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"Crown-of-thorns" starfish genetics may help protect reefs

The Great Barrier Reef, a breathtaking underwater world teeming with life, faces a formidable foe: the crown-of-thorns starfish.

These coral-munching marauders have wreaked havoc on the reef, leaving behind a trail of bleached and lifeless coral skeletons. But a glimmer of hope has emerged from an unlikely source — the starfish’s own genes.

Crown-of-thorns starfish and coral reefs

Crown-of-thorns starfish (COTS) present a significant ecological threat to coral reefs due to their voracious appetite for coral polyps, which are the living tissue that builds and sustains coral reefs. When COTS populations surge, they engage in extensive coral predation, leading to severe degradation of reef structures.

This predation reduces coral cover drastically, which has a cascading effect on the entire marine ecosystem. Healthy coral reefs are biodiversity hotspots, providing habitat and food for a myriad of marine species.

When COTS decimate coral populations, the loss of habitat and food sources results in a decline in marine biodiversity, affecting fish populations, invertebrates, and other marine life that rely on the reef.

Starfish and slow coral reef recovery rate

The impact of COTS is further exacerbated by the slow growth and recovery rates of coral reefs. Coral regeneration is a lengthy process, often taking decades to recover from damage.

Frequent or severe COTS outbreaks can thus set back reef recovery for many years, hindering the ability of these ecosystems to bounce back.

Additionally, reefs weakened by COTS predation are more susceptible to other environmental stresses such as climate change, pollution, and overfishing. These additional stressors can compound the damage, making it even more challenging for the reef to recover.

As a result, controlling COTS populations is essential for preserving the health and resilience of coral reefs, which are vital for maintaining marine biodiversity, protecting coastal regions, and supporting local economies dependent on tourism and fishing.

Starfish behavior and gene expression

In a recent study, University of Queensland researchers Marie Morin and Mathias Jönsson embarked on a genetic quest to understand the inner workings of these destructive creatures. Their mission? To decipher the genetic code behind the starfish’s key behaviors, particularly their rampant reproduction.

“By understanding how crown-of-thorns starfish genes work, we can unlock the mechanisms behind their key behaviors and find ways to stop them breeding,” explains Morin.

The researchers focused on “gene expression,” the process by which genes are translated into action, producing proteins or RNA molecules. They discovered over 2,000 protein-coding genes that showed significant changes between summer and winter.

This finding sheds light on the seasonal rhythms and behaviors of the crown-of-thorns starfish, providing crucial insights into their biology and potential vulnerabilities. By understanding these patterns, scientists can better target their efforts to control the starfish population and protect coral reefs.

Disrupting starfish reproduction genes

The research team’s most significant finding was the identification of specific genes that play a crucial role in the crown-of-thorns starfish‘s reproductive processes, such as the timing of spawning or the development of reproductive organs.

This discovery is a major advancement, as it presents the possibility of developing targeted genetic interventions. These interventions could involve manipulating these identified genes to disrupt the starfish’s reproductive cycle, potentially by preventing fertilization, inhibiting the development of reproductive cells, or altering the timing of spawning. 

By disrupting the reproductive cycle, scientists could control the population growth of these starfish and mitigate their destructive impact on coral reefs, allowing the reefs to recover and thrive.

“This is a promising sign because if we can find ways to disrupt this communication genetically, it could stop the starfish reproducing,” says Morin.

Wild side of starfish genes

Unlike previous studies that relied on captive starfish, the research ventured into the heart of the Great Barrier Reef to analyze wild populations. This approach, says Professor Bernard Degnan, is crucial for understanding the true genetic makeup and behaviors of these creatures in their natural habitat.

“Analyzing marine animals in a lab can cause changes to the animal and its functional genetics,” Degnan explains. “By capturing crown-of-thorns starfish in the deep heart of the Great Barrier Reef (GBR), we were able find out what’s really happening in wild populations.”

Coral reef conservation

The implications of this research are far-reaching. Dr. Mary Bonin, GBR Foundation COTS Control Innovation Program Director, hails it as a game-changer in the fight to protect the reef.

“This exciting research paves the way for the development of new control tools to help address this threat to reef health,” says Dr. Bonin.

While COTS are native to the Great Barrier Reef, their population outbreaks pose a grave threat to the delicate coral ecosystem. By understanding and manipulating their genetics, scientists may be able to develop targeted, environmentally friendly solutions to control their numbers and safeguard the reef’s future.

Future of starfish and coral reefs

The next phase of this research will involve further genetic analysis and the exploration of natural pest control measures. The goal is to develop innovative strategies that can be deployed on the Great Barrier Reef to mitigate the damage caused by these starfish and restore the reef’s vitality.

The battle to save coral reefs is a race against time. Climate change, pollution, and other human-induced stressors have already taken a toll on these fragile ecosystems. But with remarkable research like this, there is hope that we can turn the tide and protect these underwater wonders for generations to come.

The crown-of-thorns starfish may be a formidable adversary, but by unraveling the secrets hidden within its genes, scientists are forging a new path towards a brighter future for coral reefs and the countless marine species that call them home.

The research is published in PLOS Biology.


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