Swimming ability and physiological response to swimming fatigue in whiteleg shrimp, Litopenaeus vannamei

New insights into the immune regulation and tissue repair of Litopenaeus vannamei during temperature fluctuation using TMT-based proteomics

To investigate shrimp immunoregulation and tissue self-repair mechanism during temperature fluctuation stage, Litopenaeus vannamei (L. vannamei) was treated under conditions of gradual cooling from an acclimation temperature (28 °C, C group) to 13 °C (T group) in 2 days with a cooling rate of 7.5 °C/d and then rewarmed to 28 °C (R group) with the same rate. Tandem mass tags (TMT) -based proteomics technology was used to investigate the protein abundance changes of intestine in L. vannamei during temperature fluctuation. The results showed that a total of 5796 proteins with function annotation were identified. Of which, the abundances of 1978 proteins (34%) decreased after cooling and then increased after rewarming, 1498 proteins (26%) increased during the whole stage, 1263 proteins (22%) increased after cooling and then decreased after rewarming and 1057 proteins (18%) decreased during the whole stage. Differentially expressed proteins such as C-lectin, NFκBIA and Caspase may contributed to the regulation of immunity and tissue repair of shrimp intestine during the temperature fluctuation stage. These findings contribute to the better understanding of shrimp' regulatory mechanism against adverse environment.

Physiological Responses of Pacific White Shrimp Litopenaeus vannamei to Temperature Fluctuation in Low-Salinity Water

Temperature is a significant environmental factor in aquaculture. To investigate the physiological responses during temperature fluctuation (28~13°C), experimental shrimps (Litopenaeus vannamei) were treated with gradual cooling from acclimation temperature (AT, 28°C) to 13°C with a cooling rate of 7.5°C/day and rose back to 28°C at the same rate after 13°C for 24 h. Hepatopancreas histological changes, plasma metabolites concentrations, relative mRNA expression of unfolded protein response (UPR) pathway and apoptosis in hepatopancreas and hemocyte were investigated. The results showed that with the decline of temperature, the number and volume of the secretory cells in hepatopancreas increased significantly, the tubule lumen appeared dilatated, and the epithelial cell layer became thinner. The contents of glucose (Glu) significantly decreased to the minimum value of 13°C for 24 h. The contents of triglyceride (TG), total cholesterol (TC), and total protein (TP) increased and reached the peak of 13°C for 24 h. Alkaline phosphatase (ALP) and alanine aminotransferase (ALT) activities in plasma reached the lowest and highest value in 13°C, respectively. The expressions of all genes related to UPR and apoptosis in the hepatopancreas and hemocytes were significantly changed during the cooling process and reached the highest level of 13 and 13°C for 24 h, respectively. During re-warming stage, the histopathological symptoms got remission and each of the plasma metabolite concentrations and gene expressions returned to AT levels. These results revealed that pacific white shrimp can adapt to a certain level of temperature fluctuation by self-regulation.

Investigating the physiological responses of Pacific white shrimp Litopenaeus vannamei to acute cold-stress

Background

Litopenaeus vannamei is one of the most important aquaculture shrimps in the world and low temperatures present a serious challenge to its survival, growth, and distribution.

Methods

To investigate their physiological responses during acute cold-stress, L. vannamei were treated under acute cooling conditions from 28 to 13 °C with a cooling rate of 2.5 °C/2 h and were maintained at 13 °C for 12 h. Plasma metabolite concentrations, histological changes, and relative gene expression related to the unfolded protein response (UPR) pathway and apoptosis in the hepatopancreas and the hemocytes of L. vannamei were investigated.

Results

The results revealed that the concentrations of triglycerides, total cholesterol, and total protein in plasma reached their peaks at 23 °C, and then decreased to their minimum values at 13 °C for 12 h. The activity of alkaline phosphatase in the plasma decreased to its lowest level while the activity of alanine aminotransferase increased to its highest level at 13 °C for 12 h. The hepatic tubules became necrotic and the basement membranes were ruptured at 13 °C for 12 h. The gene expression related to UPR and apoptosis in the hepatopancreas and hemocytes was significantly altered by the decrease in the temperature.

Discussion

The results revealed that acute cold-stress caused histological damage in the hepatopancreas of L. vannamei, reducing its immunity. The three UPR pathways were involved in the process of acute cold-stress and the response of activating transcription factor 6 to UPR may be faster and more directthan the IRE1 and PERK pathways.

Visual Stimuli for the Induction of Hunting Behavior in Cuttlefish Sepia pharaonis

Cuttlefish exhibit typical hunting behavior, including elongating tentacles against specific prey such as prawn and mysid shrimp. Cuttlefish hunting behavior involves three different actions: attention, positioning, and seizure. Hunting behavior is innate and stereotypic behavior, and it is present in newly hatched juveniles. Factors associated with prey are known to induce this behavior, similar to the sign stimulus, whereby young herring chicks imitate pecking behavior against a red dot on their parent's bill. Although the hunting behavior of cuttlefish has been described and used as an indicator to test learning and memory, details of a stimulus that can elicit this behavior remain unknown. Here, we used a variety of visual stimuli presented on a computer screen to investigate the factors that induce hunting behavior of pharaoh cuttlefish, Sepia pharaonis. We found that the appearance of prey (western king prawn, Melicertus latisulcatus) and their movement at a vertical angle of 45° are specific factors that can initiate hunting behavior. We also showed that the height of prey can attract cuttlefish and initiate hunting. To the best of our knowledge, this is the first report of a stimulus that elicits stereotyped hunting behavior by coleoid cephalopods.

Predicting the effects of copper on local population decline of 2 marine organisms, cobia fish and whiteleg shrimp, based on avoidance response

The present study focuses on avoidance response to predict population decline of the marine fish Rachycentron canadum (cobia) and larvae of the estuarine shrimp Litopenaeus vannamei (whiteleg shrimp). Avoidance of approximately 60% was recorded for the cobia fry exposed to 1.0 mg Cu/L, 1.60 mg Cu/L, and 1.80 mg Cu/L. For the shrimp larvae, avoidance was approximately 80% for all Cu concentrations. The population decline of cobia fry was conditioned by avoidance in lower concentrations. However, in higher concentrations mortality begins to play an important role. The displacement toward uncontaminated habitats might determine shrimp population decline. A Cu-contaminated environment can determine the habitat selection of both species and, therefore, their local population decline.

Swimming velocity, avoidance behavior and biomarkers in Palaemon serratus exposed to fenitrothion

The aim of this study was to develop two behavioral tests (swimming velocity and avoidance behavior) specific for the common prawn, Palaemon serratus, and to investigate the effects of sublethal concentrations of fenitrothion on behavior and on several biomarkers. In a first bioassay, mortality was investigated in prawns exposed during 96 h to concentrations of fenitrothion ranging from 39 to 40000 ng L(-1). The effects on swimming velocity and biomarkers were determined in prawns exposed to the sub-lethal concentrations of fenitrothion (from 39 to 625 ng L(-1)). A specific newly bioassay was developed to assess the capability of prawns to avoid the toxicant (avoidance test). Finally, in order to determine the effects on biomarkers during the avoidance test, prawns were collected at different times of exposure (30, 60, 90 and 120 min). Results showed that prawns exposed to the sub-lethal concentrations of fenitrothion exhibited a significant inhibition of swimming velocity with a LOEC of 313 ng L(-1). A significant inhibition of both eye AChE (LOEC=78 ng L(-1)) and muscle ChE (LOEC=156 ng L(-1)) activities were also observed. Results from the avoidance test indicated that animals significantly avoided fenitrothion (78 ng L(-1)). However, this capability was not observed in prawns exposed to 156 ng L(-1) fenitrothion. Prawns exposed to fenitrothion showed alterations in enzymes involved in the production of energy (LDH and IDH) possibly in an attempt to cope with additional energetic demands. Impairment of locomotion and avoidance may lead to alterations at the population level. Thus, the present behavioral tests can be useful as ecologically relevant tools for ecological risk assessment.

Acute effects of deltamethrin on swimming velocity and biomarkers of the common prawn Palaemon serratus

The main purpose of the present study was to investigate the effects of deltamethrin on biomarkers and behavior of Palaemon serratus (common prawn), since this attempt to link different levels of biological organization will allow determining which biomarkers might be ecologically relevant and will be useful to complement the information about the effects of pesticides by using behavioral parameters. Therefore, parameters of liver antioxidant status, energy metabolism and neurotransmission were determined in different tissues of the common prawn and used to assess the effects at sub-individual level, whereas swimming velocity was used to assess the effects at the individual level. It was also investigated if the swimming velocity can be used as an endpoint in ecotoxicology bioassays and if it can be as sensitive as biomarker endpoints. Swimming velocity was significantly reduced in prawns exposed to deltamethrin, showing a lowest observed effect (LOEC) of 0.6 ng L(-1). Eye acetylcholinesterase (AChE) activity was significantly increased in prawns exposed to 0.6, 1.2 and 2.4 ng L(-1) deltamethrin, whereas muscle cholinesterase (ChE) activity was significantly increased in prawns exposed to 19 and 39 ng L(-1). On the other hand, lactate dehydrogenase (LDH) activity was significantly increased in muscle of prawns exposed to 0.6, 1.2, 2.4, 4.9 ng L(-1) deltamethrin, showing that organisms were requiring additional energy, but probably using it for detoxification processes rather than locomotion, since swimming velocity was inhibited. Glutathione S-transferase (GST) activity was significantly increased in the digestive gland of common prawn exposed to 19 and 39 ng L(-1) deltamethrin. Catalase (CAT) activity was significantly increased in digestive gland of prawn exposed to 19 ng L(-1) deltamethrin. However, CAT activity decreased in digestive gland of prawn exposed to 39 ng L(-1), suggesting an antioxidant defense system failure concomitant with high levels of lipid peroxidation. Thus, global results showed that decreased swimming velocity was not associated with cholinesterase inhibition. In fact, the impairment of swimming velocity may be due to allocation of energy for detoxification and antioxidant protection instead of swimming activity. The present study showed that swimming velocity could be used as an ecologically relevant tool and a sensitive endpoint to assess and complement the study of pesticide effects on marine organisms.

Effects of temperature, salinity, body length, and starvation on the critical swimming speed of whiteleg shrimp, Litopenaeus vannamei

The critical swimming speed (U(crit), cms⁻¹) of whiteleg shrimp, Litopenaeus vannamei, exposed to various temperatures (17, 20, 25, and 29 °C), salinities (20, 25, 30, 35, and 40), and starvation days (1, 4, and 8d), was determined in a flume tank. Body length (5.5, 6.6, 7.3, 9.4, and 10.0 cm) was also studied in relation to the U(crit). Temperature, salinity, body length and starvation significantly affected the U(crit) of whiteleg shrimp. The U(crit) increased as temperature increased from 17 to 29 °C. The relationship between temperature (t, °C) and U(crit) can be described by the linear model as U(crit)=1.5916t+0.8892, R²=0.9992 (P<0.01). The U(crit) increased and then decreased as salinity increased from 20 to 40. The optimum salinity and the corresponding maximum U(crit) are 36.17 and 42.87 cms⁻¹, respectively. The relationship between salinity (s) and U(crit) can be described by the quadratic model as U(crit)=-0.0171s²+1.2371s+20.497, R²=0.7667 (P=0.234). The U(crit) increased as body length increased from 5.5 to 10.0 cm, whereas relative critical swimming speed (U(crit)', BLs⁻¹) decreased. The relationship between body length (l, cm) and U(crit) or U(crit)' can be described by the quadratic model as U(crit)=-0.6233l²+12.302l-20.264, R²=0.9942 (P<0.01) or U(crit)'=-0.0514l²+0.5351l+3.8132, R²=0.9862 (P<0.05). The U(crit) decreased as starvation days increased from 1 to 8d. The relationship between starvation day (d, d) and U(crit) can be described by the quadratic model as U(crit)=-0.1262d²-0.0395d +40.979, R²=1. Low temperatures and salinity and starvation can reduce the swimming speed of whiteleg shrimp. Results can be of value in evaluating the locomotive ability, understanding ecological processes, and improving the capture and stock enhancement of whiteleg shrimp.

The effects of temperature and salinity on the swimming ability of whiteleg shrimp, Litopenaeus vannamei

Swimming endurance of whiteleg shrimp, Litopenaeus vannamei exposed to various temperatures (15, 20, and 25 degrees C) and salinities (15, 32, and 40 per thousand) was determined in a swimming channel against one of five flow velocities (5.41, 6.78, 8.21, 10.11, and 11.47 cm s(-1)) for up to 9000 s. No shrimp swam the full 9000 s throughout the experiment. The swimming endurance decreased as swimming speed was increased at any of the temperatures and salinities tested and was significantly affected by temperature and salinity (P<0.05). The power model (nu x t(b) = a) showed a better fit to the relationship between swimming endurance (t, in s) and swimming speed (nu, in cm s(-1)) at any of the temperatures and salinities tested. The swimming ability index (SAI), defined as SAI = integral(0)(9000) vdt x 10(-4) (cm), was found to be temperature- and salinity-dependent in L. vannamei. The optimum temperature and salinity and corresponding maximum SAI were Topt = 21.3 degrees C and SAI(max21.3) = 7.37 cm; Sopt = 27.6 per thousand and SAI(max27.6) = 7.47 cm, respectively. The range of temperatures and salinities within which SAI is >90% of the maximum was estimated between 17.6 and 24.9 degrees C and between 18.5 and 36.7 per thousand, respectively. The results suggest that the power model fits well to the observed endurance estimates and the SAI is a good index to quantitatively describe the overall swimming ability of L. vannamei. Furthermore, temperature and salinity can limit the swimming performance of L. vannamei.