Níveis de suplementação de vitamina C na ração sobre a ocorrência de ectoparasitas, sobrevivência e biomassa em alevinos de tilápia do Nilo (Oreochromis niloticus L.)

Different vitamin levels C in the ration on the ectoparasitas occurrence, survival and total biomass in fingerlings of Nile tilápia Oreochromis. Niloticus L. (Perciformes, Cichlidae) were evaluated after sexual reversion, for 57 days. Fingerlings began the experiment with approximately 0,30g and 24mm and were submitted to four diets with 300-mg (T1), 600-mg (T2), and 900mg-(T3) e 1200-mg (T4) of vitamin C/kg of ration. In the beginning the ectoparasites occurrence was of 100%, 38,0% of Trichodina and 62,0% of mixed infection (Trichodina and monogenetics). At the end, there was not significant difference for total occurrence, for Trichodina and mixed infection. Considering the occurrence of the monogeneas there were significant differences between T1 and the others. In relation to the schedules of collection, a significant difference was found in the occurrence among the schedule of the 15:00 compared to the other schedules. No significant differences were observed in relation to weigh, total and standard medium length, biomass and survival, though. Results indicated that it is unnecessary to use vitamin C in superior levels to the 300-ration mg/Kg, enough to reach the tilápias fingerlings' nutritional needs, bred in controlled system.Avaliou-se diferentes níveis de vitamina C na ração sobre a ocorrência de ectoparasitas, sobrevivência e biomassa total em alevinos de tilápia do Nilo, Oreochromis. Niloticus L. (Perciformes, Cichlidae) pós-revertidos, durante 57 dias. Alevinos com aproximadamente 0,30g e 24mm foram submetidos a 4 dietas contendo: 300 mg (T1), 600 mg (T2), 900 mg (T3) e 1200 mg (T4) de vitamina C por kg de ração. Inicialmente, a ocorrência de ectoparasitas foi de 100%, 38% de Trichodina e 62% de infecção mista (Trichodina + monogenéticos). Ao final não houve diferença significativa para ocorrência acumulada total, para Trichodina e infecção mista. Considerando a ocorrência dos monogenéticos, houve diferenças significativas entre o T1 e os demais. Em relação aos horários de coleta, foi encontrada uma diferença significativa na ocorrência entre o horário das 15h em relação aos demais horários. Em relação ao peso, comprimento médio total e padrão, biomassa e sobrevivência, não houve diferenças significativas. Conclui-se, então, que é desnecessário o uso de vitamina C em níveis superiores a 300mg/Kg de ração, sendo suficiente para atingir as exigências nutricionais a alevinos de tilápias criados em regime de manejo controlado

Allometry as evidence of sexual selection in monochromatic birds: the case of the Coscoroba Swan (Anseriformes: Anatidae)

The Coscoroba Swan, Coscoroba coscoroba (Molina, 1782), is a poorly known aberrant Anserine endemic to South America. We captured adult birds (189 male, 157 female) from the largest population in Brazil at the Taim Ecological Reserve, State of Rio Grande do Sul, Brazil. Different patterns between sexes can reflect differences in selection, and positive allometry may indicate that a character is sexually selected. We used body weight and 10 morphological measurements to examine allometric differences between males and females of C. coscoroba. Males were consistently larger than females. Analysis of scaling relationships against body mass showed that nostril, tail, wing and bill height were positively allometric (i.e., heavier birds had relatively larger character lengths), but there were no sexual differences in allometric slopes. However, for a given mass, mature females had longer tails, longer wings (up to metacarpophalangeal articulation) and shorter heads than males. In the light of current debate in the literature, we discuss whether such positively allometric traits and sexual differences in scaling may be indicative of sexual selection. Although Coscoroba Swan is a monogamous species, increasing the size of some attributes may confer some advantage for mate selection or male-male competition and, contrary to other studies, we suggest that positively allometric slopes alone should not be considered as evidence for sexual selection of the considered traits.Peer reviewe

Microsatellite analysis of the parental contribution of Piaractus mesopotamicus to the production of offspring in the semi-natural system of reproduction

The objective of this study was to evaluate the genetic diversity and the parental contribution of Piaractus mesopotamicus in the production of offspring in the semi-natural system of reproduction. Twenty parental fishes (eleven males and nine females) and the total of 100 larvae were evaluated by microsatellite marker. The parents and offspring had thirty-one alleles and heterozygosity of 0.550 and 0.563, respectively. The females were fertilised by two up to six males while the males fertilised three up to five females. The contribution of the females and males to the offspring were 66.6 and 58%, respectively. Such results indicated no loss in the genetic variability in the offspring, and the parents had multiple paternity and reasonable contribution to the offspring production.<br>O objetivo deste trabalho foi avaliar a diversidade genética e a contribuição parental de Piaractus mesopotamicus na produção de descendência no sistema seminatural de reprodução. Vinte peixes parentais (onze machos e nove fêmeas) e o total de 100 larvas foram avaliados por meio do marcador microssátelite. Os parentais e a progênie tiveram trinta e um alelos e heterozigosidade de 0,550 e 0,563, respectivamente. As fêmeas foram fertilizadas por dois até seis machos enquanto machos fertilizaram três até cinco fêmeas. A contribuição de fêmeas e machos para a descendência seja 66,6 e 58,0%, respectivamente. Tais resultados não indicam diminuição da variabilidade genética na progênie e os parentais apresentaram paternidade múltipla e razoável contribuição à produção de descendência