Spatial and temporal distribution of macrobenthos in different mangrove ecosystems of Tamil Nadu Coast, India.

This paper deals with the spatial distribution and diversity of macrobenthos and their relationships between physico-chemical parameters of the water and sediment in different mangrove habitats of Tamil Nadu, India during different seasons (2008). Among the different ecosystems of mangrove benthic faunal assemblages, macrofauna species number, density, richness, and Shannon-Wiener index were the highest and the Simpson dominance index was medial at riverine mangrove community. However, the Pielou Evenness index of riverine mangrove community was slightly lower than other communities. The similarities among the macrobenthic communities at different sampling sites were determined using Bray-Curtis similarity coefficient and ordinations of non-metric multidimensional scaling (MDS). Thirty-one species were recorded in developing (16 polychaetes, six bivalves, seven gastropods, and two crustaceans), 35 species were recorded in riverine (20 polychaetes, six bivalves, five gastropods, and four crustaceans) and 31 species were recorded in island mangrove ecosystem (19 polychaetes, four bivalves, five gastropods, and three crustaceans). Among the three ecosystems, a total of 46 benthic macrofauna consisting of 27 species of polychaetes, eight species of gastropods, seven species of bivalves, and four species of crustaceans were recorded. However, there were obvious differences among the community structures in the three mangrove habitats. This result implied that the different mangrove ecosystem had different effects on the macrofauna communities and shed light on the macrofauna adaptation capability to specific habitats.

Antibacterial activity of Acalypha indica L.

Hexane, chloroform, ethyl acetate and methanol extracts from the leaves of Acalypha indica were tested against Gram-positive (Staphylococcus aureus, Staphylococcus epidermidis, Bacillus cereus, Streptococcus faecalis) and Gram-negative (Klebsiella pneumoniae, Escherichia coli, Proteus vulgaris, Pseudomonas aeruginosa) bacteria. All the extracts exhibited antibacterial activity against Gram-positive organisms with minimum inhibitory concentrations (MIC) between 0.156 to 2.5 mg/ml. Among the Gram-negative bacteria, only the Pseudomonas aeruginosa was susceptible to the extracts.

Studies on effect of Acalypha indica L. (Euphorbiaceae) leaf extracts on the malarial vector, Anopheles stephensi Liston (Diptera:Culicidae).

The leaf extract of Acalypha indica with different solvents viz, benzene, chloroform, ethyl acetate and methanol were tested for larvicidal, ovicidal activity and oviposition attractancy against Anopheles stephensi. The larval mortality was observed after 24 h exposure. The LC(50) values are 19.25, 27.76, 23.26 and 15.03 ppm, respectively. Mean percent hatchability of the ovicidal activity was observed 120 h after treatment. The percent hatchability was inversely proportional to the concentration of extract and directly proportional to the eggs. The highest effective attractancy of 90.09%, 94.20%, 85.43% and 95.75% were observed at 100 ppm concentration viz, benzene, chloroform, ethyl acetate and methanol, respectively. The lowest effective attractancy of 47.17%, 61.94%, 49.28% and 68.12% were observed at 25 ppm concentration viz, benzene, chloroform, ethyl acetate and methanol, respectively. The results that the leaf extract of A. indica is promising as larvicidal and ovicidal activity and oviposition attractancy against malaria vector A. stephensi.