Insight into the gut microbiology of wild-caught Mangrove Red Snapper, Lutjanus argentimaculatus (Forsskal, 1775)

Documenting bacteria present in healthy individuals forms the first step in understanding the effects of microbial manipulation in aquaculture systems. Among the commensal microflora, gut microbiota has attracted extensive attention owing to their role in host metabolism and health maintenance. Basic knowledge on normal gut microbes within a particular host species is thus essential to determine how successfully these microbes can be manipulated and engineered for sustainable aquaculture systems. In spite of the good aquaculture potential of Mangrove red snapper, Lutjanus argentimaculatus, the information on microbial communities associated with the gut of this fish, and their contribution towards digestive efficiency and disease resistance is scarce. Therefore, an attempt was made to elucidate the abundance and diversity of cultivable gut microbes of wild caught L. argentimaculatus along with their digestive exoenzyme profiles and prohibitory effect against fish pathogens. Results on abundance showed similar gut bacterial loads as that of other marine fish imposing the less contribution of microflora to the volume of gut materials in fish. Eleven distinct bacterial species including two proposed novel vibrios were identified. An incidental observation of Morganella morganii throughout samples is an alarming signal, emphasizing the need for immediate de-gutting to avoid histamine intoxication. Abundance of digestive enzyme producers and excellent enzymatic potential of some isolates suggested the contribution of digestive enzymes may supplement to the symbiosis between gut flora and host and the information is of interest to aquaculture nutritionists/commercial industries. Interestingly, some isolates demonstrated estimable co-aggregation with aquatic pathogens, indicating their involvement in disease resistance and the results correlated well with gut microbial diversity. These findings highlight the significant role of gut microbes towards nutritional physiology and disease resistance of this aquaculture candidate in natural ecosystem. The culturable microbiota profiles of wild fish generated in the study can be applied for measuring the quality of husbandry routines in aquaculture facility of this marine fish. Overall, the present study fetches insights on the gut microbiome of healthy L. argentimaculatus which forms a platform for follow-up studies. The study may also help in the development of “functional” fish feeds for L. argentimaculatus. The investigation also demonstrated some potential digestive enzyme-producing isolates having probiotic applications in commercial aquaculture

A Method for Rapid Demineralization of Teeth and Bones

Tooth and bone specimen require extensive demineralization for careful analysis of cell morphology, as well as gene and protein expression levels. The LacZ gene, which encodes the ß-galactosidase enzyme, is often used as a reporter gene to study gene-structure function, tissue-specific expression by a promoter, cell lineage and fate. This reporter gene is particularly useful for analyzing the spatial and temporal gene expression pattern, by expressing the LacZ gene under the control of a promoter of interest. To analyze LacZ activity, and the expression of other genes and their protein products in teeth and bones, it is necessary to carry out a complete demineralization of the specimen before cutting sections. However, strong acids, such as formic acid used for tooth demineralization, destroy the activities of enzymes including those of ß-galactosidase. Therefore, most protocols currently use mild acids such as 0.1 M ethylene diamine tetra-acetic acid (EDTA) for demineralization of tooth and bone specimen, which require a longer period of treatment for complete demineralization. A method by which hard tissue specimens such as teeth and bones can be rapidly, but gently, decalcified is necessary to save time and effort. Here, we report a suitable method for rapid demineralization of mouse teeth in 0.1M EDTA at 42˚C without any loss of ß-galactosidase activity

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Diet composition and feeding dynamics of Trichiurus lepturus Linnaeus, 1758 off Gujarat, north-west coast of India

The largehead ribbonfish, Trichiurus lepturus Linnaeus, 1758 forms a major fishery along north-west coast of India comprising the two coastal states of Gujarat and Maharashtra. Diet composition was analysed for five years (2010-2014) to understand shifts if any in the prey items. Seasonal changes in the prey items were studied for three years (2012-2014) to explore the temporal dynamics of prey availability in the ecosystem and in largehead ribbonfish guts. Feeding indices viz., Stomach fullness index (SFI), empty stomach ratio (ESR), gastrosomatic index (GaSI) and relative gut length (RLG) explained the feeding behaviour, seasonal dynamics and ontogenetic shifts in prey items. The Vacuity Index (VI) was estimated as 37.56%, indicating that T. lepturus is a carnivore and relatively edacious. Diet of T. lepturus comprised of fishes (47.16%), crustaceans (45.22%), molluscs (4.33%) and miscellaneous items (3.28%). Acetes sp. was the most dominant prey item during the study period. Feeding intensity was found to be high during the post-monsoon months which coincided with the period of gonadal maturation of the fish. Significant variations (p<0.05) were seen in the feeding indices during different months, different sizes and between sexes due to the availability of prey items, physiological changes and ontogenetic shifts. A detailed knowledge on diet composition, temporal dynamics in diet patterns and feeding indices can reveal the trophic interaction of prey-predator, resource abundance and fluctuations which are important inputs in ecology-based fishery management models/tools

Virtual Constraints and Hybrid Zero Dynamics for Realizing Underactuated Bipedal Locomotion

Underactuation is ubiquitous in human locomotion and should be ubiquitous in bipedal robotic locomotion as well. This chapter presents a coherent theory for the design of feedback controllers that achieve stable walking gaits in underactuated bipedal robots. Two fundamental tools are introduced, virtual constraints and hybrid zero dynamics. Virtual constraints are relations on the state variables of a mechanical model that are imposed through a time-invariant feedback controller. One of their roles is to synchronize the robot's joints to an internal gait phasing variable. A second role is to induce a low dimensional system, the zero dynamics, that captures the underactuated aspects of a robot's model, without any approximations. To enhance intuition, the relation between physical constraints and virtual constraints is first established. From here, the hybrid zero dynamics of an underactuated bipedal model is developed, and its fundamental role in the design of asymptotically stable walking motions is established. The chapter includes numerous references to robots on which the highlighted techniques have been implemented.Comment: 17 pages, 4 figures, bookchapte

A CFD Investigation into the Flow Distribution on a Car passing by a Truck

Abstract The flow distribution occurring on a car when it is passing by a truck is investigated using three dimensiona

Vulnerability of Coastal Fisher Households to Climate Change: A Case Study from Gujarat, India

The impacts of climate change are invariably seen on agriculture, aquatic ecosystem, energy, and economics. The fishery sector on which livelihood of world’s 36 million fishers depends is also not untouched but a little attention has been given to study the vulnerability of fisherfolk population to climate change programs. Therefore, the present study was envisaged to assess the vulnerability of fishers to the climate change in Junagadh district of Gujarat, India. The vulnerability of 1500 fisher household was assessed using PARS (parameter, attribute, resilient indicator, score) methodology, in four coastal villages namely Old light house, Bhidiya, Navabunder and Rajpara in Junagadh district. Five parameters viz., fishery, economy, social, environmental and development drivers have been assessed as indicators of sensitivity, exposure and adaptive capacity. ‘Economy’ was found to be the most impacted parameter consequent to climate change followed by the ‘social’ and ‘environmental’ parameters. The results obtained reflect low adaptive capacity of fishers that could be attributed to lack of awareness, preparation, and mitigation option. Thus, the finding of the study could be used as a vital input while developing the policy and suitable action plan to combat the impacts of climate change minimizing the risk to fisheries sector

Continuous Requirement for the Clr4 Complex But Not RNAi for Centromeric Heterochromatin Assembly in Fission Yeast Harboring a Disrupted RITS Complex

Formation of centromeric heterochromatin in fission yeast requires the combined action of chromatin modifying enzymes and small RNAs derived from centromeric transcripts. Positive feedback mechanisms that link the RNAi pathway and the Clr4/Suv39h1 histone H3K9 methyltransferase complex (Clr-C) result in requirements for H3K9 methylation for full siRNA production and for siRNA production to achieve full histone methylation. Nonetheless, it has been proposed that the Argonaute protein, Ago1, is the key initial trigger for heterochromatin assembly via its association with Dicer-independent “priRNAs.” The RITS complex physically links Ago1 and the H3-K9me binding protein Chp1. Here we exploit an assay for heterochromatin assembly in which loss of silencing by deletion of RNAi or Clr-C components can be reversed by re-introduction of the deleted gene. We showed previously that a mutant version of the RITS complex (Tas3WG) that biochemically separates Ago1 from Chp1 and Tas3 proteins permits maintenance of heterochromatin, but prevents its formation when Clr4 is removed and re-introduced. Here we show that the block occurs with mutants in Clr-C, but not mutants in the RNAi pathway. Thus, Clr-C components, but not RNAi factors, play a more critical role in assembly when the integrity of RITS is disrupted. Consistent with previous reports, cells lacking Clr-C components completely lack H3K9me2 on centromeric DNA repeats, whereas RNAi pathway mutants accumulate low levels of H3K9me2. Further supporting the existence of RNAi–independent mechanisms for establishment of centromeric heterochromatin, overexpression of clr4+ in clr4Δago1Δ cells results in some de novo H3K9me2 accumulation at centromeres. These findings and our observation that ago1Δ and dcr1Δ mutants display indistinguishable low levels of H3K9me2 (in contrast to a previous report) challenge the model that priRNAs trigger heterochromatin formation. Instead, our results indicate that RNAi cooperates with RNAi–independent factors in the assembly of heterochromatin