Volume 60, Issues 1-4, 2008

Genetic Diversity and Population Structure of the Peanut Worm (Sipunculus nudus) in Southern China as Inferred from Mitochondrial 16S rRNA Sequences

Xiadong, Du; Zian, Chen; Yuewen, Deng; Qingheng, Wang; Ronglian, Huang — Tue, 01 Jan 2008 00:00:00 GMT

Genetic diversity and population structure of the peanut worm (Sipunculus nudus) were investi- gated by using 536 base-pair fragments of the mitochondrial 16S ribosomal gene. Populations were collected from three locations along the southern coast of China - Beihai, Sanya, and Xiamen. Amplified polymerase chain reaction products were sequenced in both directions and data were analyzed using ClustalX, Arlequin, and MEGA. A total of 69 polymorphic sites and 21 distinct haplotypes were revealed. The mean haplotype and nucleotide diversity of the three pop- ulations were 0.814% and 0.37%, respectively. The Beihai population had the greatest haplo- type and nucleotide diversity, followed by the Xiamen and Sanya populations. Analysis of mole- cular variance (AMOVA) showed significant genetic differentiation among the three populations (Fst = 0.0619, p<0.05) and distinct population structures among the three sites.

Optimal Dietary Protein Levels in Juvenile Electric Blue Cichlid (Sciaenochromis fryeri)

Gullu, Kenan; Guroy, Derya; Celik, Ihsan; Tekinay, Adem — Tue, 01 Jan 2008 00:00:00 GMT

A feeding trial was conducted to determine the dietary protein requirement of juvenile electric blue cichlids (Sciaenochromis fryeri). Groups of fish (0.50±0.01 g) were fed one of four isocaloric diets containing protein levels ranging 35-50% for 12 weeks. According to the broken-line model, the dietary protein requirement was estimated as 38.8%. The feed conversion ratio ranged from 1.73 in the 50%-protein group to 2.16 in the 35% group. There were statistically significantly dif- ferences in feed intake and protein efficiency ratio. In general, the protein efficiency ratio decreased as the dietary protein level increased. For optimum growth, feed conversion, and pro- tein utilization, a diet containing 39-40% protein, 11% crude lipid, and 20.7 MJ gross energy/kg diet is recommended for juvenile S. fryeri.

Digestive Enzymes and Hormones in Gilthead Seabream Larvae (Sparus aurata) Fed Artemia Nauplii Enriched with Free Histidine

Naz, Mehmet; Turkmen, Mustafa — Tue, 01 Jan 2008 00:00:00 GMT

The digestive enzymes and hormones of gilthead seabream (Sparus aurata) larvae fed live prey (Artemia nauplii) enriched with free histidine were investigated for 16 days (from day 24 to day 40 after hatching). Larvae were sampled at 4-day intervals. The control group had significantly lower growth than the enriched group (p<0.05). Trypsin activity was higher in the control (p<0.05). Bombesin activity significantly differed between treatments, periods, and period x treatment interac- tions and the cholecystokinin level was significantly higher in the enriched groups (p<0.05). Results indicate that Artemia nauplii can successfully be enriched with free histidine, bombesin and chole- cystokinin activity can be stimulated by free histidine, and mechanisms controlling the adaptation of trypsin activity to the amount of dietary protein were not activated within the 40-day study period.

Comparison of Periphyton Grown on Different Substrates as Food for Organic Tilapia Culture

Milstein, Ana; Peretz, Yakov; Harpaz, Sheenan — Tue, 01 Jan 2008 00:00:00 GMT

Regulations regarding organic tilapia culture result in increased feed costs. To reduce such costs, experiments were conducted to enhance the natural production of periphyton, on which tilapia feed. Strips of substrates of different textures and colors were placed in the water column of tilapia culture ponds to induce periphyton growth. Some strips were placed in cages to protect them from fish grazing and some where placed in the open pond, accessible to the fish. Periphyton development was evaluated by the contents of chlorophyll, dry matter (DM), and ash free dry matter (organic matter) and by an autotrophic index. The first experiment tested growth on substrates of different textures including natural (palm leaves) and artificial (agricultural nets, plastic surfaces) materials. The second experiment tested the effect of different colored nets. The differences between periphyton grown in cages and in the open pond indicate that tilapia grazed on the periphyton. Palm leaves decomposed too quickly to be of practical use in large- scale aquaculture. Periphytic material seemed to be more easily dislodged from smooth plastic substrates than from rough nets, changing the structure of the residual attached periphyton. Growth was greater on nets with a fine mesh (5.3-9.6 mg/cm2 DM) than with a coarse mesh (3.7- 4.0 mg/cm2 DM) or on smooth plastic surfaces (1.4-2.6 mg/cm2 DM). The color of the substrate did not affect the chlorophyll content of periphyton but did affect its dry and organic matter con- tent. The white substrate had 40% more dry matter (11.5 vs 7.9-8.2 mg/cm2) and 50% more ash free dry matter (2.1 vs 1.4 mg/cm2) than the blue and black substrates.

Immunization of Rainbow Trout (Oncorhynchus mykiss) against Lactococcus garvieae Using Vaccine Mixtures

Kubilay, A.; Altun, S.; Ulukoy, S.; Ekici, S.; Diler, O. — Tue, 01 Jan 2008 00:00:00 GMT

The effectiveness of vaccine mixtures against lactococcosis was tested in rainbow trout (Oncorhynchus mykiss). The M1 strain of Lactococcus garvieae, isolated from a recent outbreak of lactococcosis at a rainbow trout farm in Turkey, was used in a trial comparing five immuniza- tion treatments: (a) formalin inactivated bacterin (vaccine), (b) the above bacterin together with Freund’s Incomplete Adjuvant (FIA), (c) the bacterin combined with β-glucan, (d) β-glucan only, and (e) phosphate buffered saline-PBS (control). Fish were given intrapritoneal injections and challenged by exposure to the bacteria 30, 75, or 125 days after vaccination. In fish exposed to the bacteria 30 days after injection, the relative percent survival (RPS) was 88.89% in the group that received only bacterin and 100% in the group that received the bacterin combined with FIA. Immunity remained high in the bacterin+FIA group, as the RPS in this group remained 100% in fish challenged at 75 days, significantly higher than in all other groups. In fish exposed to the bacteria 125 days after vaccination, the RPS was 54.55% in fish vaccinated with the bacterin only and 84.84% in fish vaccinated with bacterin+FIA. In the group that received only β-glucan, immunity did not improve after vaccination. Micro-agglutination tests of serums showed that immunized fish produced antibodies at high titers within 30 days. In short, the formalin-inacti- vated M1 strain provided longer lasting protection against Lactococcus garvieae in rainbow trout when combined with FIA than when administered alone or with β-glucan.

Screening Cage Culture Fish Species for Organic Chlorinated Pesticide and Polychlorinated Biphenyl Residues in Turkey

Tue, 01 Jan 2008 00:00:00 GMT

Organic chlorinated compounds (aldrin, α-endosulfan, β-endosulfan, 2,4’-DDT, and 4,4’-DDE) and polychlorinated biphenyles (PCB28 and PCB52) were screened in fish culture cages off the Aegean Coast of Turkey. Sea bass (Dicentrarchus labrax) and sea bream (Sparus aurata) were randomly selected from three coastal areas during June-December 2004. Samples of 114 fish were analyzed by gas chromatography (GC) with an electron capture detector and GC-mass spectrometry (GC-MS). No residues exceeding limits established by the European Union Directive were detected. However, 4,4’-DDE was found in 2.63% of the samples. The amounts of residues in all positive samples were lower than the maximum tolerance limits (0.2-1 mg/kg) accepted by the EU Directive. Contamination levels varied with species, ranging 18-200 ng/g wet weight. Other chemicals were not detected in fish samples.

Detection and Identification of Fish Pathogens: What is the Future?

Frans, I.; Lievens, B.; Heusdens, C.; Willems, K.A. — Tue, 01 Jan 2008 00:00:00 GMT

Fish diseases pose a universal threat to the ornamental fish industry, aquaculture, and public health. They can be caused by many organisms, including bacteria, fungi, viruses, and protozoa. The lack of rapid, accurate, and reliable means of detecting and identifying fish pathogens is one of the main limitations in fish pathogen diagnosis and disease management and has triggered the search for alternative diagnostic techniques. In this regard, the advent of molecular biology, especially polymerase chain reaction (PCR), provides alternative means for detecting and iden- tifying fish pathogens. Many techniques have been developed, each requiring its own protocol, equipment, and expertise. A major challenge at the moment is the development of multiplex assays that allow accurate detection, identification, and quantification of multiple pathogens in a single assay, even if they belong to different superkingdoms. In this review, recent advances in molecular fish pathogen diagnosis are discussed with an emphasis on nucleic acid-based detec- tion and identification techniques. Major features and applications of current predominant meth- ods and promising methods likely to impact future fish disease control and prevention are out- lined.

Partial Replacement of Fishmeal with Hazelnut Meal in Diets for Juvenile Gilthead Sea bream (Sparus aurata)

Emre, Yilmaz; Sevgill, Huseyin; Sanil, Murat — Tue, 01 Jan 2008 00:00:00 GMT

Hazelnut meal was evaluated as an alternative protein source to fishmeal in diets of gilthead sea bream with an initial weight of 35.08±0.29 g. Incorporation levels of hazelnut meal were 0% (con- trol), 10%, 20%, 30%, and 40%. Each diet was tested in triplicate for ten weeks. There were no significant differences between the experimental diets and the control in final body weight, weight gain, specific growth rate, or feed and protein efficiency ratios. In addition, the level of hazelnut meal did not significantly affect the whole body composition of the sea bream. In con- clusion, up to 40% hazelnut meal could be included in diets for gilthead sea bream juveniles with- out adverse effects on growth rate or body composition.

Survival and Growth of Captive Reared Juvenile Seahorse (Hippocampus kuda) Fed Live Feeds and Fishmeal

Thangaraj, M.; Lipton, A.P. — Tue, 01 Jan 2008 00:00:00 GMT

Pond and aquarium keeping of seahorse (Hippocampus kuda) is challenging because of their feeding habits. Although seahorse is a purely active predator, we successfully raised laboratory- produced young on inert feed and evaluated the effects of readily-available cost-effective food items on their growth and survival. Two-month old laboratory bred juveniles were fed live Artemia, live Mysids, minced fishmeal, or a combination of Artemia and Mysids (1:1). Juveniles fed the combination diet reached the highest wet weight (1.93±0.31g), specific growth rate (2.21±0.07), and survival (96±3.0%), significantly (p<0.05) higher than juveniles fed fishmeal (1.42±0.12 g, 2.08±0.03, and 76±3.0%, respectively). Although there were insignificant differences in growth and survival between juveniles fed the combination and those fed Mysids or Artemia, the combi- nation diet was best. This easily available feed can be used in ornamental aquaria.

Antibacterial Activity of Marine Sponge Extracts against Fish Pathogenic Bacteria

Annie Selva Sonia, G.; Lipton, A.P.; Paul Raj, R. — Tue, 01 Jan 2008 00:00:00 GMT

Secondary metabolites of the marine sponges Acanthella elongata, Axinella donnani, Callyspongia diffusa, Callyspongia subarmigera, and Echinodictyum gorgonoides were collect- ed from fishing nets and their in vitro antibacterial properties against eight virulent marine fish pathogens were studied at incubation temperatures of 20°C and 30°C. Crude methanol extracts of the tested sponges showed species-specific antibacterial activity. The most active species was A. elongata which inhibited 100% and 87.5% of the tested bacterial isolates at 20°C and 30°C, respectively. Callyspongia subarmigera was the least active as it inhibited only 62.5% and 50% of the tested bacteria at those temperatures. Results suggest that fractionation and purifi- cation of the crude methanol extract of A. elongata has potential in the development of novel antibiotic substances for managing common bacterial diseases in aquaculture.

Growth Performance, Survival, and Body Composition of Post Larvae of the Freshwater Prawn (Macrobrachium rosenbergii) Fed Graded L-Carnitine Diets

Singh, R.K.; Desai, A.S.; Chavan, S.L.; Khandagale, P.A. — Tue, 01 Jan 2008 00:00:00 GMT

The aim of this study was to investigate the efficacy of L-carnitine incorporated diets on growth, specific growth rate (SGR), feed conversion efficiency (FCE), protein efficiency ratio (PER), sur- vival, and body composition of post larvae of the freshwater prawn Macrobrachium rosenbergii. Five diets containing 0, 0.25, 0.50, 0.75, or 1 g L-carnitine/kg diet were fed to post larvae (0.105±0.028 g, 2.21±0.13 cm) for thirteen weeks. The highest SGR (3.42±0.44%/day), FCE (40.40±1.45%), and PER (1.05±0.02) were obtained in the 0.50 treatment. The lipid level in the post larvae was inversely related to the L-carnitine level in the diet (p<0.05). The protein level increased with supplementation until the 0.50 level, then decreased with higher levels. Using second-order polynomial regression analysis, the optimal weight gain, SGR, and FCE were obtained with L-carnitine levels of 0.484 g/kg, 0.466 g/kg, and 0.48 g/kg, respectively. In con- clusion, 0.50 g L-carnitine per kg feed is optimum for good growth in M. rosenbergii post larvae.

Effect of Temperature on Growth and Biochemical Composition (Sterols, α-tocopherol, Carotenoids, Fatty Acid Profiles) of the Microalga, Isochrysis galbana

Tue, 01 Jan 2008 00:00:00 GMT

The microalga Isochrysis galbana Parke was grown in 100-l polyethylene bags filled with steril- ized seawater enriched with Wallerstein and Miquel nutrient medium (3:1) at two temperatures (18°C and 26°C), 2.5% salinity, and continuous illumination. Samples of microalgae were exam- ined during the exponential growth, stationary growth, and decay phases (days 18, 35, and 58, respectively). Stigmasterol constituted the main sterol group in all phases in both treatments, except during the exponential growth phase at 18°C. The highest concentration of α-tocopherol was 5.22 mg/100 g DW, reached in the decay phase of algae raised in 18°C. Likewise, the high- est total carotenoid (4.14 mg/g DW) and chlorophyll (2.87 mg/g DW) levels were obtained in algae raised in 18°C, during the exponential phase; the main pigments were chlorophyll a, c1, c2, and fucoxanthin. At 18°C, polyunsaturated fatty acids (PUFA) were the predominant fatty acid group, reaching 37.93% of the total fatty acids in the stationary phase. At 26oC, saturated fatty acids (SAF) were the predominant group of fatty acids. The present study suggests that the nutritional value (gross biochemical composition and fatty acid profile) of I. galbana Parke is, to a large extent, determined by the temperature at which it is grown and the harvest time.

Cryopreservation of Pike Perch Sperm in Hatchery Conditions

Bokor, Zoltan; Horvath, Akos; Horvath, Laszio; Urbany, Bela — Tue, 01 Jan 2008 00:00:00 GMT

Experiments were carried out on pike perch (Sander lucioperca L.) to find a method for stripping sperm without contamination by urine, to determine sperm concentration, and to fertilize large batches of eggs with cryopreserved sperm. Induced spawning technology for pike perch, an important predator fish species in Hungarian and central-eastern European pond aquaculture, has been developed only recently. Sperm cryopreservation can be an important tool for several reasons including the simplification of hatchery work and long-term preservation of genomes of males with high genetic value. In the present study, sperm was stripped without urine contami- nation, improving sperm quality, and large amounts of eggs were fertilized using 0.25 ml sperm, resulting in hatching percentages of 55±3% for 30-g batches of eggs and 87% for a 50-g batch.

Partial Replacement of Fishmeal by Defatted Soybean Meal in Diets for Black Sea Turbot (Psetta maeotica): Growth and Nutrient Utilization in Winter

Ergun, Sabahattin; Yigit, Murat; Turker, Ali; Harmantepe, Burcu — Tue, 01 Jan 2008 00:00:00 GMT

The objective of the present study was to evaluate replacement of white fishmeal by soybean meal in practical diets for Black Sea turbot (Psetta maeotica) at levels of 0, 10%, and 20%. The diets were fed to triplicate groups of juvenile Black Sea turbot (initial body weight 18 g) for 60 days. At the end of the trial, there were no differences in growth performance, feed utilization, and nitrogen retention between the control group fed 100% fishmeal and the experimental groups fed 10% or 20% soybean meal. In conclusion, 20% inclusion of soybean meal can allow reduction of white fishmeal by up to 14%, leading to savings on fishmeal protein.

Activity of the Digestive Protease, Chymotrypsin, in Larvae of the Cultured Sharpsnout Sea Bream (Diplodus puntazzo)

Tue, 01 Jan 2008 00:00:00 GMT

Specific and total activity of the digestive protease, chymotrypsin, was studied in cultured sharp- snout sea bream larvae (Diplodus puntazzo) for 35 days from hatching and in a variety of pH lev- els. Activity was detected upon hatching (2.8±0.34 mm total length), before the onset of exoge- nous feeding. Specific chymotrypsin activity exponentially increased from mouth opening on day 3 until day 25, then dropped until the end of the experiment. Total chymotrypsin activity sharply increased to day 10, then continued to increase, but slightly, until the end of the experiment. As expected, pH strongly affected both specific and total chymotryptic activity in the digestive tracts of larvae. Both were significantly lower when pH was acidic (1.5, 3.0, 4.0) than when it was alka- line (8.0, 9.0, 10.0) although there were no significant differences within either the acidic or the alkaline range. Our results indicate that chymotrypsin activity is capable of digesting protein before mouth opening and may be a valuable tool for better understanding the nutritional capa- bilities of young larvae.

Dietary Ascorbic Acid Requirements of Fingerlings of Genetically Improved Rohu (Labeo rohita Ham)

Sahoo, Minakshi; Mukhopadhyay, P.K. — Tue, 01 Jan 2008 00:00:00 GMT

Indian major carp, including Labeo rohita, are incapable of biosynthesizing ascorbic acid due to the absence of the enzyme L-gulono-γ-lactone oxidase. To assess their ascorbic acid require- ments, improved rohu fingerlings (2.33±0.18 g) were fed one of six semi-purified formulated diets containing 0, 20, 40, 60, 80, or 100 mg ascorbyl-2-polyphosphate (APP) per kg feed for 60 days in water of 28-30°C. Fish fed diets deficient in ascorbic acid had a significantly lower weight gain, poor feed conversion (FCR) and protein efficiency (PER) ratios, lower survival, and behavioral abnormalities such as lethargic movements and poor feed intake. The best FCR and PER were recorded in the 60 mg APP diet. Ascorbic acid in the kidney dropped from 36.62 to 5.09 mg/kg by the end of the experiment. Weight gain analysis by regression indicated that the dietary ascor- bic acid requirement for maximum growth and survival of rohu fingerlings can be achieved with 53.5 mg APP incorporated into 1 kg diet.

Population Growth of the Freshwater Cladoceran, Diaphanosoma excisum, Fed Different Densities of the Alga, Scenedesmus acuminatus

Ovie, Solomon I.; Ovie, Stella O. — Tue, 01 Jan 2008 00:00:00 GMT

The freshwater cladoceran, Diaphanosoma excisum Sars 1885, was fed the micro-alga Scenedesmus acuminatus, at one of six densities (0.5, 1.0, 1.5, 2.0, 3.0, or 4.0 x 106 cells/ml) in 40-l glass aquaria. The D. excisum density increased as the Scenedesmus density increased to 1.5 x 106 cells/ml, in which it peaked at 7345 individuals per liter. Population growth was inhibit- ed at higher algae densities. The percent of egg-bearing females and the number of eggs per egg-bearing female followed a similar pattern. Production of approximately 7000 individuals per liter was encouraging from a mass production point of view and indicates that S. acuminatus is suitable for use as a live starter feed for D. excisum which, in turn, is a live feed for larvae of induced-breeding in fish hatcheries.

Ontogeny of Fertilized Eggs and Yolk Sac Larvae of Sea Bass (Dicentrarchus labrax)

Naz, Mehmat — Tue, 01 Jan 2008 00:00:00 GMT

The biochemical compositions of fertilized eggs, yolk sac larvae, and larvae at the beginning of exogenous feeding of sea bass (Dicentrarchus labrax) were determined. Eggs and yolk sac lar- vae contain more monounsaturated and polyunsaturated fatty acids than saturated fatty acids. Essential and non-essential amino acid contents tended to drop at hatching, then sharply increase by the end of endogenous feeding. Amylase and trypsin activity was detected in fertil- ized eggs. Trypsin activity peaked at the beginning of exogenous feeding. The alkaline phos- phatase activity was lowest in fertilized eggs, higher at hatching, and highest at the end of the experiment. Leucine alanine peptidase activity was higher than other enzymatic activity in all three stages. Aminopeptidase N activity increased until hatching, then stabilized until the begin- ning of exogenous feeding.

Effect of Betaine as a Feed Attractant on Growth, Survival, and Feed Utilization in Fingerlings of the Indian Major Carp, Labeo rohita

Shankar, R.; Murthy, Shivananda; Pavadi, Prakash; Thanuja, K. — Tue, 01 Jan 2008 00:00:00 GMT

The study evaluated the efficiency of betaine as a feed attractant on growth, survival, and feed utilization in fingerlings of rohu (Labeo rohita). Betaine was incorporated at 0 (control), 0.25%, 0.50%, or 0.75% in a 30% protein diet and fed to fingerlings for 120 days in a closed and aerat- ed recirculating system. Feed was offered twice daily at a rate of 5% of the fish biomass during the first 15 days and 3% afterwards. Significantly better growth, specific growth rate, survival, food conversion ratio, and protein efficiency ratio were obtained in the group fed 0.25% betaine.

Analysis and Characterization of Expressed Sequence Tag (EST) and Simple Sequence Repeats (SSR) from Red Sea Bream, Chrysophrys major, and Gilthead Sea Bream, Sparus aurata

Liu, Yun-Guo; Chen, Song-Lin; Liu, Chun-Ying; Li, Fang-Zheng — Tue, 01 Jan 2008 00:00:00 GMT

A total of 101 and 119 simple sequence repeats (SSR) were obtained from expressed sequence tags (EST) of the red sea bream (Chrysophrys major) and gilthead sea bream (Sparus aurata), respectively. Dimeric repeats were the most abundant class of SSR in both red (70.30%) and gilthead (51.26%) sea bream. Trimeric, tetrameric, and pentameric repeats occurred in decreas- ing proportions, i.e., 21.36%, 6.8%, and 0.97% in red sea bream and 45.38%, 3.36%, and 0 in gilthead. There were no hexameric repeats in EST of either species. The frequency of every class of SSR (dimeric, trimeric, tetrameric, and pentameric) decreased with increasing repeat length. In cross-species amplification of 20 existing microsatellite loci from gilthead sea bream in 20 red sea bream specimens, twelve loci showed positive amplification and four loci showed polymorphic amplification with two or three alleles.