Knockdown of double-stranded RNases (dsRNases) enhances oral RNA interference (RNAi) in the corn leafhopper, Dalbulus maidis.

The leafhopper Dalbulus maidis is a harmful pest that causes severe damage to corn crops. Conventional chemical pesticides have negative environmental impacts, emphasizing the need for alternative solutions. RNA interference (RNAi) is a more specific and environmentally friendly method for controlling pests and reducing the negative impacts of current pest management practices. Previous studies have shown that orally administered double-stranded RNA (dsRNA) is less effective than injection protocols in silencing genes. This study focuses on identifying and understanding the role of double-stranded ribonucleases (dsRNases) in limiting the efficiency of oral RNAi in D. maidis. Three dsRNases were identified and characterized, with Dmai-dsRNase-2 being highly expressed in the midgut and salivary glands. An ex vivo degradation assay revealed significant nuclease activity, resulting in high instability of dsRNA when exposed to tissue homogenates. Silencing Dmai-dsRNase-2 improved the insects' response to the dsRNA targeting the gene of interest, providing evidence of dsRNases involvement in oral RNAi efficiency. Therefore, administering both dsRNase-specific and target gene-specific-dsRNAs simultaneously is a promising approach to increase the efficiency of oral RNAi and should be considered in future control strategies.

The impact of food provisioning on parasite infection in wild black capuchin monkeys: a network approach.

Nonhuman primates host a variety of gastrointestinal parasites that infect individuals through different transmission routes. Social contact among group members (e.g., body contact, grooming) brings the risk of parasite infection, especially when the pathogen infection is directly transmitted. Along with this, accidental provisioning (i.e., food provisioning occurring during close tourist-wildlife interactions) is also considered to increase the risk of infection, as aggregation during feeding can cause higher exposure to parasite infective stages. However, while some attention has been paid to the relationship between social behavior and parasites, the link between accidental food provisioning and characteristics of parasite infection in primates has thus far received less attention. This study examines the potential effect of accidental provisioning on patterns of inter-individual spatial association, and in turn on parasite infection risk in a wild group of black capuchin monkeys (Sapajus nigritus) in Iguazú National Park, Argentina. To do so, we simulated events of accidental provisioning via researcher-managed provisioning experiments and tested whether experimental provisioning affects the inter-individual spatial distribution within groups. In addition, we determined whether patterns of parasite infection were better predicted by naturally occurring spatial networks (i.e., spatial association during natural observations) or by provisioning spatial networks (i.e., spatial interactions during experimental provisioning). We found a significant increase in network centrality that was potentially associated with an overall increase in individual connections with other group members during experimental trials. However, when assessing the effects of natural and provisioning network metrics on parasite characteristics, we did not observe a significant effect of centrality measures (i.e., closeness and betweenness) on parasite richness and single infection by Filariopsis sp. Taken together, our findings suggest that alterations of within-group spatial networks due to accidental provisioning may have a limited influence in determining the characteristics of parasite infections in black capuchin monkeys.

Rickettsia rickettsii Co-feeding Transmission among Amblyomma aureolatum Ticks.

Amblyomma aureolatum ticks are vectors of Rickettsia rickettsii, the etiologic agent of Rocky Mountain spotted fever in Brazil. Maintenance of R. rickettsii in nature depends on horizontal transmission along tick generations. Although such transmission is known to occur when uninfected and infected ticks feed simultaneously on susceptible animals (co-feeding systemic transmission), we investigated co-feeding nonsystemic transmission, which was based on R. rickettsii-infected and -uninfected A. aureolatum ticks feeding simultaneously on guinea pigs immune to R. rickettsii. Our acquisition and transmission infestations demonstrated that horizontal transmission of R. rickettsii by co-feeding ticks on immune hosts with no systemic infection did not occur when uninfected larvae fed distantly from infected nymphs but did occur in a few cases when uninfected larvae fed side-by-side with infected nymphs, suggesting that they shared the same feeding site. The co-feeding nonsystemic transmission type might have no epidemiologic importance for Rocky Mountain spotted fever.

Estratégia de coalimentação na sobrevivência e no crescimento de larvas de Betta splendens durante a transição alimentar / Co-feeding strategy on survival and growth of Betta splendens larvae during weaning

Conduziu-se um experimento com o objetivo de avaliar a influência do período de coalimentação na sobrevivência e no crescimento de larvas de Betta splendens. As larvas foram alimentadas com náuplios de Artemia durante sete dias e, posteriormente, submetidas aos seguintes tratamentos: jejum contínuo; ração contínua; quatro dias de coalimentação + 14 dias de ração; oito dias de coalimentação + 10 dias de ração; 12 dias de coalimentação + seis dias de ração; náuplios de Artemia durante todo o período experimental. Os valores das variáveis de desempenho das larvas do tratamento 12 dias de coalimentação + seis dias de ração e do tratamento náuplios de Artemia foram superiores aos demais tratamentos, exceto para sobrevivência, em que não houve diferença significativa com o tratamento oito dias de coalimentação + 10 dias de ração. Considerando-se apenas o tempo de oferta de Artemia (em dias), obteve-se a equação de regressão para as variáveis analisadas. A sobrevivência e a taxa de crescimento específico (TCE) apresentaram efeito quadrático, e as demais variáveis apresentaram efeito linear. O ponto de máxima para sobrevivência foi de 21,7 dias (88,92%) e para TCE foi de 26,2 dias (23,47% dia-1). O período de co-feeding influencia no crescimento e na sobrevivência de larvas de Betta splendens. Após o período de 19 dias de oferta de alimento vivo, com 12 dias de coalimentação, as larvas estão aptas a aproveitar de maneira eficiente o alimento inerte sem prejuízos ao crescimento e à sobrevivência.(AU)

An experiment was carried out to evaluate the influence of the period of co-feeding on survival and growth of Betta splendens larvae. The following strategies for co-feeding were used: continuous fasting, 18 days of inert diet, 4 days of co-feeding + 14 days of inert diet; 8 days of co-feeding + 10 days of inert diet; 12 days of co-feeding + 6 days of inert diet, nauplii of Artemia throughout the experiment period. The values of performance variables for larvae with 12 days of treatment for co-feeding + 6 days of inert diet and the nauplii treatment with Artemia were higher than the other treatments, except for survival, which did not differ significantly from the treatment with 8 days of co-feeding + 10 days of inert diet. Considering only the supply time for Artemia (in days) the regression equation was obtained for the variables analyzed. The survival and specific growth rate (SGR) showed a quadratic effect and other variables showed a linear effect. The point of maximum survival was 21.7 days (88.92%) and for SGR it was 26.2 days (23.47 % day-1). The co-feeding period influences the survival and growth of the Betta splendens larvae. After the period of 19 days of supply of live food, with 12 days of co-feeding, larvae can be fed exclusively on inert diet, without negative effects on growth and survival.(AU)

Estratégia de coalimentação na sobrevivência e no crescimento de larvas de Betta splendens durante a transição alimentar / Co-feeding strategy on survival and growth of Betta splendens larvae during weaning

Conduziu-se um experimento com o objetivo de avaliar a influência do período de coalimentação na sobrevivência e no crescimento de larvas de Betta splendens. As larvas foram alimentadas com náuplios de Artemia durante sete dias e, posteriormente, submetidas aos seguintes tratamentos: jejum contínuo; ração contínua; quatro dias de coalimentação + 14 dias de ração; oito dias de coalimentação + 10 dias de ração; 12 dias de coalimentação + seis dias de ração; náuplios de Artemia durante todo o período experimental. Os valores das variáveis de desempenho das larvas do tratamento 12 dias de coalimentação + seis dias de ração e do tratamento náuplios de Artemia foram superiores aos demais tratamentos, exceto para sobrevivência, em que não houve diferença significativa com o tratamento oito dias de coalimentação + 10 dias de ração. Considerando-se apenas o tempo de oferta de Artemia (em dias), obteve-se a equação de regressão para as variáveis analisadas. A sobrevivência e a taxa de crescimento específico (TCE) apresentaram efeito quadrático, e as demais variáveis apresentaram efeito linear. O ponto de máxima para sobrevivência foi de 21,7 dias (88,92%) e para TCE foi de 26,2 dias (23,47% dia-1). O período de co-feeding influencia no crescimento e na sobrevivência de larvas de Betta splendens. Após o período de 19 dias de oferta de alimento vivo, com 12 dias de coalimentação, as larvas estão aptas a aproveitar de maneira eficiente o alimento inerte sem prejuízos ao crescimento e à sobrevivência.

An experiment was carried out to evaluate the influence of the period of co-feeding on survival and growth of Betta splendens larvae. The following strategies for co-feeding were used: continuous fasting, 18 days of inert diet, 4 days of co-feeding + 14 days of inert diet; 8 days of co-feeding + 10 days of inert diet; 12 days of co-feeding + 6 days of inert diet, nauplii of Artemia throughout the experiment period. The values of performance variables for larvae with 12 days of treatment for co-feeding + 6 days of inert diet and the nauplii treatment with Artemia were higher than the other treatments, except for survival, which did not differ significantly from the treatment with 8 days of co-feeding + 10 days of inert diet. Considering only the supply time for Artemia (in days) the regression equation was obtained for the variables analyzed. The survival and specific growth rate (SGR) showed a quadratic effect and other variables showed a linear effect. The point of maximum survival was 21.7 days (88.92%) and for SGR it was 26.2 days (23.47 % day-1). The co-feeding period influences the survival and growth of the Betta splendens larvae. After the period of 19 days of supply of live food, with 12 days of co-feeding, larvae can be fed exclusively on inert diet, without negative effects on growth and survival.

Time of feed transition and inclusion levels of exogenous protease in rations for piabanha-do-Pardo Brycon sp. hatchery - doi: 10.4025/actascianimsci.v34i4.14471

Two experiments were conducted which consisted of determining the ideal time to make a feed transition from larvae of curimba Prochilodus hartii to ration (from third, fifth and seventh days of life, with three days of co-feeding), and assess inclusion levels of exogenous protease (0, 0.02 and 0.2%) in the diet of larvae of piabanha-do-Pardo Brycon sp., in a completely randomized experimental design and duration of 15 and 17 days, respectively. Biomass, survival, total length, weight and specific growth rate were measured at the end of the experiments. Water quality parameters were measured every three days. The different transition periods and levels of exogenous protease did not affect water quality. The animals subjected to feed transition on the seventh day of life showed better results for length (23.1 mm), weight (110.9 mg) and SGR (25.5%), being similar in biomass and survival at the fifth day of life. Therefore, the transition can be made on the fifth day of life. The inclusion levels of exogenous protease in the commercial diet had no effect on performance.

Time of feed transition and inclusion levels of exogenous protease in rations for piabanha-do-Pardo Brycon sp. hatchery - doi: 10.4025/actascianimsci.v34i4.14471

Two experiments were conducted which consisted of determining the ideal time to make a feed transition from larvae of curimba Prochilodus hartii to ration (from third, fifth and seventh days of life, with three days of co-feeding), and assess inclusion levels of exogenous protease (0, 0.02 and 0.2%) in the diet of larvae of piabanha-do-Pardo Brycon sp., in a completely randomized experimental design and duration of 15 and 17 days, respectively. Biomass, survival, total length, weight and specific growth rate were measured at the end of the experiments. Water quality parameters were measured every three days. The different transition periods and levels of exogenous protease did not affect water quality. The animals subjected to feed transition on the seventh day of life showed better results for length (23.1 mm), weight (110.9 mg) and SGR (25.5%), being similar in biomass and survival at the fifth day of life. Therefore, the transition can be made on the fifth day of life. The inclusion levels of exogenous protease in the commercial diet had no effect on performance.

Time of feed transition and inclusion levels of exogenous protease in rations for piabanha-do-Pardo Brycon sp. hatchery / Momento para a transição alimentar e níveis de inclusão de protease exógena na ração da larvicultura de piabanha-do-Pardo Brycon sp

Two experiments were conducted which consisted of determining the ideal time to make a feed transition from larvae of 'curimba' Prochilodus hartii to ration (from third, fifth and seventh days of life, with three days of co-feeding), and assess inclusion levels of exogenous protease (0, 0.02 and 0.2%) in the diet of larvae of piabanha-do-Pardo Brycon sp., in a completely randomized experimental design and duration of 15 and 17 days, respectively. Biomass, survival, total length, weight and specific growth rate were measured at the end of the experiments. Water quality parameters were measured every three days. The different transition periods and levels of exogenous protease did not affect water quality. The animals subjected to feed transition on the seventh day of life showed better results for length (23.1 mm), weight (110.9 mg) and SGR (25.5%), being similar in biomass and survival at the fifth day of life. Therefore, the transition can be made on the fifth day of life. The inclusion levels of exogenous protease in the commercial diet had no effect on performance.

Foram realizados dois experimentos, que consistiram em determinar o momento ideal de se realizar a transição alimentar de larva de curimba Prochilodus hartii para ração (a partir do terceiro, quinto e sétimo dia de vida, com três dias de coalimentação), e avaliar níveis de inclusão de protease exógena (0; 0,02 e 0,2%) na dieta de larvas de piabanha-do-Pardo Brycon sp., em delineamento inteiramente casualizado e duração de 15 e 17 dias, respectivamente. A biomassa, sobrevivência, comprimento total, peso médio e taxa de crescimento específico foram mensurados ao final dos experimentos. Já os parâmetros de qualidade de água foram aferidos a cada três dias. Os diferentes períodos de transição alimentar e níveis de protease exógena não interferiram na qualidade da água. Os animais submetidos à transição alimentar no sétimo dia de vida apresentaram melhores resultados para comprimento (23,1 mm), peso (110,9 mg) e TCE (25,5%), sendo similares em biomassa e sobrevivência aos do quinto dia de transição. Portanto, o início da transição pode ser realizada no quinto dia de vida. Os níveis de inclusão de protease exógena na ração comercial não influenciaram no desempenho dos animais.

Produção de juvenis do linguado Paralichthys orbignyanus: efeito da duração do período de co-alimentação durante o desmame / Production of Brazilian flounder Paralichthys orbignyanus juveniles: the effect of co-feeding period during the weaning

O desmame, ou seja, a substituição do alimento vivo por alimento inerte é uma etapa crítica para a produção de alevinos de peixes marinhos. Este trabalho teve por objetivo avaliar o efeito do período de co-alimentação (alimento vivo e inerte) sobre a sobrevivência, o crescimento e os custos de produção de juvenis do linguado Paralichthys orbignyanus. Durante o período de co-alimentação, os juvenis (idade inicial 32 dias) receberam Artemia enriquecida juntamente com ração. Foram testados três períodos de co-alimentação: 15, 20 e 25 dias, mais um grupo controle alimentado com Artemia enriquecida. Ao final do experimento (76 dias), os juvenis alimentados exclusivamente com Artemia enriquecida apresentaram sobrevivência (82 por cento), peso (480±157mg) e comprimento (35,5±5,0mm) significativamente maiores (P<0,05) que os juvenis alimentados com ração. Não houve diferença significativa (P>0,05) no crescimento entre os juvenis alimentados com ração nos diferentes períodos, entretanto, um período maior de co-alimentação favoreceu a sobrevivência. Os resultados obtidos demonstram que os linguados alimentados exclusivamente com Artemia apresentam melhor performance do que aqueles alimentados com ração. Entretanto, o custo de produção quando a Artemia é substituída por ração aos 58 dias de vida é menor do que quando o desmame é realizado mais cedo ou quando os alevinos são alimentados apenas com Artemia.

Weaning is a critical period for production of marine fish juveniles. The objective of this research was to evaluate the effect of co-feeding on survival, growth, and cost of production after the weaning of juveniles of Brazilian flounder Paralichthys orbignyanus. Juvenile flounder (32 days after hatching) were fed on HUFA enriched Artemia and subsequently three periods of co-feeding with dry diets (15, 20, and 25 days) were tested, a control group, where flounder were fed exclusively on Artemia was also followed until the end of the experiment. Juveniles fed on Artemia showed significantly higher (P<0.05) survival (82 percent), weight (480±157mg) and total length (35.5±5.0mm) than flounder weaned into dry diets, independent of the co-feeding period. Growth was similar (P>0.05) for juveniles fed on dry diets, but a higher survival rate was registered when the co-feeding period was longer. The results obtained demonstrate that flounder fed exclusively on Artemia have a better performance than those weaned into dry diets. However, unitary cost of production is reduced when juveniles are weaned 58 days after hatching.

Produção de juvenis do linguado Paralichthys orbignyanus: efeito da duração do período de co-alimentação durante o desmame

Weaning is a critical period for production of marine fish juveniles. The objective of this research was to evaluate the effect of co-feeding on survival, growth, and cost of production after the weaning of juveniles of Brazilian flounder Paralichthys orbignyanus. Juvenile flounder (32 days after hatching) were fed on HUFA enriched Artemia and subsequently three periods of co-feeding with dry diets (15, 20, and 25 days) were tested, a control group, where flounder were fed exclusively on Artemia was also followed until the end of the experiment. Juveniles fed on Artemia showed significantly higher (P 0.05) survival (82%), weight (480±157mg) and total length (35.5±5.0mm) than flounder weaned into dry diets, independent of the co-feeding period. Growth was similar (P>0.05) for juveniles fed on dry diets, but a higher survival rate was registered when the co-feeding period was longer. The results obtained demonstrate that flounder fed exclusively on Artemia have a better performance than those weaned into dry diets. However, unitary cost of production is reduced when juveniles are weaned 58 days after hatching.

O desmame, ou seja, a substituição do alimento vivo por alimento inerte é uma etapa crítica para a produção de alevinos de peixes marinhos. Este trabalho teve por objetivo avaliar o efeito do período de co-alimentação (alimento vivo e inerte) sobre a sobrevivência, o crescimento e os custos de produção de juvenis do linguado Paralichthys orbignyanus. Durante o período de co-alimentação, os juvenis (idade inicial 32 dias) receberam Artemia enriquecida juntamente com ração. Foram testados três períodos de co-alimentação: 15, 20 e 25 dias, mais um grupo controle alimentado com Artemia enriquecida. Ao final do experimento (76 dias), os juvenis alimentados exclusivamente com Artemia enriquecida apresentaram sobrevivência (82%), peso (480±157mg) e comprimento (35,5±5,0mm) significativamente maiores (P 0,05) que os juvenis alimentados com ração. Não houve diferença significativa (P>0,05) no crescimento entre os juvenis alimentados com ração nos diferentes períodos, entretanto, um período maior de co-alimentação favoreceu a sobrevivência. Os resultados obtidos demonstram que os linguados alimentados exclusivamente com Artemia apresentam melhor performance do que aqueles alimentados com ração. Entretanto, o custo de produção quando a Artemia é substituída por ração aos 58 dias de vida é menor do que quando o desmame é realizado mais cedo ou quando os alevinos são alimentados apenas com Artemia.

Produção de juvenis do linguado Paralichthys orbignyanus: efeito da duração do período de co-alimentação durante o desmame

Weaning is a critical period for production of marine fish juveniles. The objective of this research was to evaluate the effect of co-feeding on survival, growth, and cost of production after the weaning of juveniles of Brazilian flounder Paralichthys orbignyanus. Juvenile flounder (32 days after hatching) were fed on HUFA enriched Artemia and subsequently three periods of co-feeding with dry diets (15, 20, and 25 days) were tested, a control group, where flounder were fed exclusively on Artemia was also followed until the end of the experiment. Juveniles fed on Artemia showed significantly higher (P 0.05) survival (82%), weight (480±157mg) and total length (35.5±5.0mm) than flounder weaned into dry diets, independent of the co-feeding period. Growth was similar (P>0.05) for juveniles fed on dry diets, but a higher survival rate was registered when the co-feeding period was longer. The results obtained demonstrate that flounder fed exclusively on Artemia have a better performance than those weaned into dry diets. However, unitary cost of production is reduced when juveniles are weaned 58 days after hatching.

O desmame, ou seja, a substituição do alimento vivo por alimento inerte é uma etapa crítica para a produção de alevinos de peixes marinhos. Este trabalho teve por objetivo avaliar o efeito do período de co-alimentação (alimento vivo e inerte) sobre a sobrevivência, o crescimento e os custos de produção de juvenis do linguado Paralichthys orbignyanus. Durante o período de co-alimentação, os juvenis (idade inicial 32 dias) receberam Artemia enriquecida juntamente com ração. Foram testados três períodos de co-alimentação: 15, 20 e 25 dias, mais um grupo controle alimentado com Artemia enriquecida. Ao final do experimento (76 dias), os juvenis alimentados exclusivamente com Artemia enriquecida apresentaram sobrevivência (82%), peso (480±157mg) e comprimento (35,5±5,0mm) significativamente maiores (P 0,05) que os juvenis alimentados com ração. Não houve diferença significativa (P>0,05) no crescimento entre os juvenis alimentados com ração nos diferentes períodos, entretanto, um período maior de co-alimentação favoreceu a sobrevivência. Os resultados obtidos demonstram que os linguados alimentados exclusivamente com Artemia apresentam melhor performance do que aqueles alimentados com ração. Entretanto, o custo de produção quando a Artemia é substituída por ração aos 58 dias de vida é menor do que quando o desmame é realizado mais cedo ou quando os alevinos são alimentados apenas com Artemia.