Although we know the deep sea is strange, ‘carnivorous sea sponges’ still sound like something out of 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 into the ocean, and it’s starting to look 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 which we’ve never seen.
“It just shows how many of our deep oceans still need to be explored – these particular sponges are quite unique because they are only found in this particular region of The Great Australian Bight – a region that is planned to explore deep – sea oil,” he said. Merrick Ekins, manager of the collection of the Sessile Marine invertebrate collection in Queensland, said.
Sea sponges are usually multicellular filter feeds – they have perforated tissues for flowing water, from which their cells extract oxygen and food. These are fairly simple creatures, without nervous system, digestive system or circulatory system, but have existed for more than 500 million years in one form or another.
Electron microscope image of Abyssocladia oxyasters. (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 small crustaceans and other prey use neighboring filaments or hooks.
The researchers in this study found three new types of carnivorous sponges – Nullarbora heptaxia, Abyssocladia oxyasters and Lycopodina hystrix, which are also all new generations, as well as a closely related species of non-carnivorous sponge, Guitar davidconryi. All these species have been found at depths between 163 and more than 3000 meters deep.
“Here we report on four more new species of sponges discovered from the Great Australian Arc, South Australia. This area was recently explored using a Smith-McIntyre Grab and a Remote Operated Vehicle (ROV) around the marine to photograph and harvest biota, “the researchers write in their new paper.
“This new species is the first recorded carnivorous species from South Australia and increases the number of species recorded from across Australia to 25.”
The sponges are also prettier than you might think, looking like flowers with their protrusions, but not like sponges.
Closing of A. oxyaster. (Ekins et al., Zootaxa, 2020)
Carnivorous sponges have a little moment. We have known since 1995, but much more has recently been discovered around the world.
“Over the past two decades, our knowledge of carnivorous sponge diversity has almost doubled,” the same team explained in a previous article, where they described their discovery of 17 new species of carnivorous sponges.
“[This is] partly due to rapid advances in deep-sea technology, including ROVs and submarines capable of photographing and harvesting carnivorous sponges intact, and also due to the vigorous efforts of a number of modern taxonomists that many of the older species that described in the 19th and 20th centuries. ‘
Nearly every species of carnivorous sponge found in Australia was discovered during a CSIRO RV Investigator Voyage in 2017, showing how important these deep-sea investigations are.
With the bottom of the ocean still mostly unexplored, we think we will still see many kinds of carnivorous sponges and other strange and wonderful sea creatures.
The research was published in Zootaxa.