Fish biomarker responses reflect landscape anthropic disturbance in savanna streams.

Disturbance in the landscape surrounding streams can interfere with water quality and cause harm to aquatic organisms. In this study, we evaluate the influence of land use on the genetic and biochemical biomarkers of fish in streams of Brazilian savanna (Cerrado). We also evaluated whether biomarker responses are seasonally consistent. For this purpose, individuals of the Neotropical tetra fish Astyanax lacustris were exposed in cages for 96 h, in 13 streams draining agroecosystems with different degrees of disturbance during the dry and wet seasons. After exposure, blood, liver, and gills were collected for multibiomarker analyses (micronuclei, erythrocytic nuclear abnormalities, lipid peroxidation, antioxidant enzymes, and biotransformation enzyme). The results showed that the gradient of anthropic disturbance was positively associated with genotoxic damage (erythrocytic nuclear abnormalities) and negatively associated with antioxidant and biotransformation enzymes of the liver in both seasons. No association of the gradient of anthropic disturbance with the frequency of micronuclei and for most gill enzymes was found for both seasons. Landscape disturbance was also negatively associated with water quality in the wet season. These results indicate that changes in land use interfere with the genetic and biochemical processes of organisms. Thus, the multibiomarker approach may represent an effective strategy for assessing and monitoring terrestrial landscape disturbance.

Changes in trophic characteristics of two fish species of Astyanax (Teleostei: Characidae) in response to aquatic pollution

The trophic plasticity of most fish species of Astyanax Baird & Girard, 1854 in response to environmental changes and resource availability is high. This work evaluates the differences in the trophic characteristics of two congeneric species, Astyanax taeniatus (Jenyns, 1842) and Astyanax lacustris (Lütken, 1875), in Rio das Velhas Basin, which is highly impacted by the discharge of sewage from the Metropolitan Region of Belo Horizonte (MRBH). Eight sites were sampled and grouped into three regions: upper course (two sites upstream of the MRBH); middle course (three sites located in the middle portion of the Rio das Velhas, region with greater influence of the MRBH), and lower course (three sites downstream of the MRBH). Samples of fish and food resources were collected from all sites to obtain the isotopic composition of nitrogen (δ15N) and carbon (δ13C), and the stomach contents of the two species was analized. The most common items in the stomach of A. lacustris and A. taeniatus, respectively, were from plants and insects, followed by algae/periphyton (especially at the low course of Rio das Velhas). In contrast, stable isotope analyses indicated that algae (in polluted sites) and periphyton (in least-disturbed sites) were best assimilated both species. Both analyses indicated that the trophic niches of the two species overlap more in more polluted sites relative to less polluted sites. Astyanax taeniatus and A. lacustris only presented different isotopic composition of carbon and nitrogen in the upper course of the Rio das Velhas, probably in response to the greater diversity of food items consumed by each species. In the other regions, the species presented similar isotopic signatures, with δ15N and δ13C notably enriched in the most polluted regions (middle and low course)...(AU)

Changes in trophic characteristics of two fish species of Astyanax (Teleostei: Characidae) in response to aquatic pollution

The trophic plasticity of most fish species of Astyanax Baird & Girard, 1854 in response to environmental changes and resource availability is high. This work evaluates the differences in the trophic characteristics of two congeneric species, Astyanax taeniatus (Jenyns, 1842) and Astyanax lacustris (Lütken, 1875), in Rio das Velhas Basin, which is highly impacted by the discharge of sewage from the Metropolitan Region of Belo Horizonte (MRBH). Eight sites were sampled and grouped into three regions: upper course (two sites upstream of the MRBH); middle course (three sites located in the middle portion of the Rio das Velhas, region with greater influence of the MRBH), and lower course (three sites downstream of the MRBH). Samples of fish and food resources were collected from all sites to obtain the isotopic composition of nitrogen (δ15N) and carbon (δ13C), and the stomach contents of the two species was analized. The most common items in the stomach of A. lacustris and A. taeniatus, respectively, were from plants and insects, followed by algae/periphyton (especially at the low course of Rio das Velhas). In contrast, stable isotope analyses indicated that algae (in polluted sites) and periphyton (in least-disturbed sites) were best assimilated both species. Both analyses indicated that the trophic niches of the two species overlap more in more polluted sites relative to less polluted sites. Astyanax taeniatus and A. lacustris only presented different isotopic composition of carbon and nitrogen in the upper course of the Rio das Velhas, probably in response to the greater diversity of food items consumed by each species. In the other regions, the species presented similar isotopic signatures, with δ15N and δ13C notably enriched in the most polluted regions (middle and low course)...

A new species of Wallinia Pearse, 1920 (Digenea: Allocreadiidae) collected from Astyanax fasciatus (Cuvier, 1819) and A. lacustris Lucena and Soares, 2016 (Characiformes: Characidae) in Brazil based on morphology and DNA sequences.

Wallinia brasiliensis n. sp. is described from the intestine of two species of tetras-Astyanax fasciatus (Cuvier, 1819) and Astyanax lacustris Lucena and Soares, 2016-collected from the Batalha River in São Paulo State, Brazil. The new species can be clearly distinguished from the other three congeneric species by its vitelline follicles extending from the genital pore to the end of the caeca, eggs lacking operculum, a larger egg size with a consequently lower number relative to the other three species, and the ovary located opposite the anterior testis. The validity of the new species was confirmed through a phylogenetic analysis of the 28S rRNA gene which showed that the new species is the sister taxon to Wallinia mexicana Pérez-Ponce de León, Razo-Mendivil, Mendoza-Garfía, Rubio-Godoy and Choudhury, 2015, a species infecting Astyanax mexicanus (De Filippi, 1853) in Mexico.

Ontogenetic development of tetra Astyanax lacustris (Characiformes: Characidae)

Ontogenetic development of the tetra Astyanax lacustris was studied under laboratory conditions. Larvae obtained by induced reproduction were maintained individually in tissue-culture plates, at 25°C. Daily observations and morphometric measurements were performed. Larvae hatched with a total length (TL) of 3.02 ± 0.34 mm (average ± standard deviation) without pigmentation and 0.06 ± 0.02 mm³ of yolk reserves. The yolk-sac larval period lasted 26 h post-hatching (hph). During this period, eye pigmentation started, the digestive tract emerged, the anus opened, and the animals began to show steady movements. Inflation of the swimming bladder initiates the preflexion stage, which extended until 230 hph. During this stage, the transition from endogenous to exogenous feeding was observed, with the yolk reserve being completely absorbed after 74 hph (TL: 4.17 ± 0.36 mm). Up to 86 hph it was possible to observe the first food ingested within the digestive tract. This period was followed by the flexion stage, with the folding of the notochord tip and development of the caudal fin (11-13 days post-hatching). Finally, during the last larval developmental stage (postflexion), the segmentation of the fin rays was completed, and the emergence of scales was observed (TL: 5.97 ± 0.65 mm). The larval ontogenetic development of A. lacustris was completed after 22 post-hatching days (dph).(AU)

O desenvolvimento ontogenético do lambari Astyanax lacustris (Pisces, Characidae) foi estudado em condições ambientais controladas. Larvas obtidas através de reprodução induzida, foram mantidas individualmente em placas de cultivo celular, a 25°C. Diariamente foram realizadas observações e medições morfométricas. As larvas eclodiram com 3,02 ± 0,34 mm (média ± desvio padrão) de comprimento total (CT); sem pigmentação e com 0,06 ± 0,02 mm³ de reserva vitelínica. O período larval vitelino estendeu-se durante as primeiras 26 horas pós-eclosão (hpe) e durante este período teve início o processo de pigmentação dos olhos, o surgimento do tubo digestório, abertura anal e os animais passaram a apresentar movimentação constante. Com o inflamento da bexiga natatória tem início o estágio de pré-flexão, que se estendeu por até 230 hpe. Durante este estágio, foi observada a transição entre a alimentação endógena e a exógena, sendo a reserva vitelínica totalmente absorvida após 74 hpe (com os animais atingindo 4,17 ± 0,36 mm de CT) e em até 86 hpe foi possível observar a primeira alimentação no trato digestório. Após esse período, teve início o estágio de flexão da parte final da notocorda e da estruturação da nadadeira caudal (11 e 13 dias após a eclosão). Por fim, no último estágio de desenvolvimento larval (pós-flexão), foi observada a segmentação completa dos raios das nadadeiras e o início do aparecimento das escamas (CT: 5,97 ± 0,65 mm). O desenvolvimento ontogenético larval de A. lacustris foi concluído após 22 dias pós-eclosão (dpe).(AU)

Ontogenetic development of tetra Astyanax lacustris (Characiformes: Characidae)

Ontogenetic development of the tetra Astyanax lacustris was studied under laboratory conditions. Larvae obtained by induced reproduction were maintained individually in tissue-culture plates, at 25°C. Daily observations and morphometric measurements were performed. Larvae hatched with a total length (TL) of 3.02 ± 0.34 mm (average ± standard deviation) without pigmentation and 0.06 ± 0.02 mm³ of yolk reserves. The yolk-sac larval period lasted 26 h post-hatching (hph). During this period, eye pigmentation started, the digestive tract emerged, the anus opened, and the animals began to show steady movements. Inflation of the swimming bladder initiates the preflexion stage, which extended until 230 hph. During this stage, the transition from endogenous to exogenous feeding was observed, with the yolk reserve being completely absorbed after 74 hph (TL: 4.17 ± 0.36 mm). Up to 86 hph it was possible to observe the first food ingested within the digestive tract. This period was followed by the flexion stage, with the folding of the notochord tip and development of the caudal fin (11-13 days post-hatching). Finally, during the last larval developmental stage (postflexion), the segmentation of the fin rays was completed, and the emergence of scales was observed (TL: 5.97 ± 0.65 mm). The larval ontogenetic development of A. lacustris was completed after 22 post-hatching days (dph).(AU)

O desenvolvimento ontogenético do lambari Astyanax lacustris (Pisces, Characidae) foi estudado em condições ambientais controladas. Larvas obtidas através de reprodução induzida, foram mantidas individualmente em placas de cultivo celular, a 25°C. Diariamente foram realizadas observações e medições morfométricas. As larvas eclodiram com 3,02 ± 0,34 mm (média ± desvio padrão) de comprimento total (CT); sem pigmentação e com 0,06 ± 0,02 mm³ de reserva vitelínica. O período larval vitelino estendeu-se durante as primeiras 26 horas pós-eclosão (hpe) e durante este período teve início o processo de pigmentação dos olhos, o surgimento do tubo digestório, abertura anal e os animais passaram a apresentar movimentação constante. Com o inflamento da bexiga natatória tem início o estágio de pré-flexão, que se estendeu por até 230 hpe. Durante este estágio, foi observada a transição entre a alimentação endógena e a exógena, sendo a reserva vitelínica totalmente absorvida após 74 hpe (com os animais atingindo 4,17 ± 0,36 mm de CT) e em até 86 hpe foi possível observar a primeira alimentação no trato digestório. Após esse período, teve início o estágio de flexão da parte final da notocorda e da estruturação da nadadeira caudal (11 e 13 dias após a eclosão). Por fim, no último estágio de desenvolvimento larval (pós-flexão), foi observada a segmentação completa dos raios das nadadeiras e o início do aparecimento das escamas (CT: 5,97 ± 0,65 mm). O desenvolvimento ontogenético larval de A. lacustris foi concluído após 22 dias pós-eclosão (dpe).(AU)

Diet of fish (Characiformes: Characidae) during early developmental stages in the Upper Paraná river basin, Brazil / Alimentação de peixes (Characiformes: Charicidae) nas fases iniciais de desenvolvimento da bacia do Alto rio Paraná, Brasil

This study analyzed the diet during early developmental stages of Astyanax lacustris (AA),Piaractus mesopotamicus (PM), Megaleporinus obtusidens (MO) and Prochilodus lineatus (PL), under experimentalconditions. Fish larvae, 350 of each species, were stocked separately in 16 fiber-cement tanks (500 L), fromwhich, three larvae of each species were collected every three days, for 36 days. Tanks were fertilized (1.5 gNPK-7: 14: 8) and had 50% of the surface with macrophytes. Larvae were grouped in age classes = I: 5 to11, II: 14 to 20, III: 23 to 29 and IV: 32 to 38 days and, dissected for analysis of the digestive tract.Methodologies of dominance, frequency of occurrence and points of food items were used. For AA andPM larvae, measurements were taken for the number and size of organisms to determine the percentparticipation in biovolume. Changes in diets of larvae in different age classes were found as well as betweendifferent species, with the same age. Rotifers were dominant in the content of digestive tracts of all speciesat Class I, and the larvae diets became more distinct with increasing age, in which AA consumed mainlyrotifers, PM, larger organisms (mainly cladocerans), PL, algae (diatoms as the main item) and PP with amore diversified diet (rotifers, ostracodes and algae). In conclusion, early stages of these species presenteddistinct diets, undergoing remarkable changes in the first 38 days of life.(AU)

Estudou-se a alimentação dos estágios iniciais de desenvolvimento de Astyanax lacustris (AA),Piaractus mesopotamicus (PM), Megaleporinus obtusidens (MO) e Prochilodus lineatus (PL) em condiçõesexperimentais. As larvas, 350 cada espécie, foram estocadas separadamente, em 16 tanques de fibrocimento(500 L) dos quais foram coletados três indivíduos de cada um, a cada três dias, por 36 dias. Os tanquesforam fertilizados (1,5 g de NPK-7:14:8) e tinham 50% da superfície com macrófitas. As larvas foramagrupadas em classes de idade = I: 5 a 11, II: 14 a 20, III: 23 a 29 e IV: 32 a 38 dias e, dissecadas para aabertura do trato digestório. Foram empregadas as metodologias de dominância, frequência de ocorrência epontos dos itens alimentares. Para as larvas de AA e PM, foram contados e tomadas medidas das dimensõesdos organismos para determinar a participação percentual do biovolume. Observaram-se mudanças nasdietas das larvas em diferentes classes de idade e também entre larvas de espécies diferentes, com mesmaidade. Houve predomínio de rotíferos nos conteúdos dos tratos digestórios de todas as espécies na classe I,as dietas das larvas passaram a ser mais distintas com o incremento da idade, com AA consumindoprincipalmente rotíferos, PM organismos maiores (principalmente cladóceros), PL tendo algas(diatomáceas como item principal) e PP com uma dieta mais variada (rotíferos, ostracodes e algas).Conclui-se que as formas jovens destas espécies apresentaram dietas distintas, passando por nítidasalterações nos primeiros 38 dias de vida.(AU)

Diet of fish (Characiformes: Characidae) during early developmental stages in the Upper Paraná river basin, Brazil / Alimentação de peixes (Characiformes: Charicidae) nas fases iniciais de desenvolvimento da bacia do Alto rio Paraná, Brasil

This study analyzed the diet during early developmental stages of Astyanax lacustris (AA), Piaractus mesopotamicus (PM), Megaleporinus obtusidens (MO) and Prochilodus lineatus (PL), under experimental conditions. Fish larvae, 350 of each species, were stocked separately in 16 fiber-cement tanks (500 L), from which, three larvae of each species were collected every three days, for 36 days. Tanks were fertilized (1.5 g NPK-7: 14: 8) and had 50% of the surface with macrophytes. Larvae were grouped in age classes = I: 5 to 11, II: 14 to 20, III: 23 to 29 and IV: 32 to 38 days and, dissected for analysis of the digestive tract. Methodologies of dominance, frequency of occurrence and points of food items were used. For AA and PM larvae, measurements were taken for the number and size of organisms to determine the percent participation in biovolume. Changes in diets of larvae in different age classes were found as well as between different species, with the same age. Rotifers were dominant in the content of digestive tracts of all species at Class I, and the larvae diets became more distinct with increasing age, in which AA consumed mainly rotifers, PM, larger organisms (mainly cladocerans), PL, algae (diatoms as the main item) and PP with a more diversified diet (rotifers, ostracodes and algae) . In conclusion, early stages of these species presented distinct diets, undergoing remarkable changes in the first 38 days of life.

Estudou-se a alimentação dos estágios iniciais de desenvolvimento de Astyanax lacustris (AA), Piaractus mesopotamicus (PM), Megaleporinus obtusidens (MO) e Prochilodus lineatus (PL) em condições experimentais. As larvas, 350 cada espécie, foram estocadas separadamente, em 16 tanques de fibrocimento (500 L) dos quais foram coletados três indivíduos de cada um, a cada três dias, por 36 dias. Os tanques foram fertilizados (1,5 g de NPK-7:14:8) e tinham 50% da superfície com macrófitas. As larvas foram agrupadas em classes de idade = I: 5 a 11, II: 14 a 20, III: 23 a 29 e IV: 32 a 38 dias e, dissecadas para a abertura do trato digestório. Foram empregadas as metodologias de dominância, frequência de ocorrência e pontos dos itens alimentares. Para as larvas de AA e PM, foram contados e tomadas medidas das dimensões dos organismos para determinar a participação percentual do biovolume. Observaram-se mudanças nas dietas das larvas em diferentes classes de idade e também entre larvas de espécies diferentes, com mesma idade. Houve predomínio de rotíferos nos conteúdos dos tratos digestórios de todas as espécies na classe I, as dietas das larvas passaram a ser mais distintas com o incremento da idade, com AA consumindo principalmente rotíferos, PM organismos maiores (principalmente cladóceros), PL tendo algas (diatomáceas como item principal) e PP com uma dieta mais variada (rotíferos, ostracodes e algas). Conclui-se que as formas jovens destas espécies apresentaram dietas distintas, passando por nítidas alterações nos primeiros 38 dias de vida.

Laser-induced fluorescence in fish scales to evaluate the environmental integrity of ecosystems.

The aim of this study was to evaluate the fluorescence of Astyanax lacustris fish scales when excited in the UV-A and blue regions for use as a bioindicator of aquatic ecosystems. This species was firstly defined as Astyanax altiparanae, popularly known as "lambari-do-rabo-amarelo". Currently, abiotic/biotic environmental integrity is generally assessed using limnological and physicochemical parameters related to biological indicators in streams or rivers, which are not sufficient to evaluate the real environmental conditions: in some cases, these parameters can be strongly dependent on local weather conditions. In this study, after the fish scales were excited with UV-A (360nm) and blue (405nm) photons, a strong and broad visible fluorescence band (from blue to red) could be observed that was mainly related to collagen and hydroxyapatite, independent of whether the excitation was applied to the inside or outside of the scale. Selected emission wavelengths were used as variables and the fluorescence intensities were interpreted using multivariate discriminant statistical analysis to compare streams with known different levels of integrity. The fluorescence data showed strong correlation with the electrical conductivity of the water, indicating that the scales of A. lacustris could be employed as bioindicators of environmental integrity on water chemistry monitoring programs.