DNA in a bottle-Rapid metabarcoding survey for early alerts of invasive species in ports.

Biota monitoring in ports is increasingly needed for biosecurity reasons and safeguarding marine biodiversity from biological invasion. Present and future international biosecurity directives can be accomplished only if the biota acquired by maritime traffic in ports is controlled. Methodologies for biota inventory are diverse and now rely principally on extensive and labor-intensive sampling along with taxonomic identification by experts. In this study, we employed an extremely simplified environmental DNA (eDNA) sampling methodology from only three 1-L bottles of water per port, followed by metabarcoding (high-throughput sequencing and DNA-based species identification) using 18S rDNA and Cytochrome oxidase I as genetic barcodes. Eight Bay of Biscay ports with available inventory of fouling invertebrates were employed as a case study. Despite minimal sampling efforts, three invasive invertebrates were detected: the barnacle Austrominius modestus, the tubeworm Ficopomatus enigmaticus and the polychaete Polydora triglanda. The same species have been previously found from visual and DNA barcoding (genetic identification of individuals) surveys in the same ports. The current costs of visual surveys, conventional DNA barcoding and this simplified metabarcoding protocol were compared. The results encourage the use of metabarcoding for early biosecurity alerts.

Dietary ß-glucan improved growth performance, Vibrio counts, haematological parameters and stress resistance of pompano fish, Trachinotus ovatus Linnaeus, 1758.

This study evaluated effects of graded levels of dietary ß-glucan (0, 0.5, 1, 2 and 4 g kg(-1)) on growth performance, haematological parameters, intestinal Vibrio counts, dose requirement and salinity stress resistance in pompano fish Trachinotus ovatus (6.45 g ± 0.06 (SEM)). After 8-weeks of diet feeding, growth was significantly higher in fish fed diets with 0.10% ß-glucan compared to fish fed control diet (no ß-glucan). Survival increased significantly in fish fed 0.05 and 0.10% ß-glucan compared to control diet. There were significant increases in red blood cells (in 0.20% ß-glucan diet), in total leukocytes (in 0.05-0.20% ß-glucan diet), in both lymphocyte and monocyte count in fish fed 0.10%-0.40% ß-glucan diet. However, dietary ß-glucan did not affect neutrophil, eosinophil and basophil counts. Intestinal Vibrio counts were reduced in fish fed any level of ß-glucan compared to control. In addition, dietary ß-glucan levels highly correlated with growth, survival, intestinal Vibrio counts and haematological index. Optimal ß-glucan levels for maximal growth of fish were predicted to be 0.122% at day 21 (R(2) = 98.53%), 0.120% at day 28 (R(2) = 78.55%), 0.115% at day 42 (R(2) = 62.21%) and 0.090% at day 56 (R(2) = 75.18%), showing a decreasing ß-glucan requirement with increasing fish size. Furthermore, optimal ß-glucan levels for maximal haematological parameters based on lymphocyte count, was estimated to be 0.120% (R(2) = 98.53%) at day 56. Also, fish fed 0.05%-0.20% ß-glucan showed better resistance against salinity stress. In conclusion, ß-glucan supplementation is effective for improving growth, intestinal Vibrio counts and boosted stress resistance of the pompano fish, T. ovatus.