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Male and female zebra fish Danio rerio were given choices of shoals that differed in sex and size. Male zebra fish preferred to associate with female shoals over male shoals, but had no preference when given a choice between a mixed-sex shoal and either a male or female shoal. Female zebra fish showed no significant preference when given a choice between male and females shoals, nor between mixed-sex shoals and either male or female shoals. When given choices between shoals of differing size, females preferred to associate with the larger shoal, whether or not they were composed of males or females. Males, however, had no preference for larger shoals over smaller shoals, whether or not they were composed of males or females. These results showed that male zebra fish were capable of distinguishing between males and females solely on the basis of visual cues. Furthermore, these results demonstrated a significant difference between the shoaling choices of male and female zebra fish, which may indicate a difference in the function of shoaling for the two sexes. [ABSTRACT FROM AUTHOR]

This study aimed to explore the reproductive histology and oocyte differentiation of the longnose seahorse Hippocampus trimaculatus (Leach, 1814) in captivity. Five mature healthy females were histologically observed. The reproductive systems of the five specimens exhibited similar morphological characteristics with a pair of saccular creamy white ovaries merging caudally into a single gonoduct. There were two germinal ridges lined with a layer of germinal epithelium (GE). The ovarian maturation of this species was considered asynchronous. The oogenic cells were classified into oogonia and oocytes at several developmental phases based on their size and characteristics. Oogonia were identified among the connective tissue in the middle area of the GE. The stromal compartment contained oocytes that were classified into four distinct phases: the primary growth (PG) phase having two steps (perinucleolar and oil droplets-cortical alveolar steps) and the secondary growth (SG) phase with three oocyte types, including early SG oocytes, late SG oocytes, and fully grown oocytes. The atretic oocytes (AO) were observed in all stages of oogenesis. Postovulatory follicles were also seen among the ovarian connective tissue. The occurrence of postovulatory follicles suggested that the specimens analysed in this study were in the spawning period. This research provides new insights into the identification of the reproductive cycles and morphological characteristics of the ovary of H. trimaculatus., (© 2024 Fisheries Society of the British Isles.)

The outbreaks of fungal diseases in cultured fish have been severe in recent years, which is harmful to the healthy and sustainable development of fish farming. In this study, an investigation was conducted for significant fungal infections of 12 species of fish in four regions in Xinjiang, China, to understand the distribution of local fish fungal pathogens. Twenty-six fungal strains with pathogenicity were isolated, and the challenge experiment showed that eight strains from Changji area had high infection rate to fish eggs. Based on internal transcribed spacer sequence data and molecular analysis, the 26 strains were classified into nine different species of six fungal genera. Phylogenetic analysis showed that all strains were divided into two clades, namely Cluster 1 (contains only the genus Mucor) and Cluster 2 (consists of five small branches), and the distribution of strains from the same region was scattered in two clusters. There is no strict host selectivity for these fungi to infect fish. Mucor sp. are the main fungal pathogen of fish in these four regions, whereas Hypophthalmichthys molitrix and Carassius auratus are two types of fish that were susceptible to pathogen. In addition, the environmental adaptability experiments showed that eight highly pathogenic strains have different adaptability to the environment, and their optimum temperature and pH were 25°C and 7.0, respectively, whereas the concentration of NaCl was negatively correlated with the growth of strains. Therefore, these results indicated that the coinfection of multiple fungal pathogens in a culture region should be considered in the future study., (© 2021 Fisheries Society of the British Isles.)

The skin color of the large yellow croaker (Larimichthys crocea) is a crucial indicator to determine its economic value. However, the location of pigment cells in the skin structure is uncertain. To determine the pigment cell type in the skin, the vertical order and ultrastructure of pigment cells were examined using light microscopy and transmission electron microscopy. Both dorsal and ventral skins comprise the epidermis, dermis, and hypodermis. Xanthophores, melanophores, and iridophores were observed in the dermis of the dorsal skin, whereas the latter two were in the dermis of the ventral skin. Interestingly, the size of xanthophores in the dorsal skin was significantly smaller than that of xanthophores in the ventral skin; however, the density of dorsal xanthophores was significantly higher than that of ventral xanthophores. The type L-iridophores with large crystalline structures were observed in the uppermost area of the upper pigment layer, which contributed to the strikingly metallic luster shown by the ventral skin. The melanophores were exclusively found in the dorsal skin, offering the purpose of camouflage. Taken together, our results indicated that the pigment cells display different arrangement patterns between dorsal and ventral skin, and the golden color in the ventral skin results from the coexistence of light-reflecting iridophores and light-absorbing xanthophores., (© 2024 Fisheries Society of the British Isles.)

Gynogenetic embryos – those inheriting only maternal DNA – can be experimentally created by fertilizing eggs with radiation‐treated sperm containing inactivated paternal chromosomes. Diploidy in the zygotes can be maintained through prevention of the second meiosis or restored by preventing the first mitosis after the maternal chromosome complement has been replicated. These gynogenetic organisms are useful in many fields including aquaculture, evolutionary biology and genomics. Although gynogenetic organisms have been created in numerous species, the completeness of uni‐parental inheritance has often been assumed rather than thoroughly quantified across the genome. Instead, when tests of uni‐parental inheritance occur, they typically rely on well‐studied genetically determined phenotypes that represent a very small sub‐set of the genome. Only assessing small genomic regions for paternal inheritance leaves the question of whether some paternal contributions to offspring might still have occurred. In this study, the authors quantify the efficacy of creating gynogenetic diploid three‐spined stickleback fish (Gasterosteus aculeatus). To this end, the authors mirrored previous assessments of paternal contribution using well‐studied genetically determined phenotypes including sex and genetically dominant morphological traits but expanded on previous studies using dense restriction site‐associated DNA sequencing (RAD‐seq) markers in parents and offspring to assess paternal inheritance genome‐wide. In the gynogenetic diploids, the authors found no male genotypes underlying their phenotypes of interest – sex and dominant phenotypic traits. Using genome‐wide assessments of paternal contribution, nevertheless, the authors found evidence of a small, yet potentially important, amount of paternally "leaked" genetic material. The application of this genome‐wide approach identifies the need for more widespread assessment of paternal contributions to gynogenetic animals and promises benefits for many aspects of aquaculture, evolutionary biology and genomics. [ABSTRACT FROM AUTHOR]

Despite the use of Terminalia catappa (TC) leaf by traditional fish farmers around the world to improve the health status of cultured fish, there is a paucity of information on comprehensive metabolite profile and the maximum safe dose of the plant. This study aims at profiling the methanol leaf extract of T. catappa, quantifying total phenolic content (TPC) as well as the total flavonoid content (TFC) and evaluating its acute toxicity on blood, plasma biochemical parameters and histopathology of some vital organs in red hybrid tilapia (Oreochromis sp.). The experimental fish were acclimatised for 2 weeks and divided into six groups. Group (1) served as a control group and was administered 0.2 ml,g−1 of phosphate buffer saline (PBS). Groups 2–6 were orally administered T. catappa leaf extracts (0.2 ml.50 g−1) in the following sequence; 31.25, 62.5, 125, 250 and 500 mg.kg−1 body weight. The metabolites identified in T. catappa using liquid chromatography‐tandem mass electrospray ionisation spectrometry (LC‐ESI‐MS/MS) revealed the presence of organic acids, hydrolysable tannins, phenolic acids and flavonoids. Phenolic quantification revealed reasonable quantity of phenolic compounds (217.48 μg GAEmg−1 for TPC and 91.90 μg. QCEmg−1 for TFC). Furthermore, there was no significant difference in all the tested doses in terms of blood parameters and plasma biochemical analysis except for the packed cell volume (PCV) at 500 mg.kg−1 when compared to the control. Significant histopathological changes were observed in groups administered with the extract at 125, 250 and 500 mg.kg−1 doses. To a very large extent it is therefore safe to administer the extract at 31.25 and 62.5 mg.kg−1 in tilapia. [ABSTRACT FROM AUTHOR]

Larval growth and survival of catfishes are largely influenced by the various biotic and abiotic factors. The present study investigated the effect of different light intensities and photoperiods on growth and survival of Ompok bimaculatus larvae. Three separate trials of 21 days each were carried out in an aquarium tank. The first trial investigated the embryonic changes (based on hatching rate and time) upon exposure to varied light intensity (0, 300, 500, 900 and 1200 lx) and photoperiodic regime (24l:0d, 16l:8d, 12l:12d, 8l:16d and 0l:24d). Subsequently, hatched-out larvae were subjected to the aforementioned intensities (Trial II) and photoperiod (Trial III, intensity of 300 lx) for growth and survival attributes. Eight hundred healthy larvae (average body weight = 0.003 g) were randomly distributed into five treatment groups for the last two trials. Results suggest a higher embryo hatching rate and larval survival at 0 and 300 lx, whereas the largest larval growth was observed at 900 lx. In Trial III, survival was highest in 0l:24d and growth in 24l:0d and 16l:8d was higher (P < 0.05). Performance index was higher (P < 0.05) in both 0 and 300 lx light and decreased at higher intensities. The overall interpretation from the present study concludes that a completely dark rearing environment is recommended for better survival of O. bimaculatus although growth was compromised., (© 2020 The Fisheries Society of the British Isles.)

Surface‐dwelling C. catla were exposed to different photoperiods (8L:16D, 12L:12D, 12D:12L and 16L:8D) and the mRNA level profile of enzymes involved in melatonin synthesis was evaluated in the pineal gland and retina. Furthermore, a comparative analysis of the serum melatonin profile with the mRNA level was also performed. The results indicated diurnal variations in the transcripts of tph1, aanat and hiomt in the pineal organ and retina, and these variations change with the change in lighting regime. The serum melatonin profile showed rhythmicity in the natural photoperiod, but the serum melatonin level increased proportionally with increasing daylength. In short photoperiods, the peak value (though lower than in long photoperiods) of melatonin maintains a longer duration in serum. Moreover, the comparative analysis revealed a similar profile of mRNA of pineal aanat1 and aanat2 with serum melatonin under the same lighting conditions. This indicates that serum melatonin is produced by the pineal gland. Our results specify the importance of day length and the timing of onset or offset of the dark for maintaining the oscillating levels of serum melatonin and mRNA levels of melatonin biosynthesizing enzyme genes in the pineal organ and retina as well. The findings in this study highlight the distinctive pattern of mRNA levels in the pineal organ and retina under different photoperiods. The pineal melatonin biosynthesizing enzyme genes showed a similar pattern with serum melatonin levels while the retinal genes changed dramatically with photoperiod. We also revealed a light‐dependent transcriptional regulation of pineal aanat genes in C. catla. Moreover, our results suggest that ALAN and skyglow can influence the levels of serum melatonin and its biosynthesis, resulting in desynchronization of the entire biological clock as well as the overall physiology of the animal. [ABSTRACT FROM AUTHOR]

Two experiments were conducted to investigate the in vitro effects of Eucommia ulmoides (E. ulmoides) and its active components on the growth, lipid metabolism and collagen metabolism of grass carp's (Ctenopharyngodon idellus) hepatocytes and intramuscular fibroblasts. In experiments 1 and 2 (Expt. 1, 2), hepatocytes and intramuscular fibroblasts were treated with 2.5, 5, 10, 20, 40 and 80 μg ml–1 of Eucommia bark extract (EBE), Eucommia leaf extract (ELE), pinoresinol diglucoside (PDG), chlorogenic acid (CGA), quercetin (QC) and aucubin (AU) for 24 h, respectively, then the cell growth, lipid and collagen metabolism‐related gene expressions were evaluated. The results showed that the cell proliferation rate of hepatocytes and intramuscular fibroblasts was significantly improved by the supplementation of EBE, ELE, CGA, QC and AU. Moreover, triglyceride concentration of hepatocytes was significantly decreased by the EBE, ELE, CGA and QC supplementations compared to the control. Meanwhile, EBE, ELE, CGA, QC and AU supplementations significantly upregulated the relative gene expressions of insulin‐like growth factor‐1 (igf1), protein kinase B (akt), target of rapamycin (tor) and eukaryotic initiation factor 4E binding protein 1 (4ebp1) in hepatocytes, and ribosomal protein S6 kinase 1 (s6k1) transcription was significantly activated by ELE, CGA and QC supplementations. Nonetheless, phosphatidylinositol 3‐kinase (pi3k) was unaffected by any of the supplements. In addition, the mRNA expressions of genes associated with lipid metabolism (peroxisome proliferator activated receptor α pparα, carnitine palmitoyltransferase 1 cpt1, adipose triglyceride lipase atgl, hormone‐sensitive lipase hsl, peroxisome proliferator activated receptor γ pparγ) were significantly upregulated by EBE, ELE, CGA and QC. In intramuscular fibroblasts, the EBE, ELE, CGA, QC and AU supplementations significantly increased in vitro hydroxyproline concentrations, promoted the relative expressions of transforming growth factor‐β1 (tgfβ1), connective tissue growth factor (ctgf), collagen type I alpha 1/2 chain (col1a1, col1a2), lysine oxidase (lox) and tissue inhibitor of matrix metalloproteinase‐2 (timp2), and decreased matrix metalloproteinase‐2 (mmp2) gene expression. Also, the gene expressions of drosophila mothers against decapentaplegic protein 2/4 (smad2, smad4) and proline hydroxylase (phd) were significantly upregulated by ELE, CGA, QC and AU supplementations. Based on the present in vitro results of grass carp, EBE, ELE, CGA, QC and AU improved the growth and lipid metabolism (except AU) in hepatocytes, and promoted the collagen deposition in intramuscular fibroblast, which is partly attributed to the signalling pathways of AKT/TOR, PPARα and TGF‐β/Smads/CTGF. [ABSTRACT FROM AUTHOR]

The authors studied the morphology of the upper and lower jaws, vertebrae and dorsal‐fin rays of the teleost fish Xiphias gladius to analyse the skeletal architecture and ossification pattern. The analogies and differences among these segments were investigated to identify a common morphogenetic denominator of the bone tissue osteogenesis and modeling. The large fat glands in the proximal upper jaw and their relationship to the underlying cartilage (absent in the lower jaw) suggested that there is a mechanism that explains rostral overgrowth in the Xiphiidae and Istiophoriidae families. Thus far, the compact structure of the distal rostrum has been interpreted as being the result of remodeling. Nonetheless, no evidence of cutting cones, scalloped outer border of osteons and sequence of bright–dark bands in polarized light was observed in this study, suggesting a primary osteon texture formed by compacting of collagen matrix and mineral deposition in the fat stroma lacunae of the bone, but without being oriented in layers of the collagen fibrils. A similar histology also characterizes the circular structures present in the other examined segments of the skeleton. The early phases of fibrillogenesis carried out by fibroblast‐like cells occurred farther from the already‐calcified bone surface inside the fat stroma lacunae. The fibrillar matrix was compacted and underwent mineral deposition near the previously calcified bone surface. This pattern of collagen matrix synthesis and calcification was different from that of mammalian osteoblasts, especially concerning the ability to build a lacuno‐canalicular system among cells. Necrosis or apoptosis of the latter and refilling of the empty lacunae by mineral deposits might explain the anosteocytic bone formation. [ABSTRACT FROM AUTHOR]

The present study was undertaken to investigate the adverse effects of mercuric chloride (HgCl2) overload in the fish Channa punctatus. Two sublethal test concentrations of HgCl2 (1/20th and 1/10th of 96 h LC50i.e., 0.03 mg l−1 (low concentration) and 0.07 mg l−1 (high concentration), respectively, were used for exposure. Blood, liver and kidney tissues of the control and exposed specimens were sampled at intervals of 15, 30, and 45 days to assess alterations in oxidative stress, genotoxicity haematological parameters and histopathology. Significant changes in Hb%, RBC count, WBC count, antioxidant enzyme activity, i.e., superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) and glutathione reductase (GR), were recorded. Micronuclei (MN) induction, nuclear abnormalities (NAs) and histopathological alterations were also observed in the exposed fish. Significant (P < 0.05) increase in the activities of SOD, CAT, GSH and GR was observed. After 45 days, a decrease in the level of GSH and GR was noticed which suggests an undermined anti‐oxidative defence system in the fish exposed to HgCl2. Histological examination of the liver and kidney showed serious tissue injury and histological alterations. Significant increases in MN and NA frequencies reveal the DNA damage in erythrocytes of fish, and haematological changes show the toxicological potential of HgCl2. The observed changes in the antioxidant defence system, genotoxicity and haematological and histological changes in the present study provide the most extensive insight into HgCl2 stress in C. punctatus. [ABSTRACT FROM AUTHOR]

The mandarin fish (Siniperca chuatsi) DNA methyltransferase gene 1 (dnmt1) was highly expressed in the mesonephros, head kidney and gonad, whereas dnmt2 was expressed in most tissues. dnmt3a was highly expressed in the brain and spleen, but dnmt3b was mainly expressed in the brain and head kidney. The genes dnmt1 and dnmt2 were highly expressed in the early stages of embryonic development, and dnmt3a and dnmt3b were expressed later. These genes also showed certain changes after artificial diet acclimation, salinity adaptation and immune stress. [ABSTRACT FROM AUTHOR]

Selenium, as an essential trace element, interferes through selenoproteins in many physiological processes of plants and mammals. Its antiviral activity has recently attracted much attention because selenium improves the antiviral capacity of animal cells against a few viruses relevant to human diseases. In this study, the red elemental selenium was purified from the fermentative culture of Herbaspirillum camelliae WT00C and then used to culture epithelioma papulosum cyprinid (EPC) cells or feed crucian carp and zebrafish. Finally, its antiviral effects were investigated at the cell level and living fishes after spring viraemia of carp virus infection. At the cell level, 5, 10 and 20 μg ml–1 red elemental selenium significantly induced the expression of interferon (IFN) and ISG15 genes in EPC cells. The viral TCID50 (50% tissue culture infective dose) values in the EPC cells incubated with 5, 10 and 20 μg ml–1 red elemental selenium were significantly less than those of the control. More expression of IFN and ISG15 genes and less TCID50 values indicate that red elemental selenium indeed improves the antiviral capability of EPC cells. In the crucian carp fed with the food containing 5 and 10 μg g–1 red elemental selenium, IFN expressions showed 13‐ and 39‐fold increases at the 16th day of post‐injection, and its expression was dependent on selenium concentrations. Meanwhile, no fish death occurred in all the experimental groups. In the zebrafish fed with the red worm containing 5 μg g–1 red elemental selenium, IFN and Mx expressions and survival rate were significantly higher than those of the control. The results of this study show that red elemental selenium indeed improves the antiviral activity of fish. The antiviral effects of selenium mainly come from its immune regulation through its incorporation into selenoproteins. The optimum level of selenium contributes to improving fish immunity, whereas excess selenium causes excessive immune and inflammatory responses. [ABSTRACT FROM AUTHOR]

Boldness and risk‐taking behaviours in animals are important traits to obtain advantages such as habitation, food resources, reproductive success and social dominance. Risk‐taking behaviour is influenced by physiological and environmental conditions; however, whether individual fish become bolder by the presence of conspecifics remains unknown. In this study, a light–dark preference test was conducted using medaka fish (Oryzias latipes) with or without a neighbouring conspecific. It was found that individual medaka male fish preferred a light environment and avoided a dark environment, whereas the display of a neighbouring conspecific enhanced the time the male spent in the dark environment (i.e., this condition encouraged risk‐taking). The blood glucose level increased in fish confined to the dark condition but did not increase in light‐preferring fish and risk‐taking fish. Large somata expressing tyrosine hydroxylase, which is the rate‐limiting enzyme in dopamine synthesis, were detected in the telencephalic and diencephalic brain regions in risk‐taking medaka, whereas large somata were detected in the diencephalic region in medaka confined to the dark condition. These findings indicated that medaka is a good fish model to explore the central roles of dopaminergic neurons in the telencephalon and the diencephalon, which regulate risk‐taking behaviour. [ABSTRACT FROM AUTHOR]

Environmental enrichment involves increasing the complexity of a fish's environment in order to improve welfare. Researchers are legally obliged to consider the welfare of laboratory animals and poor welfare may result in less robust data in experimental science. Laboratory zebrafish Danio rerio are usually kept in bare aquaria for ease of husbandry and, despite being a well‐studied species, little is known about how laboratory housing affects their welfare. This study shows that environmental enrichment, in the form of the addition of gravel substratum and plants into the tank, affects survivorship, growth and behaviour in laboratory‐maintained D. rerio. Larvae reared in enriched tanks had significantly higher survivorship compared with larvae reared in bare tanks. Effects of the tank conditions on growth were more variable. Females from enriched tanks had a higher body condition than females maintained in bare tanks, but intriguingly this was not the case for males, where the only difference was a more variable body condition in males maintained in bare tanks. Sex ratio in the rearing tanks did not differ between treatments. Resource monopolisation was higher for fish in enriched tanks than for those in bare tanks. Fish from enriched tanks displayed lower levels of behaviours associated with anxiety compared with fish from bare tanks when placed into a novel environment. Thus, this study demonstrates differences in welfare for D. rerio maintained under different environmental conditions with enhancements in welfare more commonly associated with tank enrichment. [ABSTRACT FROM AUTHOR]

Gynogenetic zebrafish Danio rerio were obtained by activating D. rerio oocytes with UV irradiated common carp Cyprinus carpio sperm and then applying one of four different shocks [two (early) meiotic and two (late) mitotic shocks]. Gynogens produced by three of the shocks survived to maturity. All adult gynogens (n = 52) except one were found to be male. There was no difference in growth rate between the biparental controls and gynogens produced through the most effective shock, thereby eliminating growth rate as a possible cause of the skewed sex ratio. Gynogen males had reduced fertility compared to biparental controls, with about half of gynogens being unable to reproduce through natural spawning (all controls reproduced successfully). Gynogen males that did reproduce gave lower fertilization rates compared with controls. This demonstrates the negative effects of increased homozygosity on male reproductive function. Families sired by meiotic gynogen males were more likely to be female biased (33% of families) compared with families sired by biparental control males (11%). In addition to confirming the polygenic nature of sex determination in D. rerio, these observations suggest that recessive or over‐dominant male‐determining alleles are present in domesticated D. rerio populations. [ABSTRACT FROM AUTHOR]

Selenium, as an essential trace element, interferes through selenoproteins in many physiological processes of plants and mammals. Its antiviral activity has recently attracted much attention because selenium improves the antiviral capacity of animal cells against a few viruses relevant to human diseases. In this study, the red elemental selenium was purified from the fermentative culture of Herbaspirillum camelliae WT00C and then used to culture epithelioma papulosum cyprinid (EPC) cells or feed crucian carp and zebrafish. Finally, its antiviral effects were investigated at the cell level and living fishes after spring viraemia of carp virus infection. At the cell level, 5, 10 and 20 μg ml -1 red elemental selenium significantly induced the expression of interferon (IFN) and ISG15 genes in EPC cells. The viral TCID 50 (50% tissue culture infective dose) values in the EPC cells incubated with 5, 10 and 20 μg ml -1 red elemental selenium were significantly less than those of the control. More expression of IFN and ISG15 genes and less TCID 50 values indicate that red elemental selenium indeed improves the antiviral capability of EPC cells. In the crucian carp fed with the food containing 5 and 10 μg g -1 red elemental selenium, IFN expressions showed 13- and 39-fold increases at the 16th day of post-injection, and its expression was dependent on selenium concentrations. Meanwhile, no fish death occurred in all the experimental groups. In the zebrafish fed with the red worm containing 5 μg g -1 red elemental selenium, IFN and Mx expressions and survival rate were significantly higher than those of the control. The results of this study show that red elemental selenium indeed improves the antiviral activity of fish. The antiviral effects of selenium mainly come from its immune regulation through its incorporation into selenoproteins. The optimum level of selenium contributes to improving fish immunity, whereas excess selenium causes excessive immune and inflammatory responses., (© 2020 Fisheries Society of the British Isles.)

To gain a deeper understanding of how environmental conditions affect brain plasticity, brain size was explored across different seasons using the invasive round goby Neogobius melanostomus. The results show that N. melanostomus had heavier telencephalon in the spring compared to the autumn across the two years of study. Furthermore, fish in reproductive condition had heavier telencephala, indicating that tissue investment and brain plasticity may be related to reproductive needs in N. melanostomus. [ABSTRACT FROM AUTHOR]

Offspring of a highly inbred gynogenetic line of Oreochromis aureus displayed 12-fold increase in twinning rate compared to the outbred population. Asymmetric conjoined twins, which consist of a normal embryo attached to a malformed-atrophic twin, were frequently encountered in both gynogenetic (90·7%) and outbred (38·2%) embryos. The monozygotic origin of these twins was determined using five microsatellite markers. Progeny of heterozygous parents for the microsatellite UNH159 were separated into sub-sets of twins and normal full-sibs. Consistent with previous reports, the normal embryo sub-set exhibited elimination of both types of homozygotes for the UNH159 genetic marker at 2-8 days after fertilization. Unexpectedly, this elimination was less frequent in twins. The UNH159 marker as well as RNA-binding motif protein, X-linked ( rbmx), SRY-box containing gene 3 ( sox3) and alpha-thalassemia/mental retardation syndrome X-linked ( atrx) genes were mapped to linkage group 2. These gene orthologues are all located on the mammalian X chromosome and atrx is necessary for the X-chromosome inactivation. [ABSTRACT FROM AUTHOR]

The goal of this study was to determine the effect of the changes in gill morphology induced by dietary salt feeding on several aspects of gill function in rainbow trout Oncorhynchus mykiss maintained in fresh water with specific emphasis on Cl− uptake ( JINCl−) and acid-base regulation. The addition of 11% NaCl to the diet caused JINCl− to be reduced by c. 45% from 214·4 ± 26·7 to 117·3 ± 17·4 µmol kg−1 h−1 (mean ± s.e.). Rates of Cl− efflux ( JOUTCl−), net Cl− flux ( JNETCl−), JNETNa+ and plasma levels of Na+ or Cl− were unaffected by salt feeding. On the basis of significant effect of the salt diet on decreasing the maximal uptake rate of Cl− ( JMAXCl−), it would appear that internal salt loading caused a decrease in the number of functional ion transport proteins involved in Cl− uptake ( e.g. Cl−-HCO3− exchangers) and decreased the transporting capacity of existing proteins. The acid-base regulating capacity of control fish and salt-loaded fish was assessed by monitoring arterial blood acid-base status [partial pressure of CO2 ( PCO2), pH and HCO3−] during exposure to external hypercapnia (nominally 7·5 mm Hg). Both groups of fish exhibited typical compensatory responses to sustained hypercapnia consisting of the gradual accumulation of plasma HCO3− and thus metabolic restoration within 24 h of the initial respiratory acidosis elicited by hypercapnia. Overall, the results demonstrate that while Cl− uptake capacity is reduced in salt-fed fish, there is no associated alteration in acid-base regulating capability. [ABSTRACT FROM AUTHOR]

Whole-body concentrations of cortisol and glucose were measured in three-spined sticklebacks Gasterosteus aculeatus from two rivers (Rivers Ray and Ock) in southern England during a 30 month period in order to assess effects on the stress axis of (1) remediation of a wastewater treatment works (WWTW) effluent (River Ray) and (2) episodic changes in flow rate arising from periods of high rainfall (Rivers Ray and Ock). The postcapture concentrations of cortisol and glucose in fish from both rivers did not exhibit a seasonal periodicity but did show significant between-sample, between-site and between-river variation, superimposed upon a consistent downward trend for each analyte during the monitoring period. Corticosteroid and glucose concentrations following capture were inversely linked with a progressive increase in condition of the fish during this period. Site-dependent trends possibly related to exposure to the WWTW effluent were detected for both analytes in fish from the River Ray. For fish in the River Ray, a significant proportion of variation in both corticosteroid and glucose concentrations, additional to the downward trend with time, was accounted for by temporal proximity of the sample to exceptional flow events arising from episodes of high rainfall and high turbidity. This relationship was not statistically significant for fish from the River Ock. These data suggest that the responsiveness of the stress axis in free-living G. aculeatus may be altered by exposure to WWTW effluent and by exposure to physical changes in the aquatic environment such as those arising from extreme weather events. The magnitude of these effects may be increased by exposure to both stressors concurrently. [ABSTRACT FROM AUTHOR]

Shoaling and sexual behaviour of wild-type male and female white cloud mountain minnow Tanichthys albonubes were measured in the presence of the red fluorescent transgenic conspecifics under laboratory conditions. Wild-type female test fish showed no significant preference, whereas wild-type male test fish preferred to be near a shoal of red transgenic fish rather than wild-type fish. When placed in a potentially reproductive context, wild-type males had a higher competitive ability over transgenic males; wild-type females spent more time with wild-type males in visually mediated experiments, but wild-type males performed more courtship displays towards transgenic females. These results suggest that the red body colouration does not appear to disturb signal communication between wild-type and transgenic T. albonubes in shoaling behaviour; transgenic males have no mating advantage over wild-type males, but the red body colouration of transgenic females may affect mate choice of wild-type males. [ABSTRACT FROM AUTHOR]

Gynogenesis was induced by using UV-irradiated spermatozoa of blunt snout bream Megalobrama amblycephala to activate eggs of common carp Cyprinus carpio. The maternal genome was then duplicated by cold shock in 0 to 4° C cold water to retain the second polar body. Two kinds of fry, normal fry and abnormal tortuous fry, were hatched. Their DNA content was measured by flow cytometry. The normal fry were identified as diploid, representing the successful gynogenesis in C. carpio whereas the abnormal tortuous fry were haploid. Ten microsatellite loci were used to study the genetic diversity among C. carpio, diploid gynogenetic C. carpio and unduplicated haploid tortuous fry. The results indicated that the genetic homozygosity of gynogenetic C. carpio was significantly higher than that of C. carpio. The genetic homozygosity of the haploid C. carpio was intermediate between that of gynogenetic C. carpio and C. carpio. It might be easier for the allogenetic DNA fragments to be integrated into the haploid genome than into diploid gynogenetic genome. [ABSTRACT FROM AUTHOR]

This study examined changes in Atlantic salmon Salmo salar epidermal mucus proteins following short- and long-term handling stress. Short-term stress consisted of a single removal of fish from water for 15 s with long-term stress consisting of daily removal of fish from water for 15 s over 21 days. In the long-term handling stress study, there was a high level of individual variability with respect to mucus alkaline phosphatase, cathepsin B and lysozyme activities, with no correlation to treatment group. There was limited or no positive correlation between lysozyme, cathepsin B or alkaline phosphatase activities and plasma cortisol. There was a significant difference in lysozyme activity for both control and stressed fish at day 21 compared to other sampling days. In the short-term study, there was again high variability in mucus enzyme activities with no difference observed between groups. Immunoblotting also showed variability in mucus actin breakdown products in both short- and long-term handling stress studies. There appeared, however, to be a shift towards a more thorough breakdown of actin at day 14 in the stressed group. This shift suggested changes in mucus proteases in response to long-term handling stress. In summary, there were correlations of some mucus enzyme/protein profiles with stress or cortisol; however, the variability in S. salar mucus enzyme levels and actin fragmentation patterns suggested other triggers for inducing changes in mucus protein composition that need to be investigated further in order to better understand the role of mucus in the response of S. salar to external stressors. [ABSTRACT FROM AUTHOR]

Embryonic stem (ES)-like cells were derived from mid-blastula stage embryos of a freshwater fish, catla Catla catla, under feeder-free condition and designated as CCES cells. The conditioned media was optimized with 10% foetal bovine serum (FBS), fish embryo extract (FEE) having 100 µg ml [ABSTRACT FROM AUTHOR]

Size-dependent reproductive success of wild zebrafish Danio rerio was studied under controlled conditions in the laboratory to further understand the influence of spawner body size on reproductive output and egg and larval traits. Three different spawner size categories attained by size-selective harvesting of the F1-offspring of wild D. rerio were established and their reproductive performance compared during a 5 day period. As to be expected, large females spawned more frequently and had significantly greater clutch sizes than small females. Contrary to expectations, small females produced larger eggs when measured as egg diameter with similar amounts of yolk compared to eggs spawned by large spawners. Eggs from small fish, however, suffered from higher egg mortality than the eggs of large individuals. Embryos from small-sized spawners also hatched later than offspring from eggs laid by large females. Larval standard length ( LS)-at-hatch did not differ between the size categories, but the offspring of the large fish had significantly larger area-at-hatch and greater yolk-sac volume indicating better condition. Offspring growth rates were generally similar between offspring from all size categories, but they were significantly higher for offspring spawned by small females in terms of LS between days 60 and 90 post-fertilization. Despite temporarily higher growth rates among the small fish offspring, the smaller energy reserves at hatching translated into lower condition later in ontogeny. It appeared that the influence of spawner body size on egg and larval traits was relatively pronounced early in development and seemed to remain in terms of condition, but not in growth, after the onset of exogenous feeding. Further studies are needed to explore the mechanisms behind the differences in offspring quality between large- and small-sized spawners by disentangling size-dependent maternal and paternal effects on reproductive variables in D. rerio. [ABSTRACT FROM AUTHOR]

A 12 day growth trial was conducted to compare the effect of the variation in microcystins (MC) composition of two bloom samples of Microcystis aeruginosa on the growth performance and microcystin accumulation in common carp Cyprinus carpio larvae. Two M. aeruginosa natural bloom samples with different MC profiles were collected and larvae were exposed to cyanobacterial cells through their diet. Three diets, a basal control diet and two diets prepared from the basal diet plus the same toxins content (60 ng MC g−1 diet) of each cyanobacterial bloom, were given at the same ration level to three groups of larvae during the experimental period. Larval mass and standard length from day 9 were significantly different between cyanobacterial treatments and in both cases lower than that of the control. The MC accumulation by larvae, inversely correlated with the growth performance, was also significantly different between cyanobacterial treatments (26·96 v. 17·32 ng g−1 at the end of the experimental period). These results indicate that MC variants profile may have effects on the toxin uptake and toxicity. To date, this is the first laboratory study to show that fish accumulate MC depending on the toxin profile of the cyanobacterial bloom. [ABSTRACT FROM AUTHOR]

In most species, fish spermatozoa activate their motility on contact with the external medium (sea or fresh water depending of their reproductive habitat). Their flagella immediately develop waves propagated at high beat frequency (up to 70 beats s−1), which propel these sperm cells at high velocity (6–10 mm min−1), but for a quite short period of time, usually limited to minutes. Their specific inability to restore their energy content (mostly adenosine triphosphate) fast enough relatively to their high rate of energy consumption by flagellar contributes mainly to the activity arrest of motility, as the spermatozoa need to rely on early accumulated energy prior to activation. This review of the published data explains the present understanding of physico-chemical mechanisms by which flagellar motility is activated (mostly through osmotic and ionic regulation) and then propels sperm cells at speed. It aims also to describe the gradual arrest of their motility much of which occurs within a few minutes. [ABSTRACT FROM AUTHOR]

A large number of congenital heart defects associated with mortality in humans are those that affect the cardiac outflow tract, and this provides a strong imperative to understand its development during embryogenesis. While there is wide phylogenetic variation in adult vertebrate heart morphology, recent work has demonstrated evolutionary conservation in the early processes of cardiogenesis, including that of the outflow tract. This, along with the utility and high reproductive potential of fish species such as Danio rerio, Oryzias latipes etc., suggests that fishes may provide ideal comparative biological models to facilitate a better understanding of this poorly understood region of the heart. In this review, the authors present the current understanding of both phylogeny and ontogeny of the cardiac outflow tract in fishes and examine how new molecular studies are informing the phylogenetic relationships and evolutionary trajectories that have been proposed. The authors also attempt to address some of the issues of nomenclature that confuse this area of research. [ABSTRACT FROM AUTHOR]

Caspases (cysteine-dependent aspartyl-specific protease) belong to a family of cysteine proteases that mediate proteolytic events indispensable for biological phenomena such as cell death and inflammation. The first caspase was identified as an executioner of apoptotic cell death in the worm Caenorhabditis elegans. Additionally, a large number of caspases have been identified in various animals from sponges to vertebrates. Caspases are thought to play a pivotal role in apoptosis as an evolutionarily conserved function; however, the number of caspases that can be identified is distinct for each species. This indicates that species-specific functions or diversification of physiological roles has been cultivated through caspase evolution. Furthermore, recent studies suggest that caspases are also involved in inflammation and cellular differentiation in mammals. This review highlights vertebrate caspases in their universal and divergent functions and provides insight into the physiological roles of these molecules in animals. [ABSTRACT FROM AUTHOR]

A subject and author index for the volume 73 issues of the "Journal of Fish Biology" is presented.

African catfish Clarias gariepinus hatched with morphologically immature features; however, sensory organs developed rapidly with fish growth. Although the eyes of newly hatched larvae were immature without pigment, in 2 day-old larvae, the retina of the eyes had already developed except for the rod cells. No free neuromasts were observed in newly hatched larvae. In 1 day-old larvae, however, free neuromasts were observed on the head and trunk. Free neuromasts increased with larval growth. Newly hatched larvae had simple round-shaped otic vesicles; however, all sensory epithelia of the inner ear were observed until the larvae were 3 days old. Two day-old larvae swam horizontally, had sharp teeth, commenced ingesting rotifers and also artificial feed (small-size pellets) under both light and dark conditions; by then the larvae already had many taste buds. Three day-old larvae showed negative phototaxis and cannibalism by eating their conspecifics. Most of the free neuromasts observed in this study had the peculiar feature of many microvilli around the sensory cells on the apical surface. Detected free neuromasts as ordinary type lateral-line organs were not observed in previous reports in teleosts. In 10 day-old larvae, there were two lines of free neuromasts on the flank and lower edge of the trunk; presumptive canal neuromasts were oval shaped and had begun to sink under the skin. The direction of maximum sensitivity of the neuromasts was parallel with the longitudinal axis of their elliptical apical surface. [ABSTRACT FROM AUTHOR]

The article introduces a series of articles about molecular and cell science investigations and developments in fish biology. It identifies seven interesting topic areas in fish molecular study including the targeted gene inactivation, molecular evolution of blind cavefish, fish toxicogenomics, imaging of dynamic cell processes in vivo, development of microarrays from fish genomes, advances in use of Bayesian statistics in mitochondrial and microsatellite analysis, and DNA barcoding in fishes.

The sub-chronic (28–56 days) effects of exposure to low concentrations of cadmium (Cd; 0·05, 0·25, 0·50 and 2·50 μg l−1) shortly following fertilization on embryos, larvae and juvenile rainbow trout Oncorhynchus mykiss were examined. Premature hatching occurred at lower concentrations (0·05 and 0·25 μg l−1 Cd), however, delayed hatching was seen in the 2·50 μg l−1 Cd group, with >90% of hatching occurring on the last day of the hatching period. Larval growth was negatively affected by Cd exposure in a concentration-dependent manner. Larvae exposed to 2·50 μg l−1 Cd were 13·9 ± 0·8% shorter in total length ( LT) and weighed 22·4 ± 3·5% (mean ±s.e.) less than controls at the end of the exposure period. Plasma sex steroid concentrations (oestradiol in juvenile females and 11-ketotestosterone in juvenile males) were elevated (four- to 10-fold over controls) in exposed fish in both males and females, following 28 days of exposure to 0·05, 0·25 and 0·50 μg l−1 Cd, respectively. These results suggest that environmentally realistic concentrations (in the μg l−1 range) of Cd can affect the development of O. mykiss impacting embryos, larvae and juvenile fish. [ABSTRACT FROM AUTHOR]

A bioenergetics model was developed from observed consumption, respiration and growth rates for zebrafish Danio rerio across a range (18–32° C) of water temperatures, and evaluated with a 50 day laboratory trial at 28° C. No significant bias in variable estimates was found during the validation trial; namely, predicted zebrafish mass generally agreed with observed mass. [ABSTRACT FROM AUTHOR]

An oligonucleotide microarray containing 50-mer oligonucleotides representing 9277 unique Atlantic halibut Hippoglossus hippoglossus genes has been designed, printed and is currently being used for the study of gene expression in developing halibut. The oligonucleotides are based on all the Atlantic halibut data available at the time of printing, these included expressed sequence tags (ESTs) and complete cDNAs derived from the Pleurogene sequencing project as well as sequences deposited in GenBank by other groups as of September 2006. Of the Pleurogene ESTs, 5040 are functionally annotated; the remainder are unknown (1016) or are similar to unannotated sequences in GenBank (1626). In addition to Atlantic halibut features, several control features have been incorporated, including an oligonucleotide representing a heterologous plant gene (92 spots) and empty spots containing buffer only (1344). The array contains 48 subgrids, each comprised of 32 columns and 26 rows. Every feature is printed at least four times as side-by-side quadruplicates, resulting in a microarray containing 39 936 features. This microarray has been utilized to identify genes differentially expressed in larval Atlantic halibut during the developmental period from post-hatch to post-metamorphosis. Early in development, transcription of the gene for hatching enzyme was down-regulated, whereas a gene involved in eye development was up-regulated. Midway to metamorphosis, transcription of genes encoding several key digestive enzymes was up-regulated, and in pre-metamorphic larvae, transcription of genes encoding muscle proteins was prominent. [ABSTRACT FROM AUTHOR]

Kryptolebias marmoratus ( Rivulus marmoratus till 2004, order Cyprinodontoformes; family Rivulidae) is the only known self-fertilizing hermaphrodite vertebrate. Because of this uniqueness, there has been great interest in its biology, physiology, developmental biology and genomics along with other basic and applied areas of environmental genomics and molecular carcinogenesis. In laboratory studies, K. marmoratus has shown susceptibility to a number of xenobiotics including carcinogens. Toxicologists are interested in the mechanisms of action of environmental chemicals of contemporary interest such as endocrine disruptors and may consider this as a suitable fish model for the study of chemically induced carcinogenesis. Single short-term exposure to model chemical carcinogens is sufficient to induce tumourigenesis in K. marmoratus in a relatively short time span. In recent years, considerable data have been generated about gene sequences of K. marmoratus. Laboratory maintenance of K. marmoratus is relatively easy. Gene bank data are readily available, though not as extensive as for zebrafish Danio rerio or Japanese madaka Oryzias latipes. The expressed sequence tag (EST) data, differential display real-time reverse-transcriptase polymerase chain reaction and Gene Sequencer 20™ sequencing data have recently been helpful in understanding the genomics and proteomics of this species. Recently, sequences of the oncogene, ras, and tumour suppressor gene, p53, have been reported in K. marmoratus. The expression of these important genes that play significant roles not only in carcinogenesis but also in other signal transduction pathways was observed to be modulated by environmental endocrine-disrupting chemicals. Having a large sequence database (cDNA sequences and ESTs), it is expected that the use of a microarray in the near future will open new vistas for this fish with applications in cancer research, aquatic toxicology, endocrinology and genomics. This review discusses potential uses of K. marmoratus in new biotechnological approaches of aquatic toxicology. [ABSTRACT FROM AUTHOR]

The recent discovery that small regulatory RNAs have diverse roles in eukaryotic intracellular life, such as fine tuners of endogenous gene expression, as inhibitors of viral replication and as suppressors of transposon activity, is now widely recognized as a major breakthrough in the understanding of cellular biology. The pathways used by these small RNAs seem to build upon a few central mechanisms in which small double-stranded RNAs (dsRNAs) are generated from various precursor RNAs of exogenous or endogenous origin and used for inhibiting expression of genes with sequence complementarity to the small RNA. In particular, one class of small gene-regulatory RNAs, known as small interfering RNAs (siRNAs), has the potential for highly specific gene silencing. These are c. 21 nucleotide perfectly complementary dsRNAs with 3′ end overhangs. They are produced by cleavage of long dsRNA believed to be of viral origin. Subsequently, a large cytoplasmic protein complex known as the RNA-induced silencing complex (RISC) uses the antisense strand of the siRNAs for targeting complementary mRNA strands followed by cleavage of these transcripts in the mechanism called RNA interference (RNAi). Accordingly, synthetic siRNAs may have a potential for treating diseases caused by intracellular pathogens like viruses by specifically targeting the expression of their molecular components. Furthermore, as target sequences need not be of viral origin, siRNAs hold a promise for the treatment of various cellular diseases and as a tool in reverse genetic studies. SiRNAs are currently exploited for such purposes in diverse organisms ranging from plants and invertebrates to human beings. But due to initial difficulties, when using RNAi for gene silencing in fishes, only a few such studies have been conducted in fishes. The purpose of this review is to inspire further experimental work. [ABSTRACT FROM AUTHOR]

In the context of conservation hatcheries that seek to bolster wild populations by releasing captively-reared fishes into the wild, steelhead Oncorhynchus mykiss were used to test the hypothesis that naturalistic rearing environments promote adaptive behaviour that might otherwise not develop in typical hatchery environments. When comparisons were made among fish reared in barren, structured or structurally variable environments ( i.e. the location of the structure was repositioned every 2–3 days), structure in the rearing environment increased future exploratory behaviour, but only if the structure was stable. Under conditions of high perceived predation risk, the fish no longer exhibited increased exploratory behaviour, suggesting that it is expressed in an adaptive, context-dependant manner. Another concern with hatcheries is that relaxed selection over multiple generations in captivity can increase maladaptive behavioural variation. Compared to rearing in hatchery-typical barren environments, rearing in structured-stable environments decreased behavioural variation. This effect, which occurred during development and did not involve selection, demonstrates a different mechanism for change in behavioural variation in captivity. These experiments show that effects of structure and structural stability occur at the level of both average behaviour and behavioural variation, and suggest that these effects should be considered when fishes are reared in hatcheries for later release into the wild. [ABSTRACT FROM AUTHOR]

An orthologue of hadh2 (hydroxyacyl-coenzyme A dehydrogenase type II) has been isolated from amphioxus. At the amino acid level, hadh2 exhibits high sequence similarity between amphioxus and vertebrates, including zebrafish. Similarities also exist in the developmental expression patterns of amphioxus and zebrafish hadh2, which may provide information on the molecular mechanisms responsible for some human disease phenotypes caused by hadh2 mutation. [ABSTRACT FROM AUTHOR]

Feeding rate, growth and nutritional condition as well as nodularin concentration of juvenile three-spined sticklebacks Gasterosteus aculeatus were assessed in an experimental study where field-collected fish were given a diet of zooplankton fed with toxic Nodularia spumigena for 15 days. Food consumption was higher in N. spumigena bloom conditions compared with the cyanobacterium-free control, but despite this the growth rate of exposed fish did not improve. Control fish and fish fed N. spumigena-exposed zooplankton had higher RNA:DNA ratios and protein content than fish grown in cyanobacterial bloom conditions indicating good nutritional condition and recent growth of fish, whereas in bloom conditions metabolic transformation of nodularin to less toxic compounds may cause an energetic cost to the fish affecting the growth rate of the whole organism. Juvenile three-spined sticklebacks collected from the field contained higher concentrations of nodularin at the beginning of the experiment (mean 503·1 μg kg−1). After 15 days, the lowest nodularin concentrations in fish were measured in the control treatment, suggesting that fish fed with non-toxic food are able to detoxify nodularin from their tissues more effectively than fish in continuing exposure. [ABSTRACT FROM AUTHOR]

The insulin-like growth factor-binding proteins (IGFBPs) are evolutionarily conserved components of the insulin-like growth factor (IGF) system. The six forms of IGFBPs (IGFBP-1–6) bind the IGF ligands (IGF-1 and -2) with high affinity and regulate the IGFs available to their receptors, therefore providing additional flexibilities in regulating IGF signalling. IGFBP-1, the first identified member of the IGFBP family is highly inducible under a variety of catabolic conditions, such as food deprivation, malnutrition, stress, injury and hypoxia. Recent in vivo studies have indicated that the induced IGFBP-1 serves as a molecular switch by restricting IGF signalling and diverts the limited energy resources away from growth and development towards those metabolic processes essential for survival. This article reviews the recent understandings of the molecular basis of IGFBP-1 regulation and its biological functions, as revealed through research in mammalian and fish models. [ABSTRACT FROM AUTHOR]