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

Measures of fitness in Drosophila : (population genetics, Drosophila, fitness, natural selection)

Ten proposed experimental measures of fitness in Drosophila have been estimated in 8 to 38 strains of D. melanogaster with 1 to 6 replications in order to assess the degree of association among the measures. One measure is a composite of the classical fitness components viability, fecundity, and mating speed. Two tests--the Knight-Robertson method and the compound-autosome method--are based on intraspecific competitive ability; three tests are based on interspecific competitive ability with D. simulans, D. mauritiana, or D. ananassae; two measures are based on the productivity and biomass of equilibrium populations; and two measures are based on the dynamics of change in frequency of a balancer chromosome in experimental populations. The tests fall into four groups with significant correlations among tests within a group but weaker or nonsignificant correlations between groups. The first group consists of the composite index and the two intraspecific tests. We infer that these methods measure attributes strongly allied with classical darwinian fitness. The second group consists of the interspecific tests, which apparently emphasize somewhat different characteristics than those associated with darwinian fitness. The third group consists of the measures based on productivity or biomass of equilibrium populations, and these measures may be allied with Wright's mean selective value, although this interpretation is speculative. The fourth and final group consists of the measures resulting from changes in chromosome frequency in experimental populations. Each group of tests measures distinct characteristics that are probably important in particular contexts, but only the intraspecific tests correspond to darwinian fitness.Daniel L . Hartl and David S. Haymer, Department of Genetics, Washington University School of Medicine, St. Louis, Missouri

Monitoring Resistance to Spinosad in the Melon Fly (Bactrocera cucurbitae) in Hawaii and Taiwan

Spinosad is a natural insecticide with desirable qualities, and it is widely used as an alternative to organophosphates for control of pests such as the melon fly, Bactrocera cucurbitae (Coquillett). To monitor the potential for development of resistance, information about the current levels of tolerance to spinosad in melon fly populations were established in this study. Spinosad tolerance bioassays were conducted using both topical applications and feeding methods on flies from field populations with extensive exposure to spinosad as well as from collections with little or no prior exposure. Increased levels of resistance were observed in flies from the field populations. Also, higher dosages were generally required to achieve specific levels of mortality using topical applications compared to the feeding method, but these levels were all lower than those used for many organophosphate-based food lures. Our information is important for maintaining effective programs for melon fly management using spinosad

Historical perspective on the synonymization of the four major pest species belonging to the Bactrocera dorsalis species complex (Diptera, tephritidae)

An FAO/IAEA-sponsored coordinated research project on integrative taxonomy, involving close to 50 researchers from at least 20 countries, culminated in a significant breakthrough in the recognition that four major pest species, Bactrocera dorsalis, B. philippinensis, B. papayae and B. invadens, belong to the same biological species, B. dorsalis. The successful conclusion of this initiative is expected to significantly facilitate global agricultural trade, primarily through the lifting of quarantine restrictions that have long affected many countries, especially those in regions such as Asia and Africa that have large potential for fresh fruit and vegetable commodity exports. This work stems from two taxonomic studies: a revision in 1994 that significantly increased the number of described species in the Bactrocera dorsalis species complex; and the description in 2005 of B. invadens, then newly incursive in Africa. While taxonomically valid species, many biologists considered that these were different names for one biological species. Many disagreements confounded attempts to develop a solution for resolving this taxonomic issue, before the FAO/IAEA project commenced. Crucial to understanding the success of that initiative is an accounting of the historical events and perspectives leading up to the international, multidisciplinary collaborative efforts that successfully achieved the final synonymization. This review highlights the 21 year journey taken to achieve this outcome

Discovery of genes related to insecticide resistance in Bactrocera dorsalis by functional genomic analysis of a de novo assembled transcriptome.

Insecticide resistance has recently become a critical concern for control of many insect pest species. Genome sequencing and global quantization of gene expression through analysis of the transcriptome can provide useful information relevant to this challenging problem. The oriental fruit fly, Bactrocera dorsalis, is one of the world's most destructive agricultural pests, and recently it has been used as a target for studies of genetic mechanisms related to insecticide resistance. However, prior to this study, the molecular data available for this species was largely limited to genes identified through homology. To provide a broader pool of gene sequences of potential interest with regard to insecticide resistance, this study uses whole transcriptome analysis developed through de novo assembly of short reads generated by next-generation sequencing (NGS). The transcriptome of B. dorsalis was initially constructed using Illumina's Solexa sequencing technology. Qualified reads were assembled into contigs and potential splicing variants (isotigs). A total of 29,067 isotigs have putative homologues in the non-redundant (nr) protein database from NCBI, and 11,073 of these correspond to distinct D. melanogaster proteins in the RefSeq database. Approximately 5,546 isotigs contain coding sequences that are at least 80% complete and appear to represent B. dorsalis genes. We observed a strong correlation between the completeness of the assembled sequences and the expression intensity of the transcripts. The assembled sequences were also used to identify large numbers of genes potentially belonging to families related to insecticide resistance. A total of 90 P450-, 42 GST-and 37 COE-related genes, representing three major enzyme families involved in insecticide metabolism and resistance, were identified. In addition, 36 isotigs were discovered to contain target site sequences related to four classes of resistance genes. Identified sequence motifs were also analyzed to characterize putative polypeptide translational products and associate them with specific genes and protein functions

DNA barcoding using skin exuviates can improve identification and biodiversity studies of snakes

<div><p></p><p>Snakes represent a taxonomically underdeveloped group of animals in India with a lack of experts and incomplete taxonomic descriptions being the main deterrents to advances in this area. Molecular taxonomic approaches using DNA barcoding could aid in snake identification as well as studies of biodiversity. Here a non-invasive sampling method using DNA barcoding is tested using skin exuviates. Taxonomically authenticated samples were collected and tested for validation and comparisons to unknown snake exuviate samples. This approach was also used to construct the first comprehensive study targeting the snake species from Maharashtra state in India. A total of 92 skin exuviate samples were collected and tested for this study. Of these, 81 samples were successfully DNA barcoded and compared with unknown samples for assignment of taxonomic identity. Good quality DNA was obtained irrespective of age and quality of the exuviate material, and all unknown samples were successfully identified. A total of 23 species of snakes were identified, six of which were in the list of Endangered species (Red Data Book). Intra- and inter-specific distance values were also calculated, and these were sufficient to allow discrimination among species and between species without ambiguity in most cases. Two samples were suspected to represent cryptic species based on deep K2P divergence values (>3%), and one sample could be identified to the genus level only. Eleven samples failed to amplify COI sequences, suggesting the need for alternative PCR primer pairs. This study clearly documents how snake skin exuviates can be used for DNA barcoding, estimates of diversity and population genetic structuring in a noninvasive manner.</p></div

Identification of <i>B. dorsalis</i> transcripts related to insecticide target site: gamma-aminobutyric acid (GABA)-regulated chloride channel.

<p>The identities from the tblastx alignments were >90% unless noted in parentheses. The gene references belong to <i>Drosophila melanogaster</i>.</p

Results obtained using different values for <i>k</i> when invoking Velvet.

a<p>The N50 length is defined as the length N for which half of all bases in the sequences are in a sequence of length L</p

Results of PCR validation for selected sequences.

<p>Results of PCR validation for selected sequences.</p