The in vitro antibacterial activity of thirty two plant-derived compounds (26 crude herbal extraction and 6 pure citrus-based bioflavonoids) were tested on five different species of aquatic bacterial pathogens (Aeromonas hydrophila, A. salmonicida, A. sobria, Edwardsiella ictaluri, and E. tarda) over a period of 72 hours at 22 o C. From the agar diffusion test, six pure citrus-based bioflavonoids (apigenin, catechin, hesperidin, morin, naringin and quercetin) appeared to impact on growth when used at concentrations ranging from 10 ppm -1000 ppm. To confirm their effect on the growth dynamics of each bacteria, a 1000 ppm dose of the appropriate bioflavonoid was added to a bacterial culture and daily changes in culture growth were measured. Quercetin was found to be bacteriocidal against all the bacterial strains. Morin was found to be bacteriocidal against only 4 out of 6 strains while hesperidin was found to affect the growth of all the tested bacterial strains, working both as a bacteriocidal and as a bacteriostatic agent. Apigenin performed poorly and had no effect on the growth of any bacterial strain while catechin and naringin were found to be generally bacteriostatic in action but had little impact on the growth of the Aeromonad strains. From the current in vitro work, it was concluded that certain plant extracts do have an impact on the growth dynamics of select bacteria and show potential as alternatives to the use of antimicrobials, but further research is required to assess their performance in vivo.

The Arabian Sea meager Argyrosomus heinii (Steindachner, 1907) is an endemic species of the family Sciaenidae, whose geographical distribution range is limited to the Sea of Oman and Arabian Sea. Despite the economic importance of Sciaenidae fishes in other parts of the world, the biology of A. heinii off the Sultanate of Oman is poorly understood and until now there are no publications on their parasites. The present study is the first report of the occurrence of helminthes parasitizing musculature of A. heinii, which were identified as plerocercoids of cestoda belonging to the genus Poecilancistrum Dollfus, 1929 (Trypanorhyncha Diesing, 1863. This study describes infection indices of these parasites, their biological and ecological variations, and distribution of the plerocercoid cysts in the musculature of A. heinii specimens. The study was carried out in the three regions of the Arabian Sea off Southern coasts of the Sultanate of Oman.

No abstract