Anuradha Bhat | IISER-Kolkata - Academia.edu (original) (raw)

Papers by Anuradha Bhat

Applied Animal Behaviour Science

Fish inhabiting human-dominated ecosystems are prone to altered sensory environments in which the... more Fish inhabiting human-dominated ecosystems are prone to altered sensory environments in which they must live and function. Increased turbidity is one such change that they must deal with. We tested whether an increase in water turbidity and the presence of visual landmarks (coloured stones) affect the foraging efficiency of wild zebrafish. We also tested the influence of extended exposure to differing turbidity levels on the subsequent foraging efficiency of acclimatized individuals. Feeding latency (time taken to find food) increased significantly with increase in turbidity levels from a minimum of 4 s to <i>ca</i> 300 s. However, extended exposure of fish to varying levels of turbidity decreased feeding latencies in acclimatized conditions, indicating that acclimatization to the immediate visual environment plays an important role in determining foraging success. Most significantly, we found that feeding latencies in turbid conditions decreased significantly if visual ...

Shoaling in fishes is regulated by factors like predation, vegetation cover, water flow and food ... more Shoaling in fishes is regulated by factors like predation, vegetation cover, water flow and food availability. Shoals detect and respond to changes in these ecological factors using a multimodal sensory system. Here, we examine the immediate response of wild-caught zebrafish (Danio rerio)shoals to cues from its natural predator, the snakehead (Channa sp.). Zebrafish shoals were recorded upon exposure to (1) olfactory predator cues, (2) visual predator cues, (3) both cues together, and (4) no cue. We tracked individuals and analysed shoal responses across these treatments. We found that compared to control treatments, shoals receiving either visual or olfactory cues had significantly greater: (i) cohesion, (ii) polarization and (iii) velocity. Interestingly, when the shoals received both cues simultaneously, the cohesion, polarization and velocity decreased and a significantly greater number of individual freezing events occurred. Therefore, zebrafish relied on both visual and olfact...

Aquatic Sciences

As an important component of overall diversity, β-diversity is driven by spatial and temporal var... more As an important component of overall diversity, β-diversity is driven by spatial and temporal variability of several ecological factors. While changes to β-diversity can be the result of a combination of these factors, it is still unclear whether the same driving factors govern regions with similar β-diversity. We studied lower–middle-order streams in two river basins (three of them located in the state of Madhya Pradesh ‘MP’ and four located in West Bengal ‘WB’) in India, approximately 1600 km apart. Fish abundance and environmental data were collected from 2015 to 2017. While spatial variables constructed from geographic or fluvial distances are often used in evaluating dispersal effects, studies using terrain properties are relatively fewer. In tropical stream systems, which can undergo drastic seasonal transformations, terrain properties along with distances are likely to influence dispersal. Heterogeneity indices for both environment (Environmental heterogeneity, EH) and topography (Topographic heterogeneity, TH) were calculated. Influence of environmental and spatial variables (fluvial distance and TH) on β-diversity was modeled using dbRDA (distance-based redundancy analysis). β-diversity did not vary across seasons (i.e., temporally) in either regions, but did vary across streams (i.e., spatially). MP had a higher TH while WB displayed greater EH. Both regions showed a positive beta diversity–environmental heterogeneity relationship and EH–TH relationship across streams. Although both basins rest in the tropics, different mechanisms seem to explain community assembly. Variation partitioning showed a stronger influence of environmental filtering on fish communities in WB, and dispersal limitation reflected by spatial factors in MP. Our findings highlight that different mechanisms can drive β-diversity within the same tropical realm and the need to consider the role of topography, along with traditionally acknowledged spatial descriptors, in studies exploring the mechanisms driving β-diversity of fishes in riverine ecosystems.

Toxics

Environmental change poses a devastating risk to human and environmental health. Rapid assessment... more Environmental change poses a devastating risk to human and environmental health. Rapid assessment of water conditions is necessary for monitoring, evaluating, and addressing this global health danger. Sentinels or biological monitors can be deployed in the field using minimal resources to detect water quality changes in real time, quickly and cheaply. Zebrafish (Danio rerio) are ideal sentinels for detecting environmental changes due to their biomedical tool kit, widespread geographic distribution, and well-characterized phenotypic responses to environmental disturbances. Here, we demonstrate the utility of zebrafish sentinels by characterizing phenotypic differences in wild zebrafish between two field sites in India. Site 1 was a rural environment with flowing water, low-hypoxic conditions, minimal human-made debris, and high iron and lead concentrations. Site 2 was an urban environment with still water, hypoxic conditions, plastic pollution, and high arsenic, iron, and chromium co...

Mixed-species groups commonly occur across a wide range of faunal communities and are known to pr... more Mixed-species groups commonly occur across a wide range of faunal communities and are known to provide several benefits to members. While zebrafish have often been observed to form mixed-species shoals with coexisting species, the factors determining their occurrence are not yet understood. Using laboratory-based experiments, we decipher the main ecological drivers of mixed-species shoaling in these tropical fish communities. Shoals comprising zebrafish (Danio rerio), flying barbs (Esomus danricus), and whitespots (Aplocheilus panchax) were collected from a stagnant canal at Haringhata (West Bengal, India). Experiments to assess foraging efficiency were conducted where single or mixed-species shoals (comprising 5 individuals) were given low or high amounts of food. Shoal choice experiments were also conducted to assess the preferences of test subjects (zebrafish individuals) for forming associations based on shoal composition and familiarity. Results from experiments on feeding effi...

Freshwater Science

Dispersal processes, such as immigration and extinction rates, and habitat properties play a cruc... more Dispersal processes, such as immigration and extinction rates, and habitat properties play a crucial role in determining species composition and nestedness patterns within communities. In the current global scenario of changing environmental conditions and habitat fragmentation, information on the role of natural dispersal mechanisms and disturbance factors are especially important for understanding dynamics of species composition changes in stream ecosystems. We investigated spatial and temporal patterns of nestedness of fish communities in tropical stream systems of central India and the relationship of various dispersal factors (immigration–extinction rates and their variability) with habitat properties (habitat size and heterogeneity) and anthropogenic disturbances. We tested predictions of the classical model by Schlosser on immigration–extinction dynamics along longitudinal gradients in stream community composition for these streams. The results revealed significant patterns of nestedness for all study sites. Sites exposed to varying degrees of disturbance (induced by human activities) showed lower nestedness than undisturbed ones. Immigration rates did not show strong relations with nestedness but extinction rates were significantly related (negatively) to nestedness. In addition, disturbance played an important role in determining immigration rates and variability in immigration rates. Stream characteristics, such as habitat-size and habitat-variability gradients, were not statistically significant predictors of immigration and extinction rates. Our results demonstrate the influence of local anthropogenic disturbances on dispersal dynamics of species. A reduction in availability of suitable habitats could lower immigrations.

Frontiers in Psychology, 2022

Animal personality refers to the consistency of variation in behavior among individuals which may... more Animal personality refers to the consistency of variation in behavior among individuals which may be the driving force behind variations in complex behaviors as well. Individual personality could predict how well an organism would perform in behavior and cognition related tasks, as well as survive and thrive in its environment. Therefore, we would expect inter-individual variations in many behaviors, which would persist even if habituation to the experimental setup occurs, which generally results in convergence of behavior (i.e., the difference between individuals becomes less pronounced). Our study used wild-caught zebrafish (Danio rerio) from three natural habitats with differing ecological regimes, to understand how consistency and repeatability in specific traits such as boldness, exploration, and spatial ability varies across and within populations even when habituation causes change in behavior. We found that the extent of individual variation differs between populations, with...

Social behavior of RA zebrafish

ESM File1. Data on the three measured behavioural responses (Activity, Predator Inspection and Sh... more ESM File1. Data on the three measured behavioural responses (Activity, Predator Inspection and Shoal association) of each individual for the four populations.

Details of the measurements for each behavioural assay.

World Academy of Science, Engineering and Technology, International Journal of Bioengineering and Life Sciences, 2016

This study (1) investigated variation among populations and the effects of sex and body size on b... more This study (1) investigated variation among populations and the effects of sex and body size on boldness, activity and shoal-association tendency among wild zebrafish, and (2) tested for existence of correlations between behaviours, controlling for sex and body size. Individuals across four natural populations were tested for general activity in a novel situation, number of predator inspections undertaken and tendency to associate with a conspecific shoal in the presence of predators. Results showed a significant effect of population on boldness with a population from high-predation habitat being bolder than populations from low-predation habitats. Males showed significantly higher tendencies than females to associate with a conspecific shoal in the presence of predators. Further, a negative relationship was found between activity and boldness only within two low-predation populations. Individual body size had a strong effect on the activity–boldness relationship within the low-predation population from flowing water habitat. Smaller fish were bolder and less active while larger fish were more cautious and active. Overall, the results indicated that while population-level behavioural responses might be shaped by predation pressure, state-dependent factors could determine behavioural correlations among individuals within populations.

Ecological Indicators, 2021

Over the past several decades, ecologists have been striving to develop models that accurately de... more Over the past several decades, ecologists have been striving to develop models that accurately describe specieshabitat relationships across ecological communities. Statistical models that explain ecological dynamics need to consider the nuances of the complex interactions between communities and ecological factors. Here, we used multiple linear mixed models (LMM), generalized additive models (GAM), multivariate adaptive regression splines (MARS), and artificial neural networks (ANN) to model species richness and diversity of freshwater fishes in eastern and central India. The models were based on fish abundance and associated ecological data over three years across the study regions. We developed global models using all predictors after removing highly correlated variables (Pearson's r > 0.7). Results revealed conductivity, water temperature, and water velocity as the most important predictive factors of both species richness and diversity. We, then, built two subsets of selected factors to build predictive models for diversity and richness-one variable set containing common significant factors as revealed from the four different modeling methods used and the second, using an automatic feature selection technique. Amongst the modeling methods used in our study, ANN was found to create the best fit models for explaining nonlinearities between response variables and predictors. The importance of variable selection is highlighted, given that subset 1 (common consensual factors) creates more homogeneity in predictions compared to using subset 2 (automated feature selection). Contrary to similar studies in recent years, which show machine learning (ML) methods to typically outperform conventional methods, our results revealed that ANN performed at par with other methods in terms of predictive power. Our findings underline the need for a judicious choice of modeling techniques based on the availability of the data and the ecological communities being studied.

PLOS ONE, 2020

Environmental and anthropogenic factors are known to drive fish community structure in aquatic sy... more Environmental and anthropogenic factors are known to drive fish community structure in aquatic systems across the world. This study investigates fish assemblages in lower order streams across contrasting landscapes in central and eastern India. We documented the species diversity of these monsoon driven lower order streams in the two regions. We also investigated the potential common environmental drivers of richness and diversity and effect of season in these tropical streams. The study was based on seasonal data on abundance of fishes and environmental parameters collected between 2015-2017 from streams in states of Madhya Pradesh and West Bengal. Species diversity were compared across regions and seasons, based on their richness (SR) as well as diversity (Shannon index H'). Drivers of overall richness and diversity were analyzed using multiple linear regression methods, based on best subset selection. Analysis of data revealed high diversity in these streams in both regions. Cyprinidae, Bagridae and Channidae were the most dominant families in both regions. Despite the geographical and local ecological differences across the regions, common environmental parameters were found to influence richness and diversity across the two regions, indicating these as being key drivers of fish community structure. Water flow was a common factor driving both richness and diversity across both regions. Our study revealed a lack of seasonal effect in structuring fish communities in tropical streams. With stream and river ecosystems facing increasing threats due to habitat alterations and water quality degradation in countries such as India, a clear understanding of regional and local drivers of community structure of aquatic fauna is crucial. These results on the role of common environmental factors across ecoregions provides baseline information for understanding their ecological roles and developing management plans for important river basins and fish conservation in future.

Frontiers in Behavioral Neuroscience, 2020

Within populations, individual differences in behavioral and cognitive traits are dependent on th... more Within populations, individual differences in behavioral and cognitive traits are dependent on the habitat and specific contexts, such as the presence of a predator or other risks. The ability to show variable responses to changing conditions can be of immense survival advantage to organisms. We studied individual differences in specific personality traits, such as boldness, exploration, and spatial ability, and the effect of these traits on learning ability and memory in the presence of a predatory threat, among wild caught zebrafish (Danio rerio). Under laboratory conditions, individuals were trained to perform a simple navigation task, and their performance, exploration, boldness traits were measured, along with learning and memory abilities under two contexts (i.e., in the presence and absence of a predator). Our results revealed that fish showed a clear decline in emergence time, exploration time, and feeding latency over trials, indicative of learning, and further tests for memory also showed memory retention. While the presence of a predator increased emergence time and latencies for navigating, indicating declines in boldness and exploration, these were found to be correlated to different personalities among the individuals and dependent on their sex. While females tended to be bolder and learned the spatial task faster, they showed lower memory retention abilities than males. Personality traits were also found to affect cognitive abilities among individuals. In general, the presence of a predator decreased performance latencies. However, bolder individuals were less affected and emerged more quickly from the refuge chamber than shy individuals. Our results point to the complex interplay of ecological context along with inherent correlations across personality traits that decide the overall personality and cognitive responses among individuals even within populations. These findings thus highlight the importance of an inclusive approach that combines personality and cognition studies for understanding variations within populations.

Aquatic Ecosystem Health & Management, 2017

Freshwater ecosystems of the Western Ghats (comprised primarily of rivers, lakes, and wetlands; l... more Freshwater ecosystems of the Western Ghats (comprised primarily of rivers, lakes, and wetlands; less than 0.01% of the total water on Earth) harbor diverse communities of flora and fauna which are among the most threatened in the world. It is projected that habitat loss will lead to significant decline in freshwater fish diversity. Many rivers that are expected to lose fish species are located in tropical and sub-tropical countries. The freshwater diversity of the Western Ghats (one of the global biodiversity hotspots) is particularly vulnerable to recent expansion of human population and development in the region. The present study is an example of how baseline data on fish assemblages in disturbed and undisturbed river systems of the Western Ghats can be employed in developing conservation prioritization plans for tropical river systems. Analyses of beta diversity patterns along river gradients indicated the sensitivity of species turnover to altered habitats and polluting industries near study sites. Null model analyses was used to investigate assemblage structure across disturbed and undisturbed sites on the rivers, which revealed that structure of species co-occurrences depended on the extent of human disturbance in the rivers. A method of ranking based on the Index of Biotic Integrity (IBI) was used to categorize disturbance levels of different sites. A combination of approaches of assemblage structure together with ranking of the IBI will help in developing conservation strategies for the region and prioritization plans for management at local and regional scales.

Aquatic Sciences, 2018

Flow regulations, human activities and drying events have been shown to drive diversity patterns ... more Flow regulations, human activities and drying events have been shown to drive diversity patterns of stream fish communities globally. Along with alpha-diversity distributions across space and time, study of beta-diversity patterns provides a deeper understanding of the mechanisms and processes of overall diversity distributions. It has been shown that water flow conditions can determine the beta-diversity patterns in stream fish communities: in general, perennial habitats are more similar, while intermittent and regulated conditions tend to increase dissimilarities among sites. However, it is not clear whether these patterns result from changes in abundance replacement or from differences in species abundance. Here, we investigated beta-diversity patterns in tropical fish communities of central India and their relation to habitat structural properties and water conditions. We performed our analysis for the overall region (18 sites) and also across three distinct flow conditions (6 sites for each flow regime). We used a partitioning framework to uncover the contribution of abundance replacement and abundance difference to beta-diversity patterns for the overall region and for three flow conditions separately. Our results suggest that at a regional scale all the sites show an equal contribution of replacement and abundance difference components, while seasonal samples were homogeneous. Our results confirmed that intermittent and regulated sites are more heterogeneous than perennial sites. The observed changes in beta-diversity in intermittent and regulated sites were related to both abundance difference and replacement components. Dissimilarities between sites were explained by physicochemical (temperature, pH, dissolved oxygen) parameters but not by habitat structural (stream width, depth) parameters.

Royal Society Open Science, 2015

Winner–loser relations among group-living individuals are often measured by the levels of aggress... more Winner–loser relations among group-living individuals are often measured by the levels of aggressive interactions between them. These interactions are typically driven by competition for resources such as food and mates. It has been observed in recent studies on zebrafish that dominant males generally have higher total reproductive success than their less aggressive subordinate counterparts. This study aimed to test whether males who monopolized a food resource (winners) also displayed higher levels of aggression than the males who were unsuccessful (losers). Further, the study also tested whether the same ‘winner’ males were also able to monopolize interactions with females during courtship. The results from these experiments showed that while males monopolizing food resources (winners) demonstrated higher levels of agonistic interactions than the losers, the average number of courtship interactions initiated by either of the males (i.e. winners/losers) with a female was not signif...