The mysteries of ghost sharks

This summer, a team of intrepid researchers from the University of Florida and the Seattle Aquarium will embark on a unique expedition. Their goal is to unravel the mysteries surrounding a resident of the deep – the elusive ghost shark, also known as a chimera.

Scientists will use remotely operated underwater vehicles (ROVs) to explore the nesting grounds of a special species of ghost shark known as the Pacific spotted ratfish or Hydrolagus colliei. These ghostly creatures, which can be found on the ocean floor, have a mysterious appeal that has intrigued scientists for years.

Gareth Fraser, associate professor of biology at the University of Florida, is leading this bold expedition. He notes that very little is known about these elusive shark relatives and even less about their spawning habits and embryonic development. The goal of the mission is to locate the places where these ghost sharks lay their eggs.

Ghost sharks, or chimaeras as they are officially called, have been separated from their shark and ray relatives by nearly 400 million years of evolution. Often attributed to the dark depths of the ocean, this enigmatic group of fish remains one of the most understudied and mysterious creatures.

While sharks have teeth on their skin, ghost sharks have smooth skin. They are also known for their large round eyes that help them navigate in the dark. Male chimaeras have a unique bulb on their forehead called a tenaculum, with sharp teeth that resemble shark teeth.

Fraser explains that they hypothesize that chimeras use this head clasp as a second “jaw” on their head to bite and attach themselves to the female during copulation. Ghost sharks are a very strange group of shark relatives whose biology makes them a bit otherworldly.

Studying these creatures is a challenge. Despite recent success in locating adult chimeras through deep-sea trawling projects, studies of adult fish have provided limited insight into their developmental processes. An upcoming study of ghost shark nesting sites this summer is groundbreaking – the first of its kind for this species.

Last year, scientists found different stages of fish development, from newly hatched calves to fully mature adults. This year, they will return to find their nursery grounds. The expedition was funded by a grant from the National Science Foundation and a Fraser UF startup grant.

Scientists also hope to find clues about the origin of the teeth. This knowledge could uncover valuable information for regenerative dental research in humans.

Ghost shark research is an important step in understanding the marine ecosystem and its unique inhabitants. These enigmatic creatures not only attract the attention of scientists, but also pique the interest of the general public.

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