Research Projects

With changing climatic conditions and high degree of urbanization, organisms need to exhibit wide variations in adaptive trait expressions, referred to as plasticity, in response to their diverse local environments. Plasticity contributes toward increased fitness of an organism within a particular environment, thus facilitating survival. One such plastic trait largely studied across taxa, is adaptation of visual sensitivity, particularly evident in species that rely heavily on visual cues to maintain behavioural performances. Visual adaptation is mostly governed by expressions of opsins, light sensitive proteins (one rod opsin for dim light vision, and seven different cone opsins for color vision) that show wide variations across different light conditions. Though plasticity of opsin expressions have been largely documented, a limited number of studies have looked at functional (performance in behavioural tasks) significance of such adaptations and proximate (genetic) mechanisms underlying the expression. In this proposal, I aim to investigate plasticity in opsin expressions in green chromides (GC), a member of the Cichlidae family. Cichlids are known to show a large degree of visual adaptations, and GC are known to occur in diverse natural habitats, ranging from clear freshwater to turbid, brackish waters. GC is native to India, and an economically important species. Previous research from my group showed GC to be highly social with significant preferences towards conspecifics (when compared to heterospecifics) to form shoals. We also demonstrated that GCs are highly dependent on visual cues (in white light conditions, broad spectrum:400-650 nm), both for the purpose of shoaling and to find food. We conducted transcriptome sequencing and characterized opsins (SWS1, SWS2a, SWS2b, RH2a, RH1) expressed in GC under the given light conditions. Since behavioural expressions in GC are dependent on visual cues, we hypothesized that under altered light conditions, GC may need to modulate opsin expressions to recognize conspecifics (for shoaling purposes) and to localize food, in order to gain fitness. With this background, I aim to study plasticity of opsin expressions (via qPCR method) in GC, housed under laboratory conditions (objective 1), across both temporal (at fixed intervals over a period of 60 days) and spatial (different, narrow spectra, light environments) scales. The proposal will also measure natural variations (objective 2; N=4 wild populations) in opsin expressions, across temporal (for a population between winter and monsoon seasons) and spatial (populations differing in turbidity levels, and in turn in their light environments) scales. In both housed and natural populations, irradiance spectra will be measured to precisely determine the light environment. Additionally, for the laboratory populations (objective 1), I also plan to assess functional significance (via behavioural assays measuring shoaling, social preferences, and foraging) of opsin expressions, at fixed, 15-day intervals over the housing period and across different light environments. To investigate proximate mechanisms (objective 3), I plan to correlate amino acid sequence of the opsin region with expression profile for a given natural population, and compare and contrast across populations to determine population-level diversity of opsin genes. Such a comparative approach will determine whether the observed plasticity in opsin expressions is maintained by genetic effect (possibly via nucleotide polymorphism, evolutionary adaptation) or environmental effect (modulating expression in response to light cues, ecological adaptation) or an interplay of both. Overall, the proposal will draw linkages among gene, environment, protein and behavioral processes, and will showcase how such integration contributes towards overall fitness of organisms in a given environment, a fundamental step towards understanding the mechanisms that maintain biodiversity.