Biology of selected Clarias catfish species used in aquaculture

Catfish are important organisms used extensively in aquaculture. For this review, we are focusing on specific species of catfish in the genus Clarias, primarily Clarias batrachus, C. gariepinus and C. macrocephalus, because of their widespread use in aquaculture and the considerable amount of information that has been amassed on different aspects of their biology. This review summarizes information available on topics ranging from the taxonomy and geographic distribution of these catfish to work done on them at the genetic, molecular biological and genomic levels. This information may be useful in future efforts to grow and expand their use in aquaculture

Genetic variation for total fitness in Drosophila melanogaster.

We measured the heterozygous effects on net fitness of a sample of 12 wild-type third chromosomes in D. melanogaster. Effects on fitness were assessed by competing the wild-type chromosomes against balancer chromosomes, to prevent the production of recombinants. The measurements were carried out in the population cage environment in which the life history had been evolving, in an undisturbed population with overlapping generations, and replicated measurements were made on each chromosome to control for confounding effects such as mutation accumulation. We found significant variation among the wild type chromosomes in their additive genetic effect on net fitness. The system provides an opportunity to obtain an accurate estimate of the distribution of heterozygous effects on net fitness, the contribution of different fitness components including male mating success, and the role of intra-chromosomal epistasis in fitness variation

High rates of substitution of the native catfish <i>Clarias batrachus</i> by <i>Clarias gariepinus</i> in India

<div><p></p><p>The clariid catfish, <i>Clarias batrachus</i> commonly known as Magur, has declined drastically from natural habitats in India during the last decade. This fish is highly preferred fish by Indian consumers and has high market demand. As a result traders often substitute <i>C. batrachus</i> with a morphologically similar but supposedly banned exotic catfish, <i>C. gariepinus</i>, in India. This study uses rigorous morphological comparisons confirmed by DNA barcode analysis to examine the level of substitution of <i>C. batracus</i> by <i>C. gariepinus</i> in India. Our results indicate that up to 99% (in many cases) of the market samples sold as Magur or <i>C. batrachus</i> were in fact <i>C. gariepinus.</i></p></div