Even if we know the deep sea is weird, the “sea carnivorous sponges” still sound like something from a sci-fi movie. And yet, researchers have just announced the discovery of three new species off the coast of Australia.
Go a few hundred meters deep in the ocean and it begins to look like you are in a whole new world: from a creature that looks like a starfish crossed with an octopus, to fish devoured by sharks, to carnivorous sponges , we’ve never seen before.
“It will only show how much of our deep oceans are still to be explored – these sponges are quite unique in that they are found only in this special region of The Great Australian Bight – a region that has been programmed to explore deep oil.” , said one of the researchers, Merrick Ekins, manager of the Sessile Marine Invertebrates collection at the Queensland Museum.
Sea sponges are usually multicellular filters – they have tissue holes for water to flow from, from which their cells extract oxygen and food. They are quite simple creatures, without a nervous, digestive or circulatory system, but they have existed in some form for over 500 million years.
Scanning electron microscope image of Oxiastrii Acarnidae. (Ekins et al., Zootaxa, 2020)
But carnivorous sponges are a little different. Some carnivorous sponges still use the water flow system, while others (such as the three newly discovered species) have completely lost this ability and catch small crustaceans and other prey using filaments or hooks.
The researchers in this study discovered three new species of carnivorous sponges – Heptaxia Nullarbora, Oxiastrii Acarnidae and Lycopodina hystrix, which are also all new genera, as well as a closely related sponge species that is not carnivorous, Guitar davidconryi. All of these species were found at depths ranging from 163 to over 3,000 meters (535 to 9,842 feet) deep.
“Here we report four other new sponge species discovered in the Great Australian Bight, South Australia. This area was recently researched, using a Smith-McIntyre Grab device and a remotely operated vehicle (ROV) to photograph and harvest marine biota. “, write the researchers in their new paper.
“These new species are the first recorded carnivorous species in South Australia and are increasing the number of recorded species around Australia to 25.”
Sponges are also more beautiful than you might imagine, looking a little like flowers with their prickly prominences, but not much like sponges.
Close to A. oxiaster. (Ekins et al., Zootaxa, 2020)
Carnivorous sponges have a bit of a moment. We have known about them since 1995, but many more have recently been discovered around the world.
“In the last two decades, our knowledge of carnivorous sponge diversity has almost doubled,” explains the same team in a previous paper, which described the discovery of 17 new species of carnivorous sponges.
“[This is] due in part to rapid advances in deep-sea technology, including ROVs and submarines capable of photographing and harvesting intact carnivorous sponges, as well as Herculean efforts by a number of contemporary taxonomists to redefine many older species described in the 19th and 20th centuries. “
Almost every species of carnivorous sponge found in Australia was discovered during a CSIRO RV Investigator Voyage in 2017, showing how important these in-depth investigations are.
With the ocean floor still largely unexplored, we imagine that we will see many other species of carnivorous sponges and other strange and wonderful sea creatures.
The research was published in Zootaxa.