Species: Sponge of the Rossellidae family
Habitat: Deep waters off Hawaii, US
Deep in the waters off the Northwestern Hawaiian Islands lurks a 3.5-metre-long behemoth – the world’s largest known sponge that could be hundreds, if not thousands, of years old.
Sponges are some of the simplest and most ancient of animals, though they don’t look like animals as we usually know them.
Large ones provide ecosystem services such as filtering seawater, recycling nutrients on reefs and providing habitat for other species, and are estimated to be able to live for more than 2300 years.
Daniel Wagner of the NOAA Papahānaumokuākea Marine National Monument and his colleague spotted the giant, a member of the Rossellidae family, during an expedition to the islands last year.
The sponge was filmed from two remotely operated vehicles during a dive on a ridge at the Papahānaumokuākea site – one of the world’s largest marine conservation areas, containing coral reefs that host more than 7000 marine species.
Images of the sponge taken at a depth of just over 2100 metres revealed that it was 3.5 metres long, 2 metres high and 1.5 metres wide (see video below).
Its huge size trumps the dimensions of the sponge previously recognised as the largest – a colony of Aphrocallistes vastus with respective measurements of 3.4, 1.1 and 0.5 metres found in shallow waters off western Canada.
Rise of a giant
The stable, relatively undisturbed habitat of the conservation site has probably been conducive to the sponge’s unfettered growth.
“A lot of organisms in deep seas grow very slowly, so they need their habitats to remain stable over a long time to be able to grow larger and larger,” Wagner says.
We don’t know exactly how old it is. “Sponges don’t have things like growth rings that can be used to estimate age,” Wagner says. “We do know, however, that several coral species that live at those depths can live to multiple hundred to even a few thousand years: the oldest one is 4500 years. Thus, my best guess is that this is likely a very old sponge on the order of century to millennia.”
The discovery of the sponge at the site underscores the need to protect the area with strict conservation measures, says the team.
Sponges are thought to be some of the earliest animals to have evolved on Earth – perhaps even ancestors of all complex animals. They are also thought to have helped aerate ancient seas, boosting life in the oceans some 750 million years ago.
Most sea sponges feed on single-celled organisms, which they filter from water, but some are more voracious, catching small crustaceans. Dolphins use sponges as tools to help them uncover food on the seabed.
Journal reference: Marine Biodiversity, DOI: 10.1007/s12526-016-0508-z