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Increasing shares of microfibers are being detected in environmental samples and a closer look to identify the risk associated with them using ecologically relevant endpoints, especially at sensitive early life stages, is needed. To assess exposure hazards, we used rope samples representative of fiber types ubiquitous in coastal systems, where microfibers are often the most common debris type found in the water column. To compare responses to natural vs. synthetic microfibers, we used rinsed “natural” cotton, polyester, and polypropylene microfibers (80-150 µm length, 8-20 µm width) created from the rope. Larval and juvenile estuarine indicator species Inland Silverside (Menidia beryllina) and mysid shrimp (Americamysis bahia), respectively, were exposed to these three microfiber types at three concentrations (3, 10, 30 particles/ml) along a 5-25 PSU salinity gradient to mimic estuarine conditions. Behavioral responses, growth, and ingestion were measured. The cotton microfibers were not detected in the digestive tracts of Silversides, however, both the polyester and polypropylene microfibers were detected in the Silversides’ stomach and gut lining. None of the fiber types were detected in mysid shrimps. Mysids exposed to cotton microfibers had fewer behavioral effects compared to Silversides, who responded more to cotton. Cotton exerted no effect on growth in Silversides but did cause reduced growth in the mysids at the two lower salinities. In contrast, polyester and polypropylene were identified to have a significant dose dependent effect on mysid and Silverside behavior as well as growth was affected in at least one of the three salinities at concentrations as low as 3 particles/ml. Cotton impacted both the organism’s behavior more at higher salinities, whereas polyester and polypropylene had more impacts at lower salinities. This raises concerns for microfiber impacts on estuarine ecosystems and the need for policies to limit microfiber production and outfall into the aquatic environment.

The aim of this study is to develop a better understanding of seabird foraging behaviour and the anti-predator behaviour of their prey. Studies of seabirds' foraging and prey-capture behaviour, as it relates to the evasive and escape behaviour of schooling fish, are sparse. Our study was carried out at One Tree Reef on the southern end of the Great Barrier Reef, Australia. A school of hardyheads Pranesus capricornensis sheltered in the shallows over the sand flats in front of the research station for 14 non-consecutive days. In that time, Lesser Crested Terns Thalasseus bengalensis were observed for 10 hours from above the surface in 37 foraging bouts and for 40 minutes from underwater in at least one foraging bout. In each foraging bout, a single tern dived into the school. We found that terns on average dived at a rate of 0.67 ± 0.35 dives/minute from 4-5 m above the surface. The depth range of dives was 43-58 cm. Therefore, fish within 58 cm of the surface were potentially accessible. The total length of the hardyheads was 10-12 cm, which is within the size range useable by terns. Fish used flash expansion to escape diving terns and formed a vacuole around birds as they slowly ascended to the surface. This escape manoeuvre was effective about 80% of the time. The fish that were caught did not respond to the escape movements of the fish above them and, therefore, were isolated. Fish also used the C-startle response to escape terns underwater and in mid-air. The anti-predator manoeuvres of hardyheads are similar to those observed among Clupea spp. (herrings and sardines) and Ammodytes spp. (sand eels) escaping sub-surface predators. Hardyheads and sardines react in the same way to gannets Morus spp. and terns that plunge dive directly to their prey, partially confirming the prediction that results for plunge-diving gannets are generalisable to other gannets and boobies (Sula spp.), terns and gulls (Larus spp.), tropicbirds (Phaethon spp.), pelicans (Pelecanus spp.), and kingfishers (Alcedinidae). [ABSTRACT FROM AUTHOR]

Silversides are a widely distributed group across South America, with several species occupying marine, freshwater and estuarine environments. Several authors suggest main transitions among these environments took place during Pleistocene, and were accompanied with rapid speciation events. This scenario produced very limited genetic and morphological differentiation among the species. However, most of these surveys have an incomplete coverage of the intraspecific genetic diversity of the taxa studied. In this work, we reconstructed six mitochondrial genomes of O. argentinensis using transcriptomic data, and used them—in combination with several nuclear markers retrieved from the same transcriptomes—to explore the effect of additional coverage of intraspecific diversity of this species in phylogenetic reconstructions. Unlike previous works, phylogenetic analyses failed to identify O. argentinensis as a monophyletic group in relation with closely related taxa. Our results suggest that several species of the genus, especially those related to O. argentinensis, need further taxonomic revision. [ABSTRACT FROM AUTHOR]

Several New World atheriniforms have been recognized as temperature‐dependent sex determined (TSD) and yet possess a genotypic sex determinant (amhy) which is primarily functional at mid‐range temperatures. In contrast, little is known about the sex determination in Old World atheriniforms, even though such knowledge is crucial to understand the evolution of sex determination mechanisms in fishes and to model the effects of global warming and climate change on their populations. This study examined the effects of water temperature on sex determination of an Old World atheriniform, the cobaltcap silverside Hypoatherina tsurugae, in which we recently described an amhy homologue. We first assessed the occurrence of phenotypic/genotypic sex mismatches in wild specimens from Tokyo Bay for three years (2014–2016) and used otolith analysis to estimate their birth dates and approximate thermal history during the presumptive period of sex determination. Phenotypic sex ratios became progressively biased towards males (47.3%–78.2%) during the period and were associated with year‐to‐year increases in the frequency of XX‐males (7.3%–52.0%) and decreases in XY/YY‐females (14.5%–0%). The breeding season had similar length but was delayed by about 1 month per year between 2014 and 2016, causing larvae to experience higher temperatures during the period of sex determination from year to year. Larval rearing experiments confirmed increased likelihood of feminization and masculinization at low and high temperatures, respectively. The results suggest that cobaltcap silverside has TSD, or more specifically the coexistence of genotypic and environmental sex determinants, and that it affects sex ratios in wild populations. [ABSTRACT FROM AUTHOR]

Abstract Two species of heterophyid trematodes were found in the Magellanic penguin, Spheniscus magellanicus (Forster), from Patagonia, Argentina. Ascocotyle (Ascocotyle) patagoniensis Hernández-Orts et al. (2012) is re-described based on new, properly fixed specimens (original material from South American sea lion, Otaria flavescens Shaw, was from frozen hosts). Metacercariae of this species are reported and described for the first time from the heart of the silversides, Odontesthes argentinensis (Valenciennes) and O. smitti (Lahille), from Patagonia. Ascocotyle (Phagicola) cameliae n. sp. is described from the intestine of S. magellanicus. The new species is placed into the subgenus Phagicola Faust, 1920 because of the presence of a single row of circumoral spines and uterine loops and vitelline follicles being confined posterior to the ventral sucker. However, it differs distinctly from other members of this subgenus by the number (19–24) and length (23–31 μm) of massive circumoral spines and by the morphology of the ventrogenital sac with a large, simple gonotyl devoid of refractile bodies. Molecular data (partial 28S rDNA sequences) for both species are also provided. Matching sequences from metacercarial and adult stages helped elucidate partially the life-cycle of A. (A.) patagoniensis. The interspecific relationships and phylogenetic position of Ascocotyle were further assessed on a broad phylogeny on the Opisthorchioidea Looss, 1899. Ascocotyle (P.) ornamentata Shalaby, Esposito, Riegler & Carratù (1993) described from decomposed worms (all circumoral spines were detached) found in a dog in Egypt, with no type-specimens of this species deposited in a repository collection, is considered to be species inquirenda. Graphical abstract Image 1 Highlights • Two species of heterophyid trematodes are reported from the Magellanic penguin, Spheniscus magellanicus , from Patagonia. • One species is new to science and is morphologically and molecularly characterised. • Previously known species is redescribed and its life-cycle is partly elucidated. • Phylogenetic relationships of heterophyid trematodes are assessed. [ABSTRACT FROM AUTHOR]

The length–weight relationships (LWRs) for six native fish species from the Chapala Lake, Mexico, are described in this paper. The fish were caught monthly with the support of local fishermen from different landing sites. The daily catch is obtained using the nasa charalera (pot) and the gill net. Each fisherman can operate 20 pots daily at each fishing site for approximately six or seven months; this pot is a 2 m long cylinder, 0.5 m in diameter, with a mesh opening of 0.5 to 1 cm. Also, each fisherman can set between 10 and 20 gill nets each day at sunset and recover them in the morning, again for six or seven months. The length of the gill net is 30 m or more with a 2 m drop, with a 1 cm mesh size. The study provides basic data, morphometric data on length and weight of native species belonging to the genus Chirostoma. These species are of great importance for the local fishery with the Mesa Central of Mexico. [ABSTRACT FROM AUTHOR]

Accuracy in estimating occupancy of a threatened species is important for conservation but false absences bias many monitoring programs. Imperfect detection is especially relevant to surveys of rare wetland fishes which are often small-bodied and cryptic. Many factors influence probability of detection, including fish size and abundance, habitat characteristics and sampling devices. Imperfect detection can be addressed by accounting for probability of detection when estimating occupancy by modelling detection/non-detection data collected in replicate surveys. Three ecological specialists were once common in habitats associated with Lake Alexandrina at the terminus of the Murray-Darling Basin, Australia. The threatened Murray Hardyhead (Craterocephalus fluviatilis), Southern Pygmy Perch (Nannoperca australis) and Yarra Pygmy Perch (N. obscura) are now rare in the region following population collapses during a prolonged drought, and ongoing monitoring aims to assess their statuses for management purposes. This study compares probability of detection of the rare wetland fishes and cohabiting species during 2 years of multi-species monitoring using contrasting sampling devices (fyke and seine). The findings suggest large variations in estimated probability of detection can occur between devices for Murray Hardyhead and Southern Pygmy Perch. Yarra Pygmy Perch was undetected during the study. Overall, the findings show multi-species monitoring programs using a single sampling device may wrongly estimate the occupancy of a target fish. By accounting for imperfect detection, multi-species monitoring programs will improve inferences regarding population status, recovery and habitat quality of fishes to more accurately inform wetland management. [ABSTRACT FROM AUTHOR]

The triazine-based herbicide irgarol is widely used in antifouling systems as an algicide and has been detected recently in multiple coastal environments. Studies evaluating sub-lethal responses of fish following exposure to irgarol are limited. Moreover, impacts of climate change on fish endocrinology may also contribute to the sublethal toxicity of irgarol. We assessed the effects of irgarol on thyroid endpoints in juveniles of Menidia beryllina under two different treatments of salinity (10 and 20 ‰) and two temperatures (10 and 20°C). Condition factor coefficients (K) of animals were significantly affected by 0.1 to 10 μg/L of irgarol at the higher temperature. Levels of T3 were changed in whole body homogenates from both temperatures at 10‰ following exposure to 1 to 10 μg/L. T4 levels were altered only at 10°C when animals were treated with 1 to 10 μg/L (10 ‰), and in 0.1 and 10 μg/L (20 ‰). Increased transcripts of deiodinase enzymes at 10 °C may be impacted by salinity and alter thyroid hormone homeostasis. Impact on gene expression of thyroid (α and β) and growth hormone receptors were also determined. Our results highlight the relevance of environmental variable that may impact the ecological risk of irgarol in estuarine systems. [ABSTRACT FROM AUTHOR]

Eating quality attributes of pork loin ( M. longissimus thoracis et lumborum ) and silverside ( M. biceps femoris ) from female and immunocastrated male carcases hung from either the Achilles tendon or aitchbone, aged for either 2 or 7 days post-slaughter and cooked as roasts, stir fry and steak (loin only) (n = 25/gender) was assessed. A positive control treatment of moisture infusion (10% injection rate) was applied to Achilles hung sides with cuts aged for 2 d post-slaughter. Neither gender nor ageing period influenced consumer sensory scores. Beneficial effects of aitchbone hanging on eating quality compared with Achilles hanging were largely observed after 2 d ageing, with improvements (P < 0.05) in overall liking scores found for loin stir fry and silverside stir fry and roasts. Overall liking scores of all cuts, except silverside stir fry, were increased (P < 0.05) when moisture infused compared with those from aitchbone-hung sides. However, targeted fail rates of <10% were not consistently achieved across all cuts evaluated. [ABSTRACT FROM AUTHOR]

Abstract: High‐throughput cell assays that detect and integrate the response of multiple chemicals acting via a common mode of action have the potential to enhance current environmental monitoring practices. Establishing the linkage between in vitro and in vivo responses is key to demonstrating that in vitro cell assays can be predictive of ecologically relevant outcomes. The present study investigated the potency of 17β‐estradiol (E2), estrone (E1), nonylphenol (NP), and treated wastewater effluent using the readily available GeneBLAzer® estrogen receptor transactivation assay and 2 life stages of the inland silverside (Menidia beryllina). In vitro estrogenic potencies were ranked as follows: E2 > E1 >> NP. All 3 model estrogens induced vitellogenin and choriogenin expression in a dose‐dependent manner in larvae and juveniles. However, apical effects were only found for E2 and E1 exposures of juveniles, which resulted in female‐skewed sex ratios. Wastewater effluent samples exhibiting low in vitro estrogenicity (below the 10% effective concentration [EC10]), did not cause significant changes in M. beryllina. Significant induction of estrogen‐responsive genes was observed at concentrations 6 to 26 times higher than in vitro responses. Gonadal feminization occurred at concentrations at least 19 to 26 times higher than the in vitro responses. These findings indicated that in vitro cell assays were more sensitive than the fish assays, making it possible to develop in vitro effect thresholds protective of aquatic organisms. Environ Toxicol Chem 2018;37:884–892. © 2017 SETAC [ABSTRACT FROM AUTHOR]

This study investigated the effects of ageing period (2 or 7 days), endpoint temperature (70 or 75 °C), cut type (loin ( M. longissimus thoracis et lumborum), silverside (M. biceps femoris), blade (M. triceps brachii) and chuck tender (M. supraspinatus)), cooking method (roast and stir fry (all cuts) and steak (loin only)) on eating quality attributes of pork from entire and immunocastrated male pigs. Higher intramuscular fat levels were found in all cuts from immunocastrated males compared with entire males. Of the seven cut type × cooking method combinations evaluated, shoulder cuts had the lowest fail rate (P < 0.001) and loin steak and silverside cuts scored lowest (P < 0.001) for tenderness, juiciness, overall liking, quality grade and re-purchase intention. Although no differences in sensory scores due to gender were observed, boar taint was identified in 10% of entire males. Minimising adverse risks in eating quality due to boar taint in males remains a key industry issue to ensure consistent delivery of high quality pork. [ABSTRACT FROM AUTHOR]

Abstract: The diet composition and feeding strategy of the New World silverside Odontesthes argentinensis were evaluated in a temperate coastal area during austral summer. This species is an economically significant resource for the fishing industry in South America. The food preference of O. argentinensis varied with its size‐class: the smallest size‐classes preferred diatoms and annelids, larger size‐classes seemed to prefer barnacle cypris larvae, and the largest size‐classes showed a preference for decapod megalopa larvae. Plankton samples were dominated by calanoid and cyclopoid copepods; however, contrary to what was expected, O. argentinensis showed negative selectivity for both groups. A selectivity index indicated that O. argentinensis selects the food it eats with regard to prey availability in the environment. The information obtained in this study demonstrates the importance of knowing the food preference of O. argentinensis to obtain a better condition factor, which will be key to its potential farming in closed systems. [ABSTRACT FROM AUTHOR]

Female crossbred pigs were randomly allocated at 16 weeks of age to one of three dietary treatments (A: corn and soybean meal; B: wheat and canola meal; C: wheat and sorghum) matched for digestible energy (13.6 MJ DE/kg) and total lysine (0.93–0.95%) and fed for 4, 5 or 8 weeks, respectively, prior to slaughter. Loin ( M. longissimus thoracis et lumborum ) and silverside ( M. biceps femoris ) were obtained from 20 pigs per dietary treatment group and prepared into steaks and roasts, respectively, for consumer evaluation with ageing treatments of 7 and 28 days post-slaughter allocated within muscle. Neither dietary treatment/age at slaughter nor ageing treatment influenced sensory traits of either cut. Intramuscular fat levels were also not influenced by dietary treatment. Higher (P < 0.001) fail rates for silverside roasts compared with loin steaks indicate that different interventions are needed at a cut level to optimise pork eating quality consistency and consumer expectations. [ABSTRACT FROM AUTHOR]

The silverside Odontesthes argentinensis is an economically significant resource for commercial fisheries in South America. We evaluated the presence of trace elements in the stomach content and fish tissues (muscle and otoliths) of O . argentinensis . In addition, we assessed the presence of trace elements in its prey (zooplankton) and in seawater in a coastal temperate area. The most abundant trace elements found in the water, zooplankton, stomach content, and fish tissues (muscle and otoliths) constituted of Ba, Mn, Sr and Zn, while Cd, Cu and Pb were observed in lower concentrations. We concluded that O . argentinensis specimens captured from the environment, within the length range analyzed for muscle samples (total length: < 21 cm), are deemed fit for human consumption because the concentrations of trace elements mostly meet the standards established in the Argentine Food Code. The information obtained in this study is vital for O . argentinensis farming in closed systems. [ABSTRACT FROM AUTHOR]

Diel fluctuations in dissolved oxygen (DO) and pH create hypoxic conditions that alter the quality of shallow estuarine nursery habitats for juvenile fishes. Understanding how different species in these environments mitigate stress associated with intermittent hypoxia through compensatory behaviors, such as aquatic surface respiration (ASR), is important in determining the effect of these stressors on estuarine ecosystems. Behavioral responses of Atlantic silversides ( Menidia menidia ), striped killifish ( Fundulus majalis ), mummichog ( Fundulus heteroclitus ), and juvenile striped bass ( Morone saxatilis ) were independently observed during exposure to two levels of diel-cycling DO (3–9 mg O 2 l − 1 and 1–11 mg O 2 l − 1 ) each tested with both the corresponding pH cycle (7.2–7.8 and 6.8–8.1, respectively) and static pH (7.5) under controlled laboratory conditions. In treatments in which DO declined to ~ 3 mg O 2 l − 1 , none of the species examined exhibited ASR behavior either with or without the associated pH decline. However, ASR was observed during both 4-hour and extended 16-hour exposure where DO declined to ~ 1.0–1.6 mg O 2 l − 1 in M. menidia and both Fundulus species . M. saxatilis did not exhibit ASR and no mortalities occurred during 4-hour low DO/pH treatments or during 16 hour exposure to 1.5 mg O 2 l − 1 . During extended 16-hour treatments, DO thresholds for ASR were not found to be different between F. majalis and F. heteroclitus , but both differed significantly from M. menidia . Across both 4-hour and 16-hour treatments, the onset of ASR was observed in M. menidia at or near lethal levels (1.31–1.62 mg O 2 l − 1 ). No evidence of a pH ( p CO 2 ) effect on ASR or survival was found in any species in response to naturally co-varying DO and pH swings, despite pH as low as 6.8 and high p CO 2 levels of >~12,000 μatm. These results suggest that utilization of ASR is a species-specific response influenced by the magnitude and duration of hypoxic exposure. ASR may serve as a last-ditch strategy by M. menidia to prolong survival for minutes to hours, but function as a means for F. heteroclitus to mitigate or reduce negative effects of hypoxia on a scale of days to weeks, with F. majalis exhibiting an intermediate response. [ABSTRACT FROM AUTHOR]

A master sex-determining gene, the Y chromosome-linked anti-Müllerian hormone (amhy) gene, has been described in two New World atheriniform species but little is known on the distribution, evolution, and function(s) of this gene in other Atheriniformes. Interestingly, amhy has been found to coexist with temperature-dependent sex determination (TSD), providing a unique opportunity to explore the interplay between genotypic and environmental sex determination. In this study, the search for an amhy homolog was extended to an Old World atheriniform, the cobaltcap silverside Hypoatherina tsurugae (Atherinidae). The full sequences, including the coding and noncoding regions, of the autosomal amh (amha) and a putative amhy were obtained. The deduced Amha and Amhy proteins comprised 511 and 340 amino acids (aa), respectively. PCR analysis with genomic DNA from wild adults and from laboratoryreared juveniles revealed a high, but not complete association of ~95% between amhy and maleness. The spatiotemporal expression of amhy and amha during gonadal sex differentiation was analyzed by qRT-PCR and in situ hybridization (ISH). amhy transcription (in amhy-positive larvae) started before and peaked during histological differentiation of the gonads whereas amha was negligible during the same period in both genotypes. These results demonstrate that the amhy, although with some structural differences in relation to the amhy of some New World atheriniforms, is strongly associated with maleness and probably important for testicular development in this Old World atheriniform. Thus, amhy is a candidate sex determination gene in cobaltcap silverside and it will be key to scrutinize the mechanism of sex determination in this species. [ABSTRACT FROM AUTHOR]

Today most population genomic studies of nonmodel organisms either sequence a subset of the genome deeply in each individual or sequence pools of unlabelled individuals. With a step-by-step workflow, we illustrate how low-coverage whole-genome sequencing of hundreds of individually barcoded samples is now a practical alternative strategy for obtaining genomewide data on a population scale. We used a highly efficient protocol to generate high-quality libraries for ~6.5 USD from each of 876 Atlantic silversides (a teleost fish with a genome size ~730 Mb) that we sequenced to 1-4× genome coverage. In the absence of a reference genome, we developed a bioinformatic pipeline for mapping the genomic reads to a de novo assembled reference transcriptome. This provides an 'in silico' method for exome capture that avoids the complexities and expenses of using wet chemistry for target isolation. Using novel tools for analysis of low-coverage data, we extracted population allele frequencies, individual genotype likelihoods and polymorphism data for 2 504 335 SNPs across the exome for the 876 fish. To illustrate the use of the resulting data, we present a preliminary analysis of geographical patterns in the exome data and a comparison of complete mitochondrial genome sequences for each individual (constructed from the low-coverage data) that show population colonization patterns along the US east coast. With a total cost per sample of less than 50 USD (including sequencing) and ability to prepare 96 libraries in only 5 h, our approach adds a viable new option to the population genomics toolbox. [ABSTRACT FROM AUTHOR]

Significant reductions in the water volume of shallow lakes impose a restriction on species segregation promoting more interactions in the trophic relationships. The diets of three closely related zooplanktivorous silversides belonging to the Atherinopsidae species flock of lake Chapala , Mexico, were analyzed at two sites (Chirostoma jordani, C. labarcae, and C. consocium). Diets were described in critical shallow (August 2000) and volume recovery conditions (August 2005). Diets included mainly cladocerans (Bosmina, Ceriodaphnia, and Daphnia) and copepods (Cyclops). A significant difference in diets was detected when comparing years (MRPP analysis, A = 0.22, p < 0.0001) and sites at different years (MRPP analysis, A = 0.17, p = 0.004). According to niche breadth mean values, species were classified as specialized and intermediate feeders. In shallow conditions, the small range of niche breadth (1.72 to 3.64) and high diet overlap values (D = 0.64, L = 8.62) indicated a high potential for interspecific exploitative interaction. When the lake volume recovered, an increase in the niche breadth range (1.04 to 4.96) and low niche overlap values (D = 0.53, L = 2.32) indicated a reduction of the species interaction. The Mann-Whitney U-test supported this pattern by showing a significant difference between years for niche overlap (p = 0.006). The increased interaction during the low volume suggests alternative segregation in life-history variations and other niche dimensions such as spatial or temporal distribution.La reducción significativa en el volumen de agua de los lagos someros impone una restricción en la segregación de las especies y promueve una mayor interacción en las relaciones tróficas. Se analizó la dieta de tres especies cercanamente emparentadas de zooplanctívoros pertenecientes al flock de Aterinópsidos del lago de Chapala en dos sitios (Chirostoma jordani, C. labarcae y C. consocium). Las dieta fue descrita en una condición somera crítica (Agosto 2000) y en una condición de recuperación del lago (Agosto 2005). En la dieta se incluyen principalmente cladóceros (Bosmina, Ceriodaphnia y Daphnia) y copépodos (Cyclops). Se detectó una diferencia significativa en la dieta cuando se comparan los años (análisis MRPP, A = 0.22, p < 0.0001) y los sitios en los diferentes años (análisis MRPP, A = 0.17, p = 0.004). De acuerdo a los valores promedio de amplitud de nicho, las especies fueron clasificadas como especialistas y consumidores intermediarios. En condiciones someras, el pequeño intervalo de la amplitud de nicho (1.72 a 3.64) y los altos valores del traslape de nicho (D = 0.64, L = 8.62) indicaron un alto potencial para una interacción explotativa inter-específica. Cuando el lago se recupera en su volumen, un incremento en el intervalo de amplitud de nicho (1.04 a 4.96) y los bajos valores del traslape de nicho (D = 0.53, L = 2.32) indicaron una reducción en la interacción de las especies. La prueba U de Mann-Whitney refuerza este patrón al mostrar una diferencia significativa entre los años para el traslape de nicho (p = 0.006). El incremento en la interacción de las especies durante condiciones de volumen bajo, sugiere una segregación alternativa con variaciones en la historia de vida y en otras dimensiones del nicho como en el caso de la distribución espacial y temporal.

En este trabajo se dan a conocer restos fósiles de pejerreyes recuperados en secuencias sedimentarias correspondientes al Piso-Edad Bonaerense (Pleistoceno Medio) de la localidad de Centinela del Mar, provincia de Buenos Aires, Argentina. Los únicos registros fósiles previos de pejerreyes sudamericanos se restringen a tres localidades de edad Miocena de Argentina y Chile. La presencia de diversos caracteres osteológicos diagnósticos permitió referir al género Odontesthes algunas de las estructuras óseas aquí tratadas. Estos registros brindan nuevos datos acerca de la composición de las ictiofaunas pleistocénicas de Argentina, constituyendo los primeros restos fósiles de pejerreyes procedentes de la región pampeana.This paper presents the fossil remains of silversides recovered in sedimentary sequences corresponding to Centinela del Mar district Bonaerian Stage-Age (Middle Pleistocene), Buenos Aires province, Argentina. The few only previously described fossil silversides are restricted to three Chilean and Argentinean Miocene localities. The silversides studied here present several diagnostic osteological characters that allow us to refer the remains to the genus Odontesthes. These records give us new data on the composition of the pleistocenic ictiofaunas of Argentina, besides representing the first fossil records of silversides from the Pampean region.

Starved larvae of the silversides O. hatcheri (2- and 5-days-old) and Odontesthes bonariensis (5-days-old) were used to compare the oxygen consumption rates at 0, 5, 10, 20 and 30 ppt salinity. Oxygen consumption of O. hatcheri and O. bonariensis was minimal at 0 and 10 ppt, respectively, salinities close to those encountered in areas inhabited by these fishes. In both species, oxygen consumption rates thereafter increased with increasing salinity, and then abruptly decreased at 30 ppt. Lower consumption at extreme salinities might be a result of reduced activity, which in itself was salinity-modulated. Differences in activity may explain the fact that oxygen consumption rates of 5-day-old larvae were higher than 2-day-old larvae, which still possess yolk-sac. In this case, starved larvae incurred in higher metabolic demand due to the continuous swimming in the search for food.As larvas em inanição de peixe-rei O. hatcheri (2 e 5 dias de idade) e Odontesthes bonariensis (5 dias de idade) foram usadas para comparar as taxas de consumo de oxigênio em salinidades de 0, 5, 10, 20 e 30 ppt. As taxas de consumo de oxigênio de O. hatcheri e O. bonariensis foram mínimas a 0 e 10 ppt, respectivamente, salinidades próximas aquelas encontradas nas áreas onde estes peixes habitam. Em seguida, em ambas as espécies, as taxas de consumo de oxigênio aumentaram com o incremento da salinidade, e abruptamente caíram a 30 ppt. As taxas de consumo mais baixas em salinidades extremas podem ser resultado da atividade reduzida, sendo portanto modulada pela salinidade. Diferenças na atividade possivelmente explicam o fato das taxas de consumo de oxigênio de larvas de 5 dias de idade serem maiores em comparação a larvas de 2 dias, ainda com saco vitelínico. Neste caso, larvas em inanição impõem um maior gasto metabólico devido a natação contínua em busca de alimento.

The big-scale sand smelt, Atherina boyeri, is recorded from the Devegecidi Dam Lake in 2016, the first record of this invasive species in the Tigris River basin, with potential to extend to all countries in the Middle East. The smelts were caught with a trawl net mesh size of 6 mm. The captured specimens are described and compared. Records of A. boyeri from Turkish inland waters are summarised from the literature. [ABSTRACT FROM AUTHOR]

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In the southeastern USA, catfish aquaculture is burdened by predation from piscivorous birds and the digenetic trematodes they carry. In addition to cultured ictalurid fish, other forage or incidental fish species inhabit catfish production ponds. Of these, the inland silverside Menidia beryllina was recently found to harbor larval metacercariae of several trematode species. Three species of metacercariae were reported, two of which represent the first morphological descriptions of an Austrodiplostomum sp. and Bolbophorus sp. metacercaria, respectively. A total of 15 silversides were collected from a commercial catfish pond and examined for trematode infection. These fish were parasitized by metacercariae of an Austrodiplostomum sp. (100 % prevalence) in the eyes and brain, a Bolbophorus sp. (86.7 % prevalence) in the musculature, and Clinostomum marginatum (33.3 % prevalence) in the musculature and fins. All three trematode species were characterized morphologically and molecularly by sequencing of the cytochrome c oxidase subunit 1 gene (CO1). In addition, the internal transcribed spacer 1 region (ITS1), 5.8S rRNA gene, and ITS2 region were determined for the Bolbophorus sp., which linked this metacercaria to a Bolbophorus sp. cercaria from a planorbid snail Planorbella trivolvis and an unnamed Bolbophorus sp. adult from the American white pelican Pelecanus erythrorhynchos. Furthermore, Biomphalaria havanensis snails were collected from the same pond and found actively shedding cercariae morphologically and molecularly consistent with a diplostomid cercaria reported from Bi . havanensis in catfish ponds in Mississippi, USA. Sequence comparisons deemed these cercariae conspecific to the Austrodiplostomum sp. from inland silverside described here. Channel catfish fingerlings were exposed to these cercariae at doses of 50 and 100 cercariae per fish. The infectivity of this Austrodiplostomum sp. in channel catfish was assessed at 10 and 20 days post exposure (dpe). Metacercariae were observed in both the eyes and brain of infected channel catfish, supporting molecular data that suggests the cercaria and metacercaria are both stages of a previously unidentified Austrodiplostomum sp. life cycle. [ABSTRACT FROM AUTHOR]

Inland ( Menidia beryllina) and tidewater silversides ( M. peninsulae) are the most common of the Menidia fishes along the Texas coast, USA. Though genetically distinct, these species are morphologically very similar and often segregate by salinity with M. beryllina occupying fresh to brackish salinities and M. peninsulae occupying brackish to oceanic salinities. Their ranges are known to overlap, suggesting the possibility for interspecific competition, and significant hybridization has been documented. This study utilizes an integrative approach of morphological and molecular techniques to examine if divergent environmental constraints (inland freshwater impoundments versus coastal saline bays) could potentially result in parallel changes in morphology among populations of Menidia spp. occupying similar habitat types or if Menidia spp. occupying the same areas exhibit divergent changes in morphology (i.e., character displacement) suggesting historic interspecific competition. While both coastal (sympatric) and inland (allopatric) forms of M. beryllina showed significant morphological separation from M. peninsulae, coastal populations were slightly more similar to M. peninsulae than inland populations. Intraspecific comparisons revealed significant morphological and molecular variation among M. beryllina populations and limited variation among M. peninsulae populations. These findings coupled with a review of past Menidia work suggest that salinity regimes may drive the presence of M. beryllina in coastal bays, with increased salinity restricting movement of this species among river drainages resulting in both interspecific and intraspecific isolation. Thus, morphological and molecular variation in Menidia seems to be driven primarily by environmental conditions with interspecific competitive interactions of little significance. This study is the most comprehensive comparison of these species to date and conclusions may be applied broadly to the process and sequence of speciation of Menidia fishes in the Gulf of Mexico. [ABSTRACT FROM AUTHOR]

Estuaries are dynamic environments, key for the survival of innumerous ecologically or economically important fish species. Among these species are Neotropical silversides ( Atherinella brasiliensis ), which are resident and abundant in Brazilian estuaries and used as a complementary source of income and food for local communities. To better understand silverside populations in Brazil, we evaluated the genetic diversity, structure and demography of fish sampled at six estuaries from the northeastern to the southern coast, using Random Amplified Polymorphic DNA and mitochondrial DNA (D-loop) markers. High haplotype diversities (h ranging from 0.75 to 0.99) were found in all populations except Carapebus, located in Southeast Brazil (h = 0.54). A total of 69 mtDNA haplotypes were found, with Itaparica (Northeast Brazil) and Carapebus presenting only exclusive haplotypes, while some were shared among populations in the South. Strong regional structure was observed, with very high differentiation between Itaparica and Carapebus, as well as among these two populations and the ones from the Southern region (Paranaguá, Conceição, Camacho and Patos). Among southern areas, low/moderate structure was detected. Most populations showed unimodal mismatch distributions indicating recent demographic expansion, while Carapebus presented a multimodal distribution characteristic of a stable or bottlenecked population. Times since possible population expansion were highest in Itaparica (32,500 ya) and Carapebus (29,540 ya), while in the Southern region longest time was observed at Conceição (25,540 ya) and shortest at Patos (9720 ya). In a general manner, haplotype diversities were directly related to times since population expansions; again, Carapebus was the exception, displaying long time since expansion but low diversity, possibly due to a recent bottleneck caused by the isolation and human impacts this lagoon is subject to. Isolation by Distance was significant for Itaparica and Carapebus, and considering the extremely high differentiation of these populations, we suggest that they could be undergoing speciation. To adequately manage and maintain the genetic variability of silversides in Brazilian estuaries, we propose three distinct management units for this species: 1) Itaparica; 2) Carapebus; and 3) Southern Brazil. [ABSTRACT FROM AUTHOR]

Accumulation and toxicity of cyanobacterial toxins, particularly microcystin-LR (MCLR) have been extensively studied in fish and aquatic invertebrates. However, MCLR excretion mechanisms, which could reduce this toxin’s effects, have received little attention. The Patagonian silverside, Odontesthes hatcheri , is an omnivorous-planktivorous edible fish, which has been shown to digest cyanobacterial cells absorbing MCLR and eliminating the toxin within 48 h without suffering significant toxic effects. We studied the effects of MCLR on glycoconjugate composition and the possible role of multidrug resistance associated proteins (Abcc) in MCLR export from the cells in O. hatcheri intestine. We treated O. hatcheri with 5 μg MCLR g −1 body mass administered with the food. Twenty four hours later, the intestines of treated and control fish were processed for lectin-histochemistry using concanavalin A (ConA), Triticum vulgaris agglutinin (WGA), and Dolichos biflorus agglutinin (DBA). MCLR affected the distribution of glycoconjugates by augmenting the proportion of ConA-positive at the expense of WGA-positive cells. We studied MCLR effects on the transport of the Abcc-like substrates 2,4-dinitrophenyl- S -glutathione (DNP-SG) and calcein in ex vivo intestine preparations (everted and no-everted sacs and strips). In treated preparations, CDNB together with MCLR (113 μg MCLR g −1 intestine, equivalent to 1.14 μmol L −1 when applied in the bath) or the Abcc inhibitor, MK571 was applied for one hour, during which DNP-SG was measured in the bath every 10 min in order to calculate mass-specific DNP-SG transport rate. MCLR significantly inhibited DNP-SG transport (p < 0.05), especially in middle intestine (47 and 24%, for luminal and serosal transport, respectively). In middle intestine strips, MCLR and MK571inhibited DNP-SG transport in a concentration dependent fashion (IC 50 3.3 and 0.6 μmol L −1 , respectively). In middle intestine strips incubated with calcein-AM (0.25 μmol L −1 ), calcein efflux was inhibited by MCLR (2.3 μmol L −1 ) and MK571 (3 μmol L −1 ) by 38 and 27%, respectively (p < 0.05). Finally, middle intestine segments were incubated with different concentrations of MCLR applied alone or together with 3 μM MK571. After one hour, protein phosphatase 1 (PP1) activity, the main target of MCLR, was measured. 2.5 μM MCLR did not produce any significant effect, while the same amount plus MK571 inhibited PP1 activity (p < 0.05). This effect was similar to that of 5 μM MCLR. Our results suggest that in O. hatcheri enterocytes MCLR is conjugated with GSH via GST and then exported to the intestinal lumen through Abcc-like transporters. This mechanism would protect the cell from MCLR toxicity, limiting toxin transport into the blood, which is probably mediated by basolateral Abccs. From an ecotoxicological point of view, elimination of MCLR through this mechanism would reduce the amount of toxin available for trophic transference. [ABSTRACT FROM AUTHOR]

Copyright of Revista Mexicana de Biodiversidad is the property of Universidad Nacional Autonoma de Mexico, Instituto de Biologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aim of the present study was to test whether different degrees of human activity affect the diet of the Brazilian silverside Atherinella brasiliensis in two tropical estuaries. Fish were collected along the salinity gradient of two Brazilian estuaries, the heavily impacted Paraiba Estuary and the less impacted Mamanguape Estuary, in the dry and wet seasons. The findings confirm that A. brasiliensis has generalist feeding habits and is able to change its diet under different environmental conditions. The results indicate clear spatial ( i.e. along the estuarine gradient) changes in diet composition in both estuaries, but diet was also influenced by the degree of anthropogenic disturbance. During the wet season in the nutrient enriched Paraiba Estuary, when human activity was higher, the diet of A. brasiliensis was poorer and dominated by few dietary items, reflecting the potential impoverishment of prey items in this heavily disturbed system. The specimens collected in the most affected estuary also had a greater frequency of micro-plastics and parasites in their stomachs, reflecting the greater degree of human disturbance in the estuary. The present findings suggest that the diet of A. brasiliensis could be a useful indicator of changes in the ecological quality of these and other tropical estuaries of the western Atlantic Ocean. [ABSTRACT FROM AUTHOR]

Thirty-six Brook Silversides, Labidesthes sicculus, and 15 Golden Silversides, Labidesthes vanhyningi, collected from the Ouachita and Red River drainage basins of Arkansas and Oklahoma, U.S.A., were examined for parasites. Six (17%) of the L. sicculus and 3 (20%) of the L. vanhyningi were infected with Dermocystidium sp., 1 (7%) L. vanhyningi harbored an immature tapeworm, Proteocephalus sp., and I (7%) L. vanhyningi was infected with the copepod Ergasilus fimduli. We document new host records for all 3 parasites as well as 2 new state records for Dermocystidium sp. and E. funduli. [ABSTRACT FROM AUTHOR]

Chronic, 21-28-day toxicity tests of Macondo source (Massachusetts, or MASS) and weathered Slick A (CTC) and Slick B (Juniper) oils field collected during the 2010 Deepwater Horizon (DWH) Incident in the Gulf of Mexico (GOM) were conducted using standardized procedures. Standard species, Americamysis bahia and Menidia beryllina, were evaluated for changes in survival and growth during daily static-renewal tests. Both species demonstrated an increased sensitivity to low-energy water accommodated fractions (WAFs) of un-weathered MASS oil, with growth and survival decreasing as oil loading rate increased from 0.01 to 1.0 g/L. Survival and growth of mysid shrimp exposed to weathered oil (Slick A and Slick B) did not differ from that of test controls. In contrast, survival and growth of inland silversides declined relative to that of test controls at loading rates of 1 g/L for both weathered oils. Based on the concentration of total polycyclic aromatic hydrocarbons (TPAH), no observed effect concentrations were lower for inland silverside survival (5.00-7.61 µg/L) and growth (<2.02 to <7.61 µg/L) in chronic exposures to Slick B and Slick A weathered oils compared with mysids (4.75-17.9 µg/L). Average TPAH concentrations in full strength WAFs followed the weathering trend, with 165 ± 17.2, 17.9 ± 0.480, and 4.75 ± 0.521 µg/L for MASS, Slick A, and Slick B oils, respectively. The effect (LOEC, IC25) and no-effect exposure concentrations (in TPAHs) from the standardized laboratory toxicity studies with un-weathered and weathered oils are discussed relative to the actual exposure concentrations in the GOM in 2010. The exposures evaluated in the laboratory toxicity tests represent the highest concentrations of total PAHs that were rarely observed in water column samples collected in the GOM during the release and post release periods of the DWH incident. [ABSTRACT FROM AUTHOR]

The point of no return ( PNR) and disappearance of the oil droplet were measured in Chirostoma estor larvae as a function of the time of first feeding. In a separate trial, growth and survival of larvae fed rotifers enriched with Chlorella sp., cod liver oil and corn oil were assessed. Fatty acid and lipid composition of eggs, oil droplets, egg yolk, feed and larvae were also evaluated. The PNR was found between 7 and 8 days posthatching (dph). Total oil droplet depletion occurred between 7 and 11 dph, depending on the time of first feeding. Best growth and survival were obtained in larvae fed with Chlorella-enriched rotifers, followed by those fed cod liver oil-enriched rotifers. In larvae fed corn oil, Chlorella and cod liver oil-enriched rotifers, total oil droplet depletion took place on days 9, 10 and 11, respectively. There was a direct relationship between presence and duration of oil droplets and the survival of larvae under different starvation conditions. The feed source could prolong the existence of the oil droplet depending on particular dietary supply of essential fatty acids; the time of its disappearance could be a useful indicator of larval vigour and health status. [ABSTRACT FROM AUTHOR]

The expression and digestive activity of pike silverside Chirostoma estor endogenous chitinases were analysed in samples from four life stages: whole eggs; larvae; juvenile intestine and hepatopancreas and adult intestine and hepatopancreas. A chitinase cDNA was cloned and partially sequenced ( GenBank accession number: FJ785521). It was highly homologous to non-acidic chitinase sequences from other fish species, suggesting that it is a chitotriosidase. Quantitative PCR showed that this chitinase was expressed throughout the life span of C. estor, with maximum expression in the hepatopancreas of juveniles. Chitotriosidase and chitobiosidase activities were found at all life stages, along with a very high level of N-acetyl glucosaminidase ( NAGase). The chitotriosidase activity could be encoded by the cloned complementary (c) DNA, although additional chitinase genes may be present. The chitotriosidase activity appeared to be transcriptionally regulated only at the juvenile stage. The expression and activity of chitinases tended to increase from the early to juvenile stages, suggesting that these variables are stimulated by chitin-rich live food. Nevertheless, the feeding of juvenile and adult fish with both live food and a balanced commercial diet seemed to provoke significant reductions in pancreatic NAGase secretion and/or synthesis in the gut. Moreover, all chitinase activities were lower in adults, probably reflecting a higher intake and use of the balanced diet. The observation of chitotriosidase and chitobiosidase activities together with a very high NAGase activity suggest the presence of a complete and compensatory chitinolytic chitinase system that enables this stomachless short-gut fish species to use chitin as an energy substrate. These novel findings suggest that dietary inclusions of chitin-rich ingredients or by-products might reduce the farming costs of C. estor without impairing performance. [ABSTRACT FROM AUTHOR]

In this study, body shape of hybrid and presumptive introgressed South American silversides was studied. Body shape of O. bonariensis and O. hatcheri from wild populations and farmed stocks was compared to provide basic information on the effects of fish farming on morphometric parameters. Subsequently, wild presumptive introgressed individuals and artificially hybridized farmed individuals were morphologically analysed to assess the effects of hybridization on the same parameters. Most farmed purebred individuals were shorter and higher than their wild counterparts, which is probably due to the favourable growth conditions compared to the wild habitat. However, the results evidenced that purebred individuals were more slender than both hybrid (farmed) fish and introgressed (wild) fish. Further studies on the growth performance of hybrid Odontesthes will be required in order to assess whether the combination of hybridization and sterilization could produce, under farming conditions, growth performances which satisfy the requirements of aquaculture. [ABSTRACT FROM AUTHOR]

In order to improve the understanding of pejerrey Odontesthes bonariensis, growth hormone (Gh)-insulin-like growth factor-1(Igf1) axis, O. bonariensis growth hormone receptor type 1 ( ghr1) and type 2 ( ghr2) mRNA sequences were obtained. Both transcripts were ubiquitously expressed except in kidney, encephalon and anterior intestine. Alternative transcripts of both receptors were found in muscle. Interestingly, two different ghr2 transcripts with alternative polyadenylation ( APA) sites located in the long 3′ untranslated region ( UTR-APA) were also found in liver. Hepatic ghr1, ghr2 and insulin-like growth factor type 1 ( igf1) transcript levels were examined under two different metabolic conditions. In the first experimental condition, fish were fasted for 2 weeks and then re-fed for another 2 weeks. Despite igf1 mRNA relative expression did not show significant differences under the experimental period of time examined, both ghr transcripts decreased their expression levels after the fasting period and returned to their control levels after re-feeding. In the second treatment, recombinant O. bonariensis growth hormone (r- pjGh) was orally administered once a week. After 4 weeks of treatment, liver igf1, ghr1 and ghr2 mRNA relative expression increased (13, 4·5 and 2·1 fold, P < 0·05) compared to control values. These results add novel information to the growth hormone-insulin-like growth factor system in teleosts. [ABSTRACT FROM AUTHOR]

Atherinopsidae are widespread freshwater and shallow marine fish with singular economic importance. Morphological, genetical and life cycles differences between marine and estuarine populations were already reported in this family, suggesting ongoing speciation. Also, coexistence and interbreeding between closely related species were documented. The aim of this study was to infer boundaries among: (A) Odontesthes bonariensis and O . argentinensis at species level, and intermediate morphs; (B) the population of O . argentinensis of Mar Chiquita Lagoon and its marine conspecifics. To achieve this, we integrated, meristic, Geometrics Morphometrics and DNA Barcode approaches. Four groups were discriminated and subsequently characterized according to their morphological traits, shape and meristic characters. No shared haplotypes between O . bonariensis and O . argentinensis were found. Significative-meristic and body shape differences between the Mar Chiquita and marine individuals of O . argentinensis were found, suggesting they behave as well differentiated populations, or even incipient ecological species. The fact that the Odontesthes morphotypes shared haplotypes with both, O . argentinensis and O . bonariensis , but also possess meristic and morphometric distinctive traits open new questions related to the origin of this morphogroup. [ABSTRACT FROM AUTHOR]

\Gene flow between populations is restricted in fragmented habitats, which can promote a more rapid genetic diversification as evolutionary forces act on isolated gene pools. Here, we compare two silverside species occurring in a continuous coastal habitat (tidewater silverside, Menidia peninsulae Goode and Bean, 1879) vs a highly fragmented habitat consisting of hypersaline pools (key silverside, Menidia conchorum Hildebrand and Ginsburg, 1927). First, we aim to better resolve the morphological and genetic relationships between the two nominal species using a haplotype analysis at two loci (NADH dehydrogenase 2, internal transcribed space r2) and geometric morphometries. Despite some haplotype sharing and incomplete lineage sorting, they were both genetically differentiated (®ST = 0.2186 and 0.4198, respectively, P < 0.0001) and showed significant discriminating morphometric characteristics. Second, we made a temporal comparison of genetic diversity and effective population size (Ne) in key silversides over time using seven polymorphic microsatellite loci and found that genetic diversity and Ne of key silversides were lower in these pools compared to tidewater silversides in the marine environment and decreased over time. We conclude that key silversides more likely represent an ecotype of the tidewater silverside and thus harbor a distinct adaptive potential. Further, our results support the hypothesis that highly fragmented aquatic habitats promote rapid genetic change and species diversification. Finally, we discuss the management applications of our study pertaining to the current listing of key silversides as a National Marine Fisheries Service Species of Concern. [ABSTRACT FROM AUTHOR]

The silverside Odontesthes bonariensis is a euryhaline species native of South America and represents a very important fishing resource for the Plata Basin (Argentina and Uruguay). This study compares the Sr:Ca ratio of water as well as the Sr:Ca ratio and morphometry of the sagittal otolith of the silverside present in different environments (one salt lake, two freshwater dams, one lagoon, and one estuary) in order to evaluate the use of these variables as markers of habitat. The pattern of the Sr:Ca ratio in the water agrees with the one found in the otoliths, showing a positive relationship with the conductivity of the water. Univariate and multivariate analyses of variance indicated significant differences (P < 0.05) among the localities studied for the morphometric indices. The discriminant function analysis provided a high percentage of correctly classified individuals for the saltwater environment (100%) and the lentic water bodies and estuary (60-80%), circularity and form factor being the most relevant morphometric variables. These results indicate that the Sr:Ca ratio and otolith morphometry are good markers of habitat for this important resource. [ABSTRACT FROM AUTHOR]

Shallow lakes are found in the Eastern region of La Pampa province which were stocked with Odontesthes bonariensis, becoming a fish catchment opportunity. Such a fish species exhibits a preference for plankton as food, but if that resource were scarce, other kind of feeds can be included in its diet as a consequence of its feeding plasticity. Diet composition varies according to fish size, with occurrence of cannibalism at an old age. The objective of this work was to assess the percentage diet composition by the total number of individuals, and by body size, of O. bonariensis feeding in the shallow lakes of Bajo Giuliani and Don Tomás. Catchment of fish was performed using gillnets of different mesh sizes. Stomachs removed from fish were fixed in 10% formol, and their contents were observed with stereoscopic optical microscope. Prey volume and its frequency of occurrence were measured. Ten types of preys in Bajo Giuliani lake, and 6 in Don Tomás lake, were identified. In both environments, the plankton was the main food for fish smaller in size, whereas the biggest ones turned out to be piscivores. Jenynsia multidentata was the most predated fish. It is considered necessary to carry out a study that allow surveying fish trophic behavior throughout the year. [ABSTRACT FROM AUTHOR]

The presence of trace elements (Cr, Mn and Zn) in soft tissues (muscle, gills, scales, liver and gonads) of silverside ( Odontesthes bonariensis ), and its relation to the concentration of these elements, in water of the Pampasic ponds were studied. Based on the results, the risk of poisoning by consumption of silverside fish was calculated. Cr had a higher concentration in the fish scales of most ponds, the gill being the secondary target organ. The highest concentrations of manganese were found in gills, liver and fish scales. Gills and liver samples from Chascomús ponds had higher values of that metal than the rest of the ponds. In the ponds of Adela, Chis-Chis, and Barrancas these concentrations were lower, with 14–34 μg/g in gills and 5–9 μg/g in liver. In Tablilla ponds, Mn concentration in all organs of silverside was very variable. Zn was the metal with the highest concentration in all fish organs analyzed with respect to the other trace elements studied. Considering the limits set by the Scientific Committee on Food (SCF) for Cr at 0.03 mg/kg, Mn at 0.07 mg/kg and Zn at 1.57 mg/kg, and given a balanced diet, with a consumption of twice a week, we could observe that in none of the cases the consumption of this species can be harmful to human health. Nevertheless, if we considered a daily consumption of this fish coming from Chascomús ponds, the limit of Mn could exceed the permitted levels and making it a human risk. [ABSTRACT FROM AUTHOR]

The Lake Eyre hardyhead (Craterocephalus eyresii) is an endemic freshwater fish living in the Lake Eyre basin in South Australia. Here, I report the full mitogenome description and the phylogenetic position of this species based on the mitogenome phylogenetics. The mitogenome is 16,602 bp-long with the standard 37 genes all included, with a genomic structure typical of a vertebrate mitogenome. A maximum likelihood phylogenetic analysis to confirm this species position was conducted, using a data set including publicly available 28 atherinomorphs, nine percomorphs, and two outgroups. The result confirms C. eyresii position's in Atherinoidei. The complete mitogenome data of C. eyresii reported here would be useful for further genetics, phylogeography, and phylogenetics studies involving this species. [ABSTRACT FROM AUTHOR]

Plastics represent the latest contaminant in the marine environment. Although plastics without doubt represent a uniquely valuable material particularly in construction, packaging and fishing gear applications. Current research on plastic debris in digestive tract content of pelagic fish is part of ongoing collaboration between University of Hasanuddin and University of California at Davis. Locally caught and consumed Silverside (Stolephorusheterolobus) or widely known as anchovies has been the subject on this studies. Freshly landed fish were collected from Paotere fish market, which is also the biggest fish wholesale location at Makassar City, South Sulawesi, Indonesia. At laboratory fish digestive tracts were removed and digested in 10% KOH at 60° C overnight, followed with plastic particles observation using binocular microscope. Four out of 10 fish investigated were found to contained plastic particles in their digestive tract. This is the first work on plastic debris in fish gut ever conducted in the region, which is in accordance to previous works on plastics debris elsewhere and will be further discussed for their possible effects, both on food safety and human toxicology. [ABSTRACT FROM AUTHOR]

Persistent colour polymorphisms can result from natural and/or sexual selection, and may occur in males, females, or both sexes. Contrary to conspicuous patterns frequently observed in courtship colouration, differences in cryptic colouration are not always perceived by the human sensory system. In sexually dimorphic sailfin silversides fishes, males show conspicuous colour polymorphisms whereas females appear monomorphic and cryptic. We measured the spectral composition of body, fin and peduncle colouration in male and female Telmatherina antoniae 'small', a sailfin silverside species endemic to ancient Lake Matano, and found evidence for a colour polymorphism in both sexes. The three colour morphs distinguished by spectral data correspond to those commonly reported for males, and are also present in the visually (to a human eye) cryptic females. Females show hue value patterns similar to those present in males, but differ from males substantially in chroma and brightness. This is, to the best of our knowledge, the first example of a cryptic colour polymorphism in fishes; however, its significance for the mating system remains unknown. The present finding highlights the need for incorporating female spectral data into analyses of colour patterns, and suggests that colour analyses should include cryptic sexes. [ABSTRACT FROM AUTHOR]

The trophic interactions between 15 native and two introduced fish species, silverside Odontesthes bonariensis and rainbow trout Oncorhynchus mykiss, collected in a major fishery area at Lake Titicaca were explored by integrating traditional ecological knowledge and stable-isotope analyses ( SIA). SIA suggested the existence of six trophic groups in this fish community based on δ13C and δ15N signatures. This was supported by ecological evidence illustrating marked spatial segregation between groups, but a similar trophic level for most of the native groups. Based on Bayesian ellipse analyses, niche overlap appeared to occur between small O. bonariensis (<90 mm) and benthopelagic native species (31·6%), and between the native pelagic killifish Orestias ispi and large O. bonariensis (39%) or O. mykiss (19·7%). In addition, Bayesian mixing models suggested that O. ispi and epipelagic species are likely to be the main prey items for the two introduced fish species. This study reveals a trophic link between native and introduced fish species, and demonstrates the utility of combining both SIA and traditional ecological knowledge to understand trophic relationships between fish species with similar feeding habits. [ABSTRACT FROM AUTHOR]

The present study was conducted to determine the effects of use silverside meal to enhance palatability, growth performance and body composition of fingerlings sole fish fed on plant based diets. Two sources of plant protein (soybean and corn glutein meal) were replacing silverside meal in tested diets. Five diets were formulated with different inclusion levels of plant protein based diets (PP0, PP25, PP50, PP75 and PP100%). The silverside fish (Atherina boyeri) was added to the diets as local animal protein source, replacer to fish meal and to enhance palatability of the test diets. Fingerlings sole with an initial weight of (8.65±0.2g) were distributed 100 fingerlings in each tank, with a volume of 2m³. Fish were fed on the artificial diets as 3% of the fish biomass daily divided into two equal portions. Fish were organized in triplicate groups/diet and the experimental period lasted 120 days after start. The results showed significant differences (P<0.05) in growth performance and feed efficiency between diets. The highest performances in terms of (Final weight, Weight gain, Average daily gain, Specific growth rate, Condition factor, Feed conversion ratio, Protein efficiency ratio, Net protein utilization and Hepatosomatic index) were obtained with the PP75, PP0, PP50 and PP25%, without significance difference between them. However, fish fed on PP100 % diet showed significant differences (P<0.05) with decreased growth performance and feed efficiency compared to the other tested diets. Non-significant differences (P<0.05) in the whole body chemical composition (dry matter, crude protein, crude lipid and ash) were found between fish fed on all experimental diets. The results of the present study indicated that PP75% inclusion level, which reduce silverside meal and increase alternative plant protein sources in fingerlings sole, Solea aegyptiaca diet can be used without negative effects on growth performance and feed efficiency. [ABSTRACT FROM AUTHOR]

Freshwater systems are one of the environments most impacted by human activity, with pollution being a highly important factor. In Chile, several rivers exhibit varied levels of pollution, one of which is the Maipo River basin where the city of Santiago is located. The silverside Basilichthys microlepidotus (Jenyns) is an endemic fish species that inhabits this basin, thus we hypothesized that pollution has affected gene diversity and migration in populations of B. microlepidotus from the Maipo River basin. The aim of this study was to identify the population structure of B. microlepidotus in this basin and to determine if the populations of the silverside inhabiting polluted sites present differences in gene diversity and gene flow compared to populations inhabiting non-polluted areas. Using the variability of eight microsatellites, five populations of silverside were detected; three inhabiting non-polluted sites and two inhabiting polluted sites. From this, it was inferred that B. microlepidotus has been able to tolerate pollution in the Maipo River basin. No differences in gene diversity or migration were detected between polluted and non-polluted sites but comparison with historical estimation revealed an increase in the current migration rate when all the data from the basin were compared. A reduction in current effective population size was also observed when compared to historical values, and this is probably due to river degradation. Despite the disappearance of other fish species recorded at this basin, our results suggest that B. microepidotus is tolerant to pollution, thus indicating that native species respond differently to this environmental factor. [ABSTRACT FROM AUTHOR]

The present paper integrates phylogenetic and population genetics analyses based on mitochondrial and nuclear molecular markers in silversides, genus Odontesthes, from a non-sampled area in the SW Atlantic Ocean to address species discrimination and to define Managements Units for sustainable conservation. All phylogenetic analyses based on the COI mitochondrial gene were consistent to support the monophyly of the genus Odontesthes and to include O. argentinensis, O. perugiae-humensis and some O. bonariensis haplotypes in a basal polytomy conforming a major derivative clade. Microsatellites data revealed somewhat higher genetic variability values in the O. argentinensis-perugia populations than in O. bonariensis and O. perugia-humensis taxa. Contrasting population genetics structuring emerged from mitochondrial and microsatellites analyses in these taxa. Whereas mitochondrial data supported two major groups (O. argentinensis-perugia-humensis vs. O. bonariensis-perugiae-humensis populations), microsatellite data detected three major genetic entities represented by O. bonariensis, O. perugiae-humensis and an admixture of populations belonging to O. argentinensis-perugiae respectively. Therefore, the star COI polytomy in the tree topology involving these taxa could be interpreted by several hypothetic scenarios such as the existence of shared ancestral polymorphisms, incomplete lineage sorting in a radiating speciation process and/or reticulation events. Present findings support that promiscuous and recent contact between incipient species sharing asymmetric gene flow exchanges, blurs taxa boundaries yielding complicated taxonomy and Management Units delimitation in silverside genus Odontesthes from SW Atlantic Ocean basins. [ABSTRACT FROM AUTHOR]

The marine atherinid fishes of the genus Hypoatherina Schultz (Atherinidae: Atherinomorinae) were redefined from both morphological and molecular analyses, and eight of the ten included species were redescribed. In the molecular phylogeny, four regions of mitochondrial DNA were analyzed. The results of both trees of maximum likelihood and Bayesian analyses indicated the paraphyly of the former Hypoatherina. ' Atherina' valenciennei and ' Atherina' woodwardi, both formerly belonging to Hypoatherina, show closer relationships with Atherinomorus duodecimalis and Atherinomorus aetholepis. ' Hypoatherina' celebesensis is also apart from the clade including the majority of Hypoatherina species. In contrast, H. panatela, formerly regarded as a member of the genus Stenatherina Schultz , is included in the present Hypoatherina clade. The present molecular phylogeny of the genus Hypoatherina can be supported by morphology. The genus Hypoatherina is redefined by the following combinations of characters: ascending process of premaxilla long and slender, its height more than 2.7 times the maximum width; both anterior and posterior lateral processes of premaxilla narrow and deep, the anterior process almost the same as or slightly deeper than the posterior process; premaxilla not tapering posteriorly; posterior upper margin of dentary with a prominent process; upper posterior limb of dentary with round or somewhat angular posteroventral corner; anterior preopercular ridge with a deep notch just above the corner; anus situated posterior to or slightly anterior to appressed pelvic-fin tip in adults; dorsoventral height of exposed area in the midlateral scale (third) row wide, almost equal to the maximum height of the scale, and almost the same height as scales just above or below the midlateral row. The redefined Hypoatherina includes the following ten species: H. barnesi-widely distributed in the Indo-Pacific; H. gobio (lectotype designated herein)-restricted to the Red Sea; H. golanii-restricted to the Gulf of Aqaba, inner Red Sea; H. klunzingeri-from Mozambique to eastern South Africa; H. lunata-distributed in Japan and Indonesia; H. panatela-from western and central Pacific Ocean; H. temminckii-widely distributed in the Indo-West Pacific (neotype designated herein); H. tropicalis-restricted to the northeastern coast of Australia; H. tsurugae-occurring in Japan and South Korea; and H. uisila-distributed in the western and central Pacific Ocean. [ABSTRACT FROM AUTHOR]