How Do Hammerhead Sharks Form Their Unusual Heads? Scientists Capture the Formation of These Snouts in Developing Embryos

Among the many predators in the ocean, one of the most distinctive and recognizable are the hammerhead sharks, which the unusual shape of their heads can easily identify. For the first time, experts have unveiled this hammer's step-by-step formation in developing shark embryos.

Unusual Characteristics of Hammerhead Sharks

Hammerhead sharks are a unique species of shark that belong to the family Sphyrnidae. They are best known for their hammer-shaped head, flattened and laterally extended into a cephalofoil.

This unique head structure enables hammerhead sharks to gain excellent depth perception and vision since their eyes are positioned on either end of the cephalofoil. Aside from this, they also have serrated teeth, which are used as weapons in capturing crabs, bony fish, lobsters, and cephalopods.

Unveiling the Secrets of Hammerhead Formation

In an unprecedented study of one of the strangest aquatic animals, experts from the University of Florida documented how hammerhead sharks stretch and distort their skulls to form their unusually flat heads. According to UF biology professor Gareth Fraser, this study provides insight into the development of nature's wonder, which has not been seen before.

In this research, Fraser and his graduate student Steven Byrum led the detailed observation of the development of bonnethead sharks (Sphyrna tiburo), the smallest species of hammerhead shark. These animals abundantly thrive in the Gulf of Mexico and the Atlantic Ocean, where they spend their time near the shore, making them relatively easy to study.

They are looking at hammerhead development, which used to be a challenging task for scientists. Like most fish, sharks lay eggs that can be easily gathered and investigated in the laboratory. Meanwhile, hammerhead sharks give birth to live young, and it is exceedingly difficult to watch the step-by-step development of the embryos. Since most species are endangered, authorities prohibit the harvesting of sharks for research studies.

In response to this challenge, Fraser's team made the most of the existing specimens. With the help of their collaborators, the scientists gained access to embryos preserved from bonnetheads caught during other biological studies. According to the research team, such a close look at embryonic development may never happen again due to the difficulty of studying hammerheads.

A series of striking pictures reveal the development of hammerhead sharks during gestation. They discovered that the two-inch-long embryo suddenly widened their heads roughly halfway through gestation. The eyes that are still growing are then pushed out by the growing skull at unusual angles. The hammer's front pounds out in the following weeks as it pushes backward towards the gills. This creates the final form of the head with a shovel-like shape. After a couple of months, the one-foot-long shark is born with its fully-formed hammerhead.

This detailed documentation sets up future experiments determining how hammerheads control their head shape. It also provides insight into why these aquatic animals evolved their unusual features, which were thought to improve their vision and help detect the electrical movements of prey.