Lateralized female topminnows can forage and attend to a harassing male simultaneously

Animals engaged in a complex task are often unable to allocateenough attention to a second concurrent task. We tested thehypothesis that cerebral lateralization is advantageous becauseit enables separate and parallel information processing andallows for a more efficient performance of concurrent cognitivetasks. Lateralized and nonlateralized (NL) female Girardinusfalcatus, obtained through a selective breeding experiment,were compared in a situation requiring sharing attention betweentwo simultaneous tasks, retrieving food items scattered on thesurface, and avoiding unsolicited male mating attempts. In thepresence of a sexually harassing male, lateralized females weresignificantly more efficient than NL females in retrieving food,while no difference between these groups was found in controlexperiments in which the male was absent and subjects were notrequired to share attention between foraging and vigilance.Lateralized females showed a negligible decrease in foragingrate while attending the additional task, suggesting that theymay be able to partition the two processes in different partsof the brain.     

Diversification and functional evolution of reef fish feeding guilds

A core eco‐evolutionary aim is to better understand the factors driving the diversification of functions in ecosystems. Using phylogenetic, trophic, and functional information, we tested whether trophic habits (i.e. feeding guilds) affect lineage and functional diversification in two major radiations of reef fishes. Our results from wrasses (Labridae) and damselfishes (Pomacentridae) do not fully support the ‘dead‐end’ hypothesis that specialisation leads to reduce speciation rates because the tempo of lineage diversification did not substantially vary among guilds in both fish families. Our findings also demonstrate a tight relationship between trophic habits and functional roles held by fish in reef ecosystems, which is not associated with a variation in the tempo of functional diversification among guilds. By illustrating the pivotal importance of the generalist feeding strategy during the evolutionary history of reef fishes, our study emphasises the role of this feeding guild as a reservoir for future diversity.     

Promotion of sustainable capture fisheries and aquaculture in Asian reservoirs and lakes

A collaborative international project funded by the European Union's INCO-DC programme is undertaking limnological, fish biological, environmental and socio-economic research in five tropical lakes and reservoirs in Sri Lanka, Thailand and the Philippines over the period 1998–2001. The aim is to determine their trophic structure and their capacity to sustain both their existing fisheries and present and future aquaculture. In some cases, these activities could potentially be expanded for the benefit of rural communities and of the local market within the bounds of social and environmental sustainability. This paper describes the concepts and methods involved in this innovative multidisciplinary project which aims to integrate limnological, fisheries and socio-economic issues in a comparative approach involving Asian and European research teams.Deceased.     

Some but not All Tetrahymena Species Destroy Monolayer Cultures of Cells from a Wide Range of Tissues and Species

The activities of Tetrahymena corlissi, Tetrahymena thermophila, and Tetrahymena canadensis were studied in coculture with cell lines of insects, fish, amphibians, and mammals. These ciliates remained viable regardless of the animal cell line partner. All three species could engulf animal cells in suspension. However, if the animal cells were monolayer cultures, the monolayers were obliterated by T. corlissi and T. thermophila. Both fibroblast and epithelial monolayers were destroyed but the destruction of human cell monolayers was done more effectively by T. thermophila. By contrast, T. canadensis was unable to destroy any monolayer. At 4 °C T. thermophila and T. corlissi did not carryout phagocytosis and did not destroy monolayers, whereas T. canadensis was able to carryout phagocytosis but still could not destroy monolayers. Therefore, monolayer destruction appeared to require phagocytosis, but by itself this was insufficient. In addition, the ciliates expressed a unique swimming behavior. Tetrahymena corlissi and T. thermophila swam vigorously and repeatedly into the monolayer, which seemed to loosen or dislodge cells, whereas T. canadensis swam above the monolayer. Therefore, differences in swimming behavior might explain why T. corlissi has been reported to be a pathogen but T. canadensis has not.     

Trophic flexibility and opportunism in pike Esox lucius

The first comprehensive investigation of pike Esox lucius trophic ecology in a region (Ireland) where they have long been thought to be a non‐native species is presented. Diet was investigated across habitat types (lake, river and canal) through the combined methods of stable‐isotope and stomach content analyses. Variations in niche size, specialization and the timing of the ontogenetic dietary switch were examined, revealing pronounced opportunism and feeding plasticity in E. lucius, along with a high occurrence of invertivory (up to 60 cm fork length, L_F) and a concomitant delayed switch to piscivory. Furthermore, E. lucius were found to primarily prey upon the highly available non‐native roach Rutilus rutilus, which may alleviate predation pressure on brown trout Salmo trutta, highlighting the complexity of dynamic systems and the essential role of research in informing effective management.     

Blood and tissue fatty acid compositions,lipoprotein levels,performance and meat flavor of broilers fed fish oil: changes in the pre- and post-withdrawal design

Administration of fish oil (FO) in broiler diets can elevate α-linolenic acid (ALA), eicosapentanoic acid (EPA) and docosahexanoic acid (DHA) levels, which are protective against cardiovascular disease. However, optimization based solely on n-3 polyunsaturated fatty acid (n-3 PUFA) enrichment in chicken meat could lead to lower meat quality, unless the withdrawal period (plan) is applied for 1 week. The present study investigated whether the incorporation of FO in the diet for 32 days followed by its withdrawal for 1 week affected blood lipid profiles, lipoprotein particles, performance and meat flavor in male broiler chickens. Two hundred and forty birds (1-day-old, Ross 308) were assigned to 1 of 4 dietary groups: 0%, 1%, 2% or 3% FO with four replicates. Broilers were fed for 49 days according to a 4-phase feeding program. The experimental phase comprised day 11 to 42, and FO was removed on day 42. Blood samples were collected during the pre- and post-withdrawal period after the recordings before slaughter. The FO groups demonstrated decreased low-density lipoprotein (LDL) and increased high-density lipoprotein levels on day 42 (P < 0.01); however, these values were not significant after design withdrawal. Diet supplementation with FO elevated the blood levels of palmitic acid (C16:0) and n-3 PUFAs, especially long-chain (LC) PUFAs (EPA, C20:5n-3 and DHA, C22:6n-3), and caused a decline in the level of arachidonic acid (AA, C20:4n-6; P < 0.05). Application of a one-week withdrawal period resulted in a decrease in (P < 0.05) linoleic acid (C18:2n-6) and an increase in the level of AA, unlike their amounts on day 42. Although blood and tissue LC n-3 PUFA levels on day 49 were significantly higher in the FO groups compared with the control, they demonstrated a substantial decrease on day 49 compared with day 42. The best results, mainly the lowest n-6/n-3 fatty acids (FAs) and feed conversion ratio (FCRs), were observed for 3% FO (group T4), even after institution of the withdrawal design. Degradation of total n-3 FAs deposited in tissues occurred after instituting the withdrawal plan diet, but deposited levels of EPA and DHA in tissues could ensure omega-3 enrichment of broiler meat in groups 3 and 4. On the basis of the dissatisfaction of the panelists toward group 4 meats (scored as near to acceptable) and their satisfaction with cooked samples of T3 (scored as good), group 3 meats were selected as good-quality n-3-enriched broiler meat.     

膳食脂肪、肠道微生物与宿主健康的研究进展

作为三大主要营养物质之一,膳食脂肪为人体提供能量和营养。膳食脂肪摄入不当会破坏肠道微生物的稳态,影响宿主的代谢状况,增加慢性疾病发生的风险。建立疾病动物模型是研究肠道微生物与宿主健康的重要手段。文中综述了膳食脂质的数量和种类、肠道微生物和宿主代谢之间的相互作用及其可能的作用机制,阐述了基于不同的疾病动物模型,膳食脂质影响肠道微生物的结构和功能,以及对宿主代谢的调节,为深入了解膳食脂质、肠道微生态和宿主健康三者之间的关系提供了依据。     

A genetically distinct hybrid zone occurs for two globally invasive mosquito fish species with striking phenotypic resemblance

Hybrid zones allow for the investigation of incipient speciation and related evolutionary processes of selection, gene flow, and migration. Interspecific dynamics, like competition, can impact the size, shape, and directional movement of species in hybrid zones. Hybrid zones contribute to a paradox for the biological species concept because interbreeding between species occurs while parental forms remain distinct. A long‐standing zone of intergradation or introgression exists for eastern and western mosquito fish (Gambusia holbrooki and G. affinis) around Mobile Bay, AL. The region has been studied episodically, over decades, making it perfect for addressing temporal dynamics and for providing a deeper understanding of the genetics of these periodically reclassified fishes (as species or subspecies). We used six microsatellite markers to assess the current population structure and gene flow patterns across 19 populations of mosquito fish and then compared our results with historical data. Genetic evidence demonstrates that the current hybrid zone is located in a similar geographic region as the historical one, even after three decades. Hybrid fish, however, demonstrate relatively low heterozygosity and are genetically distinct from western and eastern mosquito fish populations. Fin ray counts, sometimes used to distinguish the two species from one another, demonstrate more eastern (G. holbrooki) phenotype fish within the molecular genetic hybrid zone today. Mosquito fish are globally invasive, often found on the leading edge of flooded waters that they colonize, so the impact of hurricanes in the wake of climate change was also evaluated. An increase in the frequency and intensity of hurricanes in the hybrid region has occurred, and this point warrants further attention since hurricanes are known to move these aggressive, invasive species into novel territory. This work contributes to our classical understanding of hybrid zone temporal dynamics, refines our understanding of mosquito fish genetics in their native range, evaluates important genotype–phenotype relationships, and identifies a potential new impact of climate change.     

DNA damage in the kidney tissue cells of the fish Rhamdia quelen after trophic contamination with aluminum sulfate

Even though aluminum is the third most common element present in the earth''s crust, information regarding its toxicity remains scarce. It is known that in certain cases, aluminum is neurotoxic, but its effect in other tissues is unknown. The aim of this work was to analyze the genotoxic potential of aluminum sulfate in kidney tissue of the fish Rhamdia quelen after trophic contamination for 60 days. Sixty four fish were subdivided into the following groups: negative control, 5 mg, 50 mg and 500 mg of aluminum sulfate per kg of fish. Samples of the posterior kidney were taken and prepared to obtain mitotic metaphase, as well as the comet assay. The three types of chromosomal abnormalities (CA) found were categorized as chromatid breaks, decondensation of telomeric region, and early separation of sister chromatids. The tests for CA showed that the 5 mg/kg and 50 mg/kg doses of aluminum sulfate had genotoxic potential. Under these treatments, early separation of the sister chromatids was observed more frequently and decondensation of the telomeric region tended to increase in frequency. We suggest that structural changes in the proteins involved in DNA compaction may have led to the decondensation of the telomeric region, making the DNA susceptible to breaks. Moreover, early separation of the sister chromatids may have occurred due to changes in the mobility of chromosomes or proteins that keep the sister chromatids together. The comet assay confirmed the genotoxicity of aluminum sulfate in the kidney tissue of Rhamdia quelen at the three doses of exposure.     

Ecological genomics in full colour

Colour patterns in animals have long offered an opportunity to observe adaptive traits in natural populations. Colour plays myriad roles in interactions within and among species, from reproductive signalling to predator avoidance, leading to multiple targets of natural and sexual selection and opportunities for diversification. Understanding the genetic and developmental underpinnings of variation in colour promises a fuller understanding of these evolutionary processes, but the path to unravelling these connections can be arduous. The advent of genomic techniques suitable for nonmodel organisms is now beginning to light the way. Two new studies in this issue of Molecular Ecology use genomic sequencing of laboratory crosses to map colour traits in cichlid fishes, a remarkably diverse group in which coloration has played a major role in diversification. They illustrate how genomic approaches, specifically RAD sequencing, can rapidly identify both simple and more complex genetic variation underlying ecologically important traits. In the first, Henning et al. ( 2014 ) detect a single locus that appears to control in a Mendelian fashion the presence of horizontal stripes, a trait that has evolved in numerous cichlid lineages. In the second, Albertson et al. ( 2014 ) identify several genes and epistatic interactions affecting multiple colour traits, as well as a novel metric describing integration across colour traits. Albertson et al. ( 2014 ) go further, by quantifying differential expression of parental alleles at a candidate locus and by relating differentiation among natural populations at mapped loci to trait divergence. Herein lies the promise of ecological genomics – efficiently integrating genetic mapping of phenotypes with population genomic data to both identify functional genes and unravel their evolutionary history. These studies offer guidance on how genomic techniques can be tailored to a research question or study system, and they also add to the growing body of empirical examples addressing basic questions about how ecologically important traits evolve in natural populations.