Deep on the ocean floor, beneath the waters off the Pacific Northwest all the way south to Baja California, they lurk: four new species of meat-eating sea sponges, awaiting their next victims.

So say new findings by marine biologist Lonny Lundsten, from California's Monterey Bay Aquarium and Research Institute, and two Canadian researchers who describe newly-found types of carnivorous sponges that look more like bare twigs from trees or small shrubs -- but are covered with tiny hairs made up of tight bundles of microscopic hooks that trap amphipods, small shrimp-like creatures that also dwell near the ocean bottom.

According to an MBARI news release, scientists first discovered some sponges are carnivorous about 20 years ago. However, only seven such species have since been found in the northeastern Pacific.

Typically, sponges live off of the bacteria and single-celled organisms they filter from the surrounding waters with specialized cells called choancytes, which sport whip-like tails that move continuously to create an ongoing flow of water and food to be captured.

However, Lundsten explained, most carnivorous sponges don't have choancytes -- which, even if they had them, would consume a lot of effort to keep constantly moving in an environment where food is limited and body energy needs to be conserved.

"So these sponges trap larger, more nutrient-dense organisms, like crustaceans, using beautiful and intricate microscopic hooks," said Lundsten, further explaining that once an animal becomes trapped in those hooks, it takes only a few hours for sponge cells to start engulfing and digesting it.

A few days later, all that remains of the prey is an empty shell.

Lunstren's research team found the new meat-eaters through video they recorded on the ocean floor, after which they collected samples for the newly-discovered sponges for taxonomic work and species-reference collections.

Back in the lab, as Lundsten put it, the researchers found, along with the sponge samples, "numerous crustacean prey in various states of decomposition."

They still have yet to catch a sponge in the act of consuming its prey.