Biology subjects

Madhav, M.

Publications and source records attributed to Madhav, M..

7 recordsLinked to original sources

bioRxiv2026

NC4touch: An open-source networked touchscreen apparatus for rodent behavioral testing

In recent years, rodent touchscreen-based paradigms have gained popularity for their flexible task design, automated data collection and improved standardization. These devices minimize experimenter intervention and contribute to more replicable and reliable research. However, the high costs and proprietary hardware / software associated with commercially available systems present a financial barrier for smaller labs or researchers with limited resources. To address this issue, we developed "NC4Touch", an open-source scalable, modular rodent testing apparatus. It features three independent touchscreens and a feeding port for easy use in a wide array of tests comparable to those available with standard operant chambers, with the added benefit that visual stimuli can be highly customized. The system includes a user-friendly graphical interface that offers real-time control, task customization, video recording, and data management. We demonstrate its effectiveness in a visual discrimination task using both rats and mice. Several devices can be operated in parallel from the same computer and user interface, allowing high- throughput data collection. We provide detailed assembly instructions for the hardware and well- documented and easily-configurable software. We hope that the affordable open-source nature of NC4Touch will expand the scope of behavioral testing, allowing researchers to overcome traditional financial barriers and create a more collaborative community. Significance StatementTouchscreen-based testing is a powerful tool for assessing cognition in rodent models, however commercial systems remain cost-prohibitive for many researchers. NC4Touch is a rodent touchscreen apparatus that provides an open-source, customizable, and affordable alternative that enables high-throughput, cognitive testing in both mice and rats. By lowering financial barriers and promoting hackability, this system enables greater accessibility and collaboration in research.

animal behavior and cognition↗

bioRxiv2026

Hippocampal theta frequency as a readout of path-integration recalibration

Understanding how the brain represents hidden variables is a fundamental challenge. In navigation, the internal path-integration gain is often masked by external landmarks that override the path integrator. Path integration can recalibrate its gain when allothetic and idiothetic cues conflict, but the real-time dynamics of this process are hidden to direct observation. Here, we demonstrate that theta frequency provides an error signal between the observable hippocampal gain and the internal path-integration gain. Theta frequency decreased as conflict between landmark-driven hippocampal gain and path-integration gain increased and recovered as the path-integration gain recalibrated to the new gain. A continuous attractor model replicated these dynamics, suggesting that the theta-frequency drop is driven by the misalignment of allothetic and idiothetic inputs, reducing the excitatory drive to the network. Thus, theta frequency provides a real-time readout of internal gain-error signals, offering a novel methodology to estimate hidden cognitive variables through observable physiological oscillations.

neuroscience↗

bioRxiv2022

Advances in non-invasive tracking of wave-type electric fish in natural and laboratory settings

Recent technological advances greatly improved the possibility to study freely behaving animals in natural conditions. However, many systems still rely on animal-mounted devices, which can already bias behavioral observations. Alternatively, animal behaviors can be detected and tracked in recordings of stationary sensors, e.g. video cameras. While these approaches circumvent the influence of animal-mounted devices, identification of individuals is much more challenging. We take advantage of the individual-specific electric fields electric fish generate by discharging their electric organ (EOD) to record and track their movement and communication behaviors without interfering with the animals themselves. EODs of complete groups of fish can be recorded with electrode arrays submerged in the water and then be tracked for individual fish. Here, we present an improved algorithm for tracking electric signals of wave-type electric fish with unprecedented accuracy. Our algorithm benefits from combining and refining previous approaches of tracking individual specific EOD frequencies (EODf) and spatial electric field properties. In this process, the similarity of signal pairs in extended data windows determines their tracking order, making the algorithm more robust against detection losses and intersections. We quantify the performance of the algorithm and show its application for a data set recorded with a 64-electrode array in a stream in the Llanos, Colombia, where we managed, for the first time, to track Apteronotus leptorhynchus over many days. These technological advances make electric fish a unique model system for a detailed analysis of social and communication behaviors, with strong implications for our research on sensory coding.

animal behavior and cognition↗

bioRxiv2019

Transinfection of buffalo flies (Haematobia exigua) with Wolbachia and effect on host biology

A widespread insect endosymbiont Wolbachia is currently of much interest for use in novel strategies for the control of insect pests and blocking transmission of insect-vectored diseases. Wolbachia-induced effects can vary from beneficial to detrimental depending on host biology and the genetic background of the infecting strains. As a first step towards investigating the potential of Wolbachia for use in the biocontrol of buffalo flies (BF), embryos, pupae, and adult female BF were injected with three different Wolbachia strains (wAlbB, wMel and wMelPop). BF eggs were not easily injected because of their tough outer chorion and embryos were frequently damaged resulting in less than 1% hatch rate of microinjected eggs. No Wolbachia infection was recorded in flies successfully reared from injected eggs. Adult and pupal injection gave a much higher survival rate and resulted in somatic infection and germinal tissue infection in surviving flies with transmission to the succeeding generations on a number of occasions. Investigations of infection dynamics in flies from injected pupae confirmed that Wolbachia were increasing in numbers in BF somatic tissues and ovarian infections were confirmed with wMel and wMelPop in some instances, though not with wAlbB. Measurement of fitness traits indicated reduced longevity, decreased and delayed adult emergence, and reduced fecundity in Wolbachia-infected flies in comparison to mock-injected flies. Furthermore, fitness effects varied according to the Wolbachia strain injected with most marked reductions seen in the wMelPop-injected flies and least severe effects seen with the wAlbB strain.

microbiology↗

bioRxiv2019

Wolbachia successfully replicate in a newly established horn fly, Haematobia irritans irritans (L.) (Diptera: Muscidae) cell line

BACKGROUNDHaematobia spp., horn flies (HF) and buffalo flies (BF), are economically important ectoparasites of dairy and beef cattle. Control of these flies relies mainly on the treatment of cattle with chemical insecticides. However, the development of resistance to commonly used compounds is compromising the effectiveness of these treatments and alternative methods of control are required. Wolbachia are maternally transmitted endosymbiotic bacteria of arthropods that cause various reproductive distortions and fitness effects, making them a potential candidate for use in the biological control of pests. RESULTSHere we report the successful establishment of a continuous HF cell line (HIE-18) from embryonic cells and its stable transinfection with Wolbachia strain wAlbB native to mosquitoes, and wMel and wMelPop native to Drosophila melanogaster. The established HIE-18 cells are typically round and diploid with ten chromosomes (2n = 10) or tetraploid with 20 chromosomes (4n=20) having a doubling time of 67.2 hours. Wolbachia density decreased significantly in the HIE-18 cells in the first 48 hours of infection, possibly due to overexpression of antimicrobial peptides through the Imd immune signalling pathway. However, density recovered after this time and stably Wolbachia-infected HIE-18 cell lines have now all been subcultured more than 50 times as persistently infected lines. CONCLUSIONThe amenability of HF to infection with different strains of Wolbachia suggests the potential for use of Wolbachia in novel approaches for the control of Haematobia spp. Further, the availability of the HIE-18 cell line will provide an important resource for the study of genetics, host-parasite interactions and chemical resistance in Haematobia populations.

microbiology↗

bioRxiv2019

Complete genome assembly of the Wolbachia endosymbiont of the horn fly Haematobia irritans irritans: a supergroup A strain with multiple horizontally acquired cytoplasmic incompatibility genes

The horn fly, Haematobia irritans irritans, is a hematophagous parasite of livestock distributed throughout Europe, Africa, Asia, and the Americas. Welfare losses on livestock due to horn fly infestation are estimated to cost between USD 1-2.5 billion annually in North America and Brazil. The endosymbiotic bacterium Wolbachia pipientis is a maternally inherited manipulator of reproductive biology in arthropods and naturally infects laboratory colonies of horn flies from Kerrville, USA and Alberta, Canada, but has also been identified in wild-caught samples from Canada, USA, Mexico and Hungary. Reassembly of PacBio long-read and Illumina genomic DNA libraries from the Kerrville H. i. irritans genome project allowed for a complete and circularised 1.3 Mb Wolbachia genome (wHae). Annotation of wHae yielded 1249 coding genes, 34 tRNAs, three rRNAs, and five prophage regions. Comparative genomics and whole genome Bayesian evolutionary analysis of wHae compared to published Wolbachia genomes suggests that wHae is most closely related to and diverged from Wolbachia supergroup A strains known to infect Drosophila spp. Whole-genome synteny analyses between wHae and closely related genomes indicates that wHae has undergone convoluted genome rearrangements while maintaining high nucleotide identity. Comparative analysis of the cytoplasmic incompatibility (CI) genes of wHae suggests two phylogenetically distinct CI loci and acquisition of another CifB homolog from phylogenetically distant supergroup A Wolbachia strains suggesting horizontal acquisition of these loci. The wHae genome provides a resource for future examination of the impact Wolbachia may have in both biocontrol and potential insecticide resistance of horn flies.\n\nImportanceHorn flies, Haematobia irritans, are obligate hematophagous parasites of cattle having significant effects on production and animal welfare. Control of horn flies mainly relies on the use of insecticides, but issues with resistance have increased interest in development of alternative means of control. Wolbachia pipientis is an endosymbiont bacterium known to have a range of effects on host reproduction such as induction of cytoplasmic incompatibility, feminization, male killing, and also impacts on vector transmission. These characteristics of Wolbachia have been exploited in biological control approaches for a range of insect pests. Here we report the assembly and annotation of the circular genome of the Wolbachia strain of the Kerrickville, USA horn fly (wHae). Annotation of wHae suggests its unique features including the horizontal acquisition of additional transcriptionally active cytoplasmic incompatibility loci. This study will provide the foundation for future Wolbachia-induced biological effect studies for control of horn flies.

microbiology↗

bioRxiv2019

Spooky interaction at a distance in cave and surface dwelling electric fishes

Glass knifefish (Eigenmannia) are a group of weakly electric fishes found throughout the Amazon basin. We made recordings of the electric fields of two populations of freely behaving Eigenmannia in their natural habitats: a troglobitic population of blind cavefish (Eigenmannia vicentespelaea) and a nearby epigean (surface) population (Eigenmannia trilineata). These recordings were made using a grid of electrodes to determine the movements of individual fish in relation to their electrosensory behaviors. The strengths of electric discharges in cavefish were larger than in surface fish, which may be a correlate of increased reliance on electrosensory perception and larger size. Both movement and social signals were found to affect the electrosensory signaling of individual Eigenmannia. Surface fish were recorded while feeding at night and did not show evidence of territoriality. In contrast, cavefish appeared to maintain territories. Surprisingly, we routinely found both surface and cavefish with sustained differences in electric field frequencies that were below 10 Hz despite being within close proximity of less than one meter. A half century of analysis of electrosocial interactions in laboratory tanks suggest that these small differences in electric field frequencies should have triggered the jamming avoidance response. Fish also showed significant interactions between their electric field frequencies and relative movements at large distances, over 1.5 meters, and at high differences in frequencies, often greater than 50 Hz. These interactions are likely envelope responses in which fish alter their EOD frequency in relation to changes in the depth of modulation of electrosocial signals.

neuroscience↗