Biology subjects

Ng, T. H.

Publications and source records attributed to Ng, T. H..

3 recordsLinked to original sources

bioRxiv2025

A Controlled Test of Risk-Dependent Immune Investment in a Clonal Ant

Biological systems can benefit from distributing defensive investment unevenly, concentrating protection in parts of the system that face higher risk or hold greater strategic value. In social groups, individuals often face asymmetric infection risks based on their behavioural roles, raising the possibility that immune defences are plastically adjusted according to risk. In social insects, this idea has led to the hypothesis that individuals performing high-risk tasks, such as foraging, should invest more in constitutive immune defences to reduce transmission within the colony. However, testing this hypothesis has been hindered by confounding effects of genotype, age, and infection history. We use the clonal raider ant Ooceraea biroi to overcome these limitations. In this system, spontaneous behavioural specialisation between genetically identical, age-matched individuals creates variation in infection risk, while controlling for other sources of variation. We first annotated the O. biroi immune gene repertoire and sequenced the transcriptomes of 77 individuals that showed considerable behavioural variation. We then combined fine-scale individual behavioural tracking with three complementary measures of immune investment: immune-related gene expression, antibacterial activity, and survival following infection. Despite behavioural specialisation, we find no evidence that individuals engaging in higher-risk behaviours invest more in constitutive immune defences. These results contradict a long-standing hypothesis in the field and suggest limits to plastic immune allocation based on infection risk in social insect colonies.

ecology↗

bioRxiv2024

Dissecting the heat stress altering immune responses and skin microbiota in fish in a recirculating aquaculture system in Singapore

Environmental factors, probiotics and feed additives affect microbiota diversity in fish. Water temperature disrupts the composition and diversity of microbiota, with temperature changes triggering stress and immune responses in fish. In Singapore, water heat treatment is used to control and prevent disease outbreaks in farmed fish. Although gut microbiota responses to heat stress have been reported, little is known about the effects of heat treatment on fish immune responses and fish skin microbiota dynamics. Over a 3-mo interval, we investigated microbiota dynamics and fish immune responses associated with a heat treatment practice in a commercial fish farm with a recirculating aquaculture system (RAS). Tank water temperature was raised to 37-39 {degrees}C for 1 hour, every 2 weeks. Tank water and fish microbial communities were analysed by 16S amplicon sequencing, and host molecular expressions were determined by qPCR. We inferred that heat treatment increased stress and immune responses that protected fish from opportunistic infections. However, overreaction to temperature stress can cause dysbiosis of the skin microbiota and death. We also suggested the value of the skin microbiota Pseudomonadota: Bacteroidota (P:B) ratio as a biomarker for aquaculture fish health. IMPORTANCEAquaculture is an emerging economic activity to supply high-quality animal protein and reduce reliance on wild-caught fish products. Recently, there has been emphasis on intensive aquaculture, using a Recirculating Aquaculture System (RAS). In RAS, management of pathogens/parasites prevalence is a major challenge. Developing practical solutions for producing healthy juveniles in nursery systems will make profound contributions to sustainable aquaculture. In this study, we used an unconventional strategy, exposing juveniles to the pathobiome in the environment, followed by non-lethal heat shock treatments to enhance immunity. Short-term stress induced heat shock proteins that protected fish from opportunistic infections. We concluded that manipulating environmental-microbial-host interactions, together with enhanced functional capacity of fish immune response, has potential for disease control in aquaculture.

systems biology↗

bioRxiv2018

Meta-analysis of Reward Processing in Major Depressive Disorder: Distinct Abnormalities within the Reward Circuit?

Many neuroimaging studies have investigated reward processing dysfunction in major depressive disorder. These studies have led to the common idea that major depressive disorder is associated with blunted responses within the reward circuit, particularly in the ventral striatum. Yet, the link between major depressive disorder and reward-related responses in other regions remains inconclusive, thus limiting our understanding of the pathophysiology of major depressive disorder. To address this issue, we performed a coordinate-based meta-analysis of 41 whole-brain neuroimaging studies encompassing reward-related responses from a total of 794 patients with major depressive disorder and 803 healthy controls. Our findings argue against the common idea that major depressive disorder is primarily linked to deficits within the reward system. Instead, our results demonstrate that major depressive disorder is associated with opposing abnormalities in the reward circuit: hypo-responses in the ventral striatum and hyper-responses in the orbitofrontal cortex. The current findings suggest that dysregulated corticostriatal connectivity may underlie reward-processing abnormalities in major depressive disorder, providing an empirical foundation for a more refined understanding of abnormalities in the reward circuitry in major depressive disorder.

neuroscience↗