Population Substructuring in a Migratory Freshwater Fish Prochilodus argenteus (Characiformes, Prochilodontidae) from the São Francisco River

The construction of hydroelectric dams, pollution of rivers and other environmental changes are responsible for the disappearance of many natural fish stocks. The purpose of this work was to analyze the fish Prochilodus argenteus inhabiting the region of the Três Marias dam in the São Francisco River (Brazil) collected in two sites having distinct environmental characteristics. Three novel homologous and one known cross-specific microsatellites were used to assess genetic variation within and between the two collection sites (namely A and B) in order to confirm the occurrence of population substructuring previously suggested using RAPD markers. A higher number of exclusive alleles and a greater genetic variability in region B strongly reinforce the co-existence of different reproductive units in this area. F _ST estimates showed a significant population differentiation between the two sites, indicating the possible existence of distinct gene pools. Considering the economic importance of this fishery resource in the São Francisco River, these findings could provide very important information for fisheries management, aquaculture and conservation of the stocks of this species.     

Biogeographical distribution and ecological ranges of benthic cyanobacteria in East Antarctic lakes

For the first time, the cyanobacterial diversity from microbial mats in lakes of Eastern Antarctica was investigated using microscopic and molecular approaches. The present study assessed the biogeographical distribution of cyanobacteria in Antarctica. Five samples were taken from four lakes spanning a range of different ecological environments in Larsemann Hills, Vestfold Hills and Rauer Islands to evaluate the influence of lake characteristics on the cyanobacterial diversity. Seventeen morphospecies and 28 16S rRNA gene-based operational taxonomic units belonging to the Oscillatoriales, Nostocales and Chroococcales were identified. The internal transcribed spacer was evaluated to complement the 16S rRNA gene data and showed similar but more clear-cut tendencies. The molecular approach suggested that potential Antarctic endemic species, including a previously undiscovered diversity, are more abundant than has been estimated by morphological methods. Moreover, operational taxonomic units, also found outside Antarctica, were more widespread over the continent than potential endemics. The cyanobacterial diversity of the most saline lakes was found to differ from the others, and correlations between the sampling depth and the cyanobacterial communities can also be drawn. Comparison with database sequences illustrated the ubiquity of several cyanobacterial operational taxonomic units and their remarkable range of tolerance to harsh environmental conditions.     

Ultrastructure of Triangulamyxa amazonica n. gen. and n. sp. (Myxozoa, Myxosporea), a parasite of the Amazonian freshwater fish, Sphoeroides testudineus (Teleostei, Tetrodontidae)

Triangulamyxa amazonica n. gen. and n. sp. (Myxozoa, Ortholineidae), found in the lumen of the intestine of the freshwater fish Sphoeroides testudineus, is described. The fish were collected from the Amazon River near the city of Algodoal, State of the Pará, Brazil. Numerous irregular plasmodia containing different stages of sporogony, including spores, were observed. The plasmodia were lying free in the lumen or had slender pseudopodia-like cytoplasmic processes in contact with intestinal epithelial cells with microvilli projections. Spores, which are equilaterally triangular in valvar view with rounded pointed ends and ellipsoidal in transverse section, are 8.5 μm long, 7.6 μm wide, and 3.8 μm thick. The anterior end of the spores contains two equal drop-shaped polar capsules measuring 2.6 μm in length, each having an isofilar polar filament with 5–6 turns. The characteristics of the spore shape, the spore wall structure and its ridge organization, the plasmodial characteristics and the identity of the host suggest that the parasite is a new genus and species, which is herein designated T. amazonica.     

Growth of Lactobacillus plantarum in media containing hydrolysates of fish viscera

AIMS: To compare growth of Lactobacillus plantarum on media containing hydrolysates (peptones) from cod viscera with growth on commercial media. METHODS AND RESULTS: Growth of Lact. plantarum on various fish peptones and commercial peptones/extracts was evaluated using both a Bioscreen apparatus (microtiter plates, no pH control) and fermentors (with pH control). Generally, the performance of the fish peptones was good and only beaten by the performance of yeast extract. Replacement of the 22 g l(-1) complex nitrogen source in standard MRS medium with only 5 g l(-1) fish peptone reduced the biomass yield with only 10%, whereas replacement with a mixture of 2.5 g l(-1) fish peptone and 2.5 g l(-1) yeast extract increased the biomass yield by 10%. CONCLUSIONS: Peptones derived from cod viscera support excellent growth of Lact. plantarum. SIGNIFICANCE AND IMPACT OF THE STUDY: We show that peptones derived from cod viscera are promising constituents of growth media for fastidious food bacteria such as lactobacilli. Media containing these peptones show excellent performance while problems associated with the use of meat-derived peptones (BSE, kosher status) or plant-derived peptones (genetically modified organisms) are avoided.     

Development of polymorphic microsatellites for the invasive Asian fish tapeworm Schyzocotyle acheilognathi

We describe the development of ready-to-use set of fifteen polymorphic microsatellite markers to benefit future population biology and phylogeographic studies on the invasive Asian fish tapeworm Schyzocotyle acheilognathi. The microsatellite loci were selected from partial Illumina shotgun genome sequences of three parasite specimens and their universality tested on a set of 12 geographically distant populations of the parasite. Particularly low levels of heterozygosity have been detected in the Chinese population pointing towards possible hidden population structure that deserves further attention in future population genetic studies.     

Evaluation of satellite retrievals of water quality parameters for Lake Victoria in East Africa

Lake Victoria in East Africa is a major ecosystem, whose size and importance has warranted the exploration of MODIS imagery to provide continuous and accurate water quality information. To this effect, two sea expeditions (in November 2014 and February 2015) were carried out to collect in situ lake surface temperature (LST), chlorophyll a (Chl) and Secchi disk depth (SDD) to compare with the corresponding satellite derived variables. Comparisons were made based on the following error matrices: coefficient of correlation (r), mean square error (MSE), root mean square error (RMSE), mean absolute deviation (MAD) and mean absolute percent error (MAPE). In general the results showed that satellite derived LST gives a good estimate of in situ LST. Conversely, the error matrices indicated that satellite derived Chl yielded more uncertainty when compared with in situ Chl. This could be because of the fact that the MODIS Chl product algorithm was designed for oceans and may not be appropriate for inland lakes. Satellite derived SDD compared fairly well with in situ SDD. From these results it is evident that with more in situ observations and improved algorithms, MODIS can be useful to improve how water quality is monitored on Lake Victoria.     

Stress‐induced peak (but not resting) metabolism correlates with mating display intensity in male guppies

Recent empirical and conceptual papers have highlighted the potential for metabolism to act as a proximate mechanism for behavior that could explain animal personality (consistency over time). Under this hypothesis, individuals with consistently high levels of behavioral activity should also have high resting metabolic rate (RMR) as it can reflect capacity to process food and generate energy. We tested for the predicted positive covariance between RMR and three behaviors that differ in energy demands in 30 male guppies, using multivariate mixed models; we repeatedly measured their activity (10 times each), courtship displays (nine times), voracity (10 times), and metabolism (four‐times). Resting metabolic rate (measured overnight in respirometry trials) did not consistently differ among males, whereas initial peak metabolism measured during those same trials (R = 0.42), and all behaviors were repeatable (R = 0.33–0.51). RMR declined over time suggesting habituation to the protocol, whereas peak metabolism did not. Initial peak metabolism was negatively correlated with courtship display intensity, and voracity was positively correlated with activity, but all other among‐individual correlations were not significant. We conclude that RMR does not provide a proximate explanation for consistent individual differences in behavior in male guppies, and therefore the potential for independent evolution of these physiological and behavioral traits seems possible. Finally, we identify peak metabolism as a potential measure of the stress response to confinement, which highlights the value of considering various aspects of metabolic rates recording during respirometry trials.     

Impacts of cage culture on physico-chemical and bacteriological water quality in Lake Volta,Ghana

The effects of cage fish farming on physico-chemical and bacteriological water quality in Lake Volta, Ghana, were investigated in 2013–2014. Farmed and unfarmed (control) areas of the lake were selected for monitoring. Nutrients, temperature, dissolved oxygen, conductivity, turbidity, pH, total coliforms, Pseudomonas and Vibrio spp. in the water were monitored monthly. Analyses of the water samples were carried out according to standard procedures. Physico-chemical quality of the water in both farm and control sites were within ranges typical of minimally impacted water and did not vary significantly between the two contrasting sites. The bacteriological analysis, however, revealed contamination of the lake water by fish farming. The bacterial counts at the farmed sites were significantly higher (p < 0.05) than those of the control sites, with figures at the farmed sites ranging from 132 to 1 708 cfu 100 ml?1 for total coliforms, 514 to 5 170 cfu 100 ml?1 Pseudomonas spp. and 14 to 516 cfu 100 ml?1 for Vibrio spp. The results suggested that cage fish farming has increased bacterial loads in the lake water, but has had minimal impact on its physico-chemical quality.     

Feeding of larval blue whiting and Atlantic mackerel: a comparison of foraging strategies

Fish larvae employ different feeding strategies depending on area and season of spawning and hatching of larvae. Feeding and growth of larvae of blue whiting Micromesistius poutassou and mackerel Scomber scombrus from Porcupine Bank and the Celtic Shelf Break, west of Ireland, were compared based on prey concentrations in the environment and larval feeding behaviour. Both species were adapted to different environmental conditions. The mesopelagic blue whiting spawned in oceanic water that was well mixed. It was characterized by low production and low prey densities with minimum prey densities <1.0 organism 1⁻¹. Larvae of the Atlantic mackerel hatched later in the season in more productive water that was well stratified. Prey densities in the mackerel environment reached up to 1001⁻¹. Blue whiting larvae displayed a rather random distribution in the water column. Mackerel larvae <7 mm standard length ( L _s) were concentrated above the thermocline, while larvae >7 mm traversed the thermocline into deeper layers. Mackerel larvae >5mm L _s displayed marked cannibalism, exceeding 70%. Daily ration calculated on the basis of gut contents was rather low in both species: between 2.6 and 5.0% in blue whiting, but only 0.6 to 5.4% in mackerel. The results are discussed in relation to the respective environment both species encounter during their early larval life.     

Testing alternative explanations of character shifts against ecological character displacement in brook sticklebacks (<Emphasis Type="Italic">Culaea inconstans</Emphasis>) that coexist with ninespine sticklebacks (<Emphasis Type="Italic">Pungitius pungitius</Emphasis>)

Ecological character displacement (ECD) provides opportunities to test how resource competition generates diversifying selection that results in adaptive divergence. We quantify an association between phenotypic and ecological divergence between two similar small fishes, brook (Culaea inconstans) and ninespine (Pungitius pungitius) sticklebacks, in replicate northern Ontario lakes, Canada. The two species partition resources and habitat, where they coexist, and brooks that coexist with ninespines are more benthically specialized in body form and diet than brooks from local allopatric populations. Here we test various explanations for this pattern. Chance is unlikely to have been the primary cause because divergence is replicated in three separate populations. Preliminary comparisons indicate that resource availability and a variety of abiotic ecological conditions are generally similar between sympatric and allopatric sites, and so do not readily account for the divergence. Biased colonization or extinction is less likely to account for the divergence because character values in sympatry tend to exceed those in allopatry, as expected if they have repeatedly evolved under diversifying selection. Recent studies have also demonstrated that these two species compete, and that competitive effects are more severe for allopatric compared to sympatric brook forms, as predicted if divergence reflects the ghost of competition past. Ongoing studies indicate heritable variation in this system. Our results suggest that even small amounts of character shifts can influence competition and hence relative fitness, further implicating a role for ECD in the evolution of biodiversity.Electronic Supplementary Material Supplementary material is available for this article at