With 2,300 different species in existence, all of which suck saltwater in through their mucus-covered gills to feed on its nutrients before ejecting the leftovers out the other side, it’s arguable that the sea squirt is already a pretty unusual character.

It counts as something, then, when scientists spot one they call particularly peculiar.

Which is precisely what scientists exploring the reefs of Rakiura Stewart Island off the coast of New Zealand did note, when they discovered an “unusual” egg-shaped sea squirt – one previously unseen and unheard of in any other part of the region – thriving on the deep seafloor.

It’s thought that what this team of marine biologists from Te Herenga Waka – Victoria University of Wellington discovered is, in fact, a species of sea squirt completely new to science, adding to an extensive library of life within the Ascidiacea order.

“We were off Port Pegasus at the southern end of Rakiura and we could see all these really unusual ‘egg’ shapes on the seafloor,” said Professor James Bell, a marine biologist at the university. “Closer inspection revealed they were large, 30cm tall sea squirts that we haven’t found in any other part of Aotearoa.”

Marine ecologist Mike Page, an emeritus scientist from the National Institute of Water and Atmospheric Research, later supported the belief that the sea squirt in question is likely to be a new species, yet to be named.

Sea squirts, also known as ascidians, play a key role in maintaining water quality. They are filter feeders, meaning they feed on nutrients in the water column through the process described above. They are commonly found in waters all over the world, usually in shallow regions with salinities over 2.5%.

The waters off Stewart Island stand quite unique in this regard.

“Unusually, sea squirts dominated the marine communities on the deep-water reefs that we explored off Stewart Island,” said Professor Bell. “We typically find sponges are the dominant player on deep-water reefs in other parts of the country.”

This new species of sea squirt was also discovered at a depth of 115 metres.

“The water off Stewart Island was really clear down at this depth. This probably reflects the fact there are no major rivers draining into the sea and there are still large areas of native forest on the island,” Professor Bell continued. “Finding this sea squirt is a reminder that we still have so much to learn about the rich diversity of life in the ocean.

“It’s also a reminder of the need to ensure we protect our marine environment and the unique species it supports.”

Video footage of the reef explored by the researchers shows a number of different species of sea squirt, all varying in colour from bright white to pinks, blues, and yellows. The footage was captured using a remotely operated vehicle (ROV) that can film in waters more than 100 metres deep.

Check out the video footage below:

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