Biology subjects

Wan, A. H. L.

Publications and source records attributed to Wan, A. H. L..

4 recordsLinked to original sources

bioRxiv2024

Colour preference in juvenile European lobster (Homarus gammarus)

Lobsters are high-value marine-fished species, and re-stocking efforts are essential for replenishing depleted wild populations and ensuring the longevity of these valuable marine species. The need for stock enhancement and hatcheries for aquaculture is vital to reduce the strain on wild populations. Therefore, environmental colours should be acknowledged when rearing lobsters in terms of behaviour, growth, movement, and survival. However, the behavioural effects the surrounding colour poses are virtually unknown. To better understand this behaviour, the movement of juvenile European lobsters (Homarus gammarus) was analysed through videos in two sub-trials. Lobsters were acclimated to custom-made alternating colour chambers, allowing for colour preferences based on individual movement. Sub-trial one alternated between black, red, blue, green, white, and yellow. The study identified that there was a significant preference for black (1 hour and 51 minutes) and red (1 hour and 33 minutes), indicating a potential underlying benefit for juvenile H. gammarus development. Despite this, little is known about the overall association of colour and lobster perception. A better understanding of environmental colour preference may guide the construction of aquaculture units to suit colour preference and enhance acclimation into newly released environments. This experiment aims to determine the preferred colours of stage four juvenile H. gammarus in a controlled laboratory setting and inspire further research to explore this unfamiliar field.

animal behavior and cognition↗

bioRxiv2023

Enhancing farmed striped catfish (Pangasianodon hypophthalmus) robustness using dietary β-glucan

{beta}-glucan is a well-documented feed additive for its potent immunostimulatory properties in many farmed fish species. This study examined how it can also be a promising growth promoter, modulate antioxidant enzyme activities, and act as an anti-stress agent in striped catfish (Pangasianodon hypophthalmus). A 12-week feeding experiment was untaken to determine the effects of dietary {beta}-glucan supplementation at graded levels (0, 0.5, 1.0, and 1.5 g kg-1). Measured indicators suggest that a dietary inclusion level of 1.5 g kg-1 {beta}-glucan gave the highest positive responses: weight gain (120.10 g fish-1), survival (98.30 %), and lower FCR (1.70) (P<0.05). Whole body proximate analysis had only revealed that crude protein was significantly affected by the dietary inclusion of {beta}-glucan (P<0.05), with the highest protein content (19.70 %) being in fish that were fed with 1.5 g kg-1 {beta}-glucan. Although other inclusion levels (i.e., 0.5 and 1 g kg-1) of {beta}-glucan did not enhance body protein content (P>0.05). The assessment of fatty acid composition in muscle, liver, and adipose tissues showed modifications with the inclusion of {beta}-glucan. Antioxidative-related enzyme activities (inc. catalase, glutathione peroxidase, and superoxide dismutase) that were measured in the liver had higher levels when fed with {beta}-glucan inclusion diets (P<0.05). Following the feed trial, fish were subjected to crowding stress treatment. It was subsequently found that catfish fed with {beta}-glucan-based diet groups had lower levels of blood stress-related indicators compared to the control group with no dietary {beta}-glucan. The use of 1.5 g kg-1 of dietary {beta}-glucan resulted in the lowest measured levels of cortisol (43.13 ng mL-1) and glucose (50.16 mg dL-1). This study has demonstrated that the dietary inclusion of {beta}-glucan can have functional benefits beyond the immunological enhancements in striped catfish. Furthermore, its use can increase production levels and mitigate the stress associated with intensive farming practices.

zoology↗

bioRxiv2023

Influence of pseudo-green water on growth, colouration, and survival in European lobster (Homarus gammarus) larvae

With the depletion of European lobster (Homarus gammarus) wild stocks from historic overexploitation, the attention has turned towards restocking, stock enhancement programs and farming potential. The early life larval stages of the European lobster present a major barrier to hatchery production efforts due to low survival rates. Green water techniques are rapidly growing due to their ability to improve nutrition quality. This study explores the potential benefits of using pseudo-green water. This is determined by adding microalgae to the rearing environment of larvae by analysing the effects on growth and survival. The commonly used algal species: Tetraselmis suecica (TS), Dunaliella salina (DS), and Nannochloropsis sp. (N) were added as monoculture or mixture treatments to a controlled European lobster larvae-rearing environment over thirteen days. The trial consisted of seven permutations of algal treatments (TS, DS, N, TS+DS, TS+N, DS+N, and TS+DS+N) and one control group, with clear water conditions using length measurements, survival rates and colouration to determine treatment impacts at the end of the trial. Results indicate that mixtures of algal species outperformed monocultures and clear water regarding growth performance. Nannochloropsis sp. is of significant benefit to growth performance. Algal mixes containing Nannochloropsis sp. resulted in significantly better growth than D. salina monoculture treatment. There were no significant differences in survival rates between treatment groups.

developmental biology↗

bioRxiv2021

Key Drivers of Ecological Assembly in the Hindgut of Atlantic Cod (Gadus morhua) when Fed with a Macroalgal Supplemented diet - How Robust Is the Gut to Taxonomic Perturbation?

The microbiota in the gastrointestinal tract of any species is shaped by internal and external cues in addition to random events which can be difficult to disentangle from a range of interacting variables. Estimating ecological assembly processes can help elucidate these factors. In our study, farmed Atlantic cod (Gadus morhua) were fed a diet of 10% macroalgae supplement (Ulva rigida species [ULVA] or Ascophyllum nodosum [ASCO] or a non-amended control diet [CTRL]) over a 12-week period and the ecological assembly processes quantified. The CTRL samples showed selection (variable selection - divergence in communities related to selective environmental conditions) as a key assembly process, while dispersal limitation (limited movement results in divergent communities through stochastic processes) was a driver of the gut microbiome for fish fed the macroalgae supplemented diet at Week 12 (i.e., ASCO and ULVA). Fish from the ASCO grouping diverged into ASCO_N (normal) and ASCO_LG (lower growth), where ASCO_LG individuals found the diet unpalatable. The recruitment of new taxa over time was altered in the ASCO_LG fish, with the gut microbiome showing phylogenetic under dispersion (nepotistic recruitment of species). Finally, the gut microbiome (CTRL and ULVA only) showed increasing robustness to taxonomic disturbance over time and an increase in functional redundancy. This study advances our understanding of the ecological assembly and succession in the hindgut of juvenile Atlantic cod across dietary regimes. Understanding the processes driving ecological assembly in the gut microbiome, in fish research specifically, could allow us to manipulate the microbiome for improved health or resilience to disease for improved aquaculture production.

microbiology↗