Interaction of free-living marine nematodes in the artificial mangrove environment (Southeast Coast of India).

Free-living marine nematode diversity was analyzed between Avicennia marina and Rhizophora mucronata mangrove covers of the Vellar Estuary (southeast coast of India). A total of 4,976 specimens of free-living marine nematodes were collected in 56 species. Comparatively, a higher species richness was obtained for A. marina (52 species) than for R. mucronata (44 species), whereas 40 species commonly existed in both mangrove covers. A higher density of nematodes was found in sediments of sandy nature, whereas there was lower total organic carbon compared to silt/clay composition; epigrowth feeders were dominant over the other feeding groups based on organic enrichment in surface sediments. Principal component analysis clearly explained the relationship between the environmental parameters of various months. Higher R values of analysis of similarities revealed significant differences in nematode assemblages between months, and it was quite evident by non-metric multidimensional scaling. Diversity indices showed higher values in the dry months. RELATE analysis explained serial changes in nematode species composition between months, and a relationship between biotic and abiotic variables was clarified using the BIO-ENV procedure. Viscosia spp., Metachromadora spp., Theristus spp., and Sphaerolaimus spp. were candidate species of A. marina leaf interaction by observation.

Diversity of macrofauna from continental shelf off Singarayakonda (southeast coast of India).

The present study was undertaken to study the benthic productivity of shelf region off Krishna River mouth. Standing stock of macrobenthos and its distribution were studied. Sampling was done onboard FORV Sagar Sampada from depths as 30, 50, 75, 100, 150 and 200 m using Smith-McIntyre grab having a bite area of 0.2 m2. After identification, data were treated using statistical package PRIMER v6. The nature of the sediment was medium sand up to 150 m depth and fine silt at 200 m. The benthic biomass (0.2977-3.1091 mg 0.2 m(-2)), abundance (58-289 nos. 0.2 m(-2) and number of species (12-48) decreased with increase in depth. The total number of species recorded was 69. Species estimators showed the possibility of collecting 129 species (Chao1) with intense sampling. Polychaetes formed the largest group with 40 species followed by molluscs (15 species) and crustaceans (14 species). The Spearman rank correlation (Rho) value (0.513) which was significant at 1.1% showed gradual change in species composition with increase in depth. The Pi value (3.78) comparing the similarity of benthos at 200 m depth with those of other depths (30, 150, 100, 75 and 50 m) showed significant differences (0.6%). Matching of biotic variables with that of environment showed the influence of dissolved oxygen on the distribution of macrobenthos (Rho 0.757). Intense sampling should be done to record all the species as shown by species estimators besides studying shelf productivity off other rivers and relating it with nutrient discharge and other environmental factors including sediment nature.

Feeding and reproductive biology of Saurida undosquamis (Richardson, 1848) from Parangipettai coast, Southeast coast of India.

The feeding biology, spawning season, size at first maturity, sex ratio and fecundity of the commercially important lizardfish (Saurida undosquamis) were studied in Parangipettai waters of the southeast coast of India. Fishes formed the predominant food item. Diversity of the prey items showed maximum value (H'log 2-3.61 +/- 0.11) during the postmonsoon season and minimum during the monsoon season (2.89 +/- 0.17). The richness (1-lambda') also showed a similar trend and varied from 0.81 +/- 0.13 (monsoon) to 0.91 +/- 0.01 (postmonsoon). The size at first maturity (50% incidence of mature fish) was 195 mm. But when the size at first maturity was calculated by adjusting the proportion of maturity percentages, the maturity size was found to be 140 mm. This method is advantageous from the point of view of fisheries management as this species can be exploited above 140 mm rather than above 195 mm. The gastrosomatic index was found maximum during postmonsoon and minimum during the monsoon season showing the inverse relationship between feeding and spawning. This species was found to spawn from August to January with a peak in November. The fecundity ranged from 19, 856 in a fish measuring from 20.1 cm in length (97 g) to 79,282 in a fish of 29 cm (290 g). The overall sex ratio (1:1.19) was found to deviate significantly from the expected 1:1 ratio. (chi2 = 19.1, p < 0.005). Month- wise, it conformed to the expected 1:1 ratio during most of the months except January, June, September, November and December. Higher gonado-somatic index values observed during October-December suggested spawning activity during this period. This species is found to a total spawner in the Parangipettai waters.

Length-weight relationship and condition factor of Liza subviridis (Valenciennes, 1836) of Parangipettai waters, southeast coast of India.

Determination of Length-weight Relationship (LWR) of any commercially important fish is crucial to validate the wild stock level, to predict their wellbeing in the natural habitat and for various sustainable fishery management practices. Liza subviridis (Valenciennes) is noted to be highly abundant along the coast of Parangipettai, South east coast of India. Hence, the present study was aimed to establish Length-weight relationship and condition factor of Greenback mullet, Liza subviridis (Valenciennes) occurring in Vellar estuary, Parangipettai (lat. 11 degrees 30' N, long. 79 degrees 46' E) using least square method. To determine the actual relationship between length and weight of L. subviridis exponent coefficient or equilibrium constant (b) and relative condition factor (Kn) analysis were adopted. The females were found to be heavier than males at similar length. The equilibrium constant 'b' was found to be 2.7106 in males and 2.8927 in females. The corresponding parabolic representation for male was W = 0.0462L(2.7106) and for female W = 0.0382L(2.8927). The equilibrium constant did not obey the cube law as it deviated significantly from 3 in the case of males. The relative condition factor around 1 and little over it revealed the well-being of L. subviridis in Parangipettai waters.

Length-weight relationship of Mugil cephalus (Linnaeus 1758) in Vellar estuary, southeast coast of India.

A detailed study on the length weight relationship of Mugil cephalus in Vellar estuary was conducted between January 2004 and December 2005. Statistical tests such as regression coefficient 'b' and 'a' tests were performed to compare the b values of males and females from the hypothetical value of 3. The b value of male (2.7658) differed significantly from the hypothetical value of 3 (t = -2.8586 < 0.05), the b value of female (2.8586) did not differ significantly from the hypothetical value (t = -1.0158 > 0.05). Values of both males and females were less than 3 which proved the negative allometry growth pattern.

Biodiversity of brackish water amphipods (crustacean) in two estuaries, southeast coast of India.

The present study about the gammarid amphipods of Vellar and Uppanar estuaries was performed during two seasons (pre-monsoon and post-monsoon, 2005-2006), respectively, in nine habitats: five in the Vellar estuary and four in the Uppanar estuary. Amphipod samples were collected from sediments, oyster beds, seaweeds, sea grass, and mangroves. A total of 29 species of gammarid amphipods were collected in each area. The surface water temperature ranged from 16°C to 26°C, the salinity from 20 to 32 psu, and the pH between 7.5 and 8.3. Dissolved oxygen ranged from 5.3 to 7.8 ml/l. The maximum abundance of amphipods was observed during the pre-monsoon (July to September) in Vellar mangrove, and it was minimum during the pre-monsoon in Uppanar sea grass. It was found that several physicochemical factors, such as salinity, temperature, dissolved oxygen, pH, and the substrate have a marked effect on the distribution and the relative abundance of amphipods. The ranges of species diversity, richness, dominance, and evenness in the Vellar and Uppanar estuaries were 1.58-4.15, 1.82-5.29, 0-0.11, and 0.96-1, respectively. Using multivariate analyses, in each estuary, it was possible to identify different communities of amphipod species according to their habitats.

Biodiversity and seasonal variation of macro-benthic infaunal community in the inshore waters of Parangipettai Coast.

This paper deals with the diversity and seasonal variations of macro-benthic infauna and associated environmental factors influencing the benthic community in the inshore waters of southern Indian coast. Four seasonal collections (2006-2007) were made at three different depths (5, 15 and 25 m) in the inshore waters of Pazhayar, Parangipettai and Cuddalore and at 5 m near State Industrial Promotion Council of Tamilnadu (SIPCOT), covering 10 stations in Bay of Bengal. Altogether, 80 infaunal samples (Van-veen grab 0.1 m(2)) were collected which revealed the occurrence of 132 species representing five diverse groups. Polychaetes were the dominant group (45%), followed by bivalves (31%) and gastropods (16%). Diversity (H'log2) was maximum (4.601) at Parangipettai 25 m during the pre-monsoon season, and the minimum (0.954) was in SIPCOT during monsoon. Multivariate analyses were used to define assemblages.

Biogeochemical processes in the continental slope of Bay of Bengal: I. Bacterial solubilization of inorganic phosphate

Microorganisms play a vital role in the biogeochemical cycles of various marine environments, but studies on occurrence and distribution of such bacteria in the marine environment from India are meager. We studied the phosphate solubilizing property of bacteria from the deep sea sediment of Bay of Bengal, India, to understand their role in phosphorous cycle (and thereby the benthic productivity of the deep sea environment). Sediment samples were obtained from 33 stations between 10 degrees 36'N-20 degrees 01' N and 79 degrees 59' E-87 degrees 30' E along 11 transects at 3 different depths i.e. ca. 200 m, 500 m, 1000 m in each transect. Total heterotrophic bacterial (THB) counts ranged from 0.42 to 37.38 x 10(4) CFU g(-1) dry sediment weight. Of the isolates tested, 7.57% showed the phosphate solubilizing property. The phosphate solubilizing bacterial genera were Pseudomonas, Bacillus, Vibrio, Alcaligenes, Micrococcus, Corynebacterium and Flavobacterium. These strains are good solubilizers of phosphates which ultimately may play a major role in the biogeochemical cycle and the benthic productivity of the Exclusive Economic Zone (EEZ) of Bay of Bengal, because this enzyme is important for the slow, but steady regeneration of phosphate and organic carbon in the deep sea.

Biogeochemical processes in the continental slope of Bay of Bengal: I. Bacterial solubilization of inorganic phosphate.

Microorganisms play a vital role in the biogeochemical cycles of various marine environments, but studies on occurrence and distribution of such bacteria in the marine environment from India are meager. We studied the phosphate solubilizing property of bacteria from the deep sea sediment of Bay of Bengal, India, to understand their role in phosphorous cycle (and thereby the benthic productivity of the deep sea environment). Sediment samples were obtained from 33 stations between 10 degrees 36'N-20 degrees 01' N and 79 degrees 59' E-87 degrees 30' E along 11 transects at 3 different depths i.e. ca. 200 m, 500 m, 1000 m in each transect. Total heterotrophic bacterial (THB) counts ranged from 0.42 to 37.38 x 10(4) CFU g(-1) dry sediment weight. Of the isolates tested, 7.57% showed the phosphate solubilizing property. The phosphate solubilizing bacterial genera were Pseudomonas, Bacillus, Vibrio, Alcaligenes, Micrococcus, Corynebacterium and Flavobacterium. These strains are good solubilizers of phosphates which ultimately may play a major role in the biogeochemical cycle and the benthic productivity of the Exclusive Economic Zone (EEZ) of Bay of Bengal, because this enzyme is important for the slow, but steady regeneration of phosphate and organic carbon in the deep sea.

Acute toxicity effect of the venom of the marine snail, Conus zeylanicus.

Acute toxicity of the venom of Conus zeylanicus was studied to evaluate its risk and toxic factors in view of human safety The lethality of the crude venom (LD50 -60 mg/kg via i.p.) in mice was associated with increased heart rate and strong muscular hind limb paralysis, skeletal muscle paralysis, dyspnea, loss of spontaneous activity followed by respiratory failure. The effect on vital tissues revealed liver tissues were disrupted with hemorrhagic necrosis and the lung showed the pathogenic changes of diffused inflammation of the parenchyma and obliteration of the alveolar space. In brain, edema was observed throughout the parenchyma and the kidney shows the tubules with cloudyswelling of the lining cells and the parenchyma inflammation and few inflammatory cells infiltration.