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In a surprising discovery, the vibrant clownfish, known for its orange and white stripes and popularized by the film “Finding Nemo,” has demonstrated an incredible survival mechanism. A recent study reveals that these resilient fish are capable of shrinking in size to enhance their odds of enduring marine heat waves. This remarkable adaptation sheds light on the potential for some marine life to adjust to the escalating challenges of climate change.
Clownfish Shrink to Survive Marine Heatwaves
A research team from Newcastle University, England, conducted a five-month observation of 134 clownfish at a conservation facility in Papua New Guinea during a 2023 marine heatwave. The university released a statement detailing the findings of the study.
Monitoring Clownfish in a Changing Climate
Melissa Versteeg, the study’s lead author and a PhD candidate at Newcastle University, diligently measured the length of each fish monthly. Water temperatures were also recorded every 4-6 days to correlate environmental changes with the clownfish’s physical responses.
Key Findings: Size Reduction and Survival
Versteeg’s meticulous measurements revealed a direct correlation between rising temperatures and shrinking fish size. Her findings marked the first documented instance of a coral reef fish exhibiting size reduction in response to changing environmental conditions.
- Shrinking Phenomenon: As temperatures increased, the clownfish exhibited a noticeable decrease in length.
- Survival Advantage: This size reduction boosted their survival rate during periods of heat stress by as much as 78%.
Growth Plasticity: An Unexpected Adaptation
“I was very surprised by the findings,” Versteeg told CNN, highlighting the “incredible growth plasticity” displayed by the clownfish. She emphasized the species’ remarkable ability to adapt to environmental stressors.
“We’re seeing that they have a great capacity to respond to what the environment throws at them,” she said.
Implications of Size Reduction
While shrinking provides an immediate survival advantage, it may have long-term consequences for the clownfish population. Theresa Rueger, a senior study author and marine ecologist at Newcastle University, noted that smaller fish typically reproduce less, potentially impacting population numbers.
“But our study also found that because they can shrink and they have this great growth plasticity, they survive better during marine heatwaves,” she said.
“That could be a very positive thing, that they have that capacity and can adapt to their circumstances in that way.”
Other Species Exhibiting Similar Traits
Clownfish are not alone in their ability to shrink. Marine iguanas, for example, can reabsorb bone material to reduce their size during times of environmental stress, according to Versteeg.
Social Dynamics and Survival
The study also uncovered a connection between shrinking and social dynamics. Clownfish that shrank in tandem with their breeding partners had a greater likelihood of survival. This is closely linked to the hierarchical structure of the species, with the larger female dominating the smaller male.
Shrinking together helps maintaining symbiotic relationship between male and female and prevents conflicts.
The Symbiotic Relationship with Anemones
Clownfish share a symbiotic relationship with sea anemones, specifically Heteractis magnifica and Stichodactyla gigantea. These anemones offer protection to the clownfish, which Rueger describes as “bad swimmers.”
“If they leave the anemone they have very little time before they get eaten, frankly,” she added, which means it is important for them not to fight with their partner and risk being forced out into the open sea.
Future Research Directions
The research team is now focused on unraveling the mechanisms that enable this growth and shrinkage capacity. They also plan to examine whether other fish species possess similar abilities.
“If individual shrinking were widespread and happening among different species of fish, it could provide a plausible alternative hypothesis for why the size (of) many fish species is declining,” said Rueger.
Versteeg’s Perspective on Clownfish Research
- Why they’re ideal for long period studies.
- Unique markings and ease of tracking.
The symbiotic relationship with their home anemone is another reason why clownfish are so fascinating, said Versteeg.
“They don’t move, that’s where they’re at. You’re able to just track them over time, and they’re uniquely marked and they’re relatively easy to catch,” she said.
“You really know who you’re dealing with, and you can really follow them over extensive periods of time, which is unique,” added Versteeg.
The study’s findings were published in the journal Science Advances.