A news study from Swansea University found that for a species of shark to become giant, it would need to first evolve adaptations that enhance feeding. This includes its ability to control body temperature or become a filter feeder.
Swansea University’s Dr. Catalina Pimiento and associates examined the biological traits of all elasmobranchs and ran a series of evolutionary models to seek how gigantism evolved over time. Pimiento used the two species with vastly different feeding behaviors — the megalodon and the modern whale shark — to map characteristics relating to body size, thermo-regulatory capacity, feeding mechanism and diet.
“Sharks provide an ideal case study to understand the evolutionary pathways leading to gigantism in the oceans because they display contrasting lifestyles and adaptations, and because they have an evolutionary history of at least 250 million years,” Pimiento said.
Pimiento and her associates found that sharks could become giants by following one of two possible evolutionary pathways; the mesothermic pathway, which consists of evolving the ability to self-control the temperature of their most important organs—or the filter-feeding pathway, which consists of evolving the ability to feed on microscopic plankton.
The mesothermic adaptation allows sharks to live in different types of habitats—including cold waters—and also hunt more effectively. The filter-feeding adaptation allows sharks to eat the most abundant food in the ocean—plankton.
However, there are risks involved for any shark following the evolutionary pathways that lead to gigantism. The mesothermic species need to consume big prey to maintain their high energetic demands, but when these prey are scarce, giant sharks are more susceptible to extinction. The scarcity of large prey in times of rapid climatic change was the most likely cause of the extinction of Megalodon.
These finding were published in the most recent issue of the scientific journal, Evolution.