We studied the effect of two probiotic Bacillus subtilis strains on the growth performance, digestive enzyme activity, immune gene expression and disease resistance of juvenile white shrimp (Litopenaeus vannamei). A mixture of two probiotic strains, L10 and G1 in equal proportions, was administered at two different doses 10(5) (BM5) and 10(8) (BM8) CFU g(-1) feed to shrimp for eight weeks. In comparison to untreated control group, final weight, weight gain and digestive enzyme activity were significantly greater in shrimp fed BM5 and BM8 diets. Significant differences for specific growth rate (SGR) and survival were recorded in shrimp fed BM8 diet as compared with the control; however, no significant differences were recorded for food conversion ratio (FCR) among all the experimental groups. Eight weeks after the start of the feeding period, shrimp were challenged with Vibrio harveyi. Statistical analysis revealed significant differences in shrimp survival between probiotic and control groups. Cumulative mortality of the control group was 63.3%, whereas cumulative mortality of the shrimp that had been given probiotics was 20.0% with BM8 and 33.3% with BM5. Subsequently, real-time PCR was employed to determine the mRNA levels of prophenoloxidase (proPO), peroxinectin (PE), lipopolysaccharide- and β-1,3-glucan-binding protein (LGBP) and serine protein (SP). The expression of all immune-related genes studied was significantly up-regulated (P < 0.05) in the shrimp fed BM5 and BM8 diets compared to the control group. These findings demonstrate that administration of B. subtilis strains, L10 and G1, can improve growth performance and disease resistance through an enhanced immune response in shrimp.

Seagrasses are the only flowering plants (monocotyledonous Angiosperms) that have adapted themselves to living in marine and estuarine habitats, and are submerged most of the time. They are rooted in sediments on the sea bottom, with shoots appearing above the substrate. Seagrasses occurred at 78 sites scattered in the west and east coasts of Peninsular Malaysia and in Sabah and Sarawak in East Malaysia. They are usually found along the coasts growing in association with shallow inter-tidal, mangroves, coral reefs, semi-enclosed lagoons and shoals. In these habitats, seagrass beds or meadows have distinct species assemblage completely adapted to the submerged life. There are fourteen major species of seagrasses recorded in Malaysia: Enhalus acoroides, Halophila beccarii, H. decipiens, H. ovalis, H. minor, H. spinulosa, Halodule pinifolia, H. uninervis, Cymodocea rotundata, C. serrulata, Thalassia hemprichii, Syringodium isoetifolium, Ruppia maritima and Thalassodendron ciliatum. Although seagrasses make up only a small portion of the marine ecosystem, the physical settings and their interactive community within and from outside account for their high diversity and ensure survival of an assortment of vertebrates (fish), invertebrates (shrimps, starfish, sea cucumbers, bivalves, gastropods), and seaweeds. Seagrass form the food and habitats for the vulnerable dugongs or sea cows (Dugong dugon), seahorses (Hippocampus spp.) and endangered green turtles (Chelonia mydas), and for other fish, and also a feeding ground for seasonal migratory birds, Egretta garzetta. Seagrasses provide conditions for the growth and abundance of invertebrates and fish that many local coastal communities collect and catch for their livelihood. Seagrass ecosystems are sources of food and yet they are continually threatened by human activities, causing their degradation and possible habitat loss. The purpose of this review is to give information on the significant linkages of seagrasses with the coastal inhabitants and to suggest recommendations for the protection and conservation of this important ecosystem and the associated resources.