Hemolymph Osmolality Research Articles

Do osmoregulators have lower capacity of muscle water regulation than osmoconformers? A study on decapod crustaceans

Decapod crustaceans occupy various aquatic habitats. In freshwater they are osmoregulators, while marine species are typically osmoconformers. Freshwater crustaceans are derived from marine ancestors. The hypothesis tested here was that osmoregulators, which can rely on salt transport by interface epithelia to prevent extracellular disturbance, would have a lower capacity of tissue water regulation when compared with osmoconformers. Four species of decapod crustaceans (the marine osmoconformer crab Hepatus pudibundus, and three osmoregulators of different habitats) have been exposed in vivo to a salinity challenge, for up to 24 hr. Osmoregulators were: the estuarine shrimp Palaemon pandaliformis, the diadromous freshwater shrimp Macrobrachium acanthurus, and the hololimnetic red crab Dilocarcinus pagei. H. pudibundus displayed hemolymph dilution already after 0.5 hr in 25 per thousand, reaching approximately 30% reduction in osmolality, but its muscle degree of hydration did not increase. To make the different in vivo salinity challenges directly comparable, the ratio between the maximum change in muscle hydration with respect to the control value measured for the species and the maximum change in hemolymph osmolality was calculated (x 1,000): H. pudibundus (25 per thousand, 8.1% kg H(2)O/mOsm x 10(3))>P. pandaliformis (2 per thousand, 9.2)>M. acanthurus (30 per thousand, 12.6)>P. pandaliformis (35 per thousand, 16.7)>D. pagei (7 per thousand, 60.4). Muscle slices submitted in vitro to a 30% osmotic challenge confirmed in vivo results. Thus, the estuarine/freshwater osmoregulators displayed a lower capacity to hold muscle tissue water than the marine osmoconformer, despite undergoing narrower variations in hemolymph osmolality.

Carbonic anhydrase and Na/K-ATPase activities during the molt cycle of low salinity-reared white shrimp Litopenaeus vannamei

Changes in hemolymph osmolality, ion concentrations, and enzymatic activities of carbonic anhydrase (CA) in the gills and epidermal tissue, and Na/K-ATPase in the gills during the molt cycle were investigated in the white shrimp Litopenaeus vannamei. Hemolymph osmolality was high in the intermolt and early premolt stages, but started to decrease prior to ecdysis through to postmolt stages A and B. Changes in Na+ and Cl− ion concentrations paralleled those in hemolymph osmolality. CA activity levels in the anterior and posterior gills were low at intermolt stage C0 and premolt stage D0, and maximum at premolt stage D3. In the epidermal tissue, activity was relatively high at intermolt stage C0 and premolt stage D0, but fluctuated towards premolt stage D3 and postmolt stage A. On the other hand, Na/K-ATPase activity in the gills decreased between intermolt stage C0 and premolt stage D2, but increased at premolt stage D3 and postmolt stage A. The changes in patterns of CA activity during the molt cycle suggest that CA may be involved in supplying counter-ions for Na+ and Cl− uptake during molting. Branchial Na/K-ATPase appears to be involved in producing local osmotic gradients in order to support water influx across the epithelium.

The effects of diclofenac on the physiology of the green shore crab Carcinus maenas

In recent years there has been increasing concern regarding the influx of pharmaceuticals into aquatic environments. One group of pharmaceuticals that has been identified as being of particular concern are the non-steroidal anti-inflammatory drugs (NSAIDs). This study examined the effects of one of the most commonly reported NSAID contaminants, diclofenac, on the physiology of Carcinus maenas. Two environmentally realistic concentrations were examined in this study (10 ng/l and 100 ng/l) at two salinities (35 and 17.5 psu). Female and male crabs were exposed to these two concentrations for 7 days. Following exposure, haemolymph samples were taken from the animals. Measurements were taken for oxyhaemocyanin and lactate concentrations. The effects of this compound on osmoregulatory capacity (OC) in C. maenas were also measured. Exposure to diclofenac had no significant effect on haemolymph lactate and oxyhaemocyanin concentrations suggesting that exposure to this compound does not elicit a stress response in this species. However, exposure to this pharmaceutical did have significant effects on both the OC and the haemolymph osmolality in C. maenas. At both salinities the data suggests that the osmoregulatory ability of C. maenas is impaired when exposed to diclofenac.

Survival, osmoregulation and ammonia-N excretion of blue swimmer crab, Portunus pelagicus, juveniles exposed to different ammonia-N and salinity combinations

Ammonia-N toxicity to early Portunus pelagicus juveniles at different salinities was investigated along with changes to haemolymph osmolality, Na +, K +, Ca 2+ and ammonia-N levels, ammonia-N excretion and gill Na +/K +-ATPase activity. Experimental crabs were acclimated to salinities 15, 30 and 45‰ for one week and 25 replicate crabs were subsequently exposed to 0, 20, 40, 60, 80, 100 and 120 mg L − 1 ammonia-N for 96-h, respectively. High ammonia-N concentrations were used to determine LC 50 values while physiological measurements were conducted at lower concentrations. When crabs were exposed to ammonia-N, anterior gill Na +/K +-ATPase activity significantly increased ( p < 0.05) at all salinities, while this only occurred on the posterior gills at 30‰. For crabs exposed to 20 and 40 mg L − 1 ammonia-N, both posterior gill Na +/K +-ATPase activity and ammonia-N excretion were significantly higher at 15‰ than those at 45‰. Despite this trend, the 96-h LC 50 value at 15‰ (43.4 mg L − 1 ) was significantly lower ( p < 0.05) than at both 30‰ and 45‰ (65.8 and 75.2 mg L − 1 , respectively). This may be due to significantly higher ( p < 0.05) haemolymph ammonia-N levels of crabs at low salinities and may similarly explain the general ammonia-N toxicity pattern to other crustacean species.

Physiological responses of pink abaloneHaliotis corrugata(Gray, 1828) exposed to different combinations of temperature and salinity

Physiological responses of pink abalone Haliotis corrugata were determined under different temperature and salinity conditions. Oxygen consumption rate was not affected by temperature and salinity. Ammonium excretion of pink abalone was inversely related to salinity. The O:N ratio indicated that abalone maintained in lower salinities had an interval of 4.9–7.7, which is indicative of a protein-dominated metabolism, whereas the O:N in 35‰ was 28.8–35.5 for both temperatures, suggesting that carbohydrates were used as energy substrate. Haemolymph osmolality of abalone exposed to 20 and 24 °C was slightly hyperiso-osmoconformic in salinity ranges of 20–35‰. The results of this study suggested that for optimized culture, pink abalone should be cultivated at 24 °C at a salinity of 35‰.

Cyclomorphosis in Tardigrada: adaptation to environmental constraints

Tardigrades exhibit a remarkable resilience against environmental extremes. In the present study, we investigate mechanisms of survival and physiological adaptations associated with sub-zero temperatures and severe osmotic stress in two commonly found cyclomorphic stages of the marine eutardigrade Halobiotus crispae. Our results show that only animals in the so-called pseudosimplex 1 stage are freeze tolerant. In pseudosimplex 1, as well as active-stage animals kept at a salinity of 20 ppt, ice formation proceeds rapidly at a crystallization temperature of around -20 degrees C, revealing extensive supercooling in both stages, while excluding the presence of physiologically relevant ice-nucleating agents. Experiments on osmotic stress tolerance show that the active stage tolerates the largest range of salinities. Changes in body volume and hemolymph osmolality of active-stage specimens (350-500 microm) were measured following salinity transfers from 20 ppt. Hemolymph osmolality at 20 ppt was approximately 950 mOsm kg(-1). Exposure to hypo-osmotic stress in 2 and 10 ppt caused (1) rapid swelling followed by a regulatory volume decrease, with body volume reaching control levels after 48 h and (2) decrease in hemolymph osmolality followed by a stabilization at significantly lower osmolalities. Exposure to hyperosmotic stress in 40 ppt caused (1) rapid volume reduction, followed by a regulatory increase, but with a new steady-state after 24 h below control values and (2) significant increase in hemolymph osmolality. At any investigated external salinity, active-stage H. crispae hyper-regulate, indicating a high water turnover and excretion of dilute urine. This is likely a general feature of eutardigrades.

Osmoregulation and salinity tolerance in the Antarctic midge,Belgica antarctica: seawater exposure confers enhanced tolerance to freezing and dehydration

Summer storms along the Antarctic Peninsula can cause microhabitats of the terrestrial midge Belgica antarctica to become periodically inundated with seawater from tidal spray. As microhabitats dry, larvae may be exposed to increasing concentrations of seawater. Alternatively, as a result of melting snow or following rain, larvae may be immersed in freshwater for extended periods. The present study assessed the tolerance and physiological response of B. antarctica larvae to salinity exposure, and examined the effect of seawater acclimation on their subsequent tolerance of freezing, dehydration and heat shock. Midge larvae tolerated extended exposure to hyperosmotic seawater; nearly 50% of larvae survived a 10-day exposure to 1000 mOsm kg(-1) seawater and approximately 25% of larvae survived 6 days in 2000 mOsm kg(-1) seawater. Exposure to seawater drastically reduced larval body water content and increased hemolymph osmolality. By contrast, immersion in freshwater did not affect water content or hemolymph osmolality. Hyperosmotic seawater exposure, and the accompanying osmotic dehydration, resulted in a significant correlation between the rate of oxygen consumption and larval water content and induced the de novo synthesis and accumulation of several organic osmolytes. A 3-day exposure of larvae to hyperosmotic seawater increased freezing tolerance relative to freshwater-acclimated larvae. Even after rehydration, the freezing survival of larvae acclimated to seawater was greater than freshwater-acclimated larvae. Additionally, seawater exposure increased the subsequent tolerance of larvae to dehydration. Our results further illustrate the similarities between these related, yet distinct, forms of osmotic stress and add to the suite of physiological responses used by larvae to enhance survival in the harsh and unpredictable Antarctic environment.

Changes to the histological gill structure and haemolymph composition of early blue swimmer crabPortunus pelagicusjuveniles during elevated ammonia-N exposure and the post-exposure recovery

It is yet unclear whether sub-lethal ammonia-N levels cause irreparable damage to aquatic crustaceans, or if recovery is possible, the potential factors involved. The aim was to investigate the effect of 0.706 and 2.798mmol L1 ammonia-N exposure on the haemolymph osmolality, Na1, K1, Ca21, pH, ammonia-N, total haemocyte counts (THC) and gill histopathology of Portunus pelagicus juveniles at 0, 3, 6, 12, 24 and 48 h respectively. Following 48 h, crabs were transferred to pristine seawater allowing a recovery period up to 96 h and similarly measured. In addition moribund crabs, induced from lethal ammonia-N levels of 7.036 and10.518mmol L1, were measured for haemolymph osmolality/ions and pH levels. The results demonstrate that despite severe gill damage within 6- and1h of 0.706 and 2.798mmol L1 ammonia-N exposure, respectively, no significant change (P40.05) in the haemolymph osmolality, Na1, K1, Ca21 or pH levels occurred or by ammonia- N-induced morbidity. Although the gills can completely recover within 24 and 48 h post exposure to 0.706 and 2.798mmol L1 ammonia-N, respectively, likely facilitated by significant haemocyte increases (Po0.05) within the haemolymph and gill lamellae, dependent factors were the previous ammonia-N concentration and recovery duration while individual variability was also noticed.

Role of an aquaporin in the sheep tick Ixodes ricinus: Assessment as a potential control target

Ticks undergo tremendous osmoregulatory stress as they take on up to 100 times their body weight in blood, returning about 75% of the ingested water and ions via their saliva into the host. We postulated that water channels, or aquaporins, involved in this mass water transport might be good targets for acaricide development. An aquaporin ( IrAQP1) identified in the sheep tick, Ixodes ricinus, was present only in tissues involved in mass water flux, namely the gut, rectal sac and especially abundant in the salivary glands. IrAQP1 was localised by in situ hybridisation in specific cell and acini types, possibly Type III acini, but absent from the type I acini that are responsible for rehydration of ticks in the non-feeding phase. Gene knockdown of IrAQP1 in isolated salivary glands completely inhibited dopamine-stimulated secretion. Further, IrAQP1 knockdown adult females had 50% reduced body weight gains over the first 5 days feeding on an artificial feeding apparatus and 21% at the point of engorgement on hosts. Haemolymph osmolarity was increased in the IrAQP1-knockdown ticks. Importantly, the blood volume ingested per body weight was reduced by 30%. Overall, it would appear that water passage from the gut to the saliva was disrupted and tick guts were simply too “full” to ingest more blood. However, double-stranded RNA interference of IrAQP1 did not affect mortality of the ticks which successfully fed to detachment at day 9. Overall, our data indicate that IrAQP1 plays a pivotal role in blood meal water handling through the gut and salivary gland, and although its disruption by double-stranded RNA interference dramatically affects feeding performance, ticks remained feeding on the host with subsequent potential pathogen transmission and, therefore, IrAQP1 is not a suitable candidate target for tick control.

The influence of multiple environmental stressors on the limpet Cellana toreuma during the summer monsoon season in Hong Kong

Although environmental stressors affect natural systems in a multitude of ways, the interactive effect of multiple stressors on ecological assemblages remains largely misunderstudied. On tropical shores which experience seasonal monsoons, rocky intertidal habitats are physiologically stressful environments, being strongly affected by high temperatures and monsoon rains during emersion. In Hong Kong the limpet, Cellana toreuma, often takes refuge in mid-shore tidepools. In summer, these populations experience high mortality, probably as a result of stressful environmental conditions during low-spring tide days with high temperatures and/or intense rainfall periods can occur. Laboratory experiments were designed to mimic the effects of temperature stress (and increasing pool salinity) and reduced salinity as a result of monsoon rains on C. toreuma in tidepools . In general, haemolymph osmolality increased with salinity and limpet mortality increased with temperature. As salinity decreased after simulated rainfall, haemolymph osmolality (after 60 min) and survival (after 180 min) were significantly lower than in control treatments. Salinity fluctuations, coupled with high temperatures during emersion had both sub-lethal physiological effects and lethal effects on limpets in tidepools. Conducting experiments of multiple stressors simultaneously, however, revealed no interaction between hot temperatures and salinity variation, both of which operated independently for different response variables. Individually, therefore, hot temperatures and large salinity changes associated with the wet monsoon season are likely to play an important role in the population dynamics of intertidal species such as C. toreuma, and as a result will influence the structure and functioning of tropical rocky shores.

Hemolymph osmolality, ion concentrations and calcium in the structural organization of the cuticle of the giant freshwater prawn Macrobrachium rosenbergii: Changes with the molt cycle

In the giant freshwater prawn, Macrobrachium rosenbergii, hemolymph osmolality was low at post-molt stages A and B, and increased gradually until intermolt stage C 0, reaching a maximum at stage D 2. Levels were lowest at the ecdysis (E) stage. Na + and Cl - hemolymph concentrations showed a pattern similar to that of osmotic concentrations during the molt cycle. On the other hand, Ca 2+ hemolymph concentrations decreased significantly between stages A and C 0, and then increased significantly by nearly 60% up until stage E. Total calcium levels in the hepatopancreas were highest at stage C 0. In parallel with hemolymph ionic changes, the distribution of calcium in the cuticle was analyzed using scanning electron microscopy–electron dispersion spectrometry (SEM–EDS). At the post-molt stage, calcium content was low, and the cuticle consisted of one layer. At stage C 0, the cuticle was highly calcified, and calcium occurred until a distance of 135 μm from the surface at stage C 0. In addition, the cuticle consisted of the present layer and a newly-forming layer. Calcium content was lower at stage D 2, but calcium still existed in the exocuticle. At stage E (discarded cuticle), the cuticle consisted of the exocuticle layer only.

Seasonal variation in glucose and neutral amino acid uptake in the estuarine crab Neohelice granulata

This study investigates the mechanisms of glucose and amino acid transport in gills and jaw muscle of N. granulata collected from an estuarine natural population. The physicochemical parameters of the estuarine environment and of this crustacean′s hemolymph were measured during different seasons of the year. In summer, the lagoon water osmolality increased (5–6 times), and hemolymph osmolality decreased. In fall, water pH increased, whereas hemolymph pH decreased markedly. In all seasons, 2-deoxi glucose (DG) uptake in gills was significantly higher than 3-O methyl-glucose (MG) uptake. Phloretin reduced DG uptake in gills; phloretin and phlorizin did not affect MG uptake in this organ. DG and MG uptake was highest in gills during spring and summer. In jaw muscle, MG uptake in winter and spring was higher than DG uptake. In fall, gill methyl aminoisobutyric acid (MeAIB) uptake increased. In jaw muscle, MeAIB uptake was higher in spring. The observed changes in glucose uptake and in the type of glucose and amino acid transporter used in gills and muscle appear to be strategies used by N. granulata to minimize seasonal oscillations in the environmental parameters of their estuarine habitat.

Short-Term Responses of the Adults of the Common Japanese Intertidal Crab, Hemigrapsus Takanoi (Decapoda: Brachyura: Grapsoidea) at Different Salinities: Osmoregulation, Oxygen Consumption, and Ammonia Excretion

Abstract Intermolt to premolt males of Hemigrapsus takanoi were exposed to salinities of 0, 10, 20 (control), 30, and 40 ppt. After 2, 4, and 6 h of exposure, oxygen consumption and ammonia excretion were measured. Hemolymph osmolality was measured at the end of 8 h. No mortalities were observed until hemolymph sampling. Hemolymph osmolality was maintained between 570 to 840 mmol/kg. Oxygen consumption increased significantly only at 0 ppt, compared to the control (20 ppt). Ammonia excretion levels showed a remarkable increase at 0 ppt. These results indicate that this species expends increased metabolic effort to tolerate abrupt salinity changes to freshwater compared to brackish or seawater.

Acute Response of the Estuarine Crab Eurypanopeus Depressus to Salinity and Desiccation Stress

Abstract Hemolymph osmolality changes following exposure to abrupt salinity change in the range of 5–40 ppt (T = 26°C, full air saturation) and upon exposure to air (T = 23°C, r.h. = 30%) were investigated in the flatback mud crab Eurypanopeus depressus (Smith, 1869), a dominant species on oyster reefs in Southwest Florida. During salinity trials, hemolymph osmolality of E. depressus ranged from 751 ± 123 mOsmol kg−1 at 5 ppt (214 ± 32 mOsmol kg−1) to 1188 ± 81 mOsmol kg−1 at 40 ppt (1188 ± 29 mOsmol kg−1). In the salinity range of 5–15 ppt E. depressus exhibited a hyperosmotic pattern of osmoregulation while at 30 and 40 ppt it conformed. In all cases stable hemolymph osmotic concentration was reached in less than 24 h. During desiccation trials, hemolymph osmolality of E. depressus ranged from 971 ± 121 mOsmol kg−1 for unexposed crabs to 1132 ± 169 mOsmol kg−1 after 90 min of exposure. The information obtained from this study adds to knowledge of crustacean stress physiology and may give a clearer...

Why does the Namib Desert tenebrionid Onymacris unguicularis (Coleoptera: Tenebrionidae) fog-bask?

Dehydration of Onymacris unguicularis (Haag) for 10 days at 27°C resulted in a weight loss of 14.9%, and a 37% decrease in haemolymph volume. Although there was an overall decrease in the lipid content during this period, metabolic water production was insufficient to maintain total body water (TBW). Rehydration resulted in increases in body weight (6.2% of initial weight), TBW (to normality), and haemolymph volume (sub-normal at the end of rehydration). Despite an increase of 44.0 mg in the wet weight of O. unguicularis after drinking for 1h, there was little change in the water content at this time, although the total lipid content increased significantly. Increases in haemolymph osmolality, sodium, potassium, chloride, amino acid and total sugar concentrations during dehydration were subject to osmoregulatory control. No evidence of an active amino acid-soluble protein interchange was noted during dehydration or rehydration. Haemolymph trehalose levels were significantly increased at the end of rehydration (relative to immediate pre-rehydration values), indicating de novo sugar synthesis at this time. Osmotic and ionic regulation was evident during rehydration, but control of OP during haemolymph-dilution is poor and accomplished largely by the addition to the haemolymph of free amino acids and solute(s) not measured in this study. There was little mobilization of sodium and chloride ions from storage sites at this time. The lesser osmoregulatory ability of Onymacris unguicularis and perhaps earlier susceptibility to osmotic stress, a significantly high normal blood glycerol level (relative to other diurnal adesmiine tenebrionids), and a water storage mechanism associated with synthesis of fat, probably all contribute to the development of fog-basking behaviour in this species. Water gain in O. unguicularis during periods of relative drought is probably largely accomplished by a greater food consumption.

Cold Hardiness and Postfreeze Metabolism in Caterpillars ofHypercompe scribonia(Arctiidae: Lepidoptera)

Insects evolve levels of cold hardiness that are sufficient to meet the severity of thermal conditions in their hibernacula. This study examined freeze tolerance and related features in caterpillars of Hypercompe scribonia, which is the overwintering stage for this species, to compare with existing data for more northerly distributed species in Arctiidae that also overwinter as caterpillars. All specimens were collected from western Pennsylvania during mid-October 2004 and 2006 and eventually acclimated to 3°C for ≥4 wk. All caterpillars initially survived freezing at −3°C, which converted ≈45% of their body water into ice, and one third of them developed into moths. In contrast, freezing at −10°C was invariably lethal to caterpillars, even in the short term. Body composition (hemolymph osmolality, hemolymph glycerol, body mass, and water content) of caterpillars was stable between the 2 yr, with glycerol accounting for 3–5% of their solute. Thawed caterpillars showed an initial decline in routine aerobic metabolism that persisted through the first 6 h of the recovery period. H. scribonia caterpillars have a level of freeze tolerance that is adequate for hibernaculum conditions in western Pennsylvania; however, it is limited with respect to the tolerance levels of other arctiid caterpillars whose ranges extend northward well into colder regions of North America.

Cold Hardiness and Postfreeze Metabolism in Caterpillars of &lt;I&gt;Hypercompe scribonia&lt;/I&gt; (Arctiidae: Lepidoptera)

Insects evolve levels of cold hardiness that are sufficient to meet the severity of thermal conditions in their hibernacula. This study examined freeze tolerance and related features in caterpillars of Hypercompe scribonia, which is the overwintering stage for this species, to compare with existing data for more northerly distributed species in Arctiidae that also overwinter as caterpillars. All specimens were collected from western Pennsylvania during mid-October 2004 and 2006 and eventually acclimated to 3 degrees C for > or = 4 wk. All caterpillars initially survived freezing at -3 degrees C, which converted approximately 45% of their body water into ice, and one third of them developed into moths. In contrast, freezing at -10 degrees C was invariably lethal to caterpillars, even in the short term. Body composition (hemolymph osmolality, hemolymph glycerol, body mass, and water content) of caterpillars was stable between the 2 yr, with glycerol accounting for 3-5% of their solute. Thawed caterpillars showed an initial decline in routine aerobic metabolism that persisted through the first 6 h of the recovery period. H. scribonia caterpillars have a level of freeze tolerance that is adequate for hibernaculum conditions in western Pennsylvania; however, it is limited with respect to the tolerance levels of other arctiid caterpillars whose ranges extend northward well into colder regions of North America.

Larval anopheline mosquito recta exhibit a dramatic change in localization patterns of ion transport proteins in response to shifting salinity: a comparison between anopheline and culicine larvae

Mosquito larvae live in dynamic aqueous environments, which can fluctuate drastically in salinity due to environmental events such as rainfall and evaporation. Larval survival depends upon the ability to regulate hemolymph osmolarity by absorbing and excreting ions. A major organ involved in ion regulation is the rectum, the last region for modification of the primary urine before excretion. The ultrastructure and function of culicine larval recta have been studied extensively; however, very little published data exist on the recta of anopheline larvae. To gain insight into the structure and functions of this organ in anopheline species, we used immunohistochemistry to compare the localization of three proteins [carbonic anhydrase (CA9), Na+/K+ P-ATPase and H+ V-ATPase] in the recta of anopheline larvae reared in freshwater and saline water with the localization of the same proteins in culicine larvae reared under similar conditions. Based on the following key points, we concluded that anophelines differ from culicines in larval rectal structure and in regulation of protein expression: (1) despite the fact that obligate freshwater and saline-tolerant culicines have structurally distinct recta, all anophelines examined (regardless of saline-tolerance) have a structurally similar rectum consisting of distinct DAR (dorsal anterior rectal) cells and non-DAR cells; (2) anopheline larvae undergo a dramatic shift in rectal Na+/K+-ATPase localization when reared in freshwater vs saline water. This shift is not seen in any culicine larvae examined. Additionally, we use these immunohistochemical analyses to suggest possible functions for the DAR and non-DAR cells of anopheline larvae in freshwater and saline conditions.

Injection of biogenic amines modulates osmoregulation of Litopenaeus vannamei: Response of hemolymph osmotic pressure, ion concentration and osmolality effectors

In this paper, we compared systematically the temporal and dose response relationship and physiological significance among biogenic amines injection, changes of ion concentration, FAA concentrations and composition and protein in context of osmoregulatory ability in marine euryhaline shrimp: Litopenaeus vannamei. The dopamine (DA) and 5-hydroxytryptamine (5-HT) injection all had transient effects on hemolymph osmolality, ion concentrations but which occurred in different time and were dose-dependent. The highest concentrations of FAAs in hemolymph of L. vannamei were alanine, glycine, argnine, proline, lysine which were considered to be specific osmotic effectors. Contrary to the reduction of hemocyanin, injection of DA 10 − 6 mol shrimp − 1 and 5-HT 10 − 6 mol shrimp − 1 induced notable protein increase respectively, which led to the rapid reduction of hemocyanin/protein ratio in range of 63.2% to 78.3%. The increase of hemolymph FAAs might come from the new amino acid synthesis or degradation of muscle protein to FAAs or denovo synthesis of FAAs. Our study showed that dopamine plays an important role in neurotransmission and causes osmoregulation response modulation and 5-HT has different activation mechanism on osmoregulation.

Sexual dimorphism in desiccation responses of the sand scorpion Smeringurus mesaensis (Vaejovidae)

The osmoregulatory and respiratory responses of male and female Smeringurus mesaensis (Vaejovidae) to prolonged desiccation were measured. No significant effect of sex on mass-loss rates (MLRs) was found. Still, females maintained their haemolymph osmolality when desiccated to 10% mass loss, whereas that of males increased significantly after loss of as little as 5% of initial mass. Females had a 3-fold larger hepatopancreas, significantly higher hepatopancreas water content and higher metabolic rates when adjusted to hepatopancreas-free dry mass. Thus, females not only store more water in the hepatopancreas but also mobilise it to the haemolymph at a higher rate during desiccation, thus maintaining haemolymph osmolality.Gas exchange rates of both males and females decrease as desiccation progresses. An initial respiratory exchange ratio (RER) of ∼0.9 is followed by a significant increase at mass loss levels of 7.5% and higher. RER values greater than 1.0 may result from partial shift to anaerobic catabolism, which allows closure of the book lung spiracles for longer duration, thus minimising respiratory water loss.The effects of gas exchange rates on rates of water mobilisation between body compartments and water loss to the environment suggest a trade-off between maintaining osmotic stability and conserving body water stores under stressful conditions.