Indian Council of Agricultural Research
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Signals of selection in the mitogenome provide insights into adaptation mechanisms in heterogeneous habitats in a widely distributed pelagic fish

Signals of selection in the mitogenome provide insights into adaptation mechanisms in heterogeneous habitats in a widely distributed pelagic fish – Nature Scientific Reports (2020)

 

Indian oil sardine (Sardinella longiceps) is a widely distributed pelagic species in the Indian Ocean exhibiting wide fluctuations in landings. We investigated the molecular mechanisms of adaptation of Indian oil sardine to wide environmental clines to understand the potential for resilience in this species in the present scenario of climate change. Signals of diversifying selection indicating adaptive capacity were observed in key functional regions involved in oxidative phosphorylation pathway of the mitochondrial genome. These changes were more prevalent in South Eastern Arabian Sea (SEAS), which is one of the most dynamic seas due to fluctuations in productivity, temperature and dissolved oxygen. Northern Arabian Sea (NAS) populations also exhibited selective mutations albeit at a lower level than South East Arabian sea populations and these mutations were rare in Bay of Bengal (BoB) Populations. The present study provided evidence for the presence of locally adapted populations in the Indian oil sardines. The study also provided insights into the excellent adaptive capacity and resilience of this species to climatic fluctuations and the mechanisms by which pelagic species thrive in the changing oceans. The most resilient populations were observed in the SEAS which encompasses the Malabar upwelling zone, a historically productive region for the Indian oil sardine. The locally adapted populations with specific mutations can be monitored over space and time to understand climate change impacts and to devise management measures. Management measures can be implemented at a zonal level considering that SEAS populations are the most diverse followed by NAS and BoB populations.


This study is the outcome of a fruitful collaboration between ICAR-Central Marine Fisheries Research Institute (CMFRI) and CSIR-National Institute of Oceanography (NIO). 



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Growth pattern of stock cultures of marine microalgae maintained under indoor and outdoor conditions

Growth pattern of five species of microalgae viz., Chaetoceros calcitrans, Dunaliella sp., Isochrysis galbana, Tetraselmis tetrahele and Nannochloropsis salina were studied under indoor controlled conditions (at 230C) and under outdoor (at 28-30°C) conditions. The variations in ammonia and pH levels in the culture flasks over a period of 90 days were also studied. Results revealed that the pattern of growth of all five species of algae were significantly different (p<0.05) in the two different conditions. The results clearly showed that the growth of all the five species of algae were faster in outdoor conditions and outdoor cultures were able to maintain only for a maximum period of three months. Ammonia and pH levels recorded were higher in outdoor cultures which indicated higher physiological activities and growth. Ammonia and pH levels were found to increase gradually in all the cultures, upto 30 days under both conditions and subsequently found almost constant throughout the study. Even though ammonia levels were found to rise with increase in pH and temperature, it did not increase to a level that is detrimental to the microalgal cultures.


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Growth performance of goldfish, Carassius auratus and basil, Ocimum basilicum in media bed aquaponics

An experiment of 36 days duration was conducted to study growth performance of goldfish Carassius auratus and basil Ocimum basilicum reared in a media bed aquaponic system. Goldfish fry (3.32 ± 0.45 g and 4.20 ± 0.39 cm) were stocked in rectangular 75 l capacity (water volume of 50 l) plastic tanks at three different stocking densities viz., 500 m-3 (T1), 600 m-3 (T2) and 700 m-3 (T3), respectively and basil plants were planted at a density of 20 m-2, i.e., 10 plants 0.44 m-2 in the rectangular plastic tanks filled with crushed stone media. The goldfish fry were fed with artificial feed (33% protein) at 5% of body weight in equal proportions, two times a day. Control (C) group was set with only basil plants. Growth parameters of goldfish such as length gain (%), weight gain (%) and specific growth rate (% d-1) were significantly higher in T3 (p<0.05) as compared to T1 and T2. However, feed conversion ratio (FCR) and protein efficiency ratio (PER) did not differ between treatments. Similarly, basil plant growth in terms of height gain (%) and leaves yield (nos. plant-1) were found to be highest in T3 which was significantly different from T1, T2 and control (C). Throughout the experimental period, values of water parameters in all the treatments were found to be in favourable ranges. From the results of the present study, it could be concluded that for maintaining good water quality with highest production in media bed aquaponics, the optimum stocking density is 700 m-3 for goldfish fry and 10 plants per 0.44 m2 for basil plants.


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Fishery and geospatial mapping of pelagic elasmobranchs from mechanised gillnetters

The pelagic elasmobranchs fishery of multiday gillnetters (MGNs) of Tharuvaikulam, Thoothukudi was studied during 2015-2016. Fishery data revealed that MGNs targeting scombrids and other large pelagic fishes also contribute to the pelagic elasmobranch landings accounting for 7.67 and 5.3% of total elasmobranchs landed at Tharuvaikulam during 2015 and 2016 respectively. The catch per unit effort (CPUE) varied from 2.09 to 175 kg (2015) and 13 to 124.95 kg (2016). In total, 15 species of pelagic elasmobranchs were recorded during the study period, which includes 7 species of sharks and 8 species of rays. The pelagic elasmobranchs fishery of Tharuvaikulam depends mainly on two species namely bigeye thresher, Alopias superciliosus and spinetail devilray, Mobula japanica. The geospatial mapping revealed that fishing grounds of MGNs was between 77° to 80°E longitudes and 7° to 9° N latitudes with depth ranging from 50 to 200 m. The persistence of fishing grounds of pelagic elasmobranchs was identified by classifying the fishing areas of Gulf of Mannar Biosphere Reserve (GOMBR) into seven zones. The results showed that more fishing happens in Zone 4, off Thoothukudi between 78° to 79°E and 8° to 9°N followed by Zone 7, off Kanyakumari between 77° to 78°E and 7° to 8°N. Seasonal analysis revealed that along with the targeted groups, the CPUE of pelagic elasmobranchs was higher during the pre-monsoon season. The present paper illustrates the zonal distribution of pelagic elasmobranchs in the fishing grounds of MGNs in GOMBR, along the south-east coast of India and the results of the study would serve as baseline information for formulating future management plans.


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Effect of dietary supplementation on growth performance, survival and disease resistance of Lates calcarifer

The present study aimed to assess growth performance and health status of Lates calcarifer larvae fed with crude microalgal extracts. Larvae weighing 5.96 ± 0.39 mg were randomly divided into four experimental groups in triplicates, with each replicate having 35 larvae. Four diets formulated to contain 55% protein and 12% lipid, were prepared with pigment rich microalgal extracts at 0% (T1) and 1% each of crude phycocyanin (T2), chlorophyll (T3) and astaxanthin (T4) extracts. The experiment was carried out in 30 l plastic tanks by feeding experimental diets to satiation. There was no significant difference (p<0.05) in growth performance in larval groups fed different experimental diets. Percentage survival during the feeding experiment was significantly higher in the astaxanthin fed group (77.14±1.65) and lower in chlorophyll fed group (36.19±0.95) compared to control group. Cannibalism (%) was significantly reduced in the treatments fed astaxanthin (7.61±0.95) and phycocyanin (8.57±0.3) pigmented diets compared to chlorophyll fed group (13.33±0.95) and control group. Bacterial challenge with pathogenic Vibrio alginolyticus revealed highest resistance in astaxanthin and phycocyanin fed larvae. The study confirms that astaxanthin and phycocyanin at 1% dietary levels improve survival and disease resistance in Asian seabass larvae but do not affect growth performance.


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First report of antioxidative abeo-oleanenes from red seaweed as dual inhibitors of starch digestive enzymes

Carbolytic enzyme-associated cascades have been considered as potential curative target in attenuating diabetic mellitus pathogenesis. Two oleanene class of triterpenoids characterised as 24(4?23), 27(8?26), 30(20?29)-tris-abeo-olean-(12- oxo)-1,15,22-triene-methyl hept-5-enoate (1) and 24(4?23)-abeo-olean-(12-oxo)-3,5-diene-deconoate (2) with potential inhibitory activities against the starch digestive enzymes ?-glucosidase and ?-amylase, were purified from the organic extract of intertidal red seaweed Gracilaria salicornia (family Gracilariaceae). Structural interpretation of compounds was carried out by detailed spectroscopic analysis, and their antioxidant/anti-diabetic potentials were assessed. Inhibitory potential of abeo-oleanene derivative (2) towards the starch digestive enzymes, ?-glucosidase (IC50 0.29 mM) and ?-amylase (IC50 0.32 mM) were greater than those displayed by its abeo-oleanene chemotype 1 (IC50 0.34–0.40 mM). The molecular modelling studies were performed to designate the ?-amylase and ?-glucosidase inhibitory mechanism of oleanene analogues, and the comparison of docking parameters suggested that compound 2 exhibited least binding energy of ?10.04 and ?9.84 kcal mol?1 towards ?-amylase and ?-glucosidase respectively, and those results were corroborated with its greater inhibition potential against carbolytic enzymes. These results demonstrated that abeo-oleanene derivative (2) might constitute prospective anti-hyperglycaemic pharmaceutical candidate to moderate the likelihood of type-II diabetes.


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