Farm evaluation of formulated diets on the growth and body composition of Etroplus suratensis reared in cages in low-saline coastal ponds

A 90-day on-farm feeding experiment was carried out in the installed cages in brackishwater ponds to evaluate the efficiency of three formulated diets on the growth performance and body composition of Etroplus suratensis. Two diets DI and DII were in-house formulations based on optimum macronutrient requirements (protein and fat) derived from an indoor nutritional evaluation of E. suratensis, and diet three DIII was a commercially available pellet meant for pearl spot fish. A sum of 900 fishes were randomly distributed with an average weight of 18.2±0.02g into three different treatment groups each in triplicate, and each replicate had 100 fishes stocked in cages with dimensions 2×2×1.5 m. At the end of the feeding trial, the fish were weighed to assess growth parameters in terms of % gain in weight, feed conversion ratio (FCR), and specific growth rate (SGR). The diet (DI) displayed significantly (p<0.05) higher % weight gain, and SGR than (DII) and (DIII). The FCR of diet (DI) was significantly (p<0.05) lower than diets (DII) and (DIII). Diet (DI) showed better growth when compared with other feeds. The study emphasized the need for species-specific diets for application at the farm level for an effective return on investment

Assessment of minimum inhibitory concentration to vancomycin, tigecycline, linezolid, daptomycin, ceftaroline and mupirocin against methicillin resistant Staphylococcus aureus clinical isolates by antibiotic gradient strips

Background: Staphylococcus aureus infections are one of the most common and serious hospital-acquired infections seen in developing countries. Methicillin resistant Staphylococcus aureus (MRSA) is an important human pathogen and normally colonized in body parts including skin, nose, perineum and throat. MRSA is resistant not only to all β-lactam groups but also other antibiotics including aminoglycosides, tetracycline and macrolides. In the present study the efficacy of agents used in the management of MRSA infections was determined by antibiotic gradient testing. Methods: A total of 60 clinical isolates of MRSA strains were collected from various diagnostic labs in central Kerala. Clinical isolates were reconfirmed as MRSA by gram staining, yellow-coloured colonies on mannitol salt Agar (MSA). Antibiotic susceptibility testing was done by disc diffusion method as recommended by CLSI guidelines. S. aureus isolates resistant to cefoxitin (30 µg) was identified as MRSA. Antibiotic gradient testing was performed to determine the MIC of vancomycin, tigecycline, linezolid, daptomycin, ceftaroline and mupirocin against MRSA isolates. Results: All the 60 MRSA isolates tested were sensitive to vancomycin, tigecycline, linezolid, daptomycin, ceftaroline and mupirocin (100%) and none of the MRSA isolates show resistance.  Conclusions: Results of present study indicates that these agents may be used alongside vancomycin in management of infection caused by MRSA

Hemolymph of healthy Doclea rissoni Leach, 1815: A pool for Vibrionaceae?

As diseases have a great impact on the population dynamics, evolution and immune biology of affected organisms, it is important to understand the modes and mechanisms of interaction among the lower animals and their microbial symbionts in nature function together for survival. To achieve this, it is important to understand the community structure of the native flora of these animals. Spider crabs are well known for their tolerance to various pollutants. Nevertheless, the microbiology of their circulatory systems and their role in disease transmission are unknown. Therefore, the bacteria associated with the hemolymph of a spider crab, Doclea rissoni in its natural ecosystem was characterized. Nine healthy crabs were collected from the coastal areas of Kochi, and their hemolymphs were collected. Enumeration of viable bacteria using various media revealed a similar count in all the media (7-10×102 CFU/ml). Characterization of representative isolates by conventional microbiological methods and 16S rRNA gene sequencing was followed. Despite using three different media, all isolates belonged to a single family Vibrionaceae. There were two genera as Vibrio (86.67%) and Photobacterium (13.33%). Among Vibrio, five species belonging to three different clades were isolated, of which two could not be assigned to any known species. These were classified as novel species (belonging to Harveyi clade and, Brasiliensis clade) and their description is underway. The order of relative abundance was V. alginolyticus>Novel Vibrio-II>P. damselae>V. furnissii / V. parahaemolyticus / Novel Vibrio-I. Of these, V. alginolyticus, P. damselae and V. furnissii are implicated in occasional disease outbreaks in humans and animals, posing an increased risk to human economic activity, notably aquaculture practices. Therefore, further investigations are required to find the basis for the mutualistic relationship of vibrios in different crabs

Antimicrobial resistance and virulence characteristics of Vibrio vulnificus, Vibrio parahaemolyticus and Vibrio harveyi from natural disease outbreaks of marine/estuarine fishes

Vibrio vulnificus, Vibrio parahaemolyticus and Vibrio harveyi are the causative agents of the most severe diseases of marine and brackish aquaculture systems. These are also associated with serious ailments in humans. The present paper unravels the virulence features/genes and antimicrobial resistance (AMR) phenotypes/genes of these Vibrio spp. isolated from natural disease outbreaks of marine/estuarine fishes of India for the first time. Results on virulence features showed that V. vulnificus infected fish can pose public health risk. While, it has been found clinically that V. parahaemolyticus without tdh and trh genes are pathogenic to fish, even though they are reported to be, not associated with human diseases. It was significant to note that virulence features of V. harveyi were induced at increased salinity. Analysis based on the percentage prevalence of susceptible isolates and variation coefficient of zone diameters categorized 17 antibiotics in terms of their efficiency against each fish pathogenic species. Multiple antibiotic resistance index (MARi) of the isolates ranged between 0.058 and 0.47. Results on MARi and percentage of multidrug resistance strains indicated that >50% of the isolates were from low antibiotic usage area. The study generated tetH sequence from V. parahaemolyticus for the first time, and the sequence revealed high identity to that of clinical strains. Presence of tetB/ tetH gene was identified as the predictor for the resistance against the first generation tetracycline, the most commonly used antibiotic against Vibrio spp. in aquaculture practices. The data on associations between AMR features predicted certain cross-resistance between antimicrobials within Vibrio spp. Altogether, the paper serves as the baseline for epizootic tracking of public health significant vibrios from diseased fishes, to devise practical guidelines for antibiotic use and to formulate efficient control measures against three Vibrio spp. in aquaculture, targeting final applications in the implementation of national green and healthy aquaculture practices

Pathological investigations of Vibrio vulnificus infection in Genetically Improved Farmed Tilapia (Oreochromis niloticus L.) cultured at a floating cage farm of India

An outbreak of skin ulcers with morbidity and mortality rate of 80% and 20% respectively, among Genetically Improved Farmed Tilapia (GIFT) sub-adults reared in a brackish water floating cage farm of Kochi, Kerala, India was reported. Bacterial isolation attempts from various internal organs (blood, kidney, liver, spleen and brain) of different diseased fish indicated a common bacterial etiology. Organisms were identified as Vibrio vulnificus based on conventional microbiological methods followed by molecular confirmation. Additionally, V. vulnificus marker specific for fish virulence was present in the isolates. Fish pathogenicity was confirmed by challenge tests. LD50 was calculated as 2.1 × 105.13 CFU/fish and 2.1 × 106.12 CFU/mL in injection and immersion route respectively. pilF polymorphism-based PCR and vvhA gene sequence indicated potential danger for humans. The strain was positive for siderophore, hemolysin, capsule, polar and lateral flagella. The strain could multiply rapidly in healthy fish serum. All these results indicated that the isolate could act as a primary pathogen for tilapia fish. Interestingly, serum survival ratio of the pathogen was significantly larger at higher temperatures (p ≤ .05); which may explain the increase in infective capacity of V. vulnificus at higher temperature. Multiple antibiotic resistance index of the strain was ≤0.2. In conclusion, the paper provides detailed descriptions of clinical signs, microscopic and macroscopic lesions of a natural disease outbreak among tilapia raised in brackish water cage farms of India. The concurrent attempts to identify and characterize the etiology fetches the basis for future development of effective control and preventive measures against V. vulnificus, the most infectious and lethal of all zoonotic vibrios

Glimpse towards cultivable hemolymph microbiota of marine crabs: Untapped resource for aquatic probiotics/antibacterial agents

Bacterial diseases have turned out to be the primary constraint in sustainable aquaculture production, where, probiotics can play an important role to prevent or control fish and shellfish diseases. As the autochthonous preparations would be more effective than commercial products, continued search for novel antibacterial strains native to aquatic environment are warranted against aquatic pathogens. Further, knowledge on abundance, composition and role of hemolymph microbes is also essential to predict the health status and disease diagnosis. Hence, in present study, 4 commercially significant marine crabs that are important for aquaculture were used to unravel the implication and significance of cultivable hemolymph microbes. Bacterial abundance was found to be individual- and species-dependent; and statistically significant interaction was present between growth media and abundance. Gram negative isolates represented 84% of hemolymph microbes. Vibrio was the principal genera in all species; each carrying a specific hemolymph microbiota (both in terms of abundance and diversity). The present study forms the first report of genera viz., Enterovibrio, Pantoea, Kluyvera and Enterobacter in crustacean hemolymph. Interestingly, new Vibrio species were also found. Further, the study forms the first observation on inhibitory activity of marine crab hemolymph microbes against aquatic pathogens. Overall, the results highlight marine crab hemolymph microbiota as a promising moreover, an untapped resource for probiotics/ antimicrobial agents to combat aquatic pathogens. Concurrently, the present study fetches a platform for the prediction of health and disease diagnosis of 4 potentially important aquaculture crab species

Multi-proxy evidence for an arid shift in the climate and vegetation of the Banni grasslands of western India during the mid- to late-Holocene

Tropical semi-arid grasslands are a widespread and ecologically and economically important terrestrial biome. Here, we use paleoecology to understand woodland–grassland transitions across the mid- to late-Holocene period in the Banni grassland, western India. Multi proxy analyses involving palynology, phytoliths and elemental geochemistry were carried out on two sediment cores retrieved from wetlands (Chachi and Luna), to understand temporal fluctuations in vegetation, moisture availability and other environmental parameters. Based on the results, the Chachi core was divided into two major climatic phases. Phase 1 (4600–2500 cal. yr BP) was characterised by high precipitation and abundance of pollen types and phytolith morphotypes that indicate the presence of woody savanna, and mesic herbaceous taxa. Phase 2 (2500 cal. yr BP to the present) was characterised by lower precipitation, lower abundance of mesic taxa and an increase in grass phytolith abundance. However, the period from ~1000 cal. yr BP to the present was characterised by the increased abundance of leguminous taxa, dryland herbs/shrubs and a decline in grass phytolith abundance. The Luna core (~1000 cal. yr BP to the present) also showed results matching with the Chachi core for this latter period. Overall, moisture availability in the ecosystem appears to have declined since 4600 cal. yr BP, and the vegetation has responded to this. Although the balance between tree, shrub and grass elements has fluctuated, overall, the region has remained as an open ‘grass and shrub savanna’ with sparse woody vegetation throughout this period. Our study provides insights into the vegetation dynamics and environmental settings in a poorly understood tropical arid-grassland ecosystem from Asia during the mid-late-Holocene

Hydrological status and outlooks

Chapter 6. Water is critical for the sustenance of livelihoods, economic and social development, and the natural environment. With many parts of the world experiencing more variable hydrological conditions and more severe, and more frequent extremes, water resources management is increasingly critical for human and environmental well-being (Kundzewicz & Matczak, 2015). Hydrological status and outlook systems make use of current, historic, and forecast hydro-meteorological data to appraise current hydrological status in relation to that localities “normal”. This indicates the status of water resources, as well as whether the area may be susceptible to drought or flooding in the near future. Sub-seasonal to seasonal forecasting then enables assessments of whether current conditions are likely to get better or worse over the coming weeks and months. In this chapter, hydrological status and outlooks systems are presented as a critical tool for the long-term management of water resources, as well as risk planning, in India

Anomalous transverse effects in nodal line compounds Co2TaX (X = Al, Ga)

The magnetic ground state, electronic, and elastic properties of Co2TaX (X = Al, Ga) are investigated using Density functional theory calculations. The compounds are found to possess mechanical and dynamical stability. Both the compounds exhibit nodal line features in the majority spin channel without the inclusion of spin-orbit coupling (SOC) and become gapped lines when SOC is added. The anomalous Hall effect and anomalous Nernst effect caused by Berry curvature are investigated. Within the region of +/- 300meV around Fermi level, the maximum values of anomalous Hall conductivities (AHC) are -602.8 S/cm and -593.8 S/cm, while anomalous Nernst conductivities (ANC) are -4.989 Am-1K-1 and 4.934 Am-1K-1 respectively, for Co2TaX (X = Al, Ga) compounds. Through the Heisenberg magnetic exchange interactions, the Curie temperatures (T-C) for both Co2TaX (X = Al, Ga) compounds are calculated to be 560.7 K and 556.3 K within the mean-field approximation (MFA). The magneto-optical response is also examined, and the polar Kerr rotation angles for Co2TaAl and Co2TaGa at normal incidence were determined to be 0.11 degrees and 1.35 degrees, respectively. As a result, this study may pave the way for precise property engineering in real-world applications

Anomalous Hall and Nernst Conductivities in Co2NbGa: A first principles study

The ground state electronic, magnetic and elastic properties of Co2NbGa are studied using first-principles calculations. The investigated system is mechanically and dynamically stable which is confirmed through Born mechanical stability criteria and positive phonon modes. Two kinds of disorders B2 and D03-types are studied to ensure the experimental magnetic moment in Co2NbGa within coherent potential approximation(CPA). The intrinsic anomalous Hall effect and anomalous Nernst effect are analysed from the Berry curvature point of view. The values of anomalous Hall conductivity and anomalous Nernst conductivity are 214.2 S/cm and −2.53 Am-1K-1 within the range of ±300meV around Fermi level respectively, and the same are comparable with the values of other Heusler alloys. The Curie temperature (TC) is estimated up to 548.7 K through the Heisenberg magnetic exchange interactions within mean-field approximation. Half-metal to a metal transition under pressure is evidenced through band structure and Fermi surface topology. Also the magnetic, Heisenberg exchange, elastic properties are probed under pressure