The diet of Indian mackerel Rastrelliger kanagurta (Cuvier, 1816) is reported based on the gut content analysis of specimens collected along the central Kerala coast, India. The study indicated ontogenetic variations in diet with diet breadth being highest in the largest size class of >231 mm total length (TL). Copepods followed by diatoms were the preferred food items. Detritus was an important diet component, especially during the pre-monsoon season and in the larger (>231 mm TL) size groups. The Preponderal Index (Ip) indicated seasonal differences in proportions of the various prey consumed. Spearman Rank Correlation Coefficient indicated similar diet quality during monsoon (June-September) and post-monsoon (October-January) seasons; but significant differences as compared to pre-monsoon season (February-May). Based on the results of the study, Indian mackerel was classified as an opportunistic feeder with a diet component that broadly reflects its seasonal-spatial habitats and local food availability.

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Increasing levels of salinity in coastal and freshwater environments as a result of rise in sea level is linked to climate change and it impacts fish growth adversely. Etroplus suratensis (Pearlspot) is the largest species among the indigenous cichlid which is essentially brackishwater fish that has become naturally acclimated to freshwater. Understanding the basis of tolerance and acclimatization to increased environmental salinity and freshwater condition can help the regional aqua-farmers to mitigate predicted impacts of climate change in that region. Technically the last decade contributed many methodologies to understand the salinity adaptation mechanisms; suppression subtractive hybridization (SSH) library generation being one of them. In this study we performed SSH technique to identify genes involved in salinity adaptation and osmoregulation in gills of E. suratensis, generating from fishes exposed to seawater (SW-36 ‰) as compared to freshwater (FW-0 ‰). Here, SSH was used to identify alterations in gene transcription of E. suratensis after exposure to 36‰. A random 105 clones were selected and sanger sequenced from the subtractive c-DNA libraries which gave a total of 80 gene fragment sequences.

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Macrocyclic compounds of multifaceted structural scaffolds are being increasingly reported from the marine environment, and gaining commercial importance due to their ability to inhibit the pro-inflammatory mediators. An unreported polyether macrocyclic polyketide characterized as 6-(butoxy)-13,15,22-trihydroxy-3,18-dioxatricyclo[18.3.1.011,16]tricosa-9,20-diene- 4,8-dione was isolated from the marine gastropod mollusc Chicoreus ramosus (family Muricidae). The compound displayed potential anti-inflammatory property by inhibiting 5-lipoxygenase (IC50 0.42 mg mL?1), which was analogous to the nonsteroidal anti-inflammatory agent aspirin (IC50 0.38 mg mL?1) and superior to ibuprofen (IC50 0.90 mg mL?1). Free radical scavenging abilities of the purified compound against oxidative agents (IC50 0.22 mg mL?1) were comparable to the commercially available antioxidants (butylated hydroxyanisole, IC50 0.25 mg mL?1; butylated hydroxytoluene, IC50 0.27 mg mL?1), and greater than ?-tocopherol (IC50 0.60 mg mL?1). Molecular docking studies of the studied polyketide analog against 5-lipoxygenase indicated that the docked ligand could potentially bind to the target site of the enzyme with a less binding energy (?9.33 kcal mol?1) and docking score (?10.23 kcal mol?1). The present study recognized the potential of macrocyclic polyketide possessing tricosa-9, 20-diene-4,8-dione framework isolated from C. ramosus as a potential antioxidant and anti-inflammatory lead that could find its use in medicinal formulations.

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Two undescribed polyoxygenated furanocembranoid derivatives, methyl 15-(9-hydroxy-8-methoxy-2,12-dimethyl-15-oxa-bicyclo [10.2.1]pentadeca-2,4,6,11-tetraen-3-yl)propanoate (salmacembrane A) and 1-(16-methyl-2,16-dihydrofuran)-8-methoxy-12- methyl-20-oxabicyclo[10.2.1]pentadeca-2,4,6,11-tetraen-9-ol (salmacembrane B), were isolated from the organic extract of sea urchin Salmacis bicolor (family Temnopleuridae) by extensive chromatographic purification. Their structures were elucidated using detailed spectroscopic evidence. Salmacembrane A displayed significantly greater attenuation property against pro-inflammatory cyclooxygenase-2 (IC50 1.71 mM) than that exhibited by salmacembrane B (IC50 1.99 mM). Salmacembrane A could potentially inhibit 5-lipoxygenase (IC50 1.87 mM) and its activity was significantly greater than that exhibited by anti-inflammatory agent ibuprofen (IC50 4.50mM, p < 0.05). The greater selectivity index (anti-cyclooxygense-2/anti-cyclooxygense-1) of salmacembrane A (1.06) than ibuprofen (0.43) further supported higher selectivity toward pro-inflammatory isoenzyme cyclooxygenase-2. Salmacembrane A displayed higher antioxidant properties against 2,2?-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) and 2,2- diphenyl-1-picrylhydrazyl (IC50 1.57 and 1.65mM, respectively) than those exhibited by salmacembrane B (IC50 > 1.85mM). In addition, these antioxidant activities were comparable to the standard ?-tocopherol (IC50 DPPH 1.51 mM, IC50 ABTS+ 1.70mM p < 0.05). The higher electronic parameters obtained from structure–activity relationship analysis along with greater binding affinities of salmacembrane A at the active site of cyclooxygenase-2 ascribed its potential anti-inflammatory activity.

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Two aryl-enclosed polyketides were identified from the ethyl acetate extract of mangrove sediment associated bacterium Bacillus amyloliquefaciens, and were characterized as 1-(8-hydroxy-1-oxoisochroman-3-yl)propyl 4?-(6?-hydroxy-8?- oxotetrahydrofuran-5?-yl)acetate (compound 1) and 6?a-(3?-(1?-(8-hydroxy-1-oxoisochroman-3-yl)propoxy)-3?-oxoethyl)- 8?-oxotetrahydrofuran-6?-yl butyrate (compound 2) by detailed spectroscopic techniques encompassing two-dimensional nuclear magnetic resonance and mass spectroscopic experiments. Polyketide compound 2 bearing oxotetrahydrofuran-6?-yl butyrate moiety exhibited potential antioxidant activities against the free radicals, 2,2-diphenyl-1-picrylhydrazyl radical and 2,2?-azino-bis-3-ethylbenzothiozoline-6-sulfonic acid (IC50 1.01 and 1.22 mM, respectively), and were found to be significantly greater than those displayed by polyketide 1 and standard (?-tocopherol IC50 1.45–1.63 mM, p < 0.05). Compound 2 also exhibited greater anti-inflammatory properties as determined by 5-LOX inhibitory assay (IC50 1.11 mM) than those displayed by compound 1 (IC50 1.23 mM) and standard (ibuprofen IC50 4.50 mM). Greater electronic parameters of compound 2 could further support its greater bioactive potentials.

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The Indian mackerel Rastrelligerkanagurta(Cuvier, 1816) is one of the most important marine fishery resources along the south-eastern Arabian Sea along the coast of Kerala, south India. The effect of selected environmental variables on the Relative effort (Effort) and weighted catch per unit effort (cpue)of the fish were investigated using simple correlation and Path analysis. Six major oceanographic variables, namely sea surface temperature (SST), sea surface chlorophyll-a concentration (SSC), sea surface salinity (SSS), Precipitation (Pr) Indian Ocean Dipole (IOD) and Southern Oscillation Index (SOI) (ENSO index) were selected for the present study. Among these SST had the highest direct negative effect (-0.282, p<0.01), followed by SSS (-0.152, p<0.1) and IOD (-0.006, p<0.01). The highest positive direct effect on the cpue was exhibited by Pr (0.514, p<0.001) followed by SSC and SOI (0.178, p<0.01). The environmental variables also exerted indirect effects on cpue through Effort. The residual variance indicated that there are spurious effects exerted by environmental variables not included in the study. According to the coefficient of determination (R2), the relative importance of the influence of causally dependent environmental variables on the cpue of Indian mackerel is Pr> SSC >SSS.

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