Spatial learning-induced <Emphasis Type="Italic">egr</Emphasis>-<Emphasis Type="Italic">1</Emphasis> expression in telencephalon of gold fish <Emphasis Type="Italic">Carassius auratus</Emphasis>

The immediate-early gene (egr-1) expression was used to examine the neuron’s response in telencephalon of goldfish during spatial learning in small space. Fishes were pre-exposed in the experimental apparatus and trained to pick food from the tray in a rectangular-shaped arena. The apparatus was divided into identical compartments comprising three gates to provide different spatial tasks. After the fish learned to pass through the gate one, two more gates were introduced one by one. Fish made more number of attempts and took longer time (P < 0.05) to pass through the first gate than the gate two or three. This active learning induces the expression of egr-1 in telencephalon as established by western blot analysis. Subsequently, the fish learn quickly to cross the similar type of second and third gate and make fewer errors with a corresponding decline in the level of egr-1 expression. As the fish learned to pass through all the three gates, third gate was replaced by modified gate three. Interestingly, the level of egr-1 expression increased again, when the fish exhibit a high exploratory behavior to cross the modified gate three. The present study shows that egr-1 expression is induced in the telencephalon of goldfish while intensively acquiring geometric spatial information to pass through the gates.     

Monitoring of <Emphasis Type="Italic">Francisella noatunensis</Emphasis> subsp. <Emphasis Type="Italic">orientalis</Emphasis> in farmed Nile tilapia (<Emphasis Type="Italic">Oreochromis niloticus</Emphasis>) in Brazil

Francisella noatunensis orientalis is a bacterium that causes emerging bacteriosis in Nile tilapia (Oreochromis niloticus) in many parts of the world, including Brazil. It is a non-motile, Gram-negative, strictly aerobic, facultative intracellular coccobacillus. This species of bacteria is responsible for low to high mortality in fish farms, causing economic losses for fish farmers. This study aimed to detect the presence of F. noatunensis orientalis using qPCR (real-time polymerase chain reaction) and to describe lesions caused by the bacterium in O. niloticus in Brazilian aquaculture. For this purpose, 360 fish from six fish farms (30 per farm) were sampled at two time points (n = 180 per sampling). Necropsies and histopathology were performed for lesion observation, in addition to qPCR and sequencing for detection and identification of Francisella species. Environmental data were collected using a multiparameter sonde YSI EXO2. All measured limnological variables were within the optimum range for cultivation of Nile tilapia. The major lesions present were melanization of the skin, splenomegaly, granulomas, and inflammatory cell responses. The prevalence of francisellosis varied from 0 to 86.66% between time periods and fish farms analyzed, and an outbreak was observed during the second sampling period. This study describes the prevalence of francisellosis in O. niloticus and reports that the lesions found are not exclusively associated with this bacterial disease.     

Anti-oxidative functions of <Emphasis Type="Italic">mt2</Emphasis> and <Emphasis Type="Italic">smtB</Emphasis> mRNA expression in the gills and brain of zebrafish (<Emphasis Type="Italic">Danio rerio</Emphasis>) upon cadmium exposure

There were not any past studies about metallothionein isoforms (smtB and mt2) having anti-oxidative functions on zebrafish after Cd²⁺ exposure. On the other hand, the anti-oxidative enzymatic factors such as superoxide dismutase (sod), glutathione peroxidase (gpx1a), and catalase (cat) are used as references to investigate whether the smtB and mt2 have anti-oxidative responses on the gills and brain of zebrafish after 1–6 h of 0 and 1.78 μM Cd²⁺ exposure. The anti-oxidative system such as sod, cat, and gpx1a mRNA expressions demonstrated a cascade response upon Cd²⁺-induced oxidative stress in the present study. Interestingly, the smtB mRNA expression levels increased by 3.2- to 6.1-fold, and mt2 raised by 4.1- to 11.3-fold in gills at 1 and 3 h after exposure to Cd²⁺, respectively. On the other hand, the smtB mRNA levels increased by 10.6- to 58.6-fold, but mt2 mRNA levels increased by 2.3- to 11.1-fold in brain at 1 and 3 h after exposure to Cd²⁺, respectively. In addition, both tissues showed increased apoptosis levels at 3 h, and recovery after 6 h of Cd²⁺ exposure. From the results, we suggest that both mt2 and smtB play a role in anti-oxidation responses within 6 h after exposure to Cd²⁺. In conclusion, the smtB mRNA levels have a higher response than mt2 in the brain, but both mRNA expressions appear to have a similar pattern in the gill. We suggest that smtB plays an important role to defend oxidative stress in the brain of adult zebrafish upon acute Cd²⁺ exposure.     

Potential of cinnamon (<Emphasis Type="Italic">Cinnamomum verum</Emphasis>) oil to control <Emphasis Type="Italic">Streptococcus iniae</Emphasis> infection in tilapia (<Emphasis Type="Italic">Oreochromis niloticus</Emphasis>)

In this study, four essential oils—cinnamon oil, leech lime oil, lemongrass oil, and turmeric oil—were examined for their antimicrobial activities against Streptococcus iniae, a bacterium that is pathogenic in fish, in which it causes streptococcosis. Cinnamon oil was the most potent antimicrobial agent among these oils, with a minimal inhibitory concentration (MIC) of 40 μg/ml. By using gas chromatography–mass spectrometry (GC–MS), it was found that the major components of cinnamon oil were cinnamaldehyde (90.24), limonene (2.42%), cinnamyl acetate (2.03%), linalool (1.16%), and α-terpineol (0.87%). Of these compounds, only cinnamaldehyde exhibited antimicrobial activity against S. iniae, with an MIC of 20 μg/ml. In an in vivo trial, no mortality was apparent in fish fed on fish diets supplemented with 0.4% (w/w) of cinnamon oil and with 0.1% (w/w) of oxytetracycline 5 days prior to infection with S. iniae. These results indicate that cinnamon oil had a protective effect on experimental S. iniae infection in tilapia, and thus has the potential to replace the antibiotics used to control this disease.     

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.     

Anesthesia induces stress in Atlantic salmon (<Emphasis Type="Italic">Salmo salar</Emphasis>), Atlantic cod (<Emphasis Type="Italic">Gadus morhua</Emphasis>) and Atlantic halibut (<Emphasis Type="Italic">Hippoglossus hippoglossus</Emphasis>)

Stress in response to anesthesia with benzocaine, MS-222, metomidate and isoeugenol was studied in Atlantic salmon (Salmo salar), Atlantic halibut (Hippoglossus hippoglossus), and Atlantic cod (Gadus morhua) with no concomitant stress from handling or confinement in association with anesthesia or sampling. All of the anesthetics tested induced a stress response in all species, displayed by a release of cortisol to the water. MS-222 anesthesia elicited the highest cortisol release rates, reaching maximum levels 0.5 h post-exposure and returning to basal levels after 3–4 h. Benzocaine anesthesia caused a bimodal response where the initial peak in cortisol release rate was followed by a second increase lasting towards the end of the trial (6 h). This bimodality was more profound in Atlantic salmon than in Atlantic halibut and Atlantic cod. Metomidate anesthesia induced the lowest release of cortisol of the agents tested in both Atlantic halibut and Atlantic cod, but resulted in a bimodal response in Atlantic salmon where the initial increase in cortisol release was followed by a larger increase peaking at 2–2.5 h post exposure before returning to basal levels after 5 h. The stress induced in Atlantic salmon by isoeugenol anesthesia resembled that of MS-222, but did not reach the same elevated level. Overall, the cortisol release was most profound in Atlantic salmon followed by Atlantic halibut and Atlantic cod.     

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.     

Demographic and competition studies on <Emphasis Type="Italic">Brachionus ibericus</Emphasis> and <Emphasis Type="Italic">Proales similis</Emphasis> in relation to salinity and algal (<Emphasis Type="Italic">Nannochloropsis oculata</Emphasis>) density

We isolated the rotifers Brachionus ibericus and Proales similis from the sediment of shrimp tanks and studied their individual demographic characters and competition between them at two food levels (0.25?×?10⁶, 1.00?×?10⁶ cells ml^?1 of Nannochloropsis oculata at 25 °C) and salinities ranging from 10 to 30‰. Our hypothesis was that growth rates would be higher with increasing food levels and salinities. Observations were taken twice a day for life table studies and daily once for population growth experiments. Using survivorship and fecundity data, we derived various life history variables. Although the average life span (7.6?±?0.4 days) and gross reproductive rate (33.8?±?2.9 neonate female^?1 day^?1) of B. ibericus were higher than those of P. similis (average life span 5.4?±?0.6 days and gross reproductive rate 13.0?±?0.6 neonate female^?1 day^?1), the population growth experiments showed that P. similis had higher r values (0.32?±?0.005 day^?1) than B. ibericus (0.23?±?0.002 day^?1) at 1.0?×?10⁶ cells ml^?1 of N. oculata. The rotifer P. similis was more adversely affected due to the presence of B. ibericus than vice versa. The data are important for developing techniques for a large-scale culture of these rotifers as food in aquaculture.     

Tissue-specific daily variation in the oxidative status of sturgeon (<Emphasis Type="Italic">Acipenser naccarii</Emphasis>) and rainbow trout (<Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>): a comparative study

The oxidative status is associated with animal lifespan, metabolism, activity and circadian rhythms. The objective of this work is to study the time course of the oxidative status over a daily cycle in the plasma, liver and brain, and the changes in the plasma cortisol levels of sturgeon and trout. The knowledge of daily oxidative status will provide a better understanding of the trout and sturgeon physiology and adequate maintenance and food supply of farmed fish in relation to photoperiod. Superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione transferase, DT-diaphorase activities, lipid peroxidation and cortisol were measured. Our results showed that the antioxidative enzyme activities and lipid peroxidation in the liver of trout and sturgeon changed through the day, with increased levels in lipid peroxidation of liver in the dark period for sturgeon. This could be related to the different activity time in both species, an issue to be taken into account when designing the guidelines of the maintenance of these species in fish farms. On the contrary, there was not clear influence of the daily rhythms on brain oxidative status. The higher efficiency of the antioxidant defences in the brain of sturgeon, which displays less lipid peroxidation and higher antioxidative activity, could be related to its longer life expectancy. The absence of any apparent daily rhythm in the plasma cortisol levels in sturgeon could indicate a lower susceptibility to stress, and that mechanisms involved in cortisol secretion in chondrosteans could be different from that described for teleosteans.     

Characterization of <Emphasis Type="Italic">kiss2</Emphasis> and <Emphasis Type="Italic">kissr2</Emphasis> genes and the regulation of kisspeptin on the HPG axis in <Emphasis Type="Italic">Cynoglossus semilaevis</Emphasis>

Reproduction allows organisms to produce offspring. Animals shift from immature juveniles into mature adults and become capable of sexual reproduction during puberty, which culminates in the first spermiation and sperm hydration or ovulation. Reproduction is closely related to the precise control of the hypothalamic–pituitary–gonadal (HPG) axis. Kisspeptin peptides are considered as the important regulator of HPG axis in mammalian. However, the current understanding of kisspeptin in flatfish is not comprehensive. In this study, we cloned and analyzed the kiss2 and kissr2 genes in Cynoglossus semilaevis. Interesting alternative splicing in the 5′-untranslated regions (UTR) of the Cskissr2 gene was found. The expression profiles of Cskiss2 and Cskissr2 showed relative high messenger RNA (mRNA) levels at the late gastrula stage during embryonic development, at total length = 40 mm during early gonadal differentiation, and in the brains and gonads of all investigated tissues. These results suggested that the kisspeptin system participated in embryogenesis and in the regulation of gonadal differentiation and development. Considering that the control and regulatory mechanisms of kisspeptin in the central reproductive axis are still unclear, we documented that the intramuscular injection of kisspeptin caused different sGnRH and cGnRH mRNA levels in a dose- and tissue-dependent manner. The mRNA expressions of FSH and LH were stimulated in the ovary and were inhibited in the testis under the kisspeptin treatments. These results provided foundations for understanding the roles of kisspeptin in the neuroendocrine system in fish. The manipulation of the kisspeptin system may provide new opportunities to control the gonadal development and even reproduction in fish.     

Farming evaluation of the brownbow triploid hybrid (<Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis><Emphasis Type="Italic">Salmo trutta</Emphasis>)

Triploid hybrids between female rainbow trout (Oncorhynchus mykiss Walbaum) and male brown trout (Salmo trutta L.) were tested for farming performances, with reference to parental species. The main drawback of hybrids lay in embryonic and larval mortalities, amounting to 60% on average, and displaying a large variability between spawns. Further survival was inferior to that of diploid, but similar to that of triploid rainbow trout. Hybrid body weight was intermediate between weights of rainbow and brown trout of the same age, mainly as a consequence of differences in precocious growth. Analysis of relative growth rates from 6 to 18 months showed that hybrids were surpassed by rainbow controls in common rearing, but not in separate rearing. Hybrid behaviour was similar to that of rainbow trout. These results are discussed in the scope of providing fisheries managers with original and sterile game fishes. An erratum to this article can be found at .     

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.     

Expression of <Emphasis Type="Italic">mep50</Emphasis> in adult and embryos of medaka fish (<Emphasis Type="Italic">Oryzias latipes</Emphasis>)

Protein arginine methylation is important for gene regulation and biological processes. Methylosome protein 50 (Mep50) is identified as a partner of protein arginine methyltransferase 5 (Prmt5), a major enzyme capable of symmetric dimethylation, in mammals and Xenopus. The isolation and characterization of medaka mep50 were reported in this paper. Medaka Mep50 is a homolog of human MEP50 with six WD40 domains. Medaka mep50 was ubiquitously expressed in the adult tissues and had maternal origin with continuous and dynamical expression during embryonic development detected by RT-PCR and in situ hybridization. A strong interaction of medaka Mep50 and Prmt5 was shown by yeast two hybridization. The expression pattern of mep50 is similar to that of prmt5 in medaka. The results suggested that medaka Mep50 could be a partner of Prmt5 and might play major roles in a variety of tissues in medaka.