Even though we are know the deep sea is strange, ‘carnivorous sea sponges’ still sound like something out of a science fiction movie. And yet, researchers have just announced the discovery of three new such species off the coast of Australia.
Go into the ocean a few hundred meters deep and it starts to feel like you’re in a whole new world: from a creature that looks like a starfish crossed with an octopus, to shark-devouring fish, to carnivorous sponges we’ve got never seen before.
“It just goes to show how many of our deep oceans have yet to be explored – these particular sponges are quite unique in that they are only found in this particular region of The Great Australian Bight – a region that was planned for deep sea oil exploration.” , said one of the researchers, Merrick Ekins, manager of the Queensland Museum Sessile Marine Invertebrates Collection.
Typically, sea sponges are multicellular filter feeders – they have hole fabric for running water, from which their cells extract oxygen and food. They are fairly simple creatures, with no nervous system, digestive or circulatory system, but have existed in one form or another for over 500 million years.
Scanning electron microscope image of Acarnidae oxyasters. (Ekins et al., Zootaxa, 2020)
But carnivorous sponges are a bit different. Some carnivorous sponges still use the water flow system, while others (such as the three newly discovered species) have lost this ability altogether, catching small crustaceans and other prey using filaments or hooks.
The researchers in this study found three new types of carnivorous sponges – Nullarbora heptaxia, Acarnidae oxyasters and Lycopodina hystrix, all of which are also new genera, as well as a closely related type of sponge that is not carnivorous, Guitarra davidconryi. All of these species were found at depths between 163 and over 3,000 meters (535 to 9,842 feet) deep.
“Here we report on a further four new species of sponges discovered in the Great Australian Bight, South Australia. This area was recently explored using a Smith-McIntyre Grab and a Remotely Operated Vehicle (ROV) to analyze the marine biota. photograph and harvest. ‘, the researchers write in their new paper.
“These new species are the first recorded carnivorous species from South Australia and are increasing the number of recorded species from around Australia to 25.”
The sponges are also more beautiful than you might think, they look a bit like flowers with their spiky protrusions, but not much like sponges.
Close up from A. oxyaster. (Ekins et al., Zootaxa, 2020)
Carnivorous sponges have a moment. We’ve known them since 1995, but many more have recently been discovered around the world.
“Over the past two decades, our understanding of carnivorous sponge diversity has nearly doubled,” the same team explained in an earlier paper, describing their discovery of 17 new types of carnivorous sponges.
“[This is] Thanks in part to the rapid advancements in deep-sea technology, including ROVs and submarines capable of photographing and harvesting carnivorous sponges intact, and also due to the tremendous efforts of a number of contemporary taxonomists re-describing many of the older species described in the 19th and 20th centuries. “
Almost every kind of carnivorous sponge found in Australia was discovered during a CSIRO RV Investigator Voyage in 2017, showing the importance of these deep-sea investigations.
With the ocean floor still largely unexplored, we imagine seeing many more types of carnivorous sponges and other strange and wonderful sea creatures.
The research is published in Zootaxa.