Navegando por Assunto "Ritmo circadiano"

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Influence of photoperiod on growth, uniformity, and survival of larvae of the Amazonian ornamental Heros severus (Heckel, 1840)
(Universidade Federal do Pará, 2016-07) VERAS, Galileu Crovatto; PAIXÃO, Daércio José de Macedo Ribeiro; BRABO, Marcos Ferreira; SOARES, Lourdes Marília Oliveira; SALES, Abner Dias
The objective of this work was to evaluate the influence of photoperiod on growth, uniformity, and survival of larvae of the Amazonian ornamental fish severum (Heros severus). A completely randomized study was used with five treatments (0L:24D, 6L:18D, 12L:12D, 18L:6D, 24L:0D) and four replicates, with the aquaria as the experimental unit. Two hundred severum larvae (3.20±0.16 mg and 5.60±0.00 mm) were distributed into 20 aquariums of one litre at a density of 10 larvae per litre. For a period of 15 days, feed was supplied four times daily with Artemia nauplii in a proportion of 160 nauplii/larvae/feeding. At the end of the experimental period, growth, uniformity, and survival data were subjected to analyses of variance and significance. Manipulation of the photoperiod showed no change in variables because there was no difference in the growth, uniformity, or survival of severum larvae. Thus, for larvae of this species of up to 20 days of age, the manipulation of the photoperiod is not advantageous due to the possible increase in production costs. Therefore, it is recommended to use the photoperiod close to the natural environment.