Physiological changes in the Norway lobster Nephrops norvegicus (L.) escaping and discarded from commercial trawls on the West Coast of Scotland: II. Disturbances in haemolymph respiratory gases, tissue metabolites and swimming performance after capture and during recovery

The physiological states of trawled and creel-caught (control) Norway Lobsters (Nephrops norvegicus (L.)) captured on grounds off the West Coast of Scotland (120–150 m) were compared. Undersized “discards” (<25–35 mm carapace length) were sampled directly from the cod-end and following recovery in underwater (u/w) cages at a mean depth of 24 m. “Escaped” animals which had passed through the cod-end meshes and collected in a small-meshed net “cover” were transferred without emersion (air-exposure) for sampling on-board. Some of these individuals were also transferred by SCUBA divers to u/w cages. Haemolymph PO₂, PCO₂ and pH measurements showed that both discarded and escaped animals experienced moderate internal hypoxia, hypercapnia and acidosis which became severe after 1 h emersion of the former on deck. A marked handling effect was evident in which haemolymph PO₂ declined and PCO₂ became elevated in both controls and recovering trawled animals. In both discarded and escaped animals haemolymph l-lactate and d-glucose concentrations were high compared to controls, but with levels significantly lower in escapes suggesting less tail-flip swimming activity within the cod-end cover. Further emersion had little effect on haemolymph l-lactate in discards. Recovery to control levels of both metabolites occurred within 24 h in u/w cages but the exercising of captured individuals (by tactile stimulation) produced further significant increases. Abdominal flexor muscle concentrations of l-lactate were also elevated in discards and escapes and positively correlated with haemolymph levels. Muscle glycogen showed severe depletion in both groups compared to unexercised controls and 1 h emersion reduced levels drastically (to 20% of normal concentrations). High haemolymph ammonia (T_amm) was characteristic of both trawled groups but was reduced rapidly during recovery. These metabolite changes were accompanied by reductions in the number of escape swimming tail-flips that could be elicited before exhaustion, particularly in discards. This reduction in performance was evident in discards even after 24 h recovery, but escapes showed almost normal responses. The severity of the physiological stresses experienced during trawling, and to a lesser extent in escaped animals, and their effects on recovery of undersized discards regaining the seabed, is discussed. These findings may help us predict the survival, longer-term recovery and fitness of fished N. norvegicus, and their potential contribution to the regeneration of exploited populations.     

Impact of capture method and trawl duration on the health status of the Norway lobster, Nephrops norvegicus

For economic and logistical reasons, an increased proportion of landings from trawl caught Nephrops norvegicus is being used in the live export trade. This paper reports a series of trials that investigate the impact of capture method and trawl duration on the levels of stress, damage and mortality of N. norvegicus. The stress of N. norvegicus captured during trials in spring and autumn by means of short trawl (1 h duration), long trawl (5 h duration) and creeling was assessed using a range of physiological measures (for haemolymph l-lactate, crustacean hyperglycaemic hormone (CHH) and abdominal muscle glycogen concentrations), the immunological status (total haemocyte counts (THC)) and physical assessments (mortality, damage indices). N. norvegicus caught by creeling were generally less stressed (i.e. significantly lower haemolymph l-lactate and CHH concentrations) than their trawled counterparts. Increased duration of trawl did not significantly alter physiological parameters, while time of landing did have a significant effect on l-lactate concentrations, as individuals landed in the morning exhibited higher concentrations. Irrespective of the season in which trawling occurred, individuals captured by short trawls in the morning suffered lowest mortalities. Damage assessment data revealed that a greater proportion of individuals was categorised as heavily damaged following longer trawls conducted in spring.     

Changes in haemolymph constituents of American bollworm, Helicoverpa armigera (Hübner), infected with nucleopolyhedrovirus

Six types of haemocytes viz., prohaemocytes, plasmatocytes (round, fusiform, vermiform and spindle shaped), granular cells, spherule cells, oenocytoids and adipohaemocytes were found in the haemolymph of larvae of American bollworm H. armigera. The total and differential haemocyte counts (THC and DHC) in H. armigera haemolymph were affected by nucleopolyhedrovirus (NPV) treatment. There was a general decrease in THC in response to NPV treatment in both young and old larvae. However the decrease was more apparent in 5 and 8 day old larvae than in 10 day old larvae. The differential haemocytes showed less of granular cells and more of spherule cells and prohaemocytes in the old larvae. Plasmatocytes and granular cells in 10 day old larvae initially phagocytosed polyhedra; however, disintegrated after 3 to 4 hr. The haemolymph of NPV treated larvae melanized slowly particularly in old larvae. Phenoloxidase (PO) activity decreased positively with granular cells and oenocytoids in 10 day old treated larvae. Cellular fraction had high level of PO activity, which was transferred to plasma in response to NPV infection in the older larvae. The role of NPV pathogenesis vis-à-vis immunity in insect is discussed.     

Effects of rutin from Toona sinensis on the immune and physiological responses of white shrimp (Litopenaeus vannamei) under Vibrio alginolyticus challenge

Rutin is a bioflavonoid with strong antioxidant activity. To investigate the regulatory roles of rutin in various functions in crustaceans, we examined physiological (haemolymph glucose, lactate, and lipid) and innate non-specific immune responses (total haemocyte count (THC), phenoloxidase activity (PO), respiratory bursts (release of superoxide anion, O(2)(-)) and superoxide dismutase (SOD) activity) to the pathogen Vibrio alginolyticus in white shrimp (Litopenaeus vannamei) that were individually injected with rutin extracted from Toona sinensis at 10, 20, or 50 microg g(-1). Results showed that PO activity and respiratory burst of L. vannamei increased obviously (P<0.05) when injected with rutin at a dose of 20 and 50 microg g(-1) after 12 and 24 h, respectively. Both the THC and SOD activities of experimental and control groups revealed no significant difference at all doses. L. vannamei injected with rutin at either dose maintained lower glucose, lactate, and lipid levels in response to V. alginolyticus challenge after 12-36, 24-48, and 24-60 h, respectively. The survival rate of L. vannamei that received rutin at either dose was significantly higher than that received saline after 48-72 h. It was, therefore, concluded that the immune ability and resistance against V. alginolyticus infection of L. vannamei receiving rutin at > or = 10 microg g(-1) increased.     

Physiological changes in the Norway lobster Nephrops norvegicus (L.) escaping and discarded from commercial trawls on the West Coast of Scotland: 1. Body fluid volumes and haemolymph composition after capture and during recovery

The Norway Lobster Nephrops norvegicus (L.) was captured by trawling at depths of 120 to 150 m off the West Coast of Scotland using commercial fishing gears. Discarded animals (normally <25–35 mm carapace length) were sampled immediately after capture, and following emersion (exposure to air) on deck for 1 or 2 h. Their recovery from, and survival of, the stresses of being fished were examined in separate groups of animals transferred by SCUBA divers to underwater (u/w) cages on the seabed at a mean depth of 24 m. “Escaped” N. norvegicus were collected in a small-meshed (40 mm) “cover” around the cod-end and sampled without emersion. It was assumed that the physiological state of these animals would be similar to those passing through the cod-end meshes directly back into the surrounding sea during normal fishing operations. Groups of escaped animals were also transferred to u/w cages for recovery and survival studies. Control animals (creel-caught from the same fishing grounds) were sampled after recovery in u/w cages. Total body water content, haemolymph (blood) volume and composition were examined at various stages after capture and during recovery of control, discarded and escaped animals. Discarded animals showed significant reductions in total body water content compared to controls but recovered after 24 h. Controls that had been artificially damaged by puncturing also showed a reduction in water content. Escaped animals showed significantly higher mean water content compared to discards. Haemolymph volumes were also reduced in discarded animals suggesting that significant blood loss occurs during capture. There was also evidence of a shift of fluid from haemolymph to tissues in discarded animals. Pericardial (haemolymph) pressures were much reduced in discards compared to undisturbed control animals but showed significant recovery in surviving animals. Pressure reduction was less in escapes but was seen in control animals that had been exercised to exhaustion. Haemolymph osmotic concentrations, [Na⁺] and [K⁺] showed increases after discarding, notably after emersion, but haemocyanin [Hcy] and total haemolymph protein concentrations were less affected. The effect of these changes on longer term survival and recovery from the stress of capture are discussed.     

The effect of different acclimation temperatures on the prophenoloxidase system and other defence parameters in Litopenaeus vannamei

Water temperature changes (higher and lower than 24 degrees C) were shown to have a significant effect on dopamine (DA) concentration, haemocyte count and the proPO system in the white shrimp Litopenaeus vannamei. No significant difference in any of the parameters was observed in the control group. DA concentration in haemolymph in the experimental groups increased to a peak value at 0.5 days; meanwhile serine protease (SP) activity and proteinase inhibitor (PI) activity decreased. Total haemocyte count (THC), differential haemocyte count (DHC) and PO activity were lowest at 1 day. All defence parameters became stable after 1-3 days, while the total haemocyte and large granular cell count stabilized after 6 days. After these stabilized, there was no significant difference in DA concentration and PI activity between the control and experimental groups, as was the case for the THC, DHC, PO and SP activities of shrimp held at higher temperatures. However these latter four parameters in the lower temperature groups were distinctly lower than the control group. alpha(2)-Macroglobulin activity in the experimental groups increased to a peak value after 1 day compared with the control and then stabilized after 6 days when the activity levels in higher temperature groups were higher than the control, while the lower temperature groups had no significant difference from the control. It was therefore concluded that water temperature changes modulated the immune system of L. vannamei.     

Physiological stress in decapod crustaceans (Munida rugosa and Liocarcinus depurator) discarded in the Clyde Nephrops fishery

Crustacean discards experience stress during commercial fishing operations, due to increased exercise while in the trawl and aerial exposure during sorting of the catch. Physiological stress and recovery were assessed following trawling of two ecologically important decapod species, regularly discarded in the Clyde Nephrops fishery. Haemolymph samples taken from trawled swimming crabs, Liocarcinus depurator, and squat lobsters, Munida rugosa, had significantly higher concentrations of ammonia (0.308 and 0.519 mmol l(-1)), D-glucose (0.14 and 0.097 mmol l(-1)) and L-lactate (6.2 and 0.87 mmol l(-1)) compared with controls, indicating an impairment of ammonia excretion and a switch to anaerobic metabolism. Concurrently, the haemolymph pH of trawled squat lobsters was low (7.47) compared with controls (7.75); however, the reverse trend was found in L. depurator. Initially elevated lactate (7.98 mmol l(-1)) and glucose (0.73 mmol l(-1)) concentrations of trawled and emersed (1 h) L. depurator were restored, 4 h after re-immersion along with pH (7.54). Crabs that had been emersed for 1 h had significantly higher concentrations of glucose (0.2 mmol l(-1)) and lactate (5.14 mmol l(-1)), and had more acidic blood (7.64) than L. depurator subject to 1 h of exercise, indicating that anoxia was the main cause of physiological stress. Crabs and squat lobsters lost 7% and 9% of their initial body wet weight following 1 h of emersion, although blood osmolarities did not change significantly. While all animals survived aerial exposure in our experiments, sorting of the catch on commercial boats takes up to 300 min, which could lead to mortality or sub-lethal chronic biochemical changes that could compromise fitness.     

Development and application of an immunoassay diagnostic technique for studying Hematodinium infections in Nephrops norvegicus populations.

Patent Hematodinium infections of the Norway lobster Nephrops norvegicus can be detected with a morphological method (pleopod diagnosis), but this fails to identify low-level haemolymph (sub-patent) and any tissue-based (latent) infections. The current study describes the development and application of an immunoassay for the detection of antigens of the parasite Hematodinium in the Norway lobster N. norvegicus. Infected tissue and haemolymph samples were detected as multiple-band reactions to a polyclonal antibody (anti-Hematodinium). The sensitivity limit of the method was 204 parasites mm(-3), approximately 10 times more sensitive than the pleopod diagnosis method. Use of the immunoassay on tissue samples taken from catches in the Clyde Sea area, Scotland, UK, showed that the pleopod method considerably under-diagnosed infection prevalence in the early part of the season, though this under-diagnosis decreased as infected lobsters in the field progressed from latent and sub-patent to patent infections. However, the immunoassay failed to detect any infected lobsters during the summer months, suggesting that infection may not be carried over from one season to the next. The data presented suggest that this immunoassay allows for the accurate estimation of Hematodinium infection prevalence in the field and should be employed, where possible, for the routine monitoring of infection prevalence in N. norvegicus.     

Examining the relationship between hemolymph phenoloxidase and resistance to a DNA virus, Plodia interpunctella granulosis virus (PiGV)

We have a detailed understanding of invertebrate immune responses to bacteria and fungal pathogens, but we know less about how insects respond to virus challenge. Phenoloxidase (PO) functions as an important immune response against many parasites and pathogens and is routinely used as a measure of immune competance. We examine the role of haemolymph PO activity in Plodia interpuncetella's response to its natural granulosis virus (PiGV). Larvae were challenged with virus by both oral inoculation of occluded virus (the natural infection route) and direct intrahaemocoelic injection of budded virus. Haemolymph was collected at time points post-viral challenge using a novel method that allows the volume of haemolymph to be quanitified. The haemolmyph was collected without killing the larvae so that haemolymph samples from individuals that developed viral disease could be distinguished from samples collected from those that fought off infection. The level of haemolymph PO activity in resistant larvae did not differ from control larvae. Therefore we have no evidence that PO is involved in resistance to virus in the haemocoel whether larvae are challenged naturally by oral innoculation or directly by intraheamocoelic injection. Phenoloxidase may therefore not be a relevant metric of immunocompetence for viral infection.     

Onset of and recovery from physiological stress in <Emphasis Type="Italic">Liocarcinus depurator</Emphasis> after trawling and air exposure under different seasonal conditions

The onset of and recovery from physiological stress in Liocarcinus depurator (Decapoda: Portunidae), that were trawled and subjected to emersion during fishing activities, was analysed in a field study in the Northern Adriatic Sea. Our working hypothesis intended to assess the development of physiological impairment due to air exposure during sorting operations, and the possible recovery trajectories after the return to sea of this by-caught species. The protocol we used included experimental trawling and quantification of physiological stress indicators (haemolymph concentrations of l-lactate, d-glucose, ammonia and pH) under different seasonal conditions. Immediately after being caught, when the fishing net was emptied on board, L. depurator showed higher physiological imbalance in the summer vs. winter experiments, highlighting the immediate effect of temperature shock due to the difference in temperature between the sea bottom and the deck (15–18 and 2°C in summer and winter, respectively). Experimental animals in the permanently emersed condition exhibited a progressive disruption of homeostasis in both seasons, as confirmed by a significant increase in lactate and a decrease in the pH of the haemolymph as a function of the emersion time. Ammonia levels were almost stable in the summer, when the physiological limits of this metabolite were reached immediately after animals were caught. In the winter, a significant increase in ammonia was observed over the time. This pattern can be attributed to the impairment of gill function, resulting in suffocation (manifested by marked haemolymph acidosis) and reduced ammonia excretion. Glucose concentration was revealed to be stable during air exposure in both seasons, though a higher concentration was recorded in the summer compared to the winter. The recovered individuals tended to return to pre-caught values for all of the haemolymph parameters we measured, though with different trajectories in the two seasons. From these results, we conclude that temperature shock, coupled with air exposure, influenced the ultimate stress level of this species to a greater extent than other effects of fishing.     

Effect of environmental parameters on immune response of the Indian spiny lobster, Panulirus homarus (Linnaeus, 1758)

The high export value of the Indian spiny lobster Panulirus homarus increasingly attracts the aquaculturists for farming and fattening. However, lack of knowledge on the effect of environmental parameters on the immune system of this animal could result in high mortality, which ultimately may cause major loss to the industry. Here, we report the effect of salinity (20, 25, 35, 40, and 45 per thousand), pH (5.0, 8.0, and 9.5), dissolved oxygen (DO) (1 and 5 mg L(-1)), and ammonia-N concentration (0, 0.5, 1.5 and 3 mg L(-1)) on the immune response of P. homarus measured in the haemolymph in terms of Total Haemocyte Count (THC), phenoloxidase (PO) activity, and NBT-reduction. Our data showed significant reduction (P<0.05) in THC, and NBT-reduction at lower (20 per thousand) and higher (45 per thousand) salinities. However, PO activity showed significant disparity, showing an increasing trend from 20 to 45 per thousand. Significant reduction (P<0.05) in THC and PO activity under acidic and alkaline conditions, under hypoxic condition (1 mg L(-1)), and at the higher ammonia-N concentrations than their respective optimal conditions were observed. Thus, suggesting that extreme environmental parameters can induce modifications in the immune system of the spiny lobster P. homarus, which may enhance their susceptibility to opportunistic pathogens. The humoral parameters such as THC, PO activity, and NBT-reduction can be used as potential stress indicators for healthy management of spiny lobsters.     

Detection of the parasitic dinoflagellate Hematodinium in the Norway lobster Nephrops norvegicus by ELISA

Norway lobsters Nephrops norvegicus from the coastal waters of Scotland are seasonally infected by a parasitic dinoflagellate of the genus Hematodinium. An enzyme-linked immunosorbent assay (ELISA) has been developed for the detection of the parasite in the haemolymph of N. norvegicus. The ELISA is simple to perform with a detection limit of 5 x 10(4) parasites ml(-1) haemolymph. The ELISA is currently being used to study the prevalence and seasonality of Hematodinium infection in N. norvegicus and other crustacean hosts.     

Phenoloxidase activity in three commercial bivalve species. Changes due to natural infestation with Perkinsus atlanticus

The phenoloxidase (PO) activity of the haemolymph and haemocytes from three clam species of commercial interest (Ruditapes philippinarum, Chamelea gallina and Tapes decussatus) has been compared. The activity was assayed spectrophotometrically by recording the formation of dopachrome from L-DOPA using sodium dodecyl sulphate, laminarin, trypsin or lipopolysaccharide as elicitors. Fewer PO units were observed in the haemolymph from T. decussatus than in the haemolymph from R. philippinarum, while the highest values were found in C. gallina. In all cases the activity was only significantly increased when sodium dodecyl sulphate was used as elicitor. PO activity in the haemocytes of all three clam species showed a very similar pattern to that found in the haemolymph from the same species. Furthermore, T. decussatus naturally parasitized by Perkinsus atlanticus (Protozoa, Apicomplexa) was used to study the influence of such infestation on PO activity, which was found to increase significantly in both haemolymph and haemocytes compared with non-infected (control) samples. PO activity in the haemocytes and in the haemolymph was higher when the level of parasitization was low or medium, respectively, and SDS was used as elicitor. No statistically significant differences were observed when the parasitization level was high. The present work constitutes the first report on the influence of this parasite on PO activity in haemolymph and haemocytes from T. decussatus.     

Investment in immune function under chronic and acute immune challenge in an insect

In this paper we investigate the relationship between the chronic burden of mid‐gut parasites (eugregarine trophozooites) and the effect of an acute haemolymph challenge (a nylon insert) on two important insect immune effector systems (phenol oxidase (PO) and the encapsulation response) in a field‐population of damselflies. PO levels in the haemolymph, and the magnitude of the encapsulation response were maintained, regardless of chronic and subsequent acute experimental immune challenges. The maintenance of these effector systems is therefore probably an important life‐history requirement in these damselflies. Investment in mid‐gut PO levels was significantly negatively related to the animal's chronic parasite burden after an acute experimental challenge in the haemolymph, suggesting that maintaining PO levels across two physiological compartments (haemolymph and mid‐gut) is costly. The results suggest that the immune effector system activity in different physiological compartments in an insect's body is affected by chronic parasite burdens in the face of the demands imposed by an acute immune insult.     

Delta-9-tetrahydrocannabinol attenuates luteinizing hormone release induced by electrochemical stimulation of the medial preoptic area.

Despite diverse pharmacological actions, drugs commonly used for blocking ovulation in the rat have not been observed to exert differential effects on the LH response to preoptic stimulation, thus suggesting blocking action above the final hypothalamic GnRH pathway. To determine if ovulatory blockade by delta-9-tetrahydrocannabinol (THC) is consistent with that scheme, LH surges evoked by preoptic stimulation were contrasted with those elicited during blockade by atropine (ATR), a classic ovulation-blocking agent with which other drugs have been compared. THC (10 mg/kg) or ATR (350 mg/kg) treatment before the proestrous critical period uniformly blocked LH release and ovulation in sham-stimulated rats. Preoptic stimulation evoked LH surges after both drug treatments (p less than 0.001), peak levels increasing with the intensity of stimulation (p less than 0.05). However, both maximum LH concentration (p less than 0.05) and total integrated LH release (p less than 0.01) were lower in THC-blocked rats. Inspection of the oviducts revealed no difference in the incidence of ovulation or the number of ova discharged. The reduced LH response during THC blockade was not attributable to variation in the extent or locus of histologically determined stimulation sites. These results distinguish THC from ATR and, by extension, other blocking drugs that do not overtly affect the LH response to preoptic stimulation. Thus, ovulatory blockade by THC may involve a different mechanism, which likely includes inhibitory action within the preoptic-to-tuberal GnRH pathway.     

The role of haemocytes from the crab Carcinus aestuarii (Crustacea,Decapoda) in immune responses: A first survey

For the first time, a functional study of haemocytes from the crab Carcinus aestuarii was performed in order to evaluate their involvement in immune responses. Total haemocyte count (THC), phagocytosis, haemolymph opsonisation properties, hydrolytic and oxidative enzyme activities, and production of intracellular superoxide anion were evaluated. A great variability in THC was recorded among individuals, and haemocyte mean number was 6.4 (×10⁶) cells/ml haemolymph. Although only hyalinocytes were able to phagocytose yeast cells or Zymosan, phagocytic index was low (3%) and did not increase significantly (4%) after pre-incubation of yeast and Zymosan in cell-free haemolymph, suggesting that haemolymph did not have opsonising properties. All haemocyte types produced superoxide anion, whereas only granulocytes were positive to the hydrolytic enzymes assayed. In addition, only granulocytes were positive to phenoloxidase activity. Both Petri dish and spectrophotometric assays revealed a very low lysozyme-like activity in cell-free haemolymph (CFH) and haemocyte lysate (HL), although enzyme activity was higher in CFH than in HL. Interestingly, normalisation of data as to total protein content in CFH and HL resulted in an opposite situation, lysozyme-like activity being higher in HL than in CFH. This demonstrated that haemolymph of C. aestuarii has a high quantity of total proteins, functional properties of which need to be better investigated in future studies. Overall, the results obtained in the present study indicated that C. aestuarii haemocytes are not very active phagocytic cells, but they are more active in terms of both hydrolytic and oxidative enzyme activities and superoxide anion production.     

Dietary beta-1,3-glucan effectively improves immunity and survival of Penaeus monodon challenged with white spot syndrome virus

The effectiveness of dietary beta-1,3-glucan (BG), derived from Schizophyllum commune, in modulating the non-specific immunity of the grass prawn Penaeus monodon and its resistance to white spot syndrome virus (WSSV) were investigated. Juvenile P. monodon (6.5+/-0.4 g) were fed for 20 days on a series of test diets containing graded levels of BG (0, 1, 2, 10, 20 g kg(-1)diet) and were then challenged by injection of WSSV. The haemolymph total haemocyte count (THC), phagocytosis (PI), phenoloxidase (PO), superoxide anion (O(2)(-)) and superoxide dismutase (SOD) production were measured at days 0, 1, 3, 6, 9, 12 and 24 after challenge, and shrimp survival rate was also recorded. All the shrimps fed on diets containing BG no more than 1 g kg(-1)died by day 12. Conversely, the survival rate of shrimp fed with the diet containing 10 g kg(-1)BG was significantly higher (P<0.05) by day 9 than that of the other groups. When screened by the WSSV PCR diagnostic procedure, the percentages of surviving juveniles of the BG 2, 10, 20 g kg(-1)groups that were 2-step WSSV negative, were 55, 65 and 65%, respectively. The haemolymph THC, PO, O(2)(-)and SOD production of the 2, 10 and 20 g kg(-1)BG diet groups dropped drastically immediately after the WSSV challenge but subsequently returned to normal. Therefore, oral administration of BG at an optimal level of 10 g kg(-1)diet for 20 days effectively enhanced the immune system and improved the survival of WSSV-infected P. monodon.     

Immune responses of Litopenaeus vannamei to thermal stress: a comparative study of shrimp in freshwater and seawater conditions

The effects of hypothermal (22–16?°C) and hyperthermal (22–28?°C) stress on the immune system responses of the shrimp Litopenaeus vannamei cultured in either freshwater or seawater were measured and compared. The following immune system indicators were measured for comparison: total hemocyte count (THC), activity of phenoloxidase (PO), nitric oxide synthase (NOS), superoxidase (SOD), and malondialdehyde (MDA) content. Thermal stress significantly decreased THC in both freshwater and seawater shrimp within 6–12?h (P?0.05). After hypothermal stress, all shrimp had a significantly lower THC level than their prechallenge levels (P?0.05). Under both types of thermal stress, the activity of PO, NOS, and SOD first increased and then decreased. After 48?h of thermal stress, shrimp PO and NOS activity decreased in both freshwater and seawater. After 48?h of thermal stress, the reduction in the SOD activity in the hemolymph of freshwater shrimp was greater than that in seawater shrimp. During exposure to stress, the MDA content in freshwater shrimp was significantly higher than in seawater shrimp, which demonstrated that lipids in freshwater shrimp were more susceptible to peroxidation than those in seawater shrimp, particularly at low temperatures. Large temperature fluctuations, particularly sudden cooling, should be avoided when rearing L. vannamei because of high rates of lipid peroxidation and decreased immunity. These effects are more marked in freshwater than in seawater.     

Haemolymph parameters of Pacific white shrimp (Litopenaeus vannamei) infected with Taura syndrome virus

Pacific white shrimp (Litopenaeus vannamei) were injected with Taura syndrome virus (TSV) to assess shrimp immune responses and survival. TSV-infected shrimp suffered high mortality, but mock-infected and untreated shrimp experienced no mortality. Moribund shrimp were a pale, reddish colour and were lethargic and soft-shelled. Their haemolymph was clear red and coagulated poorly. In TSV-infected shrimp, the total haemocyte count (THC), hyalinocyte and granulocyte counts, and total plasma protein decreased significantly to 21%, 24%, 17% and 56% of untreated control values, respectively. Haemocyanin decreased to 67%, and clottable proteins to 80% of control values (P< 0.01). Copper and calcium ions, haemocytic transglutaminase (TGase) activity and plasma growth inhibitory activity against Vibrio harveyi also decreased significantly. Generation of intrahaemocytic superoxide anion, O(-2), in TSV-infected shrimp was significantly greater (P< 0.05) than in both control groups, no matter whether glucan stimulated or unstimulated. But the relative increase of intrahaemocytic O(-2) generation in TSV-infected shrimp response to glucan stimulation was lower in both controls. Plasma phenoloxidase (PO) activity increased significantly in TSV-infected shrimp. The plasma bacterial agglutinin titre against E. coli and V. harveyi, growth inhibition of E. coli and the concentration of magnesium ions in TSV-infected shrimp did not change significantly.In conclusion, ten of thirteen haemolymph parameters changed significantly during the host-TSV interaction. These parameters might be valuable references of shrimp health status.