Biofilm viability and microbial community of non-inoculated moving bed biofilm reactor in Nile tilapia Oreochromis niloticus cultivation.

The aim of this study was to evaluate two moving bed biofilm reactors (MBBR) without nitrifying bacteria inoculation. Biofilms and viable bacterial colonies were evaluated after 124 days. MBBR bioreactors received water from Oreochromis niloticus fish farming and water quality parameters were monitored daily. Four distinct phases with different fish stocking density were established.: phase 1 (2.40 kg m-3), phase 2 (4.95 kg m-3), phase 3 (8.71 kg m-3) and phase 4 (12.23 kg m-3). The successful maturation of the bioreactors occurred around on the 100th experimental day when the nitration rate increased to 57 % in MBBR1 and 38 % in MBBR2. 105 species were identified in the biofilms, which were grouped into 65 genera, three of which were essential: Pseudomonas (21.7 %), Nitrospira (15.1 %) and Gemmobacter (11.2 %). MBBR start-up without bacterial inoculation is time-consuming, however, strengthened by important nitrifying groups.

Tank color influences the response of tomato clownfish (Amphiprion frenatus) to an acute stress challenge.

The trade of aquarium organisms is growing worldwide. This market depends on a continuous supply of healthy and colorful aquatic animals, but this sector has few initiatives. However, in the last decade, there has been a growing interest in researching captive breeding of these animals, aiming to develop a more sustainable aquarium hobby. Larviculture is an important phase in the cultivation process because the larvae are more sensitive to stress and variations in the bulk of variables, such as temperature, salinity, nutritional management, light intensity and spectrum, and environmental background colors. Because background color could be a promoter variable of proper welfare, we tested whether it affects the endocrine response of tomato clownfish Amphiprion frenatus larvae to an acute stress challenge. We show that background color influences the endocrine stress axis responsiveness in tomato clownfish. When fish were subjected to a standard acute stressor of 61 days after hatching, only fish adapted to white walls increased the whole-body cortisol levels. From the results presented herein, we recommend that white tanks be avoided for A. frenatus larviculture. Both, the less stress level and the good welfare condition of larvae reared in colored tanks may have robust, practical applications since almost all clownfish in the ornamental aquarium trade come from captive breeding.

Triterpene betulin may be involved in the acute effects of pulp and paper mill effluent on testis physiology in zebrafish.

Pulp and paper mill effluent can cause changes in the morphology and energy metabolism in the zebrafish (Danio rerio) testis. Betulin, a naturally occurring triterpene is commonly present in this type of effluent and is suspected of being involved in these effects. The aim of this study was to compare the effects pulp and paper mill effluent and betulin on various aspects of testicular physiology in the zebrafish. This included the in vitro effects of effluent and betulin on testicular lactate content and lactate dehydrogenase (LDH) activity. In addition, the effects of betulin on glucose uptake, glycogen, alanine aminotransferase (ALT), reactive oxygen and nitrogen species formation and oxidative damage in the testes were determined. Furthermore, we compared the effects and mechanism of action of betulin and effluent on calcium homeostasis in testes. In vitro exposure to both effluent and betulin decreased lactate and calcium influx, possibly due to the activation of the sodium­calcium exchanger (NCX) pump. Additionally, betulin-treated testes had higher reactive oxygen species (ROS) and reduced glutathione (GSH) content, as well as increased glutathione transferase (GST) activity and a tendency towards decreased catalase (CAT) activity. Thus, this study shows that alterations in testis physiology caused by the pulp and paper mill effluent in the testis may be due in part to the actions of betulin.

Limnoperna fortunei - Updating the geographic distribution in the Brazilian watersheds and mapping the regional occurrence in the Upper Uruguay River basin / Limnoperna fortunei - Atualização da distribuição geográfica nas bacias hidrográficas brasileiras e mapeamento da ocorrência regional na bacia do Alto Rio Uruguai

Abstract: Limnoperna fortunei is an invasive alien species (IAS) that cause serious ecological and economic problems in Brazilian freshwater environments. Due to its high dispersion capacity and the lack of new records in peer-reviewed journals we carried out an extensive survey to update the distribution of L. fortunei in the Brazilian hydrographic basins. We also performed a detailed investigation of its distribution in the Upper Uruguay River basin using a molecular method. We presented new records, showing the invasion in new basins and a wide distribution in the basins previously infested. Additionally, we confirmed that the Upper Uruguay River is fully colonized by the golden mussel, being distributed in the lentic, lotic, and transitional lotic/lentic environments presented in this region. This update is an important tool for the implementation of guidelines and the development of safety protocols and sanitary barriers to avoid the dispersion of this IAS to new environments..

Resumo: Limnoperna fortunei é uma espécie exótica invasora que causa sérios problemas ecológicos e econômicos em ambientes de água doce do Brasil. Devido à sua elevada capacidade de dispersão e à falta de novos registros em publicações científicas, o objetivo deste estudo foi realizar uma extensa pesquisa para entender e alertar sobre o atual cenário de distribuição de L. fortunei nas bacias hidrográficas brasileiras. Também realizamos uma investigação mais detalhada sobre a distribuição da espécie na bacia do Alto Rio Uruguai, utilizando um método molecular. Apresentamos novos registros de ocorrência da espécie, mostrando a invasão em novas bacias e uma ampla distribuição nas bacias anteriormente infestadas. Além disso, confirmamos que o Alto Rio Uruguai está totalmente colonizado pelo mexilhão-dourado, estando distribuído pelos ambientes lênticos, lóticos e de transição existentes na região. Esta atualização se mostra como uma importante ferramenta para a implementação de diretrizes e o desenvolvimento de protocolos de segurança e barreiras sanitárias para evitar a dispersão desta espécie invasora em novos ambientes.

Masculinization of South American catfish (Rhamdia quelen) through dietary administration of 17α-methyltestosterone / Masculinización del pez Liso (Rhamdia quelen) mediante suministro dietario de 17α-metiltestosterona / Masculinização do Jundiá (Rhamdia quelen) através da administração dietética de 17α-metiltestosterona

Abstract Background: Production of monosex cultures of females is desirable in commercial aquaculture of certain species due to their higher growth rate. Ideally, females should be free of exogenous hormones. The initial step to produce hormone-free all-female offspring is masculinization of normal females to create sex reversed animals, called neomales, which are then be bred with normal females obtaining all-female offspring. Objective: To masculinize Rhamdia quelen fry by adding 17α-methyltestosterone (MT) hormone to the feed. Methods: Larvae of R. quelen were fed diets supplemented with 60, 80, or 100 mg MT/kg feed for 21 days. A control group was fed the same diet free of MT. At 150 days post-hatching, 30 fish of each treatment group were euthanized to evaluate gonadal changes using histological techniques. Results: MT significantly affected the differentiation of female gonads in the 60 and 80 mg MT/kg feed groups. Sex reversal was observed in all MT treatment groups, with 50, 40, and 20% neomales produced with 60, 80, and 100 mg MT/kg feed, respectively. Intersex gonads were observed only in the masculinization treatment groups. Inhibitory effects on gonadal development of females and males were observed at the highest MT doses. Conclusion: Dietary administration of MT effectively masculinizes R. quelen fry; however, the lowest dose of 60 mg/kg feed is recommended, since higher doses have inhibitory effects on gonadal development in both sexes.

Resumen Antecedentes: Debido a su mayor tasa de crecimiento, la producción de peces femeninos monosexo es deseable en acuicultura comercial de determinadas especies. Idealmente, las hembras deben estar libres de hormonas exógenas. El paso inicial para generar descendencia femenina libre de hormonas es la masculinización de hembras genéticas para producir animales sexualmente revertidos, llamados neomachos, los cuales se aparean luego con hembras genéticas para producir descendencia femenina. Objetivo: Masculinizar larvas de Rhamdia quelen con 17α-metiltestosterona (MT) incorporada en el alimento. Métodos: Larvas de R. quelen fueron alimentadas con dietas suplementadas con 60, 80 y 100 mg de MT/kg de alimento durante 21 días. Un grupo control recibió la misma dieta, sin MT. A los 150 días pos-eclosión, 30 peces de cada tratamiento fueron eutanasiados para evaluación gonadal mediante técnicas histológicas. Resultados: La MT afectó significativamente la diferenciación de las gónadas femeninas en las dosis de 60 y 80 mg MT/kg de alimento. El cambio de sexo se observó en los tratamientos con las dosis de 60, 80 y 100 mg MT/kg alimento, con 50, 40 y 20% de neomachos, respectivamente. En los tratamientos de masculinización se observaron gónadas intersexuales. En las dosis más altas de MT se observó inhibición del desarrollo gonadal de hembras y machos. Conclusiones: El suministro dietario de MT masculinizó las larvas de R. quelen. Se recomienda usar 60 mg/kg, ya que dosis mayores tienen efectos inhibidores en el desarrollo gonadal para ambos sexos.

Resumo Antecedentes: O cultivo monossexo feminino é desejável na aquicultura comercial de determinadas espécies devido à maior taxa de crescimento. Idealmente, as fêmeas devem ser livres de hormônios exógenos. O passo inicial para gerar descendências femininas livres destes hormônios é a masculinização de fêmeas normais para produzir animais revertidos sexualmente, os chamados neomachos. Os neomachos podem então ser cruzados com fêmeas normais para a produção de descendências femininas. Objetivo: Masculinizar larvas de R. quelen utilizando o hormônio 17α-metiltestosterona (MT) incorporado no alimento. Métodos: Larvas de R. quelen foram alimentadas com dietas suplementadas com MT nas doses de 60, 80 ou 100 mg/kg de alimento durante 21 dias. Um grupo controle foi alimentado com dieta similar livre de MT. Aos 150 dias pós-eclosão, 30 peixes de cada grupo de tratamento foram eutanasiados para avaliação gonadal através de técnicas histológicas. Resultados: O uso de MT afetou significativamente a diferenciação das gônadas femininas nas doses 60 e 80 mg/kg de alimento. A reversão sexual foi observada em todos os grupos tratados com MT, gerando 50, 40 e 20% de neomachos nas doses 60, 80 e 100 mg MT/kg de alimento, respectivamente. Gônadas intersexuais foram observadas somente nos tratamentos masculinizantes. Nas maiores doses de MT, efeitos inibitórios de desenvolvimento gonadal foram observados em fêmeas e machos. Conclusão: A administração dietética de MT efetivamente masculinizou larvas de R. quelen. No entanto, a dose mais baixa de 60 mg/kg de alimento é recomendada devido aos efeitos inibitórios das doses mais elevadas de MT no desenvolvimento gonadal de ambos os sexos.

Changes in external osmolality and ionic composition affect Megaleporinus obtusidens sperm motility.

Understanding the effects of environmental factors on sperm motility characteristics can increase artificial reproduction efficiency in species that do not spawn naturally in captivity, such as Megaleporinus obtusidens. This study evaluated the effects of the osmolality (25, 85, 145, 205, 265, and 325 mOsm kg-1) and composition of activating solutions (NaCl, KCl, or fructose) on the percentage of motile sperm, and the swimming velocity and path straightness of M. obtusidens spermatozoa. The concentrations of major ions in the seminal fluid were also assessed and Na+ (74.46 mmol L-1), K+ (37.24 mmol L-1), and Cl- (114.29 mmol L-1) were the most abundant. When the activating solution was hypertonic (325 mOsm kg-1) compared to the seminal fluid (293 mOsm kg-1), sperm motility was completely inhibited. A wide range of osmolalities that initiated sperm motility were identified for all three solutions. Both, the percentage of motile sperm and the motility duration were reduced (P < .05) at extreme osmolalities. At 145 mOsm kg-1, the percentage of motile sperm remained high (>50%) up to 40 s after activation and the motile phase lasted for >50 s, regardless of the activating solution composition. Over the postactivation time, the curvilinear velocity and straightness were similar (P > .05) for fructose and NaCl solutions, whereas KCl solutions induced a higher (P < .05) curvilinear velocity, lower (P < .05) straight-line velocity, and a circular swimming motion in spermatozoa. Our results suggest that a reduction in osmolality, using both non-electrolyte and electrolyte solutions, is the main trigger for the onset of spermatic movement in M. obtusidens sperm.

Gonadorelin increases semen production and does not affect its quality in Leporinus obtusidens.

Use of carp pituitary extract (CPE) as a hormone inducer for Leporinus obtusidens is cost-prohibitive; moreover, CPE contains unknown concentrations of gonadotropins. We evaluated the efficacy of gonadorelin as a substitute by analyzing its effect on sperm characteristics of L. obtusidens and cost-effectiveness (20, 40, 60, 80, and 100µgkg-1). Untreated and CPE-treated (4mgkg-1) fish were used as negative and positive controls, respectively. Following a single intramuscular dose of hormones, semen was collected at 200°-h. At doses from 60µgkg-1, all fish produced higher milt volume (P<0.05) than the negative control (0.2-0.8mLkg-1), equal (P>0.05) to the positive control (3.52±0.97mLkg-1). Gonadorelin did not affect sperm concentration (P>0.05). The percentage of morphologically normal spermatozoa was >64% in all treatments. The number of spermatozoa with intact membrane (70%-85%) was equal (P>0.05) to that in the controls. Relative to the negative control, gonadorelin did not affect the motility rate (P>0.05). Curvilinear velocity was equal (P>0.05) to that in both controls. The sperm swimming path was linear (0.9) 10s after activation and was not (P>0.05) dose-dependent. Considering the response rate of gonadorelin-induced fish and the similarity of semen quality compared to controls, the lowest effective dose to produce a higher volume of semen in L. obtusidens is 60µgkg-1, and the cost to induce 1kg of L. obtusidens is 14.0% lower than that with CPE.

Winter is coming: Food web structure and seasonality in a subtropical freshwater coastal lake.

Food web studies provide a useful tool to assess the organization and complexity of natural communities. Nevertheless, the seasonal dynamics of food web properties, their environmental correlates, and potential association with community diversity and stability remain poorly studied. Here, we condensed an incomplete 6-year community dataset of a subtropical coastal lake to examine how monthly variation in diversity impacts food web structure over an idealized time series for an averaged year. Phytoplankton, zooplankton, macroinvertebrates, and fish were mostly resolved to species level (n = 120 trophospecies). Our results showed that the seasonal organization of the food web could be aggregated into two clusters of months grouped here as 'summer' and 'winter'. During 'winter', the food web decreases in size and complexity, with the number of trophospecies dropping from 106 to 82 (a 22.6% decrease in the number of nodes) and the trophic interactions from 1,049 to 637 between month extremes (a 39.3% drop in the number of links). The observed simplification in food web structure during 'winter' suggests that community stability is more vulnerable to the impact of any change during this period.

Wide reproductive period of a long-distance migratory fish in a subtropical river, Brazil

Salminus brasiliensis is a potamodromous fish species that occurs in southern South American rivers. In spite of its ecological and economic relevance, information regarding the reproductive biology of S. brasiliensis is still scarce. This study used data from 18 years of continuous sampling in the Upper Uruguay River Basin, analyzing 718 adult fish (307 males, 243 females, 168 undefined) captured at different months of the year. The results showed that the reproductive timing for S. brasiliensis is wide in the Upper Uruguay River, with the occurrence of mature fish between the month of August and March and spawned individuals between July and May of the next year. These results were sustained by the increase of gonadal somatic relationship (GSR) from August. The reproductive timing of S. brasiliensis in the Upper Uruguay River may start between the middle winter and early spring (from late July to late September), and may extend until the late summer and middle fall (from the middle February to early May). These findings contribute to information on the general biology of S. brasiliensis and provide valuable knowledge to management programs and to conservation efforts of this fisheries resource.(AU)

Salminus brasiliensis é uma espécie potamodroma que ocorre em rios da América do Sul. Apesar de sua importância ecológica e econômica, informações sobre a biologia reprodutiva de S. brasiliensis ainda são escassas. O presente estudo utilizou dados de 18 anos de amostragens contínuas na bacia do alto rio Uruguai, analisando 718 peixes adultos (307 machos, 243 fêmeas, 168 indefinidos) capturados em diferentes meses do ano. Os resultados mostraram que o período reprodutivo de S. brasiliensis é amplo na bacia do alto rio Uruguai, com a ocorrência de peixes maduros entre agosto e março, e de peixes desovados entre os meses de julho e maio do ano seguinte. A relação gonadossomática reforça essa observação, pois mostra um aumento a partir de agosto. O período reprodutivo de S. brasiliensis no alto rio Uruguai pode iniciar entre meados do inverno e início da primavera (entre final de julho e final de setembro), podendo se estender até o final do verão e meados do outono (entre meados de fevereiro e início de maio). Essas descobertas contribuem com informações sobre a biologia geral de S. brasiliensis e são relevantes para programas de gestão e para esforços de conservação desse recurso pesqueiro.(AU)

Temporal distribution of ichthyoplankton in the Forquilha river, upper Uruguay river ­ Brazil: Relationship with environmental factors / Distribuição temporal do ictioplâncton no rio Forquilha, alto rio Uruguai ­ Brasil: Relação com os fatores ambientais

This study aimed to evaluate the temporal distribution of fish eggs and larvae in the Forquilha river (upper Uruguay river/Brazil) and its relationship with environmental variables. Ichthyoplankton and abiotic factors were sampled from September 2006 to August 2007. At the laboratory, samples were sorted and larvae were identified to the lowest possible taxonomic level. For data analysis we applied One-way Anova, Tukey's test, Pearson correlation and PCA. In this study 200 eggs and 308 larvae were collected, showing differences in the temporal distribution and influence of abiotic factors. Larvae were identified in all stages of development, being distributed in three order and eight families. These results point that the lower portion of the Forquilha river is an important drift and nursery area for fish larvae of the upper Uruguay river. The breeding season for most species was greatly marked, between October and January, coinciding with the increase in temperature and decrease of the water flow. The response of reproductive intensity varies according to the environmental variables.

Este trabalho teve por objetivo avaliar a distribuição temporal de ovos e larvas de peixes no Rio Forquilha (alto rio Uruguai/Brasil) e sua relação com as variáveis ambientais. As coletas de ictioplâncton e as aferições das variáveis ambientais ocorreram mensalmente no período de setembro de 2006 a agosto de 2007. Em laboratório, as amostras coletadas foram triadas e as larvas identificadas ao menor nível taxonômico possível. Para analisar os dados foram aplicadas a Análise de Variância Unifatorial, o teste de Tukey, PCA e a correlação de Pearson. Foram coletados 200 ovos e 308 larvas, que apresentaram diferença na distribuição temporal e influência das variáveis abióticas. Foram identificadas larvas em todos os estágios de desenvolvimento, estando distribuídas em três ordens e oito famílias. Os resultados apontam que a região inferior do rio Forquilha é um importante local de deriva e de berçário para as larvas dos peixes do alto rio Uruguai. O período reprodutivo para a maior parte das espécies foi bem marcado, ocorrendo entre os meses de outubro e janeiro, e coincidindo com o aumento da temperatura e redução da vazão da água. A resposta da intensidade reprodutiva varia de acordo com as variáveis ambientais.

Biochemical changes in Salminus brasiliensis due to successive captures and stocking densities - doi: 10.4025/actascibiolsci.v35i1.13055

This study evaluated the biochemical changes associated to successive captures of Salminus brasiliensis reared at different stocking densities. The experiment was conducted in tanks with a capacity of 1,000 L, connected to a recirculating system with temperature control and continuous aeration. Fish were stocked at densities of 30, 150 and 300 fish m-3 and the successive catches were applied at the end of the experimental period of 80 days. The biochemical changes were evaluated at the end of the trial through the parameters: hematocrit, hemoglobin, glucose and lactate in plasma and Na+, K+ and Cl- and Ca2+ in the gills. The concentration of glucose increased with the increase of stocking density as also registered for lactate concentration, except for fish captured twice. Hemoglobin concentration increased with the increase of stocking density only in fish captured three times. The hematocrit and the ions in the gills had no variation under any condition and therefore, the ionic alterations characteristic of a stress response, were not found in this species. The successive captures associated to stocking density were related to biochemical changes in S. brasiliensis, but ion concentrations in gills were not indicators of this condition.

Biochemical changes in Salminus brasiliensis due to successive captures and stocking densities / Alterações bioquímicas em Salminus brasiliensis decorrentes de capturas sucessivas e da densidade de estocagem

This study evaluated the biochemical changes associated to successive captures of Salminus brasiliensis reared at different stocking densities. The experiment was conducted in tanks with a capacity of 1,000 L, connected to a recirculating system with temperature control and continuous aeration. Fish were stocked at densities of 30, 150 and 300 fish m-3 and the successive catches were applied at the end of the experimental period of 80 days. The biochemical changes were evaluated at the end of the trial through the parameters: hematocrit, hemoglobin, glucose and lactate in plasma and Na+, K+ and Cl- and Ca2+ in the gills. The concentration of glucose increased with the increase of stocking density as also registered for lactate concentration, except for fish captured twice. Hemoglobin concentration increased with the increase of stocking density only in fish captured three times. The hematocrit and the ions in the gills had no variation under any condition and therefore, the ionic alterations characteristic of a stress response, were not found in this species. The successive captures associated to stocking density were related to biochemical changes in S. brasiliensis, but ion concentrations in gills were not indicators of this condition.

O objetivo deste estudo foi avaliar as alterações bioquímicas relacionadas a capturas sucessivas em Salminus brasiliensis criados em diferentes densidades de estocagem. O experimento foi conduzido em tanques com capacidade de 1.000 L, conectados a um sistema de recirculação de água com temperatura e aeração contínua. Os peixes foram estocados nas densidades de 30, 150 and 300 peixes m-3, com aplicação de capturas sucessivas ao término do período experimental de 80 dias. As alterações bioquímicas foram avaliadas pela análise do hematócrito, hemoglobina, glicose e lactato plasmático e Na+, K+ e Cl- e Ca2+ branquial. A elevação da concentração de glicose esteve relacionada ao aumento da densidade de estocagem nos peixes submetidos a uma, duas e três capturas. A concentração de lactato apresentou resposta semelhante à registrada para a glicose, com exceção de peixes capturados por duas vezes. A elevação da concentração de hemoglobina esteve relacionada ao aumento da densidade de estocagem nos peixes capturados três vezes. Não foram observadas variações no hematócrito e nos íons após as capturas. As capturas sucessivas associadas à densidade de estocagem interferiram na resposta bioquímica em S. brasiliensis, mas a concentração de íons nas brânquias não foram indicadores dessa condição.

Spawning of migratory fish species between two reservoirs of the upper Uruguay River, Brazil

This study investigated the migratory fish spawning within the reservoirs of the Machadinho and Itá dams (upper Uruguay River, Brazil) and its relationship to environmental variables. Sampling was conducted in the lotic region of the river in two sites between the dams' reservoirs: Uruguay (main river) and Ligeiro (tributary). Sampling included nine consecutive reproductive periods (RP) spanning the period from 2001 to 2010 and was conducted at night on the water surface using cylindrical-conical plankton nets (0.5 mm mesh); environmental variables were also recorded. The spawning of the migratory species Salminus brasiliensis, Prochilodus lineatus, and Steindachneridion scriptum was registered: S. brasiliensis and P. lineatus spawned in the tributary river at the end of spring/beginning of summer, during flooding and during periods of high water temperature. Steindachneridion scriptum spawned in the main river at the beginning of spring. The study showed that S. brasiliensis, P. lineatus, and S. scriptum are able to spawn in small lotic river stretches within two reservoirs, but only under very specific and not common environmental conditions.

Este estudo verificou a presença de desova de peixes migradores entre os reservatórios das Usinas Hidrelétricas de Machadinho e Itá (alto rio Uruguai, Brasil), e sua relação com as variáveis ambientais. As amostragens foram realizadas na região lótica do rio Uruguai, no trecho situado entre os reservatórios de Itá e Machadinho, em duas estações de amostragem: Uruguai (Principal) e Ligeiro (Tributário). As coletas abrangeram nove períodos reprodutivos (PR) consecutivos, desde 2001 até 2010, e foram realizadas no período noturno, na superfície, com o uso de redes de plâncton do tipo cilíndrico-cônicas de malha 0,5 mm, quando também foram registradas as variáveis ambientais. O estudo registrou a desova de três espécies migradoras: Salminus brasiliensis, Prochilodus lineatus e Steindachneridion scriptum. As populações de S. brasiliensis e P. lineatus desovaram no rio tributário no final da primavera e início do verão em condições de enchentes e temperatura da água mais alta. Steindachneridion scriptum desovou no rio principal durante o início da primavera. O presente estudo mostra que S. brasiliensis, P. lineatus e S. scriptum conseguem desovar em pequenos trechos lóticos de rio entre dois reservatórios, porém em condições ambientais determinadas e pouco frequentes.

Temperatures for fertilization and hatching and their influence ondetermining the sex ratio of the silver catfish Rhamdia quelen / Temperatura de fertilização e incubação e sua influência na determinação da proporção sexual do jundiá, Rhamdia quelen

This study aimed to evaluate the effects of water temperature duringfertilization and egg incubation in the determination of the sex ratio of fingerlings of silvercatfish Rhamdia quelen. Water temperatures of 19, 25 and 30°C were used during the eggfertilizations, and the eggs were then incubated at temperatures of 19, 25 or 30°C for eachfertilization temperature condition. An increase in temperature reduced the fertilization rateof R. quelen, while the final number of fish was reduced when a lower temperature was usedduring egg incubation. The temperatures of fertilization and incubation that were tested didnot alter the sex ratio.

Temperatura de fertilização e incubação e sua influência nadeterminação da proporção sexual do jundiá, Rhamdia quelen. O presente estudo tevecomo objetivo avaliar o efeito da temperatura da água de fertilização e de incubação nadeterminação da proporção sexual do jundiá, Rhamdia quelen. Para tanto, foram utilizadastrês temperaturas de água de fertilização de ovos (19, 25 e 30°C), e para cada uma delas osovos foram incubados nas temperaturas de 19, 25 e 30°C. O aumento da temperaturareduziu a taxa de fertilização de Rhamdia quelen, enquanto o número final de indivíduos foireduzido quando a menor temperatura de incubação foi utilizada. As temperaturas defertilização ou incubação testadas não alteram a proporção entre os sexos.

Photoperiod influence on the cultivation of Steindachneridion scriptum (Pisces, Pimelodidae) juvenile

This study aimed to evaluate the influence of photoperiod on juvenile suruvi (Steindachneridion scriptum) in six photoperiods: 24L-0D (L= Light; D= Dark), 18L-6D, 14L-10D, 10L-14D, 6L-18D and 0L-24D. Juveniles measuring 176.8 ± 13.2mm and weighing 60.2 ± 16.0g were distributed in eighteen 150-L aquariums, stocked with 8 juveniles per aquarium. At the end of the study, treatments 24L-0D (105.7 ± 5.8g and 845.9 ±46g) and 0L-24D (93.3 ± 4.9g and 746.4 ± 39.5g) were different (P<0.05) on weight and biomass. Survival (100 ± 0.0 percent) and length (212.5 ±2.5mm) were the same (P>0.05) in all the treatments. The results showed that suruvi (Steindachneridion scriptum) reached better weight and biomass in extended light periods.

O objetivo do presente estudo foi avaliar a influência do fotoperíodo no cultivo de juvenis de suruvi Steindachneridion scriptum, nos seguintes fotoperíodos: 24L-0E (L=Luz; E= Escuro), 18L-6E, 14L-10E, 10L-14E, 6L-18E e 0L-24E. Juvenis com comprimento e peso médio de 176,8± 13,2mm e 60,2± 16,0g, respectivamente, foram distribuídos em 18 tanques de 150L, estocados na densidade de oito juvenis por tanques. Decorridos 90 dias de cultivo foram encontradas diferenças (P<0,05) para as variáveis peso e biomassa, entre os tratamentos com iluminação contínua (105,7±5,8g e 845,9±46,0g) e com escuridão contínua (93,3±4,9g e 746,4±39,5g), respectivamente. Não foram observadas diferenças (P>0,05) na sobrevivência (100,0 ± 0,0 por cento) e no comprimento total (212,5 ± 2,5mm). Nas condições apresentadas os resultados nos permitem concluir que o suruvi, Steindachneridion scriptum, atingiu melhor peso e biomassa em cultivos que apresentam períodos com iluminação.

Growth and survival of dorado Salminus brasiliensis (Pisces, Characidae) post-larvae cultivated with different types of food and photoperiods

The effect of food and photoperiod on dorado (Salminus brasiliensis) post-larvae growth and survival was investigated using the following treatments: LD (Light: Dark) 24:0 + Artemia nauplii (A), LD 24:0 + fish prey (F), LD 14:10 + A, LD 14:10 + F, LD 0:24 +A and LD 0:24 + F. Prochilodus lineatus larvae were used as fish prey. Higher survival rates were registered in fish prey treatments (P<0.05) and were not influenced by photoperiod whereas in Artemia treatments, the survival was very low, but directly proportional to light increase (P<0.05). The better growth in LD 0:24 was related to a safe-energy strategy that reduced energy consumption whereas in LD 24:0, the higher energy consumption reduced the growth. In intermediate photoperiod, the post-larvae did not define a strategy to capture preys, using alternatively the static safe-energy and the swimming consuming energy, which caused higher heterogeneity in growth.

O efeito da alimentação e do fotoperíodo sobre o crescimento e a sobrevivência de pós-larvas de dourado (Salminus brasiliensis) foi investigado utilizando-se os seguintes tratamentos: LE (Luz: Escuro) 24:0 + náuplios de Artemia (A), LE 24:0 + larva forrageira (L), LE 14:10 + A, LE 14:10 + L, LE 0:24 +A e LE 0:24 + L. Larvas de Prochilodus lineatus foram utilizadas como larva forrageira. Taxas de sobrevivência mais elevadas foram registradas nos tratamentos que utilizaram larvas forrageiras (P<0,05), que não foram influenciados pelo fotoperíodo, enquanto nos tratamentos com Artemia a sobrevivência foi muito reduzida, mas diretamente proporcional ao aumento da disponibilidade de iluminação (P<0,05). O melhor crescimento em LE 0:24 esteve relacionado ao uso de uma estratégia de baixo consumo energético enquanto em LE 24:0 o maior consumo de energia produziu menor crescimento. No fotoperíodo intermediário as pós-larvas não definiram uma estratégia única para capturar as presas, utilizando alternadamente a estratégia estática de baixo consumo de energia e a estratégia natatória, associada a um maior consumo energético, que causou maior heterogeneidade no crescimento.

Genetic variability in four fish species (Pimelodus maculatus, Prochilodus lineatus, Salminus brasiliensis and Steindachneridion scripta) from Uruguay River basin

The genetic variability of four fish species (Pimelodus maculatus, Prochilodus lineatus, Salminus brasiliensis and Steindachneridion scripta) collected in the upper Uruguay River basin was analyzed using the RAPD technique. A total of 118 amplified fragments was obtained, 11 for P. maculatus, 29 for P. lineatus, 45 for S. brasiliensis and 33 for S. scripta. Amplified fragments with monomorphic profile were not found in the studied species, except for S. brasiliensis, which presented seven monomorphic bands for Saltinho population. All species showed high levels of genetic variability among individuals.

A diversidade da vida se expressa de modo extraordinário nos ecossistemas aquáticos. A bacia do alto rio Uruguai é um exemplo desta condição, onde há registro de mais de 100 espécies de peixes. A compreensão das diferenças genéticas entre as diversas populações nativas é fundamental para a manutenção de seus estoques. A variabilidade genética de quatro espécies de peixes (Pimelodus maculatus, Prochilodus lineatus, Salminus brasiliensis e Steindachneridion scripta) coletadas na bacia do alto rio Uruguai foi analisada utilizando-se a técnica de RAPD. Obteve-se um total de 118 fragmentos amplificados, sendo 11 para P. maculatus, 29 para P. lineatus, 45 para S. brasiliensis e 33 para S. scripta. Fragmentos de caráter monomórfico não foram encontrados para as espécies estudadas, com exceção de S. brasiliensis de Saltinho que apresentou sete bandas monomórficas para estes indivíduos. As análises estatísticas mostraram altos níveis de variabilidade genética entre os indivíduos das espécies estudadas.

Growth of silver catfish Rhamdia quelen (Pisces, Pimelodidae) fingerlings in different dissolved oxygen concentrations - DOI: 10.4025/actascibiolsci.v28i1.1057 / Crescimento de alevinos de jundiá, Rhamdia quelen (Pisces, Pimelodidae), em diferentes concentrações de oxigênio dissolvido - DOI: 10.4025/actascibiolsci.v28i1.1057

This study"s aim was evaluate the growth of silver catfish (Rhamdia quelen) fingerlings on five dissolved oxygen concentrations: 1,3 (T1), 2,4 (T2), 3,7 (T3), 5,4 (T4) and 7,5 mg O2/L (T5). A completely random design experiment with three repetitions was used and the experiment was carried out during 25 days. Fingerlings were distributed in circular, 150-L fiberglass tanks kept in darkness, endowed with mechanic and biological filters and water renewal, at a stocking density of 34 individuals/tank. Survival was lower at the extreme tested levels (T1 and T5). Better growth in weight, length and food conversion were found at increasing oxygen concentrations. Even at the lowest oxygen concentration (T1) fingerlings showed growth increase. The best effects on silver catfish fingerlings development was observed at T4

O objetivo deste estudo foi avaliar o crescimento de alevinos de jundiá, Rhamdia quelen, em 5 concentrações de oxigênio dissolvido: 1,3 (T1), 2,4 (T2), 3,7 (T3), 5,4 (T4) e 7,5 mg O2/L (T5). O estudo utilizou o modelo experimental inteiramente ao acaso com 3 repetições e foi conduzido por 25 dias. Os alevinos foram distribuídos em tanques circulares de fibra de vidro de 150 L mantidos na escuridão e dotados de aeração mecânica, filtro biológico e renovação de água, na densidade de 34 indivíduos/tanque. A sobrevivência foi menor nos extremos testados (T1 e T5). Maior crescimento em peso e em comprimento e melhor conversão alimentar foram obtidos com o aumento da concentração de oxigênio dissolvido. Os alevinos de jundiá apresentaram incremento em peso, mesmo na menor concentração de oxigênio dissolvido (T1), e T4 produziu os melhores efeitos sobre o desenvolvimento

Use of different densities, diets and tank formats in the larvae culture of the piracanjuba, Brycon orbignyanus Valenciennes, 1849 (Characiformes, Characidae) - DOI: 10.4025/actascibiolsci.v25i1.2082 / Utilização de diferentes densidades, dietas e formatos de tanque na larvicultura da piracanjuba, Brycon orbignyanus Valenciennes, 1849 (Characiformes, Characidae) - DOI: 10.4025/actascibiolsci.v25i1.2082

Aiming to study the survival rate and the development of piracanjuba, Brycon orbignyanus (Characiformes, characidae) fry, three experiments were set, with three repetitions by treatment. The experiments consisted of testing three different initial stocking densities (5, 15 and 25 piracanjuba larvae/L), three diets (Artemia sp, commercial ration and curimbatá larvae, Prochilodus lineatus) and two formats of hatchery tank (square and rectangular). The parameters of water quality were measured twice a day. The feeding was offered in a 4-hour interval, beginning soon after the mouth-opening of the fry. The results showed that different stocking densities and diets didn"t influence the larvae survival, average weight, length and back-ventral height. However, the average weight and length were significantly better in the square tank

Com o objetivo de estudar a taxa de sobrevivência e o desenvolvimento de larvas de piracanjuba, Brycon orbignyanus (Characiformes, characidae), foram realizados três experimentos com três repetições por tratamento. Os experimentos consistiram em testar três diferentes estoques iniciais de densidade (5, 15 e 25 larvas de piracanjuba/L), três dietas (Artemia sp, ração comercial e larva de curimbatá, Prochilodus lineatus) e dois formatos de tanque de larvicultura (quadrado e retangular). Os parâmetros de qualidade de água foram medidos duas vezes ao dia. A alimentação foi oferecida em um intervalo de 4 horas, iniciando após a abertura da boca das larvas. Sob as condições de realização deste experimento, conclui-se que as diferentes densidades de estocagem utilizadas, assim como as três diferentes dietas, não influenciaram a sobrevivência, média de peso, comprimento e altura dorso-ventral das larvas de piracanjuba. Entretanto, o comprimento e o peso das larvas, diferentemente dos outros fatores, foi significativamente melhor no tanque de formato quadrado