Banded sand catsharks are a species of small, nocturnal sharks that live on the sea floor in the Indo-West Pacific Ocean.
They are usually found in shallow waters off the coast of northern Australia, where they feed on small fish and invertebrates.
However, a recent discovery by scientists has revealed a surprising and unique behavior of these sharks: they hide inside sea sponges.
Banded sand catsharks use sea sponges as shelters
CSIRO via Getty Images
Sea sponges are simple aquatic animals that belong to the phylum Porifera. They have porous bodies that filter water to obtain food and oxygen.
They come in various shapes, sizes, and colors, and some can grow up to a meter in diameter.
Sea sponges are often mistaken for plants, but they are actually animals that lack true tissues and organs.
Scientists from the University of Gothenburg and Martin Luther University Halle-Wittenberg found that banded sand catsharks use sea sponges as shelters during their expeditions to survey marine biodiversity in marine parks off the coast of north-western Australia.
They observed that some large sponges contained up to 30 banded sand catsharks inside them, ranging from 12 to 39 centimeters in length.
This was the first known observation of a shark species living inside a sponge.
The scientists collected some of the sponges and their shark inhabitants and examined them on board their research vessel.
They found that the sponges belonged to different species, but all had many folds, crevices, and canals that provided spaces for the sharks to enter and exit.
The sponges were found at depths ranging from 32 to 106 meters.
Another possible reason is to conserve energy, as hiding inside sponges may reduce the need for swimming and hunting.
A third possible reason is to regulate their body temperature, as sponges may provide insulation from the cold water.
The scientists also suggested that the symbiosis between banded sand catsharks and sea sponges may be mutualistic, meaning that both parties benefit from the relationship.
For example, the sharks may eat some of the sponge predators or parasites, such as snails or worms, that may harm the sponge.
The sharks may also fertilize the sponge with their waste products, which may provide nutrients for the sponge.
However, the scientists also noted that there may be some costs or risks associated with living inside sponges.
For instance, the sharks may damage or stress the sponge by entering or exiting its body. The sharks may also compete with each other for space or food inside the sponge.
The sharks may also expose themselves to potential infections or toxins from the sponge.
Banded sand catsharks are a remarkable species of sharks that hide inside sea sponges. This behavior has never been seen before in any other shark or elasmobranch species.
This discovery sheds new light on the diversity and adaptability of shark ecology and behavior.
