A new study finds that sharks adhere to the ‘two-thirds scaling law’ with mind-boggling precision. This discovery has the potential to change the way we think about foundational biological concepts across the animal kingdom. A team at James Cook University (JCU) performed the compelling research. Their results demonstrate that the scaling law, a fundamental tenet of biological science for more than 100 years, holds true in these large, linked and enigmatic ocean habitats.
Joel Gayford, the lead author and a Ph.D. candidate at JCU, directed the study. He then digitally modeled the body shapes of 54 different shark species. The study used high-resolution 3D scans. These scans, produced in partnership with computer graphics artist Johnson Martin, were used to study how sharks’ surface area and volume scales with their size. These results were recently published in the Royal Society Open Science and can be found here DOI 10.1098/rsos.242205.
Understanding the Two-Thirds Scaling Law
According to the ‘two-thirds scaling law’ as an animal gets larger and larger, its surface area to its volume ratio would decline exponentially. According to the metabolic theory of ecology, as an organism gets bigger, its volume—which is correlated with mass—expands quicker than its surface area. This principle has been fundamental for scientists working across disciplines, illuminating major processes in physiology, ecology, and evolution.
Sharks, some of the most evolutionarily distinct vertebrates thanks to their unique adaptations and ecological roles, offer a captivating model for testing this scaling law. The research ultimately found that their body forms are very close to what would be expected based on this law. This discovery demonstrates that their growth patterns are stable in all species. This discovery highlights the law’s significance in gauging sharks and in a wider biological scope.
So when Associate Professor Joel Gayford received the findings of new research, he was understandably excited. “It’s remarkable to see how well sharks conform to this longstanding theory,” he stated. Professor Rummer wrote on social media about what it felt like to save a minke whale. He noted that these findings are critical for understanding biological scaling in vertebrates.
Methodology of the Study
To solve the various aspects of this puzzle, the team used cutting-edge digital modeling techniques. They studied 54 species of sharks by making high-resolution 3D scans of them, enabling unique level of analysis into their body shapes. This well-rounded approach made a nice basis for rigorous testing of the scaling of whole-organism surface area and volume.
The partnership with Johnson Martin was key in creating scientifically accurate, yet aesthetically beautiful depictions of the shark species being researched. The researchers used these models to determine the effects of size on shark shape and structure. This foundation of work permitted fascinating new realizations about their biology’s scaling.
The complex modeling accounted for the varying sizes and conditions of each individual shark. It further measured their sizes to compare them to the two-thirds scaling law. The results were stable and striking, further establishing the predictive potency of this venerable biological truism.
Implications for Biological Understanding
The finding that sharks are such strong obeyors of the two-thirds scaling law promises profound ramifications for biology. It implies that there are more general rules about how to grow and take form, that underlie these contrasting species in the animal world. At the same time, researchers are still working to understand these patterns. They are just beginning to discover how a variety of organisms are adapting their physical make-up to their environments.
This unique approach has profound implications for evolutionary biology, especially for long-lived aquatic species such as sharks. By understanding how size affects surface area and volume in these complex animals, scientists can better comprehend their physiology and ecology.