Penaeus Semisulcatus Research Articles

Management strategies for short lived species: The case of Australia's Northern Prawn Fishery: 3. Factors affecting management and estimation performance

Management strategies for tiger prawns, Penaeus semisulcatus and P. esculentus, in Australia's Northern Prawn Fishery (NPF), are evaluated in terms of conservation- and economic-related performance measures. A two-stage process is used to determine the factors to which these performance measures are most sensitive. The first stage involves identifying the possible factors and their interactions, constructing a partial factorial design to allow the impact of first- and second-order interactions on the performance measures to be identified, and analysing the resultant performance measures using generalised linear models. The second stage entails an experiment based on a balanced design of the possible combinations of the key factors. The factors found to have the greatest impact on the performance measures are: (a) how fishing efficiency has changed over time and whether or not the assessment is based on the correct trend in fishing efficiency, (b) the catchability coefficient used to convert from fishing effort to fishing mortality, (c) the difference between the intended fishing effort and the actual fishing effort expended (implementation error), and (d) whether recruitment is spatially correlated among stocks or not.

Management strategies for short lived species: The case of Australia's Northern Prawn Fishery: 2. Choosing appropriate management strategies using input controls

A Management Strategy Evaluation framework is used to evaluate management strategies based on input controls for the fishery for two tiger prawn species ( Penaeus esculentus and Penaeus semisulcatus) in Australia's Northern Prawn Fishery. Three “assessment procedures” are considered and two forms of decision rule. The performance of the management strategies is evaluated in terms of whether stocks are left at (or above) the spawning stock size at which Maximum Sustainable Yield is achieved ( S MSY), the long-term discounted total catch and the extent of inter-annual variation in catches. The focus of the analysis is on management strategies based on the current method of stock assessment because an alternative method of assessment based on a biomass dynamics model is found to be highly variable. None of the management strategies tested is able to leave the spawning stock size of P. esculentus near S MSY if the target effort level used in the management strategy is set to E MSY. Accounting for stock structure through the application of a spatially- (stock-) structured assessment approach fails to resolve this problem. Since the assessment method is generally close to unbiased, the failure to leave the stocks close to S MSY is because the measure of control is total effort and the two species are found (and caught) together. Reducing the target effort level to below E MSY increases the final stock size, but the reduced risk comes at a cost of reduced catches. The best management strategy in terms of leaving both species close to S MSY is found to be one that changes the timing of the fishing season so that effort is shifted from P. esculentus to P. semisulcatus and sets more precautionary effort targets for P. esculentus.

Cloning and characterisation of a prophenoloxidase from the haemocytes of mud crab Scylla serrata

A prophenoloxidase (proPO) cDNA was cloned from the haemocytes of mud crab Scylla serrata using oligonucleotide primers and RT-PCR. Both 3′- and 5′-regions were isolated by rapid amplification of cDNA end (RACE) method. Analysis of the nucleotide sequence revealed that the cDNA clone has a full length of 2663 bp, with an open reading frame of 2019 bp, a 124-bp 5′-untranslated region, and a 520-bp 3′-untranslated region containing a poly A signal. It encodes a protein of 673 amino acids with a predicted molecular weight of 77.5 kDa and with an estimated p I of 5.96. It contains two putative tyrosinase copper-binding motifs with six histidine residues (copper A, 185, 189, 211, and copper B, 346, 350, 386). The proPO has thiol-ester-like motif (GCGWPQHM), which showed similar structural features of proPOs from other decapod crustaceans. It also contains five possible glycosylation sites, and a conserved C-terminal region common to all known proPOs. Sequence comparison showed that the proPO-deduced amino acid of mud crab S. serrata has an overall similarity of 78%, 57%, 56%, 51–55%, 54%, 53%, 52%, 52%, and 52% to that of Dungeness crab Cancer magister, American lobster Homarus americanus, European lobster Homarus gammarus, kuruma prawn Marsupenaeus japonicus, crayfish Pacifastacus leniusculus, white shrimp Litopenaeus vannamei, tiger shrimp Penaeus monodon, green tiger shrimp Penaeus semisulcatus, and giant freshwater prawn Macrobrachium rosenbergii, respectively. The proPO was strongly expressed in haemocytes, but not in heart, eyestalk, gill, muscle, ovary, hepatopancreas, stomach, and intestine. The proPO transcript of mud crab S. serrata increased significantly in 12 and 24 h post-lipopolysaccharide (LPS) injection, but returned to the original values in 72 h post injection.

Acute Toxicity of Ammonia to Penaeus semisulcatus Postlarvae in Relation to Salinity

Stocking densities of cultured penaeid shrimp have been intensified because of the limited availability of land for pond construction. In an intensive culture system, ammonia is the most common toxicant resulting from nitrogen excretion by cultured animals and mineralization of unconsumed feed and feces (Lin and Chen 2003). In decapod crustaceans, nitrogen is excreted mainly as ammonia (60–70% of total ammonia) (Lee and Chen 2003). Concentrations of total ammonia-nitrogen (TAN) increase directly with culture period and might reach as high as 46 mg TAN/L in intensive grow-out ponds (Chen and Lin 1992). Accumulation of ammonia-nitrogen in pond water may deteriorate water quality, reduce growth, increase oxygen consumption, alter concentrations of hemolymph protein and free amino acid levels, and even cause high mortality (Chen and Lin 1992; Chen et al. 1994). TAN is composed of NH3-N (unionized ammonia) andNH4+ (ionized ammonia) (Losordo et al. 1992; Masser et al. 1992). It is the unionized form that is most toxic to aquatic organisms as it can readily diffuse through cell membranes and is highly soluble in lipids (Chin and Chen 1987; Frias-Espericueta et al. 1999). There is an equilibrium between NH4+ and NH3-N in the water. This equilibrium is affected by pH, temperature, and salinity. The higher the pH and temperature, the higher the proportion of NH3-N, while an increase in salinity will lead to lower proportions of the unionized form, hence the toxicity of the TAN to aquatic animals (Losordo et al. 1992;Masser et al. 1992; Sampaio et al. 2002). A number of studies have been conducted on the lethal effects of ammonia at various life stages of penaeid shrimps, such as Penaeus chinensis (Chen and Lin 1992), P. monodon (Chen and Lei 1990), P. paulensis (Ostrensky and Wasielesky 1995), P. penicillatus (Chen and Lin 1991), P. semisulcatus (Wajsbrot et al. 1990), and Metapenaeus ensis (Nan and Chen 1991). However, little information is available on the lethal effect of ammonia at different salinity levels for penaeid shrimps. Chen and Lin (1992) and Lin and Chen (2003) studied ammonia toxicity in P. chinensis and Litopenaeus vannamei at three different salinity levels, but no results have been reported for other penaeid species. Green tiger shrimp (P. semisulcatus) is an Indo-Pacific species, distributed along the coast of the Eastern Mediterranean, and is one of the most important commercial species in this part of the world. This species is less tolerant to low salinity levels (Soyel and Kumlu 2003), and knowledge of the effects of ammonia toxicity at various salinity regimes that may be confronted during the culture and overwintering periods in the subtropical areas is of importance for the farmers. This paper provides information on acute toxicity of ammonia to juveniles of this shrimp species at six different salinity levels (15, 20, 25, 30, 35, and 40 ppt).

Influences of sex and seasons on levels of heavy metals in tissues of green tiger shrimp ( Penaeus semisulcatus de Hann, 1844)

Seasonal changes in heavy metal (Ag, Cr, Ni, Pb, Cu, Fe, Zn) concentrations in muscle, gill, hepatopancreas and gonad tissues of both male and female green tiger shrimp ( Penaeus semisulcatus) from Iskenderun Bay (Northern East Mediterranean Sea, Turkey) were measured for a year period by using ICP-AES. The relationships in various heavy metal concentrations in organs were compared according to sex and seasons. Heavy metal content varied with type of metals, seasons and sex. Accumulations also differed significantly in certain organs. Metal concentrations (as μg g −1 w.w.) were highest in male gonads whereas lowest in the muscle of all shrimp species. From the human consumption point of view, heavy metal concentrations except for copper in male and female green tiger shrimp’s muscle were below the admissible limits. Thus, precautions should be taken on account of higher content of heavy metals as well as in other organs that could be affected by industrial pollution.

Early Developmental Stages of the Green Tiger Prawn, Penaeus semisulcatus de Haan (Crustacea, Decapoda, Penaeidae)

Gravid females of Penaeus semisulcatus were spawned in the laboratory by natural means. The embryos were documented and the larvae were reared from hatching to postlarval stage at 28.2–30.0 °C and 33.5–34.5 g kg−1 salinity for about 10 days (223 h 55 min). Six naupliar stages, three protozoea stages, three mysis stages and the first postlarval stage were described and illustrated. The larvae were fed only with microalgae Tetraselmis tetrathele and Chaetoceros gracilis from first protozoea until the second mysis, with about 90% survival rate; from the third mysis until the first postlarva they were fed with similar microalgae coupled with rotifer Brachionus plicatilis and Artemia nauplii. The embryonic and larval stages of P. semisulcatus are generally similar to those of other closely related species in the family Penaeidae, such as Melicertus canaliculatus, Fenneropenaeus merguiensis, and Marsupenaeus japonicus, except for the size and structure of diagnostic characters, setation of appendages and duration of metamorphoses. The change in the feeding habit during ontogeny was related to morphological transformation of the feeding apparatus of larvae and postlarvae. This paper is the first comprehensive and complete account of the early developmental stages of P. semisulcatus.

Molecular characterization of a cDNA encoding vitellogenin in the banana shrimp, Penaeus (Litopenaeus) merguiensis and sites of vitellogenin mRNA expression

In order to determine the primary structure of banana shrimp, Penaeus merguiensis, vitellogenin (Vg), we previously purified vitellin (Vt) from the ovaries of vitellogenic females, and chemically analyzed the N-terminal amino acid sequence of its 78 kDa subunit. In this study, a cDNA from this species encoding Vg was cloned based on the N-terminal amino acid sequence of the major 78 kDa subunit of Vt and conserved sequences of Vg/Vt from other crustacean species. The complete nucleotide sequence of Vg cDNA was achieved by RT-PCR and 5' and 3' rapid amplification of cDNA ends (RACE) approaches. The full-length Vg cDNA consisted of 7,961 nucleotides. The open reading frame of this cDNA encoding a precursor peptide was comprised of 2,586 amino acid residues, with a putative processing site, R-X-K/R-R, recognized by subtilisin-like endoproteases. The deduced amino acid sequence was obtained from the Vg cDNA and its amino acid composition showed a high similarity to that of purified Vt. The deduced primary structure, of P. merguiensis Vg was 91.4% identical to the Vg of Penaeus semisulcatus and was also related to the Vg sequences of six other crustacean species with identities that ranged from 86.9% to 36.6%. In addition, the amino acid sequences corresponding to the signal peptide, N-terminal region and C-terminal region of P. merguiensis Vg were almost identical to the same sequences of the seven other reported crustacean species. Results from RT-PCR analysis showed that Vg mRNA expression was present in both the ovary and hepatopancreas of vitellogenic females but was not detected in other tissues including muscle, heart, and intestine of females or in the hepatopancreas of mature males. These results indicate that the Vg gene may be expressed only by mature P. merguiensis females and that both the ovary and hepatopancreas are possible sites for Vg synthesis in this species of shrimp.

Molecular cloning and characterisation of prophenoloxidase cDNA from haemocytes of the giant freshwater prawn, Macrobrachium rosenbergii, and its transcription in relation with the moult stage

Expression of prophenoloxidase (proPO) cDNA was determined from haemocytes of the giant freshwater prawn Macrobrachium rosenbergii by a reverse-transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA using oligonucleotide primers based on the proPO sequence of tiger shrimp Penaeus monodon, freshwater crayfish Pacifastacus leniusculus, green tiger shrimp Penaeus semisulcatus, kuruma shrimp Marsupenaeus japonicus, and white shrimp Litopenaeus vannamei. The proPO of M. rosenbergii was constitutively expressed. The 2547-bp cDNA contained an open reading frame (ORF) of 2013 bp, a 96-bp 5′-untranslated region, and a 438-bp 3′-untranslated region containing the poly A tail. The molecular mass of the deduced amino acid (aa) sequence (671 aa) was 76.7 kDa with an estimated p I of 7.05. It contained putative copper-binding sites, a complement-like motif (GCGWPRHM), a proteolytic activation site, and a conserved C-terminal region common to all known proPOs. However, no signal peptide sequence was detected in giant freshwater prawn proPO. Comparison of amino acid sequences showed that prawn proPO is similar to the proPO of penaeid, crayfish and lobster. Prawn proPO was only synthesised in haemocytes. The proPO transcript was significantly increased in the A stage and achieved the highest level in the B stage, and then declined sharply in the C stage and reached the lowest level in the D 2/D 3 stage.

The culture of green tiger shrimp, Penaeus semisulcatus in the Northeastern Mediterranean Area of Turkey.

The culture of green tiger shrimp, Penaeus semisulcatus in the Northeastern Mediterranean Area of Turkey.

Note. Seasonal Variations of Fatty Acid Composition in Wild Marine Shrimps (Penaeus semisulcatus De Haan, 1844 and Metapenaeus monoceros Fabricus, 1789) from the Eastern Mediterranean Sea

Seasonal fatty acid profiles of Penaeus semisulcatus and Metapenaeus monoceros were investigated. Palmitic (16:0), stearic acid (18:0), oleic (18:1), palmitooleic acid (16:1), arachidonic acid (20:4), eicosapentaenoic (EPA, 20:5 n-3) and docosahexaenoic acid (DHA, 22:6 n-3) were found to be the most abundant fatty acids in both shrimp species. Fatty acid profile showed seasonal changes. The highest EPA DHA contents were recorded during winter (January) in both species.

Molecular cloning and characterisation of prophenoloxidase from haemocytes of the white shrimp, Litopenaeus vannamei

cDNA encoding prophenoloxidase (proPO) of the white shrimp Litopenaeus vannamei was obtained from haemocytes by a reverse-transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA using oligonucleotide primers based on the proPO sequence of tiger shrimp Penaeus monodon, freshwater crayfish Pacifastacus leniusculus, green tiger shrimp Penaeus semisulcatus (accession no.: AF521949) and kuruma shrimp Marsupenaeus japonicus (accession no.: AB0733223). proPO of L. vannamei was constitutively expressed. The 2471-bp cDNA contained an open reading frame (ORF) of 2058 bp, a 96-bp 5′-untranslated region, and a 317-bp 3′-untranslated region containing the poly A tail. The molecular mass of the deduced amino acid sequence (686 amino acids) was 78.1 kDa with an estimated pI of 6.02. It contained putative copper binding sites, a complement-like motif (GCGWPQHM), a proteolytic activation site, and a conserved C-terminal region common to all known proPOs. However, no signal peptide sequence was detected in white shrimp proPO. Comparison of amino acid sequences showed that white shrimp proPO is more closely related to the proPO of another penaeid than to that of a freshwater crayfish. White shrimp proPO mRNA was synthesized in haemocytes and not in the hepatopancreas or muscle. The activation responses of the proPO of the white shrimp to an exogenous protease (trypsin), a detergent (sodium dodecyl sulphate), and algal and microbial cell wall components (laminarin, sodium alginate, zymosan, and lipopolysaccharide), and its susceptibility to protease inhibitors in vitro resemble the proPO activation system of other crustaceans. These facts suggest that the proPO system in haemocytes of the white shrimp Litopenaeus vannamei serves an important function in non-self recognition and host immune reactions.

Food consumption, moulting and survival of Penaeus semisulcatus during over-wintering

Over-wintering of Penaeus semisulcatus (20.61 g) at three different temperatures (14, 18 and 22°C) was carried out in a greenhouse in three different closed recirculating systems. Temperature significantly influenced specific growth rate (SGR) and moulting interval (MI) (P<0.05). The SGR was 15-fold higher and the MI was 2.7-fold shorter at 22°C in comparison with 14°C. The relationship between SGR and temperature (T) was: Y=−0.053+0.070T (R2=0.97). Shrimps over-wintered at 14°C consumed almost three times less food (0.43% body weight) than those at 22°C (1.28%) (P<0.05). A positive relationship (FR=0.426T–0.020, R2=0.99) was observed between feeding rate (FR) and temperature. The survival rate achieved at 14, 18 and 22°C over the experimental period of 70 days was 87%, 67% and 73% respectively. Our data indicate that it is possible to over-winter this shrimp species in the sub-tropical regions by maintaining water temperature at around 14°C and 39 ppt salinity, in which little energy expenditure is needed, and the shrimp can survive and consume minimum amount of feed.

Distribution of heavy metals in Penaeus Semisulcatus from Persian Gulf and possible role of metallothionein in their redistribution during storage

The study was conducted between January and December 2002. The main objective of this study was evaluation of effects of refrigerated storage duration on redistribution of three trace elements (Cd, Cu and Zn) in tissues (exoskeleton, abdominal muscle and hepatopancreas) of a shrimp species (Penaeus semisulcatus). Moreover, the possible roles of metallothionein (a kind of metalloprotein) in redistribution of the elements in tissues of the selected species were assessed. The specimens were sampled from northwestern part of the Persian Gulf. The concentrations of metals in the tissues were measured using Inductively Coupled Plasma-Optical Emission Spectrophotometer (ICP-OES). Metallothionein levels were determined by Differential Pulse Polarography (DPP) method. pH of the muscle samples was also measured in different stages. Different statistical methods were used for interpretation of the results. There were no size-dependent differences in metal contents of the species. The results were compared with specimens from other areas of the world and existing guidelines and limits. Concentrations of the metals in the muscle (0.103, 3.418 and 8.977 microg g(-1) wet weight in the case of Cd, Cu and Zn, respectively) samples were below the most guidelines for human consumption. The results were in general agreement with those obtained by some other researchers. There were highly significant differences between sexes in Zn and Cu contents. Levels of Zn in females were significantly higher than males. The reverse case observed for Cu. The highest mean Cu and Zn concentrations (15.939 and 43.394 microg g(-1) wet weight, respectively) were found in hepatopancreas samples, but the highest level of Cd (0.790 microg g(-1) wet weight) was observed in exoskeleton. There were significant differences between the fresh and refrigerated samples from accumulation of Cd and Zn in tissues point of view, which can be attributed to the metal binding properties of metallothioneins as well as their degradation during the storage.

An Assessment and Management of Green Tiger Shrimp (Penaeus semisulcatus) Fishery in the Jazan Area (Red Sea, Saudi Arabia)

The maximum sustainable yield (MSY) and the correspond- ing values of fishing effort (number of fishing days) were estimated for the green tiger shrimp, Penaeus semisulcatus fishery in the Jazan area of the Red Sea. The equilibrium as well as the non-equilibrium approach was used to fit the surplus-production model on the statisti- cal data of catch and fishing effort. The study area extends from Lat 17o40' N southwards to the Yemeni border which supports the activity of more than 90% of the bottom trawlers exploiting the shrimp fishery in the Saudi Red Sea coast . Results from both treatments indicated that the current fishery for the tiger shrimp is under the level of maximum sustainable exploitation. The maximum sustainable yield (MSY) was estimated at 945.3 and 829.8 tonnes by the equilibrium and non-equilibrium model, respective- ly. The corresponding levels of fishing effort required to generate the maximum sustainable yield (MSY) were estimated by the two models, respectively at 21.620 and 17.370 fishing days per fishing season.

Detection of hepatopancreatic parvovirus (HPV) in wild shrimp from India by nested polymerase chain reaction (PCR)

The prevalence of hepatopancreatic parvovirus (HPV) in wild penaeid shrimp samples from India was studied by nested polymerase chain reaction (PCR) using primers designed in our laboratory. The virus could be detected in 9 out of 119 samples by non-nested PCR. However, by nested PCR 69 out of 119 samples were positive. The PCR results were confirmed by hybridization with digoxigenin-labelled DNA probe. Shrimp species positive by non-nested PCR included Penaeus monodon, Penaeus indicus and Penaeus semisulcatus and by nested PCR Parapenaeopsis stylifera, Penaeus japonicus, Metapenaeus monoceros, M. affinis, M. elegans, M. dobsoni, M. ensis and Solenocera choprai. This is the first report on the prevalence of HPV in captured wild shrimp from India.

Seasonal amino acid profiles and mineral contents of green tiger shrimp ( Penaeus semisulcatus De Haan, 1844) and speckled shrimp ( Metapenaeus monoceros Fabricus, 1789) from the Eastern Mediterranean

The amino acid and mineral contents of green tiger shrimp ( Penaeus semisulcatus) and speckled shrimp ( Metapenaeus monoceros) from the North Eastern Mediterranean were determined for each season of the year. For both species, the highest protein values were recorded during the summer ( p < 0.05). The most abundant amino acids were, in decreasing order, glutamic acid, aspartic acid, arginine, lysine, leucine, glycine and alanine. The ratio of essential to nonessential amino acids (mean value) for green tiger shrimp and speckled shrimp were 0.60 and 0.59, respectively. Mineral contents of the two species varied with season ( p < 0.05), except for the Ca content in green tiger shrimp.

Isolation and cDNA Cloning of Ovarian Cortical Rod Protein in Kuruma Prawn Marsupenaeus japonicus (Crustacea: Decapoda: Penaeidae)

Two cortical rod proteins having molecular weights of 28.6 kDa and 30.5 kDa were isolated from the mature ovary of Marsupenaeus japonicus using gel filtration and reversed-phase HPLC. Analysis of the N-terminal amino acid sequence of the 28.6 kDa molecule revealed that amino acid residues 1-21 corresponded to residues 9-29 of the 30.5 kDa molecule. Examination of homology using BLAST showed that 21 amino acids out of 29 residues of the 28.6 kDa molecule, and 14 out of 29 residues of the 30.5 kDa molecule were identical to that of the ovarian cortical rod proteins of Penaeus semisulcatus. Positive immunohistochemical reaction to antiserum raised against the 28.6 kDa protein was observed on cortical rods forming around the periphery of oocytes at the maturation stages. Western blotting analysis revealed that both the 28.6 kDa and 30.5 kDa molecules stained with the anti-28.6 kDa antiserum. Furthermore, the 28.6 kDa and 30.5 kDa proteins were both glycosylated, as evidenced by positive carbohydrate staining using Concanavalin A and production of positive PAS reaction. These results indicate that the cortical rods are comprised of the 28.6 kDa and 30.5 kDa molecules. We subsequently cloned two full-length cDNAs based on the N-terminal sequences of the 28.6 kDa and 30.5 kDa molecules. The open reading frame of 28.6 kDa and 30.5 kDa encoded 276 amino acid residues. Comparison analysis of the two cDNAs revealed that the location of the processing site and sequence of signal peptides differed, indicating that the two cDNAs are products of two separate genes and encode the 28.6 kDa molecule and 30.5 kDa molecule, respectively. Both proteins possessed one potential N-linked glycosylation site. It is considered that both molecules are components of the cortical rods, forming a jelly layer after fertilization.

A generalised linear model for catch allocation: an example from Australia's Northern Prawn Fishery

Abstract Two biologically distinct species, Penaeus semisulcatus and P. esculentus, are caught in the tiger prawn component of Australia's Northern Prawn Fishery. These species are recorded and marketed together as ‘tiger prawns’. A generalised linear model is used to separate the logbook catches of ‘tiger prawns’ into catches by individual species, even though only fragmentary historical survey data are available. We also consider generalised additive model and generalised linear mixed model approaches, and the extra benefits they might allow.

Distribution of trace elements in tissues of two shrimp species from the Persian Gulf and roles of metallothionein in their redistribution

This study investigates the distribution of three trace elements (Cd, Cu and Zn) in tissues (exoskeleton, abdominal muscle and hepatopancreas) of two shrimp species ( Penaeus merguiensis and Penaeus semisulcatus). Special emphasis in this study was placed on evaluating the effects of storage conditions on redistribution of the elements and moreover the potential roles of metallothionein in tissue redistribution. The specimens were collected from the northern part of Persian Gulf during September 2001 and January 2002. The concentrations of metals in the tissues were measured using an Inductively Coupled Plasma-Atomic Emission Spectrophotometer (ICP-AES) and an ICP-Mass Spectrometer (ICP-MS). Metallothionein levels were determined using Differential pulse polarography. Results show a similar hierarchy for Cd and Cu concentrations among different tissues as follows: hepatopancreas>exoskeleton>muscle; and for Zn, the hepatopancreas again contained the highest levels, though there were not any significant differences in Zn concentrations between muscle and exoskeleton. Significant differences were found between the species in the case of Cd and Zn concentrations. Cd and Zn levels in P. semisulcatus were markedly higher than in P. merguiensis. In general, there were highly significant differences among the storage conditions from accumulation the selected trace elements and metallothionein in both species point of view, but in most cases, no significant differences could be observed among the fresh, refrigerated and frozen specimens of P. semisulcatus. In regards to Zn and Cu accumulation in edible (muscle) tissues of P. merguiensis, optimum conditions for frozen storage is −30 °C as ice-frozen, and in terms of short-term storage, 1-day refrigeration is recommended. The redistribution of Zn and Cu during the storage period can be attributed to the role of metallothionein in their transport from organ(s) to muscle during storage. The variations in pH values measured in the muscle of P. merguiensis in different storage conditions showed a similar trend with metallothionein, Zn and Cu. In contrast, it appears that cadmium is transported from muscle to the other tissues. Exoskeleton is probably one of the recipient tissues of cadmium. The inter-elemental relationships were assessed for each species, separately. A significant positive relationship was observed between the concentrations of Zn and metallothionein in P. semisulcatus, whereas in P. merguiensis, Cd concentrations decreased significantly with increasing metallothionein. Highly significant differences between the sexes in Cu and Zn contents could be detected. The differences between the sexes in the levels of Zn and Cu were significantly greater in P. semisulcatus. Highly significant size-related differences were found in the levels of Cd, Cu and metallothionein in the selected tissues of the shrimp species. Comparison between the mean concentrations of the elements in muscle tissue and existing guidelines indicate that in nearly all cases, the concentrations were well below permissible levels for human consumption. The only exception was observed regarding mean values of Cd, which was somewhat greater than some of the recommended levels.

Influence of neuropeptide Y (NPY) on food intake and growth of penaeid shrimps Marsupenaeus japonicus and Penaeus semisulcatus (Decapoda: Penaeidae)

The effects of neuropeptide Y (NPY) administered intramuscularly or orally on postlarvae (PLs) of two penaeid species were investigated in this study. In experiment 1, food intake (FI) of Marsupenaeus japonicus PLs (0.96 g), injected with NPY at 0.6 μg per g BW, was investigated within 48 h posttreatment. In experiment 2, oral administration of NPY (at doses of 0, 0.125, 0.25, 0.5 μg g −1 food) on feed intake and growth performance of Penaeus semisulcatus PLs (0.27 g) was examined for 6 weeks. In experiment 1, NPY injection significantly increased average daily FI of M. japonicus PLs within the first 24 h compared to the control ( P<0.05), but its stimulatory effect decreased on the second day ( P>0.05). The increase in FI was 33% during the first 24 h and 17% during the next 24 h. In experiment 2, significant ( P<0.05) differences were found among the groups in terms of weight gain and food utilization ( P<0.05). Mean FI significantly increased (as much as 1.3-fold over the control) when NPY was orally administered at doses from 0.125 to 0.5 μg g −1 feed. There was a positive relationship between FI and final weight ( y=−0.972+2.098 x, R 2=0.81) and between FCE and NPY doses in the diets ( y=45.37+3.46 x, R 2=0.91). The present findings indicated for the first time that NPY is a potent stimulator of food intake when administered either intramuscularly or orally to penaeid shrimps.