochrome c oxidase and NADH-ubiquinone reductase in gills. These results implied that dry or semi-dry approach below 12°C could exert detrimental effects on P. trituberculatus, and perturbation of energy homeostasis, which is more related with changes of energy-demanding physiological pathways, is a possible reason of crab death and poor vigor.