Larvas de linhagens de tilápia do Nilo submetidas à frequências alimentares sob baixa temperatura / Larvae of Nile tilapia lines subject to feeding frequencies under low temperature

O manejo alimentar adequado associado a animais com maior rendimento e resistência a ambientes específicos, como águas com temperaturas abaixo da adequada à espécie, são determinantes para uma maior produtividade. Portanto, objetivou-se com o presente estudo comparar o desempenho da larvicultura de duas linhagens de tilápia do Nilo (Oreochromis niloticus) submetidas a diferentes frequências alimentares com temperatura abaixo da faixa ótima para crescimento. Larvas das linhagens tailandesa (720 indivíduos com peso de 24,3 mg e comprimento total de 12,4 mm) e GIFT (720 exemplares com 22,5 mg e 12,0 mm), foram distribuídas em 24 aquários de 4L, na densidade de 15 larvas. L−1, 60 larvas aquário−1, sob aeração constante, fotoperíodo natural e temperatura a 23 °C, em sistema com recirculação com termostato. Elas foram submetidas a três frequências alimentares: 2, 5 e 8 vezes.dia−1, em delineamento inteiramente casualizado, em esquema fatorial 2 linhagens x 3 frequências, com quatro repetições cada. Exceto a temperatura, os demais parâmetros de qualidade da água, amônia, nitrito, nitrato, turbidez, condutividade e pH, mantiveram-se adequados para a espécie. A linhagem tailandesa apresentou maiores comprimentos total e padrão, peso, fator de condição de Fulton, sobrevivência e biomassa, do que a GIFT. A frequência alimentar 5 vezes.dia−1 gerou maiores valores para as larvas em peso, comprimento total e padrão, do que as submetidas à frequência de 2 vezes.dia−1, e valores iguais, quando comparadas as submetidas à frequência de 8 vezes.dia−1. Na temperatura de 23°C deve-se empregar as tilápias da linhagem tailandesa alimentadas 5 vezes.dia−1.(AU)

The adequate food management associated with animals with higher yields and resistance to specific environments, such as waters with temperatures below the appropriate temperature, are determinant for a higher productivity. Therefore, the aim of this study was to compare larviculture performance of two strains of Nile tilapia (Oreochromis niloticus) submitted to different feeding frequencies with temperature below the optimum range for growth. Larvae of Thai (720 individuals with weight of 24.3 mg and total length of 12.4 mm) and GIFT strains (720 individuals with weight of 22.5 mg and total length of 12.0 mm) were distributed into 24 aquariuns-4L, the density of 15 larvae. L−1, 60 larvae aquarium−1, under constant aeration, natural photoperiod and temperature of 23 °C, with recirculation and thermostat. The fish were subjected to three feeding frequencies: 2, 5 and 8 times.day−1 in a randomized design in a 2 strains x 3 frequencies factorial scheme, with four replicates each. Except the temperature the other parameters of water quality, ammonia, nitrite, nitrate, turbidity, conductivity and pH, remained adequate for the species. The Thai lineage showed higher total and standard length, weight, Fulton condition factor, survival and biomass, than GIFT. The feeding frequency 5 times.day-1 led to higher values larvae in weight, standard and total length in relation the frequency of 2 times.day-1 but, when compared values of frequency 8 times.day-1 was not difference. In the temperature 23oC, Thai strain fed 5 times.day-1 should be used.(AU)

Larvas de linhagens de tilápia do Nilo submetidas à frequências alimentares sob baixa temperatura / Larvae of Nile tilapia lines subject to feeding frequencies under low temperature

O manejo alimentar adequado associado a animais com maior rendimento e resistência a ambientes específicos, como águas com temperaturas abaixo da adequada à espécie, são determinantes para uma maior produtividade. Portanto, objetivou-se com o presente estudo comparar o desempenho da larvicultura de duas linhagens de tilápia do Nilo (Oreochromis niloticus) submetidas a diferentes frequências alimentares com temperatura abaixo da faixa ótima para crescimento. Larvas das linhagens tailandesa (720 indivíduos com peso de 24,3 mg e comprimento total de 12,4 mm) e GIFT (720 exemplares com 22,5 mg e 12,0 mm), foram distribuídas em 24 aquários de 4L, na densidade de 15 larvas. L−1, 60 larvas aquário−1, sob aeração constante, fotoperíodo natural e temperatura a 23 °C, em sistema com recirculação com termostato. Elas foram submetidas a três frequências alimentares: 2, 5 e 8 vezes.dia−1, em delineamento inteiramente casualizado, em esquema fatorial 2 linhagens x 3 frequências, com quatro repetições cada. Exceto a temperatura, os demais parâmetros de qualidade da água, amônia, nitrito, nitrato, turbidez, condutividade e pH, mantiveram-se adequados para a espécie. A linhagem tailandesa apresentou maiores comprimentos total e padrão, peso, fator de condição de Fulton, sobrevivência e biomassa, do que a GIFT. A frequência alimentar 5 vezes.dia−1 gerou maiores valores para as larvas em peso, comprimento total e padrão, do que as submetidas à frequência de 2 vezes.dia−1, e valores iguais, quando comparadas as submetidas à frequência de 8 vezes.dia−1. Na temperatura de 23°C deve-se empregar as tilápias da linhagem tailandesa alimentadas 5 vezes.dia−1.

The adequate food management associated with animals with higher yields and resistance to specific environments, such as waters with temperatures below the appropriate temperature, are determinant for a higher productivity. Therefore, the aim of this study was to compare larviculture performance of two strains of Nile tilapia (Oreochromis niloticus) submitted to different feeding frequencies with temperature below the optimum range for growth. Larvae of Thai (720 individuals with weight of 24.3 mg and total length of 12.4 mm) and GIFT strains (720 individuals with weight of 22.5 mg and total length of 12.0 mm) were distributed into 24 aquariuns-4L, the density of 15 larvae. L−1, 60 larvae aquarium−1, under constant aeration, natural photoperiod and temperature of 23 °C, with recirculation and thermostat. The fish were subjected to three feeding frequencies: 2, 5 and 8 times.day−1 in a randomized design in a 2 strains x 3 frequencies factorial scheme, with four replicates each. Except the temperature the other parameters of water quality, ammonia, nitrite, nitrate, turbidity, conductivity and pH, remained adequate for the species. The Thai lineage showed higher total and standard length, weight, Fulton condition factor, survival and biomass, than GIFT. The feeding frequency 5 times.day-1 led to higher values larvae in weight, standard and total length in relation the frequency of 2 times.day-1 but, when compared values of frequency 8 times.day-1 was not difference. In the temperature 23oC, Thai strain fed 5 times.day-1 should be used.

How specialists can be generalists: resolving the "parasite paradox" and implications for emerging infectious disease

The parasite paradox arises from the dual observations that parasites (broadly construed, including phytophagous insects) are resource specialists with restricted host ranges, and yet shifts onto relatively unrelated hosts are common in the phylogenetic diversification of parasite lineages and directly observable in ecological time. We synthesize the emerging solution to this paradox: phenotypic flexibility and phylogenetic conservatism in traits related to resource use, grouped under the term ecological fitting, provide substantial opportunities for rapid host switching in changing environments, in the absence of the evolution of novel host-utilization capabilities. We discuss mechanisms behind ecological fitting, its implications for defining specialists and generalists, and briefly review empirical examples of host shifts in the context of ecological fitting. We conclude that host shifts via ecological fitting provide the fuel for the expansion phase of the recently proposed oscillation hypothesis of host range and speciation, and, more generally, the generation of novel combinations of interacting species within the geographic mosaic theory of coevolution. Finally, we conclude that taxon pulses, driven by climate change and large-scale ecological perturbation are drivers of biotic mixing and resultant ecological fitting, which leads to increased rates of rapid host switching, including the agents of Emerging Infectious Disease.

How specialists can be generalists: resolving the "parasite paradox" and implications for emerging infectious disease

The parasite paradox arises from the dual observations that parasites (broadly construed, including phytophagous insects) are resource specialists with restricted host ranges, and yet shifts onto relatively unrelated hosts are common in the phylogenetic diversification of parasite lineages and directly observable in ecological time. We synthesize the emerging solution to this paradox: phenotypic flexibility and phylogenetic conservatism in traits related to resource use, grouped under the term ecological fitting, provide substantial opportunities for rapid host switching in changing environments, in the absence of the evolution of novel host-utilization capabilities. We discuss mechanisms behind ecological fitting, its implications for defining specialists and generalists, and briefly review empirical examples of host shifts in the context of ecological fitting. We conclude that host shifts via ecological fitting provide the fuel for the expansion phase of the recently proposed oscillation hypothesis of host range and speciation, and, more generally, the generation of novel combinations of interacting species within the geographic mosaic theory of coevolution. Finally, we conclude that taxon pulses, driven by climate change and large-scale ecological perturbation are drivers of biotic mixing and resultant ecological fitting, which leads to increased rates of rapid host switching, including the agents of Emerging Infectious Disease.

How specialists can be generalists: resolving the "parasite paradox" and implications for emerging infectious disease

The parasite paradox arises from the dual observations that parasites (broadly construed, including phytophagous insects) are resource specialists with restricted host ranges, and yet shifts onto relatively unrelated hosts are common in the phylogenetic diversification of parasite lineages and directly observable in ecological time. We synthesize the emerging solution to this paradox: phenotypic flexibility and phylogenetic conservatism in traits related to resource use, grouped under the term ecological fitting, provide substantial opportunities for rapid host switching in changing environments, in the absence of the evolution of novel host-utilization capabilities. We discuss mechanisms behind ecological fitting, its implications for defining specialists and generalists, and briefly review empirical examples of host shifts in the context of ecological fitting. We conclude that host shifts via ecological fitting provide the fuel for the expansion phase of the recently proposed oscillation hypothesis of host range and speciation, and, more generally, the generation of novel combinations of interacting species within the geographic mosaic theory of coevolution. Finally, we conclude that taxon pulses, driven by climate change and large-scale ecological perturbation are drivers of biotic mixing and resultant ecological fitting, which leads to increased rates of rapid host switching, including the agents of Emerging Infectious Disease.