Four new species of carnivorous sea sponge have been discovered in a place where ridiculous adaptations for sourcing food seem about as widespread as horrific ways to die – the deep sea.
Following their discovery in 2012 of the fantastic-looking carnivorous harp sponge (Chondrocladia lyra) off the coast of California and almost four kilometres deep, Monterey Bay Aquarium Research Institute (MBARI) researchers Lonny Lundsten, Henry Reiswig, and William Austin have managed to identify four more 'killer sponges' using remotely operated, cam-wielding vehicles. The species are described in the current issue of ZooTaxa.
Most sponges live their lives as filter feeders, sitting around and waiting for bacteria or single-celled organisms to float into their vicinity. An important part of capturing these little morsels is a specialised type of cell called a choanocyte. Choanocytes are like scores of delicate tails that whip around the sponge to create a constant channel towards it. Once tiny organisms are swept up and collected by the choanocytes, these organisms will be passed onto another set of specialised cells called amoebocytes, where they'll be processed as food. This strategy is perfectly suitable for sponges living in many parts of the ocean, because bacteria and other tiny organisms are usually pretty easy to come by, but in the deep sea, creatures great and small are far more scarce.
Which is probably why most deep-sea carnivorous sponges don't have choanocytes. Their habitat lacks the constant flow of food required to fuel all that whipping activity anyway, so they've figured out a way to snare much bigger, more nutrient-rich prey instead for that all-important slow burn. Or slow death, depending on which side of the decomposition you're on. These sponges are absolutely covered in what Lundsten describes as "beautiful and intricate microscopic hooks", which can snare little crustaceans that wander onto the sponge and hold onto them as their bodies are gradually absorbed.
The first new species described has been named the 'mountain-dweller', or Asbestopluma monticola. It was found at a depth of 1280 metres on the summit of Davidson Seamount, an extinct underwater volcano off the Central California coast. A number of them had small crustaceans attached to their spiny exteriors in various forms of decomposition.
The second new species, Asbestopluma rickettsi, found at two locations off the coast of Southern California and just over a kilometre below the surface, did not show any evidence of prey capture. The researchers suspect that while these sponges are waiting for tiny crustaceans to get themselves snared, they feed off the methane-loving bacteria that gather around the area.
The third new species, Cladorhiza caillieti, was found at a depth of more than two kilometres along the Juan de Fuca Ridge just off the coast of Vancouver Island. Situated on the recent lava flows of this underwater volcanic ridge, C. caillieti carries highly specialised types of spines that have only ever been found in the fossilised remains of early Jurassic and Miocene marine organisms. The team suggests then that the Chondrocladia genus, to which the killer harp sponge also belongs, is ancient.
The fourth sponge, Cladorhiza evae, also placed in this genus, was found 2299 metres down in a newly discovered hydrothermal vent field along the Alarcon Rise, just off the tip of Baja California. And here's where it got its lovely name:
Named in honor of Eve Lundsten, beautiful wife of the first author whose commitment and support have endured through the years. Eve’s love for the Gulf of California also inspired this naming as the type specimen was collected in the deep sea, east Cabo Pulmo, Baja California Sur, Mexico, near where we honeymooned in 2006.
Specimens of both C. evae and C. caillieti had numerous prey trapped among their spines, but no one has ever seen the trapping process in action.
Here's a video of the four new species: