sarah.kwong@my.jcu.edu.au
Recipient of an AIMS@JCU Scholarship
PhD
ARC Centre of Excellence Coral Reef Studies
sarah.kwong@my.jcu.edu.au
PhD
ARC Centre of Excellence Coral Reef Studies
Age determination in the Pacific crown-of-thorns seastar (Acanthaster cf. solaris): novel molecular approaches
Sarah's journey into marine biology is driven by a profound passion for the ocean. Originally trained as a pharmacist in Hong Kong, she chose to change course and follow a different calling, becoming a Scuba Diving Instructor at the Great Barrier Reef and the Maldives. Witnessing the devastating effects of the 2016 mass coral bleaching event firsthand, Sarah was inspired to dedicate her career to protecting coral reef ecosystems.
In 2019, she moved to Australia to pursue a Master of Science in Marine Biology at James Cook University (JCU). Her thesis, conducted at the Australian Institute of Marine Science (AIMS), focused on quantifying the shedding and degradation rates of environmental DNA (eDNA) from the Pacific crown-of-thorns seastar (CoTS; Acanthaster cf. solaris). This experience sparked her keen interest in scientific research, leading her to pursue a PhD in molecular ecology.
Sarah’s fascination with molecular ecology stems from its transformative potential to address pressing ecological challenges. During her PhD, she explored innovative approaches for age estimation in CoTS, developing the first epigenetic clock for this species while advancing understanding of their telomere dynamics. This research highlights her strong interest in epigenetics, particularly DNA methylation, as a powerful tool for uncovering the molecular processes that shape marine life. Sarah is passionate about utilizing cutting-edge molecular techniques and applying her expertise in bioinformatics to analyse complex datasets, contributing to meaningful advancements in marine research and conservation.
Age determination in the Pacific crown-of-thorns seastar (Acanthaster cf. solaris): novel molecular approaches
2021 to 2025
This project focuses on developing novel molecular approaches to determine the chronological age of CoTS, a coral-eating marine pest notorious for its role in coral reef degradation. This research investigates two key age markers — telomere length and DNA methylation. While these markers are well-established in vertebrate ageing studies, their applicability to invertebrates remains largely unexplored. By employing advanced technologies such as Oxford Nanopore sequencing, this study seeks to address this knowledge gap and establish a reliable ageing tool for CoTS.
Age estimation in CoTS has been challenging, in part due to their growth plasticity, which makes size-based age estimation unreliable and results in a lack of robust population age structure data. Developing a reliable ageing tool would enable the construction of population age structures in outbreak populations, allowing researchers to trace back to the years of settlement and gain valuable insights into the processes that initiate outbreaks. This is critical for designing effective management strategies that address the root causes of outbreaks. Furthermore, access to population age structure data would enhance our understanding of CoTS population dynamics, improve population modelling, and strengthen predictions of future outbreaks. More broadly, the methodologies developed in this project hold significant potential for application in other species, paving the way for advancements in age estimation in invertebrates.
Known-age specimens of CoTS, spawned and raised at the Australian Institute of Marine Science (AIMS), form the basis of this PhD research. To examine telomere length in these specimens, a quantitative PCR (qPCR) protocol adapted from human studies has been optimized. Relative telomere lengths are analysed across juveniles and adults to explore age-related patterns. Additionally, the study investigates the effect of tissue types and dietary conditions on telomere dynamics in CoTS.
For DNA methylation analysis, this project employs Oxford Nanopore Technologies (ONT) to generate high-resolution, genome-wide methylation data across five age groups. This enables the identification of age-related CpG sites within the CoTS genome, where methylation levels show significant associations with age. Using these CpG sites, an epigenetic clock — a predictive model for age estimation — is constructed, offering a reliable tool to estimate the age the CoTS.
This project provides the first evidence of age-related telomere attrition in CoTS, demonstrating that adult CoTS generally exhibit shorter telomere lengths compared to juveniles. However, significant variation in telomere length within age classes, influenced by factors such as diet, limits its reliability for resolving specific cohorts. While telomere length may not provide accurate age estimations, the findings suggest it could serve as a biomarker for factors such as health or stress status. These aspects are worth further investigation due to their potential relevance for management.
For DNA methylation, this project generated the first comprehensive methylome profile of CoTS, establishing a foundational understanding of their epigenetic landscape. Building on these methylome profiles, age-related CpG sites were identified and used to construct an epigenetic clock, an age estimation model capable of predicting the age of CoTS with a mean absolute error of 3.7 months. This level of accuracy enables differentiation between annual cohorts, offering a reliable and practical tool for monitoring population age structures and testing outbreak initiation hypotheses.
Coral reefs,
Crown of Thorn Starfish,
Echinoderms,
Ecology,
Genetics,
Management tools,
Molecular techniques