Enhancement of <Emphasis Type="Italic">Penaeus monodon</Emphasis> shrimp postlarvae growth and survival without water exchange using marine <Emphasis Type="Italic">Bacillus pumilus</Emphasis> and periphytic microalgae

We have investigated the possibility of using a consortium of marine bacterium and periphytic microalgae to improve the water quality and increase the growth and survival of the shrimp Penaeus monodon in a hatchery system. Three treatments were evaluated for their effect on P. monodon postlarvae (PL) when the culture water was not changed: Bacillus pumilus alone (B); periphytic microalgae alone (M); B. pumilus + periphytic microalgae (BM). P. monodon PL raised in a tank of unchanged water without bacterium and periphytic microalgae served as the control. The water in tanks of the M and BM treatments had significantly low levels of total ammonia-nitrogen (TAN) (0.03 and 0.01 mg l⁻¹, respectively) and nitrite-nitrogen (NO₂-N) (0.03, 0.01 mg l⁻¹, respectively) than that in the B (TAN 0.80, NO₂-N 0.68 mg l⁻¹) and control (TAN 1.11, NO₂-N 1.12 mg l⁻¹) tanks. Moreover, PL cultured in tanks M and BM had significantly higher survival and specific growth rates and a significantly higher resistance to the reverse salinity stress test than those in the B and control tanks. Compared to the control PL, the PL cultured in the BM tanks had significantly higher levels of protein, lipid, polyunsaturated fatty acids, ecosapentaenoic acid, and docosahexaenoic acid. The culture water in tanks BM also contained significantly less Vibrio than the control water. Our results illustrate the beneficial effects of a B. pumilus and periphytic microalgae consortium on improving the water quality and the growth and survival of shrimp PL grown in a hatchery system.     

Use of a <Emphasis Type="Italic">Noctiluca</Emphasis>-killing bacterium <Emphasis Type="Italic">Marinobacter salsuginis</Emphasis> strain BS2 to reduce shrimp mortality caused by <Emphasis Type="Italic">Noctiluca scintillans</Emphasis>

The ability of an algicidal bacterium Marinobacter salsuginis strain BS2, isolated from shrimp pond water, to reduce shrimp mortality was investigated under laboratory conditions. When two species of shrimp (Penaeus monodon and Litopenaeus vannamei) (body length 1.5–1.8 cm) were cultured together with the dinoflagellate Noctiluca scintillans, nearly 80 % of the shrimps died within 7 days. However, when bacterial strain BS2 was also added to the culture, N. scintillans was killed within 48 h, and shrimp survival rates on the 7th day improved from 23 to 87 % for both P. monodon and L. vannamei. The bacterium BS2 alone had no effect on shrimp condition. Under conditions of increased dissolved oxygen, the effect of using BS2 was greater, and shrimp survival rates improved even more dramatically, from 26 to 98 %. These studies provide the first evidence that the use of killing bacteria, isolated from shrimp culture water, can suppress harmful algal blooms (HABs) and thus restore the efficiency of shrimp production. The control of HABs in this way in shrimp culture farms would be a major benefit for shrimp production.     

Growth and survival of grouper <Emphasis Type="Italic">Epinephelus</Emphasis><Emphasis Type="Italic">coioides</Emphasis> (Hamilton) larvae fed free-living nematode <Emphasis Type="Italic">Panagrellus redivivus</Emphasis> at first feeding

The free-living nematode, Panagrellus redivivus, was tested as live food for grouper Epinephelus coioides larvae during the first feeding stage. A series of experiments were conducted to determine the acceptability of the free-living nematodes in grouper larvae at first feeding, the optimum nematode density and the response of the larvae to nutritionally enriched nematode. All experiments were conducted in 200-L conical tanks filled with 150-L filtered seawater and stocked at 15 larvae L⁻¹. Duration of feeding experiments was up to day 21 (experiment 1) and 14 days (experiment 2 and 3). Brachionus plicatilis and Artemia (experiment 1) and Brachionus plicatilis alone (experiment 2 & 3) was used as the control treatment. Observations indicated that the grouper larvae readily fed on free-living nematodes as early as 3 days posthatching, the start of exogenous feeding. Optimum feeding density for the larvae was 75 nematodes ml⁻¹. The enrichment of cod liver oil or sunflower oil influenced the total lipids and n-3 highly unsaturated fatty acids of P. redivivus, which in turn influenced those of the grouper larvae, however, growth and survival of the larvae were not affected (P > 0.05). The results from this investigation showed that the nematode, P. redivivus, can be used as first live food for grouper larvae from the onset of exogenous feeding until they could feed on Artemia nauplii.     

Optimisation of larval culture of the mussel <Emphasis Type="Italic">Mytilus</Emphasis><Emphasis Type="Italic">edulis</Emphasis> (L.)

The blue mussel Mytilus edulis is a commercially important species whose fishery and culture generally relies on natural spat collection. Hatchery-production could provide an alternative source of seed, enabling reliable expansion of the industry. Mussel spawning and larval rearing trials were carried out to optimise elements of hatchery production. Culturing fertilised eggs at low density (20–200 eggs cm⁻²) rather than high density (400–720 eggs cm⁻²) significantly improved the quality of first veliger larvae and differences in this improvement were evident between the eggs from different females (maternal effects). Veliger larval growth at 17 or 21°C was significantly faster than growth at 14°C. Feeding veliger larvae an identical total ration either daily or at 2–3 day intervals did not significantly affect their growth. Different microalgal diets (1: Isochrysis sp. (clone T-ISO), 2: Chaetoceros calcitrans forma pumilus, 3: C. muelleri, 4: mixed Isochrysis sp. (clone T-ISO) and C. calcitrans f. pumilus, and 5: mixed Isochrysis sp. (clone T-ISO) and C. muelleri) were tested on veliger larval growth and mixed diets outperformed single-species diets.     

Purification and characterization of carbon monoxide dehydrogenase from the aerobic hyperthermophilic archaeon <Emphasis Type="Italic">Aeropyrum pernix</Emphasis>

The aerobic hyperthermophilic archaeon Aeropyrum pernix expresses carbon monoxide (CO) oxidation activity under heterotrophic growth conditions. Using activity stain gel analysis, CO oxidation activity was detected in a protein with a molecular mass of 210 kDa. The 210 kDa CODH protein was purified to homogeneity from A. pernix. Aeropyrum Mo-CODH catalyzed the oxidation of CO with a specific activity of 2.1 μmol CO min⁻¹ mg⁻¹ at 95°C, pH 8.0 using methyl viologen as the electron acceptor. The CODH protein showed high oxygen and thermo stability. The protein contains three subunits: L (86.6 kDa), M (34.5 kDa), and S (12.6 kDa), which form the LM₂S complex. The molecular mass of the complex was calculated by gel filtration and found to be 163.7 kDa. N-terminal amino acid sequencing and peptide mass fingerprinting analysis of the subunits indicated that they corresponded to NP_148462.1, NP_148464.2, and NP_148465.1, and their genes annotated the molybdo iron-sulfur flavoprotein carbon monoxide dehydrogenase S, L, and M subunits, respectively. Phylogenetic analysis revealed that CODH belongs to a novel clade of diverse CODHs.     

The use of alternative prey (crayfish, <Emphasis Type="Italic">Procambarus clarki</Emphasis>, and hake, <Emphasis Type="Italic">Merlucius gayi</Emphasis>) to culture <Emphasis Type="Italic">Octopus vulgaris</Emphasis> (Cuvier 1797)

The effects of two alternative prey (crayfish and hake) were tested on growth and survival of both juveniles and adults of Octopus vulgaris in two experiments. Octopuses fed the control (squid) were larger (3.0 ± 0.7 kg) than those fed crayfish (2.4 ± 0.6 kg) at the end of experiment I. Similarly, overall growth rates were higher for octopuses fed squid (1.7 ± 0.3 and 1.2 ± 0.2 %BW day⁻¹, respectively). Average feeding rates for the experiment were not different, being 6.5 ± 0.9 and 7.5 ± 0.9 %BW day⁻¹, respectively, for octopuses fed either squid or crayfish. Nevertheless, food conversions for the experiment were higher (42.4 ± 2.7%) for octopuses fed squid compared to the ones fed crayfish (23.9 ± 1.9 g). For experiment II, hake and crayfish were compared to squid; the final weight of octopuses fed squid, hake or crayfish was 1,183.0 ± 242.7 g, 1,175.6 ± 240.1 g and 922.3 ± 160.1 g, respectively. Overall growth rates for the experiment were 1.9 ± 0.2 %BW day⁻¹, 1.9 ± 0.3 %BW day⁻¹ and 1.1 ± 0.3 g, respectively. Final weight and growth rates were never different (P > 0.05) between octopuses fed squid and hake, but were always higher (P < 0.05) compared to the ones fed crayfish. Average feeding rates for experiment II were similar for the three diets, and of 4.6 ± 1.5, 4.2 ± 1.3 %BW day⁻¹ and 5.1 ± 0.9 %BW day⁻¹, respectively, for octopuses fed squid, hake or crayfish. Food conversions for experiment II were of 41.0 ± 9.6%, 40.5 ± 9.9% and 21.3 ± 7.4 g, respectively, for octopuses fed squid, hake or crayfish, and were always higher for octopuses fed squid and hake compared to crayfish. The results indicate that crayfish is not an adequate replacement for the usual prey to fatten octopus, even considering its much lower market price.     

Lack of arterial PO<Subscript>2</Subscript> downregulation in Atlantic salmon (<Emphasis Type="Italic">Salmo salar</Emphasis> L.) during long-term normoxia and hyperoxia

Regulation of arterial partial pressure of O₂ (P_aO₂) in Atlantic salmon (Salmo salar) was investigated during resting conditions in normoxic and hyperoxic water. Dorsal aorta cannulated adult Atlantic salmon (1.2–1.6 kg, n = 8) were exposed to 2 week sequential periods of normoxia [16.7 ± 1.1 kPa (mean ± SD)] and hyperoxia (34.1 ± 4.9 kPa) in individual tanks containing seawater (33.7 ± 0.2 ppt) at stable temperature conditions (8.7 ± 0.7°C) and a light regime of L:D = 12:12. Tank design and sampling procedures were optimized to provide suitable shelter and current for the fish, and to allow repeated, undisturbed sampling of blood from free-swimming fish. Fish were sampled regularly through the experimental period. P_wO₂, P_aO₂, blood ion composition (Na⁺, K⁺, Cl⁻), acid–base status (pH, PCO₂, HCO₃ ⁻), haematocrit and glucose were measured. The most frequently observed P_aO₂ values were in the range of 60–80% of P_wO₂, both during normoxia and hyperoxia, and P_aO₂ values were significantly lower during normoxia than during hyperoxia. Blood pH, PCO₂ and HCO₃ ⁻ were significantly elevated during hyperoxia, while, Na⁺, Cl⁻ and Hct were significantly lower. K⁺ and glucose showed no significant differences. This study demonstrates a lack P_aO₂ regulation in Atlantic salmon to low partial pressures, in contrast to previous reports for many aquatic gill breathing animals. Both during normoxia and hyperoxia, P_aO₂ reflects P_wO₂, and alterations in external PO₂ consequently result in proportional arterial PO₂ changes. Physiological adaptation to hyperoxia, as illustrated by changes in several blood parameters, does not include down-regulation of P_aO₂ in Atlantic salmon. The lack of P_aO₂ regulation may make Atlantic salmon vulnerable to the oxidative stress caused by increased free radical formation in hyperoxic conditions.     

Dietary polysaccharide from <Emphasis Type="Italic">Angelica sinensis</Emphasis> enhanced cellular defence responses and disease resistance of grouper <Emphasis Type="Italic">Epinephelus malabaricus</Emphasis>

The purpose of this study was to determine the effect of Angelica sinensis polysaccharide (ASP) supplemented in diet on the innate cellular immune response and disease resistance in grouper, Epinephelus malabaricus. Fish were fed diets containing different doses of ASP (0, 500 and 3,000 mg kg⁻¹ diet) for 12 weeks. After 12 week feeding, the respiratory burst activity, phagocytic activity, and leukocytes proliferation in head kidney were assayed. The functional immunity in terms of cumulative mortality was also assessed by a challenge with live Edwardsiella tarda. Results showed that the respiratory burst activities in ASP-supplemented groups were increased significantly. The respiratory burst index was the highest in fish-fed 3000 mg kg⁻¹ diet and the lowest in control. The phagocytic activities in ASP-supplemented groups were significantly higher than that of control. No significant difference in phagocytic activity was observed between ASP-supplemented groups. ASP stimulated the head kidney leukocytes proliferation significantly, despite the absence of lipopolysaccharide (LPS) or not. The cumulative mortalities of fish fed with 3000 mg ASP kg⁻¹ diet were significantly lower than those fed with 500 mg ASP kg⁻¹ diet and control diet after 96 h of challenge. In conclusion, dietary ASP enhanced some cellular immune parameters and disease resistance against E. tarda in grouper.     

Development of larval culture techniques for the shore crab, <Emphasis Type="Italic">Carcinus maenas</Emphasis> (L)

The shore crab Carcinus maenas is a commercially important species, utilised as sea angling bait as well as supporting a European-wide fishery. Hatchery production could provide an alternative source of bait crabs, alleviating potential competition between these sectors and environmental concerns regarding bait collection practices. A series of experiments were carried to investigate the potential for hatchery production, focusing on effects of dietary regimes and stocking densities through the zoeal stages and the influence of tank substrates and stocking density during the megalopa stage. Inclusion of the rotifer Brachionus plicatilis as live food for early larval stages conveyed no advantage in terms of survival or rate of development compared to a diet of Artemia nauplii. Increasing zoea stocking densities (from 94 to 557 l⁻¹) had a significantly negative effect upon survival to the megalopa stage (from 75% down to 47%), although this was off-set by a significant increase in production, with 260 megalopae⁻¹ produced from an initial density of 557 zoeae l⁻¹. The inclusion of substrates for megalopa stages had no impact on production or development rate, compared to tanks with no substrate. The completely benthic behaviour of megalopae indicates that tank floor area will be a limiting factor for crab production. Increasing stocking density of megalopae was found to significantly and negatively influence survival, although above 10,000 megalopae m⁻² the rate of decline in survival stabilised and maximum production (3,114 juveniles m⁻²) of juvenile crabs could be achieved at the highest stocking densities tested (40,000 m⁻²).     

Recent expansion of Northeast Atlantic and Mediterranean populations of <Emphasis Type="Italic">Melicertus</Emphasis> (<Emphasis Type="Italic">Penaeus</Emphasis>) <Emphasis Type="Italic">kerathurus</Emphasis> (Crustacea: Decapoda)

We analysed the genetic diversity of Melicertus kerathurus (Penaeidae), a commercially valuable penaeid shrimp that is distributed in the Mediterranean Sea and eastern Atlantic Ocean. We examined the polymorphism of a 494 bp DNA segment of the mitochondrial COI region in 173 individuals, sampled in nine Mediterranean and two Atlantic samples, covering the whole range of the species from the tropical waters of the Gulf of Guinea to the eastern part of the Mediterranean Sea. The mean nucleotide and haplotype diversities were π = 0.00275 and h = 0.718, respectively, for the global data set, with the highest values occurring in the African samples and the lowest in the Adriatic Sea. A clear sample differentiation was found (F _st = 0.194), but this did not reflect a geographical pattern and there were only faint traces of an Atlantic–Mediterranean subdivision. Mismatch analysis and a high significant negative value of Tajima’s D suggested that M. kerathurus is not at mutation drift-equilibrium, but underwent a recent expansion after a period of low effective sample size. A postglacial recolonisation of the Mediterranean from an Atlantic refuge could be hypothesised based on these data.     

Occurrence of estuarine and sea eels <Emphasis Type="Italic">Anguilla japonica</Emphasis> and a migrating silver eel <Emphasis Type="Italic">Anguilla anguilla</Emphasis> in the Tokyo Bay area,Japan

Otolith microchemical analyses of the strontium (Sr) and calcium (Ca) concentrations in the eels Anguilla japonica and A. anguilla caught in Tokyo Bay were undertaken to reconstruct the eels’ migratory histories. A. japonica in the yellow stage (immature stage) were caught in a bay without any adjacent rivers or streams. A. anguilla was in the silver stage (early maturing stage), and the eel was confirmed to have just begun spawning migration to the open ocean from Tokyo Bay based on the otolith Sr:Ca ratios, which showed a typical catadromous life history with low Sr:Ca ratio values throughout the eel’s life after recruitment. The mean Sr:Ca ratios in A. japonica from the elver mark to the otolith edge indicated the eels belonged to several general categories of migratory histories, including sea eels (average Sr:Ca ratio ≥6.0 × 10⁻³) and estuarine eels (average Sr:Ca ratio 2.5 to 6.0 × 10⁻³) based on the criteria reported previously in A. japonica. All eels had a certain freshwater life period, although the period was highly variable among fish. These results indicate that A. japonica has a flexible pattern of migration, with the ability to adapt to various habitats and salinities.     

Stocking density for the intensive rearing of juvenile crayfish, <Emphasis Type="Italic">Pacifastacus leniusculus</Emphasis> (Astacidae), using <Emphasis Type="Italic">Artemia</Emphasis> nauplii to supplement a dry diet from the onset of exogenous feeding

Recent advances in intensive rearing of astacid juvenile crayfish have greatly improved the results. This challenges the current application possibilities of the studies performed previously, and new research on density is required. A 100-day experiment was carried out under controlled conditions to evaluate density effects on survival and growth rates of juvenile crayfish in optimal conditions of feeding. Juvenile stage 2 Pacifastacus leniusculus were stocked in fibreglass tanks (1 m², 200 l water) at 20 ± 1°C and fed a dry diet for salmonids supplemented with restricted amounts of Artemia nauplii. Stocking densities were 100, 300, 600 and 1,000 crayfish m⁻². Mean survival rate was reduced significantly with increased stocking density, ranging from 86.33% (100 m⁻²) to 39.13% (1,000 m⁻²). All checks showed that at the lowest initial density (100 m⁻²) animals grew significantly faster those at higher densities, recording a final carapace length of 15.28 mm and weight of 1.08 g. Among the treatments of 300, 600 and 1,000 m⁻² no differences were found either in carapace length or in weight throughout the experimental period, with a final mean growth of 14 mm carapace length and 0.72 g weight. The final proportion of animals with chelae autotomy rose significantly with increasing stocking density, ranging from 14.44% (100 m⁻²) to 41.45% (1,000 m⁻²). This study shows that diet is a decisive factor for stocking successfully high densities under controlled conditions and provides useful information to set adequate densities in accordance with the production objectives.     

Induction of diploid gynogenesis in turbot <Emphasis Type="Italic">Scophthalmus maximus</Emphasis> with left-eyed flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis> sperm

Turbot Scophthalmus maximus exhibits sexually dimorphic growth, with females growing faster and reaching larger adult sizes than males. Thus, development of techniques for preferentially producing females is necessary to optimize production of these species. In this paper, gynogenetic diploids of turbot were induced by activating egg development with ultraviolet (UV)-irradiated left-eyed flounder Paralichthys olivaceus sperm combined with cold shock to prevent extrusion of the second polar body. The results of UV irradiation experiments showed that survival, motility, and duration of activity of P. olivaceus sperm generally decreased with increase in UV dose. The typical Hertwig’s effect was observed after fertilized turbot eggs with UV-irradiated P. olivaceus sperm and the optimal UV dose for gynogenetic haploid production was 36,000 erg mm⁻². At 15°C, appropriate timing of cold shock for retention of the second polar body in turbot eggs was at 6 min after fertilization. Results of different combinations of two shock temperatures (1 or 3°C) and four shock durations (15, 25, 35 or 45 min) at 6 min after fertilization demonstrated that shock of 25 min at 1°C gave the highest production of diploid gynogens (39.58% relative to its diploid control). The results of this study reveal that the use of UV-irradiated P. olivaceus sperm for activation of turbot eggs and cold shock for polar body retention is an effective method to produce gynogenetic offspring.     

Age and growth of two gizzard shads, <Emphasis Type="Italic">Nematalosa come</Emphasis> and <Emphasis Type="Italic">N. japonica</Emphasis>, in coastal waters around Okinawa Island,southwestern Japan

The age and growth of two Nematalosa species around Okinawa Island were examined using sectioned otoliths collected from September 2003 to April 2006. Monthly changes in the frequency of the appearance of a translucent band on the outer margin of the otoliths indicated that ring formation occurred once a year from January to July for Nematalosa come and from January to March for Nematalosa japonica. The von Bertalanffy growth equations for both species were as follows: N. come: L _t  = 365.5{1 − exp[−0.111 × (t + 0.288)]} for females and L _t  = 214.7{1 − exp[−0.700 × (t – 1.110)]} for males; N. japonica: L _t  = 205.1{1 − exp[−1.068 × (t − 1.180)]} for females and L _t  = 195.5 {1 − exp[−1.293 × (t − 1.269)]} for males. The maximum ages observed for N. come and N. japonica were 11 and 6 years old, respectively. The growth of these species was characterized by the slow growth of N. come over many years, resulting in a larger size than N. japonica.     

Application of synthetic hormone LHRH-A<Subscript>2</Subscript> on the artificial propagation of Persian sturgeon <Emphasis Type="Italic">Acipenser persicus</Emphasis>

For studying the effect of LHRH-A₂ hormone on the induction of final maturation and ovulation of Persian sturgeon, 71 matured females and 20 matured males were used. Five groups of breeders were injected with sturgeon pituitary gland hormone (50 mg per fish) and LHRH-A₂ in dosages of 3.5, 7, 8 and 10 μg kg⁻¹ for females and 3 and 5 μg kg⁻¹ for males. Results showed that LHRH-A₂ successfully induced final maturation and ovulation in females, and there was no significant difference between five groups of breeders in ovulation proportion, fertilization rate, survival rate of incubation, survival of yolk-sac absorption period and active feeding period of larvae. It can be concluded that the LHRH-A₂ is a proper alternative for pituitary gland hormone in artificial propagation of Persian sturgeon.     

Econometric model of viability/profitability of octopus (<Emphasis Type="Italic">Octopus vulgaris</Emphasis>) ongrowing in sea cages

The interest in diversifying aquacultural production with new species is evident, preferably with species with a high commercial value and whose consumption is not geographically limited. In this sense, octopus would be a good choice. The present work, therefore, presents an economic-financial analysis of the commercial viability of octopus ongrowing in the Mediterranean, paying special attention to the one- or two-cycle approach. Viability–profitability equations are developed for analysing economic parameters associated with production. To estimate the investment, an offshore ongrowing installation was designed comprising 150 cages containing 30,000 individuals. Growth was estimated for the two strategies: (A) Two consecutive cycles per year (2CY), each lasting 3.5 months from October to June. Initial weight was 0.7 kg, and the mean final weight was 2.7 kg. (B) One growth cycle per year (1CY) beginning in November or December and finishing in April or May, starting with the same weight individuals (0.7 kg) and giving individuals with a final weight of 3.65 kg. The highest costs, the most important from an economic point of view, are feed (38.57 and 40.03%, respectively), fixed assets (25.26 and 17.47%, respectively), juveniles (16.65 and 23.02%, respectively), and in fourth place salaries (14.34 and 15.60%, respectively). The equations obtained for the variables NPV (Net Present Value) and IRR (Internal Ratio of Return) are the following: 1 cycle per year (1CY), NPV = −489,088 − 1.45 K − 1,439,823 C _F − 1,477,890 C _J − 1,460,627 C _O + 1,432,386 SP, IRR = 0.1328 − 7.82 × 10⁻⁸ K − 0.0416 C _F − 0.0437 C _J − 0.0427 C _O + 0.0412 SP. 2 cycles per year (2CY), NPV = −404,431 − 1.46 K − 2,118,410 C _F − 2,121,221 C _J − 2,144,755 C _O + 2,129,223 SP, and IRR = 0.0952 − 6.95 × 10⁻⁸ K − 0.0586 C _F − 0.0588 C _J − 0.0588 C _O + 0.0613 SP. The NPV and IRR values estimated with the econometric equations for each option using the initial variables confirm that 1CY has a higher NPV (3,013,569 €) and IRR (12.27%) than 2CY, with an NPV of 2,396,708 € and IRR of 10.39%. In both cases, octopus ongrowing is economically viable, although 1CY is the most favourable system.     

Effects of conventional versus organic production systems on amino acid profiles and heavy metal concentrations in the Chinese shrimp <Emphasis Type="Italic">Penaeus chinensis</Emphasis>

Amino acid composition and heavy metal concentration were examined in organic and conventional Chinese shrimp Penaeus chinensis production systems during the production cycle. The crude protein and total amino acid contents for organic shrimp samples were 0.932 and 0.945 mg/g d.w., while they were 0.849 and 0.826 mg/g d.w., respectively, for conventionally produced samples. The ratios of essential amino acids to nonessential amino acids in organic and conventional cultured shrimp were 0.58 and 0.63, respectively. Shrimp samples from the conventional system were significantly richer in Cu (2.28 vs. 1.53 mg kg⁻¹), Pb (0.13 vs. 0.08 mg kg⁻¹), Cd (0.09 vs. 0.04 mg kg⁻¹), and Zn (9.94 vs. 8.42 mg kg⁻¹) when compared with those obtained from the organic system. It is concluded that organic shrimp production systems can produce comparable growth and nutritional quality benefits.     

Probiotic bacteria <Emphasis Type="Italic">Lactobacillus rhamnosus</Emphasis> influences the blood profile in rainbow trout <Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis> (Walbaum)

This paper reports the effect of feeding probiotic diets on blood profiles in rainbow trout. Two experiments were performed: in the first, fish of average weight 75 g were offered either a commercial feed or the same incorporated with 10⁹ CFU g⁻¹ of lactic acid bacteria Lactobacillus rhamnosus for 30 days; in the second study performed for a similar duration, fish of average weight 126 g were offered formulated diets that either contained the same bacteria in heat-killed or freeze-dried form (nearly 10¹¹ CFU g⁻¹), or the basal diet without the bacteria. Blood samples were collected at different times after commencement of probiotic feeding to determine the total cholesterol, triglyceride contents, the plasma alkaline phosphatase activity, plasma protein and hematocrit value. The plasma cholesterol significantly increased upon probiotic feeding in the first experiment. A significant elevation (P < 0.05) of plasma cholesterol and triglyceride and alkaline phosphatase activity level was found in the freeze-dried probiotic fed groups at 20 and 30 days postfeeding. This was concomitant with the increased plasma protein and hematocrit values in FD group at 20 and 30 days. Likewise, the heat-killed probiotic fed group registered significantly high values of triglycerides, alkaline phosphatase activity, and plasma protein compared to the control diet fed groups after 20 days of feeding. Thus, alterations in the blood profiles could serve as supplementary information when examining the benefits of probiotics for fish.     

Carbonic anhydrase and Na/K-ATPase activities during the molt cycle of low salinity-reared white shrimp <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis>

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.     

Quantitative loop-mediated isothermal amplification method for the detection of <Emphasis Type="Italic">Vibrio nigripulchritudo</Emphasis> in shrimp

Vibrio nigripulchritudo is considered one of the major pathogens threatening shrimp aquaculture. In this study, we developed a novel and highly specific quantitative loop-mediated isothermal amplification (Q-LAMP) assay. A set of four specific primers were designed targeting the V. nigripulchritudo intergenic spacer region. The reaction time and temperature were optimized for 60 min at 63°C. Quantitative analysis was then performed by measuring the turbidity of the reaction solution using a real-time turbidimeter, allowing for quantification of the initial DNA concentration with a sensitivity of 10² copy numbers equivalent to 2.3 colony forming units/ml or 0.3 fg/μl. The LAMP assay was able to specifically detect two representative strains of V. nigripulchritudo, whereas other Vibrio and non-Vibrio species were not amplified. A standard curve was generated for V. nigripulchritudo by plotting the threshold time (T _t) versus the log of bacterial number. A high correlation coefficient (R ² = 0.9749) was observed for the Q-LAMP reaction. In conclusion, Q-LAMP assay is a sensitive, rapid, and simple tool that can be used for the detection and quantification of V. nigripulchritudo in shrimp, thereby facilitating surveillance of vibriosis infection.