Uncovering the Fascinating Discovery: Sharks Thriving in Australian Sponge Habitats

John Pogonoski, an ichthyologist in Australia, was not to be deceived by any moray eels. He knew that these serpentine fish liked to hide among the nooks and crannies of large sponges. However, during his survey of sponges collected from a remote seabed off the coast of Western Australia, he made a startling discovery – a small shark tail protruding from a sponge’s cavernous body.

The stray tail belonged to Atelomycterus fasciatus, commonly known as a banded sand catshark. And it wasn’t alone. Mr. Pogonoski, who works at the Commonwealth Scientific and Industrial Research Organization, or CSIRO, and his colleagues found up to 30 of these small predators crammed into a single sponge. The findings, published in the Journal of Fish Biology, represent the first known instance of any shark using sponges as a habitat.

“We often see sharks in small caves and hiding within crevices in coral reefs,” said David Shiffman, a shark biologist and faculty research associate at Arizona State University, who was not involved in the study. “But sponges? That’s something new.”

When we think of sharks, we often imagine massive great whites and heavy hammerheads. However, these cartilaginous carnivores come in various sizes. The banded sand catshark, reaching a maximum length of about 1.5 feet, is among the smaller species.

“Due to their small size, they are quite vulnerable to predation by larger sharks and fish,” said Helen O’Neill, a fish biologist at CSIRO’s Australian National Fish Collection in Tasmania and one of the authors of the study. During the night, catsharks hunt for prey on the seafloor, but Ms. O’Neill believes that during the day, “they safely hide within the sponges” to avoid becoming prey themselves.

It turns out that burrowing into sponges is a popular activity among these sharks. After Mr. Pogonoski’s fortunate discovery, the researchers ultimately found 57 catsharks inhabiting two types of sponge. These sharks varied in age and gender, indicating that hiding in sponges is an enjoyable experience for the entire family. Since other shark species lay their eggs on the exterior of sponges, Dr. Shiffman suggests that the catsharks might be using these porous habitats to raise their offspring. “Animals are always seeking ways to protect their young,” he added.

Another question arises: do the sponges gain any benefits from accommodating the sharks?

“Further research is needed to determine whether the sponge benefits from the presence of the sharks,” said Ms. O’Neill. She proposes that the sharks might consume small fish or invertebrates that would otherwise feed on the sponge. “They act as security guards for the hotel,” she suggested playfully.

Since this was an opportunistic observation, much remains unknown about the behavior and motivations of the sharks inside the sponges. “No one witnessed the sharks entering the sponges, or how long they stay inside, or what they do,” explained Dr. Shiffman. The unexpected nature of this discovery also means that no follow-up research is currently planned, according to Ms. O’Neill. However, she stated that they will keep a close watch during future expeditions.

With over 530 species of sharks, many as small as the banded sand catshark, it is quite likely that other sharks also spend time inside sponges. Given the limited knowledge about the banded sand catshark, the possibilities are endless for what it – and other species – might be up to.

“Sharks are not one-dimensional creatures,” remarked Dr. Shiffman. “They come in all shapes, sizes, and colors imaginable. They exhibit all sorts of unusual behaviors, and we are constantly learning new things about them.”