Tissue expression and bioinformatics analysis of the vitellogenin gene of Asian arowana (Scleropages formosus)

The RACE technique was used to clone the full‐length vitellogenin (VTG) cDNA sequence of Asian arowana (Scleropages formosus). The full‐length sequence was 5,550 bp with an open reading frame of 5,238 bp, encoding 1,745 amino acids, and 5′ and 3′ UTRs (untranslated regions) of 45 bp and 267 bp, respectively. Phylogenetic analysis showed that S. formosus and silver arowana (Osteoglossum bicirrhosum) share a close evolutionary relationship (bootstrap 100%). The quantitative real‐time PCR results showed that vtg expression was significantly higher in liver and gonads of male and female fish compared with its expression in the other tissues tested (p < 0.01). The relative expression levels of vtg in liver, gland, kidney, heart, head kidney, and brain of female fish were significantly higher than in the corresponding tissues of male fish (p < 0.05).     

Population structure of the black arowana (Osteoglossum ferreirai) in Brazil and Colombia: implications for its management

In regions with high biodiversity, where species are exploited as a source of income, it is essential to learn more about the species that are being commercialized. For the ornamental fish black arowana (Osteoglossum ferreirai), distributed only in Colombia and Brazil, there is currently a lack of information about population estimates in each location, genetic data and lastly, about the events that lead to the current distribution of the species. A genetic population study was conducted by sequencing the mitochondrial genes cytochrome b and ATPase 6, and genotyping of eight microsatellite loci. Mitochondrial gene results indicated the absence of variable sites, and the microsatellite results showed a significantly lower heterozygosity than expected demonstrating that currently the genetic diversity of the species is low. The fact that this species is been exploited and that it shows low genetic diversity means it can quickly become endangered. For this reason, conservation, management and use programs for the black arowana should include and consider the genetic data obtained as well as additional life history and ecological factors to promote its sustainable use.     

Mice on menu: opportunistic feeding behaviour of the Amazonian silver arowana Osteoglossum bicirrhosum

Two silver arowana, Osteoglossum bicirrhosum, one male (49.5 cm standard length, L_S) and one female (52.5 cm L_S) that had fed on small‐eared colilargo or small‐eared pygmy rice rat Oligoryzomys microtis, were sampled during the rising water period in the Brazilian Amazon. The identified prey were 6 and 8 cm long and occupied the entire stomachs of both individuals. This opportunistic feeding behaviour appears to be a strategy for this fish to acquire nutrients during times when its usual aquatic prey is dispersed throughout the flooded forest.     

Isolation and characterization of novel microsatellite markers in commercial selected golden Malaysian arowana fish, Scleropages formosus (Osteoglossidae)

Malaysian arowana (dragonfish; Scleropages formosus) is an ancient osteoglossid fish from southeast Asia. Due to the high demand of the ornamental fish trade and because of habitat loss, the species is close to extinction. We isolated and characterized 10 polymorphic microsatellites of this species, using 5'-anchored PCR. The number of alleles at the 10 microsatellite loci ranged from 2 to 28, with a mean of 7.8/locus. The observed heterozygosity ranged from 0.03 to 0.93 (mean: 0.39), whereas the expected heterozygosity ranged from 0.03 to 0.94 (mean: 0.46). Seven microsatellites deviated from Hardy-Weinberg equilibrium, and three conformed to Hardy-Weinberg equilibrium and were in linkage equilibrium. These 10 novel microsatellites should facilitate studies of genetic diversity and population structure of arowana to help plan actions for the conservation of the indigenous Malaysian arowana.     

Novel polymorphic microsatellites for studying genetic diversity of red Asian arowanas

Asian arowana (Scleropages formosus) is a highly endangered fish species listed in Appendix 1 of CITES since 1980. Fourteen novel polymorphic microsatellites were isolated from a CA-enriched partial genomic DNA library, and were used for studying genetic diversity of 41 red arowanas from the wild population. Surprisingly the average allele number of the 14 polymorphic microsatellites was as high as 12.4/locus. The average observed heterozygosity was 0.78 ranging from 0.51 to 0.95, and the gene diversity was quite high (0.78). All these data suggest that high level of genetic diversity existed in the red Asian arowana population.     

A comparative approach to protein-and ligand-dependence of the Root effect for fish haemoglobins

Ligand-binding equilibria, kinetics and (13)C n.m.r. spectra of bound (13)CO, of the haemoglobins from two fishes that are very distant on the evolutionary scale, i.e. the fourth haemoglobin component from Salmo irideus and the single component from Osteoglossum bicirrhosum, were studied. The C-terminal sequence was also determined for the haemoglobin from Osteoglossum. The results show that (i) the C-terminal residues of both chains are not directly responsible for the characteristic heterotropic effect known as Root effect, since for both fish haemoglobins these residues are identical with those of human haemoglobins. (ii) In all haemoglobins characterized by the Root effect a dependence of the (13)CO n.m.r. resonances on pH is observed. However, the extent of the shift(s) depends on the particular protein, and is probably the result of a combination of both tertiary and quaternary conformational changes. (iii) Both haemoglobins from trout and Osteoglossum manifest a functional heterogeneity between the two types of chains in the tetramer, which increases with proton activity. For CO, the effect is very small for trout haemoglobin IV, and very marked for Osteoglossum haemoglobin; for O(2) strongly heterogeneous binding curves were obtained at approx. pH6.2 with both haemoglobins. (iv) Estimations of the relative values of the affinity constants for the alpha and beta chains in the tetramer were obtained for both haemoglobins from (13)CO n.m.r. spectra at low fractional saturation. On the basis of these findings the molecular mechanism underlying the Root effect is discussed.     

Molecular phylogeny of osteoglossoids: a new model for Gondwanian origin and plate tectonic transportation of the Asian arowana

One of the traditional enigmas in freshwater zoogeography has been the evolutionary origin of Scleropages formosus inhabiting Southeast Asia (the Asian arowana), which is a species threatened with extinction among the highly freshwater-adapted fishes from the order Osteoglossiformes. Dispersalists have hypothesized that it originated from the recent (the Miocene or later) transmarine dispersal of morphologically quite similar Australasian arowanas across Wallace's Line, but this hypothesis has been questioned due to their remarkable adaptation to freshwater. We determined the complete nucleotide sequences of two mitochondrial protein genes from 12 osteoglossiform species, including all members of the suborder Osteoglossoidei, with which robust molecular phylogeny was constructed and divergence times were estimated. In agreement with previous morphology-based phylogenetic studies, our molecular phylogeny suggested that the osteoglossiforms diverged from a basal position of the teleostean lineage, that heterotidines (the Nile arowana and the pirarucu) form a sister group of osteoglossines (arowanas in South America, Australasia, and Southeast Asia), and that the Asian arowana is more closely related to Australasian arowanas than to South American ones. However, molecular distances between the Asian and Australasian arowanas were much larger than expected from the fact that they are classified within the same genus. By using the molecular clock of bony fishes, tested for its good performance for rather deep divergences and calibrated using some reasonable assumptions, the divergence between the Asian and Australasian arowanas was estimated to date back to the early Cretaceous. Based on the molecular and geological evidence, we propose a new model whereby the Asian arowana vicariantly diverged from the Australasian arowanas in the eastern margin of Gondwanaland and migrated into Eurasia on the Indian subcontinent or smaller continental blocks. This study also implicates the relatively long absence of osteoglossiform fossil records from the Mesozoic.     

Fish Communities in Central Amazonian White- and Blackwater Floodplains

In Amazonian floodplains, the flood cycle of the river is becoming the dominant seasonal factor, and fish communities are found to fluctuate greatly over the year. During inundation, fish migrate into floodplain forests to feed on fruits and seeds, in an area more than 300000km² in size. To document patterns of species diversity, distribution, abundance and temporal dynamics and in order to describe the ecological importance of the inundated forest, floodplain fish were captured using variously sized gill nets in white and black water areas inside and outside the floodplain forests during low, rising, high and falling water level in 1990 and 1991. Dominance varies to some extent in white water between floodplain forest (0.06) and open water (0.11) while it is unchanged in black water (0.04). Black water fish communities were more diverse. Most abundant among white water fish were Liposarcus pardalis, Pygocentrus nattereri, and Pellona flavipinnis, for example, or Plagioscion squamsissimus, Serrasalmus rhombeus, and Serrasalmus manueli in black water. Among the most abundant white water fish, Colossoma macropomum, Mylossoma duriventre and Osteoglossum bicirrhosum occurred almost exclusively in inundated forests. Of the black water species there were a large number of species which were captured only in inundated forest, such as Geophagus cf. altifrons, Hoplias malabaricus, Osteoglossum bicirrhosum and Uaru amphiacanthoides. Catches varied with sample site, water level and direction of water level change. The average CPUE in white and black water was 190 and 41g fishm^–2 and day, respectively, with maximum yields at low water and minimum yields at high water. Comparing rising and falling water levels, a significantly higher quantity of fishes was captured at falling water level. In black water, fish catches from the floodplain forest exceeded the open water catch by 183 to 550%, depending on season. Differences in respect of white water are smaller (106–281%). Fish communities in the area under investigation seem to be stochastically assembled, with significant differences between white and black water only. Many fishes move into the floodplain forest not only to feed but probably also for other reasons – to seek shelter, for example.     

Morphofunctional features of visceral apparatus of silver arawana <Emphasis Type="Italic">Osteoglossum bicirrhosum</Emphasis> (Osteoglossidae)

The structure of some muscles—previously undescribed ligaments and aponeurotic structures of the visceral apparatus—of silver arawana Osteoglossum bicirrhosum has been studied in detail. A comparative analysis of the obtained results of anatomization and literature data is carried out. The peculiarities of the functioning of the visceral apparatus of silver arawana in the process of feeding are considered. New features of similarity in the structure of muscles of the visceral apparatus of Osteoglossidae and Salmonidae (by the example of salmon Salmo salar), which can provide a basis for confirming previously detected homologous features in the feeding stages of these two primitive groups of fish, are described.     

Length‐weight relationships of five fish species from lakes of the Central Amazonian floodplains

Parameters of the length‐weight relationship (LWR) were calculated for five fish species from Amazon Basin. Samplings were carried out in ten lakes of the Solimões River floodplains during the four seasons of the hydrological cycle: rising water, high water, receding water, and low water, during two periods. The first period of eight years included samplings performed from 2001 to 2008 and the second sampling period of two years was from 2012 to 2013. Specimens were captured using gillnets (mesh sizes ranging from 30 to 120 mm between opposite knots) and standardized dimension of 20 m in length × 2 m in height. This study provides the LWR parameters for Acarichthys heckelii, Leporinus trifasciatus, Brycon amazonicus, Curimatella meyeri and Osteoglossum bicirrhosum.     

Histological and Immunohistochemical Studies of the Neurohypophysis of Primitive Teleosts,the Osteoglossidae

The neurohypophysis of three species of the Osteoglossidae (Osteoglossum bicirrhosum, Scleropages jardini and Heterotis niloticus) was studied histologically. The rostral part of the neurohypophysis abuts on the pars distalis of the adenohypophysis, but does not interdigitate with it. The caudal part of the neurohypophysis is stained densely with aldehyde fuchsin and extensively interdigitates with the pars intermedia, forming a neurointermediate lobe. This organization of the neurohypophysis is intermediate between that of holosteans and that of non-osteoglossomorph teleosts. The median eminence-like features of the rostral part of the neurohypophysis are distinct in the Osteoglossidae in contrast to non-osteoglossomorph teleosts. In Osteoglossum bicirrhosum, immunohistochemical study reveals the presence of somatotropin release-inhibiting factor-like substance in the rostral part of the neurohypophysis. Fibers immunoreactive to anti-arginine vasopressin occur in the neurointermediate lobe almost exclusively. These observations also may support the assumption that the rostral part of the neurohypophysis corresponds functionally to the median eminence. For comparison, the occurrence and distribution of somatotropin release-inhibiting factor-like substance, luteinizing hormone-releasing factor-like substance and arginine vasopressin-like substance in the neurohypophysis of Gymnarchus niloticus are described.     

Simultaneous analysis of five molecular markers provides a well-supported phylogenetic hypothesis for the living bony-tongue fishes (Osteoglossomorpha: Teleostei)

Fishes of the Superorder Osteoglossomorpha (the "bonytongues") constitute a morphologically heterogeneous group of basal teleosts, including highly derived subgroups such as African electric fishes, the African butterfly fish, and Old World knifefishes. Lack of consensus among hypotheses of osteoglossomorph relationships advanced during the past 30 years may be due in part to the difficulty of identifying shared derived characters among the morphologically differentiated extant families of this group. In this study, we present a novel phylogenetic hypothesis for this group, based on the analysis of more than 4000 characters from five molecular markers (the mitochondrial cytochrome b, 12S and 16S rRNA genes, and the nuclear genes RAG2 and MLL). Our taxonomic sampling includes one representative of each extant non-mormyrid osteoglossomorph genus, one representative for the monophyletic family Mormyridae, and four outgroup taxa within the basal Teleostei. Maximum parsimony analysis of combined and equally weighted characters from the five molecular markers and Bayesian analysis provide a single, well-supported, hypothesis of osteoglossomorph interrelationships and show the group to be monophyletic. The tree topology is the following: (Hiodon alosoides, (Pantodon buchholzi, (((Osteoglossum bicirrhosum, Scleropages sp.), (Arapaima gigas, Heterotis niloticus)), ((Gymnarchus niloticus, Ivindomyrus opdenboschi), ((Notopterus notopterus, Chitala ornata), (Xenomystus nigri, Papyrocranus afer)))))). We compare our results with previously published phylogenetic hypotheses based on morpho-anatomical data. Additionally, we explore the consequences of the long terminal branch length for the taxon Pantodon buchholzi in our phylogenetic reconstruction and we use the obtained phylogenetic tree to reconstruct the evolutionary history of electroreception in the Notopteroidei.     

Hydrogen shuttles in air versus water breathing fishes.

1. The malate-aspartate cycle was demonstrable in subcellular preparations of hearts from Arapaima, Lepidosiren, and Synbranchus (obligate air breathers), Hoplerythriunus (facultative air breather), and Osteoglossum and Hoplias (obligate water breathers). 2. Although no respiratory evidence for significant alpha-glycerophosphate cycle participation could be shown in the air breathers, this cycle was demonstrable in hearts of water breathers. 3. In agreement with the O2 uptake studies, it was possible to reconstruct the malate-aspartate, but not the alpha-glycerophosphate cycle, in isolated mitochondria from air breathers, while both shuttles could be reconstructed with heart mitochondria in the case of water breathing fishes.     

Fish oil induced increase in walking distance, but not ankle brachial pressure index, in peripheral arterial disease is dependent on both body mass index and inflammatory genotype

Peripheral arterial disease (PAD) is an atherosclerotic disease. Evidence suggests that atherosclerosis is an inflammatory condition and long chain n-3 fatty acids, found in oily fish and fish oils, have been shown to reduce inflammation. Genetic and lifestyle factors such as body mass index (BMI) also influence inflammation. In this study we have examined the effect of fish oil in patients with claudication secondary to PAD. Fish oil supplementation, providing 1g EPA and 0.7 g DHA per day for 12 weeks, increased walking distance on a treadmill set at 3.2 km/h with a 7% incline. Walking distance to first pain increased from 76.2+/-8.5 m before fish oil to 140.6+/-25.5 m after fish oil (mean+/-SEM, p=0.004) and total distance walked increased from 160.0+/-21.5 m before fish oil to 242.1+/-34.5 m after fish oil (p=0.002). Fish oil supplementation also improved ankle brachial pressure index (ABPI) from 0.599+/-0.017 before fish oil to 0.776+/-0.030 after fish oil (p<0.001). The increase in walking distance was dependent on both BMI and genotype for single nucleotide polymorphisms in the genes encoding the pro-inflammatory cytokines tumour necrosis factor-alpha and interleukin (IL)-1beta and the anti-inflammatory cytokine IL-10 (detected using amplification refractory mutation system polymerase chain reaction). Neither BMI nor any of the genotypes examined affected the ability of fish oil to increase ABPI. The mechanisms by which fish oil affects walking distance and ABPI do not appear to be the same.     

Patterns of Fish Use and Piscivore Abundance within a Reconnected Saltmarsh Impoundment in the Northern Indian River Lagoon, Florida

Nearly all saltmarshes in east-central, Florida were impounded for mosquito control during the 1960s. The majority of these marshes have since been reconnected to the estuary by culverts, providing an opportunity to effectively measure exchange of aquatic organisms. A multi-gear approach was used monthly to simultaneously estimate fish standing stock (cast net), fish exchange with the estuary (culvert traps), and piscivore abundance (gill nets and bird counts) to document patterns of fish use in a reconnected saltmarsh impoundment. Changes in saltmarsh fish abundance, and exchange of fish with the estuary reflected the seasonal pattern of marsh flooding in the northern Indian River Lagoon system. During a 6-month period of marsh flooding, resident fish had continuous access to the marsh surface. Large piscivorous fish regularly entered the impoundment via creeks and ditches to prey upon small resident fish, and piscivorous birds aggregated following major fish movements to the marsh surface or to deep habitats. As water levels receded in winter, saltmarsh fish concentrated into deep habitats and emigration to the estuary ensued (200% greater biomass left the impoundment than entered). Fish abundance and community structure along the estuary shoreline (although fringed with marsh vegetation) were not analogous to marsh creeks and ditches. Perimeter ditches provided deep-water habitat for large estuarine predators, and shallow creeks served as an alternative habitat for resident fish when the marsh surface was dry. Use of the impoundment as nursery by transients was limited to Mugil cephalus Linnaeus, but large juvenile and adult piscivorous fish used the impoundment for feeding. In conclusion, the saltmarsh impoundment was a feeding site for piscivorous fish and birds, and functioned as a net exporter of forage fish to adjacent estuarine waters.     

Effects of group size on the responsiveness of zebrafish, Brachydanio rerio (Hamilton Buchanan), to alanine, a chemical attractant

Previous studies have examined the effects of grouping on the locating (search) phase of foraging and feeding behaviour in fishes. Few studies have examined whether schooling in fishes may facilitate individual foraging by enhancing a group's responsiveness to food odours. The purpose of the current study was to assess the effect of increasing group size on the responsiveness of zebrafish, Brachydanio rerio (Hamilton Buchanan), to L-alanine, an amino acid which is an important constituent of prey odours for many fishes. Based on the results of previous studies, either an increasing or decreasing linear relationship or a unimodal (convex or concave) relationship between responsiveness and group size was expected; the results, however, were bimodal. Groups of four fish were most responsive to alanine, as determined by the mean percentage of occurrences of fish in the area of a behavioural arena (an octagonal fluviarium) into which alanine was infused (at 10⁻³, 10⁻⁴, or 10⁻⁵ M). Groups of two, six and eight fish were significantly less responsive ( P < 0.05) than either groups of four fish or individual fish. The responses of groups of two, six and eight fish were not significantly different from each other.     

Characterization of the mitochondrial genome and phylogeny of the black arowana (Osteoglossum ferreirai)

In this study, we sequenced and assembled the mitochondrial (mt) genome of Osteoglossum ferreirai to re-assess the phylogenetic relationship of the family Osteoglossidae. We determined that the mitogenome of O. ferreirai contains the entire set of 37 mt genes, and the nucleotide composition and gene arrangement were similar to those of other bonytongues. Our phylogenetic analyses exhibited monophyly of the family Osteoglossidae with high bootstrap support, which is in agreement with the currently accepted phylogenetic viewpoint that is based on both morphological and molecular approaches. These findings provide additional informative data for the further study of phylogenetic relationships and help to elucidate a key component of the species radiation process within the family Osteoglossidae.     

Human absorption of fish oil fatty acids as triacylglycerols, free acids, or ethyl esters

The transient rise in plasma triacylglycerol fatty acids after single-dose ingestion of fish oil as triacylglycerols, free acids, or ethyl esters with linseed oil as an absorption standard was used to determine the relative absorption of fish oil fatty acids in eight men. As free acids, the fish oil fatty acids were well absorbed (greater than or equal to 95%). As triacylglycerols, eicosapentaenoic acid (1.00 g) and docosahexaenoic acid (0.67 g) were absorbed only 68% and 57% as well as the free acids. The ethyl esters were absorbed only 20% and 21% as well as the free acids. The incomplete absorption of eicosapentaenoic and docosahexaenoic acids from fish oil triacylglycerols correlates well with known in vitro pancreatic lipase activity.     

乌塘鳢对51Cr、60Co、131I、141Ce的吸收和积累

本文以河口底栖鱼类,不具鳞片,对环境适应力强的乌塘鳢为材料,研究它们以摄食和渗透两种方式对~(51)Cr,~(60)Co、~(131)I和~(141)Ce的吸收。为了观察在渗透吸收期间个体的差异,测定了单条活鱼的放射性。在实验中采用多核素示踪法并用S-80智能多道分析器和Ge(Li)探头测量放射性。 结果发现,当~(131)I的浓度为3.4×10~(-7)居里/升时,在10小时内所有的乌塘鳢都被杀死,而~(131)I在鱼体各组织器官的积累是明显的。器官积累核素数量的顺序是~(131)I>~(141)Ce>~(51)Cr,在任何组织器官均未检出~(60)Co。 在渗透吸收实验里,对单条活鱼的测量结果表明,核素是能够通过皮肤的渗透积累在鱼体内,并且存在个体差异。同时表明,生命元素的同位素如~(131)I,~(60)Co容易渗透到鱼体内部器官,而非生命元素的同位素例如~(141)Ce、~(51)Cr的渗透是慢的。 ~(51)Cr、~(60)Co、~(131)I、~(141)Ce是沿海核设施常见的放射性废物成分,有的是具有生态学意义的核素(Goldberg,1957),随着沿海核电站的不断兴建,它们在河口港湾存在的机会越来越多。虽然海洋鱼类和淡水鱼类对它们的浓集有过报道(Hiyama et al.,1964),但河口生物,特别是河口的底栖鱼类对它们的吸收和积累,则研究甚少。 乌塘鳢是生活在河口滩涂的底栖鱼类,适应于半咸淡的水质,