They look like fuzzy fingers, waving gently from the depths of the ocean floor but make no mistake — they’re stone cold killers.
Scientists have discovered four new species of carnivorous sponge off the Pacific Coast, including one deadly variety found hanging from the deep-sea ridges off southern Vancouver Island.
Fortunately, these killers are about the size of a piece of spaghetti and they feed only on the tiny, shrimp-like amphipods and copepods that drift through the sea.
“Sponges characteristically feed on small particles, like bacteria, little tiny guys,” said Henry Reiswig, a retired professor of biology at McGill University, volunteer taxonomist at the University of Victoria and the Royal British Columbia Museum, and self-described “sponge guy.”
But these meat eaters feed on tiny crustaceans.
“It’s a snaring process involving spicules, pieces of glass on their surfaces that they use to snare,” said Reiswig, who is “77 or something like that.”
Two of the newly discovered species were collected by the Monterey Bay Aquarium Research Institute off the California coast and another from a hydrothermal vent field in the Gulf of California off Mexico. The fourth hails from a formation called the Endeavour Segment on the Juan de Fuca Ridge, off south Vancouver Island.
The Canadian beast, Cladorhiza caillieti, looks like a skinny bottle brush. The samples were five to seven centimetres long and only millimetres wide, found attached to the underside of overhanging ledges of basalt more than two thousand metres below sea level.
Reiswig and William Austin, of the Khoyatan Marine Laboratory on Vancouver Island, were enlisted by marine biologist Lonny Lundsten from Monterey Bay Aquarium Research Institute to help identify the sponges.
Carnivorous sponges were only discovered in 1995. Since then, only 137 species have been described, including these four. Just 11 of them were found in the North Pacific.
They’ve been described as the Venus fly traps of the deep sea, a “truly extraordinary species,” wrote Lonny Lundsten, the lead author of an article published in the most recent edition of the scientific journal Zootaxa.
Lundsten said the samples were collected by remotely operated vehicles during other research, most of it geological surveys of the sea floor.
Their meat-eating ways are believed to be an adaptation to the nutrient-poor environs of the deep sea, where most are found.
“Typical sponges must continually beat the flagella of choanocytes to create a current which flows through their bodies. From this current they strain single celled organisms and bacteria, which they eat,” Lundsten said in an email interview.
“But constantly beating these flagella is not efficient, energetically, when food is largely unavailable. Rather than creating a current, carnivores act more like spiders webs, with a matrix of tiny hooks waiting to catch any plankton that drift past them in the currents.”
They’re ancient. Specimens have been found in Jurassic sediment dating back 200 million years.
Reiswig believes a single mutation is responsible for the many descendants being discovered today.
“They’re all over the world: Sweden, Antarctic and throughout the equatorial zones,” he said. “But it only takes a million years or so for sponges to get around.”
So far, they’ve only been found in very deep water ranging from 600 to 3400 metres offshore. But we now know there are at least 11 species found in the northeast Pacific, he said.
It’s another small step in understanding the biodiversity of the largest and least known habitat on Earth, Lundsten said.
“Each time we dive, we get a sense of what the early explorers must have felt exploring new worlds and seeing things no one had ever seen before. In that sense, we will continue exploring this last remaining wild frontier on planet earth.”
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