The beneficial effects of poly-β-hydroxybutyrate (PHB) for aquaculture animals have been shown in several studies. The strategy of applying PHB contained in a bacterial carrier has, however, hardly ...been considered. The effect of administering PHB-accumulated
Alcaligenes eutrophus
H16 containing 10 or 80 % PHB on dry weight, named A10 and A80, respectively, through the live feed
Artemia
was investigated on the culture performance of larvae of the giant freshwater prawn (
Macrobrachium rosenbergii
). Feeding larvae with
Artemia
nauplii enriched in a medium containing 100 and 1,000 mg L
−1
A80 significantly increased the survival with about 15 % and the development of the larvae with a larval stage index of about 1 as compared to feeding non-enriched
Artemia
. The survival of the larvae also significantly increased with about 35 % in case of a challenge with
Vibrio harveyi
. The efficiency of these treatments was equal to a control treatment of
Artemia
enriched in an 800 mg L
−1
PHB powder suspension, while
Artemia
enriched in 10 mg L
−1
A80, 100 mg L
−1
A10, and 1,000 mg L
−1
A10 did not bring similar effects. From our results, it can be concluded that PHB supplemented in a bacterial carrier (i.e., amorphous PHB) can increase the larviculture efficiency of giant freshwater prawn similar to supplementation of PHB in powdered form (i.e., crystalline PHB). When the level of PHB in the bacterial carrier is high, similar beneficial effects can be achieved as crystalline PHB, but at a lower live food enrichment concentration expressed on PHB basis.
The industrial development of freshwater ornamental fish culture has been hampered by the lack of suitable live feeds for feeding the fish at the various production stages. This paper reports the ...recent developments in the applications of the freshwater rotifers (
Brachionus calyciflorus),
Artemia nauplii, decapsulated
Artemia cysts and on-grown
Artemia in the freshwater ornamental fish culture. Results demonstrate that the rotifers are an ideal starter feed for dwarf gourami (
Colisa lalia), a typical freshwater ornamental fish species with larvae that are too small to ingest
Artemia nauplii or
Moina at its first feeding. Compared with the conventional yolk food, the use of rotifers as a starter feed significantly improves the growth and survival of the gourami larvae (Days 2–12), and the beneficial effects are extended to the subsequent
Artemia-feeding phase (Days 13–32). The freshwater rotifers and
Artemia nauplii are also useful in raising Discus larvae in the absence of their parents, which would eliminate the risk of larvae being eaten by the parent fish. Work on decapsulated
Artemia cysts indicates that the cysts could be used as a substitute for
Artemia nauplii or
Moina in freshwater ornamental fish culture. The fry of all the five common ornamental fish species tested (guppy
Poecilia reticulata, molly
Poecilia sphenops, platy
Xiphophorus maculatus, swordtail
Xiphophorus helleri and neon tetra
Hyphessobrycon herbertaxelrodi) could readily feed on the decapsulated cysts, and their performances in terms of stress resistance, growth and survival are comparable to or better than those fed on
Artemia nauplii or
Moina. A culture system for production of on-grown
Artemia has also been developed specifically for the use in freshwater ornamental fish farms. The system, using diluted artificial seawater of 20‰ for culture, has a mean production rate of 3 kg/m
3 of water in a 12-day cycle and a production capacity of 8 metric tons of on-grown
Artemia a year. With the system, farmers could produce any specific size of on-grown
Artemia of up to 5 mm to suit the age and size of their fish, by varying the time of harvesting. This characteristic, coupled with the use of bioencapsulation technique to enhance the quality of the on-grown
Artemia, would make the organism an ideal nursery diet for freshwater ornamental fish. All these results show that the live feeds used in marine foodfish hatchery could be applied to freshwater ornamental fish culture to improve their performance.
Blue mussel (
Mytilus edulis
) broodstock collected from the Irish Sea during wintertime (November) was conditioned with three different microalgae diets. Positive flagellates (PF) treatment ...consisted of
Pavlova lutherii
,
Isochrysis galbana
(T-Iso), and
Chaetoceros calcitrans
(1:1:1). Positive diatoms (PD) treatment consisted of
Pavlova lutherii, Chaetoceros calcitrans
, and
Skeletonema costatum
(1:1:1). Broodstock animals in the PF and PD treatments were fed a total of 2.4 × 10
11
algae cells per day. Animals in the negative flagellates (NF) treatment received only 1/8th of the total amount of algae of the PF diet. The conditioning diets had an impact on spawning success and broodstock fecundity but not on hatching rate, which was similar in all three groups. The best results were obtained with the PD diet where 84% of the conditioned animals spawned and females released 5.0 × 10
6
eggs on average. Animals belonging to the PF and NF treatments released, on average, only 3.6 × 10
6
and 1.6 × 10
6
eggs, respectively. Although the amounts of algae provided to the broodstock animals had no effect on the hatching rate, the D-larvae resulting from the NF treatment were smaller in size than the larvae from the other treatments. Biochemical analysis of the different broodstock groups at the end of the experiment revealed higher carbohydrate levels in group NF than in PF and PD, supporting the theory that gametogenesis is mainly supported by the energy from the glycogen reserves. As far as we are aware this is the first study describing hatchery broodstock conditioning of blue mussels under fully controlled conditions.
This study aimed at comparing fatty acid contents of rotifers cultured with different methods after nutritional enrichment in order to evaluate the rotifer quality produced by these methods. Rotifers ...were cultured using either a batch or a continuous culture. From the batch culture, three experimental subpopulations were used, sampled from the culture at 1, 24, and 48 h after rotifer inoculation. The continuous culture was performed with two tanks; one was for cultivation with continuous feeding and water supply (cultivation tank), and another was for harvesting from the cultivation tank by overflow (harvest tank). From the continuous culture, two subpopulations were used: one from the cultivation and one from the harvest tank. Nutritional enrichment was performed after each culture. Each population was enriched with Nannochloropsis oculata or a commercial enrichment diet. When the enrichment was performed with N. oculata on populations at 24 h after inoculation originating from either of the two tanks of continuous culture or the batch culture tank, a higher quantity of arachidonic acid (ARA) and eicosapentaenoic acid (EPA) was obtained from the two tanks of continuous culture. The same results obtained when enrichment diet was used, this including docosahexaenoic acid (DHA).
This study evaluated the effects of four microbes,
Candida parapsilosis
,
Pseudoalteromonas flavipulchra
,
Lactobacillus sakei
, and
Bacillus natto
on suppression of
Vibrio
, survival rate, enzyme ...activity, chemical composition, and microbial longevity in the brine shrimp,
Artemia franciscana
. Five treatments, including four experimental groups and a control group, each with four replicates, were studied. The concentration of 10
8
CFU mL
−1
of each mentioned strain was used to feed the nauplii for 2 weeks. The results demonstrated that the use of
L. sakei
,
P. flavipulchra
, and
B. natto
significantly suppressed the concentration of
Vibrio
over 5, 10, 15, and 20 h of enrichment respectively. From the selected microbes,
B. natto
and
L. sakei
were significantly colonized in the population and increased the enzyme activity. The longevity of
B. natto
in the
Artemia
was recorded as the best bacteria for long-term inoculation as after 8 days of starvation of
Artemia
, the count of
B. natto
was increased. The findings showed that
B. natto
appears to be a promising probiotic for
Artemia
in the suppression of
Vibrio
and also in increasing population growth, enzyme activity, and long-term colonization potential.
Eight tetracycline resistant Edwardsiella ictaluri isolates obtained from diseased freshwater catfish (Pangasianodon hypophthalmus) in Vietnam, and showing different resistance phenotypes to other ...antimicrobial agents, were studied. The tet genes were determined using PCR. Conjugation experiments were performed to assess transferability of the tetracycline resistance determinant and the size and incompatibility group (Inc) of each tet-carrying plasmid were determined. PCR and sequencing were used for characterization of the co-transferred resistance genes. A tetA gene was demonstrated in the E. ictaluri isolates and for all of them, Escherichia coli transconjugants were obtained. All transconjugants contained high-molecular weight tetA-carrying plasmids (~140kb) belonging to the incK group, as was shown with the PCR-based replicon typing method. The strA-strB, dhfr1 and sul 2 genes were detected on the tetA-carrying plasmids of the transconjugants showing resistance to streptomycin, trimethoprim and sulfonamides, respectively. The dhfr1 gene was found to be located in a class 1 integron as determined by PCR and sequencing. Interestingly, the 3' CS region of class 1 integrons was not detected by PCR. This study shows the presence of incK plasmid-mediated tetracycline resistance among E. ictaluri isolates from diseased freshwater catfish in Vietnam.
In this study, we report on the known Artemia habitats worldwide. Recent literature information is incorporated about the taxonomic status of the various populations studied. The genus is composed of ...di-, tri-, tetra- and pentaploid parthenogenetic populations and of the following bisexual species: A. franciscana franciscana, A. franciscana monica, A. franciscana sp., A. persimilis, A. salina, A. urmiana, A. sinica and A. sp. from Kazakhstan. The problems of characterizing new brine shrimp populations are discussed. In view of the great importance of Artemia as part of the live food chain for the culture of fish and shellfish larvae and the present cyst shortage from the market, the need for commercial exploitation and development of new Artemia sources is now, more than ever, necessary.
Because of the risk of antibiotic resistance development, there is a growing awareness that antibiotics should be used more carefully in animal production. However, a decreased use of antibiotics ...could result in a higher frequency of pathogenic bacteria, which in its turn could lead to a higher incidence of infections. Short-chain fatty acids (SCFAs) have long been known to exhibit bacteriostatic activity. These compounds also specifically downregulate virulence factor expression and positively influence the gastrointestinal health of the host. As a consequence, there is currently considerable interest in SCFAs as biocontrol agents in animal production. Polyhydroxyalkanoates (PHAs) are polymers of β-hydroxy short-chain fatty acids. Currently, PHAs are applied as replacements for synthetic polymers. These biopolymers can be depolymerised by many different microorganisms that produce extracellular PHA depolymerases. Interestingly, different studies provided some evidence that PHAs can also be degraded upon passage through the gastrointestinal tract of animals and consequently, adding these compounds to the feed might result in biocontrol effects similar to those described for SCFAs.
The massive (mis)use of antibiotics to control infections in aquaculture has resulted in the development of resistant strains, which have rendered antibiotic treatments ineffective. Moreover, the ...horizontal transfer of resistance determinants to human pathogens and the presence of antibiotic residues in aquaculture products for human consumption constitute important threats to public health. Therefore, to make the aquaculture industry more sustainable, new strategies to control infections are urgently needed.
•The product Tex-OE® releases reactive oxygen species (ROS).•Tex-OE®-generated ROS are the stimuli responsible for Hsp70 induction in Artemia.•Tex-OE® acts prophylactically by inducing resistance ...against pathogenic vibrios.•The product elicits innate immune genes transcription, such as proPO and tgase.•Increased Vibrio-protection suggests Hsp70-mediated activation of immune system.
The cytoprotective role of heat shock protein (Hsp70) described in a variety of animal disease models, including vibriosis in farmed aquatic animals, suggests that new protective strategies relying upon the use of compounds that selectively turn on Hsp genes could be developed. The product Tex-OE® (hereafter referred to as Hspi), an extract from the skin of the prickly pear fruit, Opuntia ficus indica, was previously shown to trigger Hsp70 synthesis in a non-stressful situation in a variety of animals, including in a gnotobiotically (germ-free) cultured brine shrimp Artemia franciscana model system. This model system offers great potential for carrying out high-throughput, live-animal screens of compounds that have health benefit effects. By using this model system, we aimed to disclose the underlying cause behind the induction of Hsp70 by Hspi in the shrimp host, and to determine whether the product affects the shrimp in inducing resistance towards pathogenic vibrios. We provide unequivocal evidences indicating that during the pretreatment period with Hspi, there is an initial release of reactive oxygen species (hydrogen peroxide and/or superoxide anion), generated by the added product, in the rearing water and associated with the host. The reactive molecules generated are the triggering factors responsible for causing Hsp70 induction within Artemia. We have also shown that Hspi acts prophylactically at an optimum dose regimen to confer protection against pathogenic vibrios. This salutary effect was associated with upregulation of two important immune genes, prophenoloxidase and transglutaminase of the innate immune system. These findings suggest that inducers of stress protein (e.g. Hsp70) are potentially important modulator of immune responses and might be exploited to confer protection to cultured shrimp against Vibrio infection.
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