New species of sea urchins discovered in NZ waters

The sea urchins live so deep that divers can't reach them, and they never wash up on beaches. Photo / Owen Anderson of NIWA

Scientists dusting off half-century old archives of sea urchins have discovered seven new species they didn't know existed in New Zealand waters.

The dramatic finds include a clarification over the mystery of one giant deepwater species - whose only previous evidence of existence was destroyed when the Berlin museum it was housed in was heavily bombed in World War Two.

The sea urchins, known as Tam O'Shanters because of their likeness to the Scottish headwear, live up to 1200m underwater, most commonly in New Zealand around the Bay of Plenty seamounts.

They live so deep that divers can't reach them, and they never wash up on beaches.

Fishermen occasionally haul them up in their nets, and when an unusual find surfaces, they're given to the National Institute Of Water & Atmospheric Research (NIWA) to identify.

But much of the teeming NIWA sea urchin collection had gone unidentified since the 1960s.

Now, they've been pinpointed for the first time, thanks to the studious efforts of deep water fisheries scientist Owen Anderson.

"There are many different kinds of urchins, which I hadn't appreciated before I started researching kina (sea urchin), but now I'm hooked," he said.

"I love the symmetry and detail of the shell plating. They're very beautiful."

Mr Anderson had the privilege of naming the seven new species - Araeosoma bidentatum, Araeosoma migratum, Araeosoma anatirostrum, Araeosoma tertii, Araeosoma leppienae, Araeosoma bakeri and hapalosoma amynina.

He is now researching, identifying, and describing a further seven species.

The research resolves confusion around the Tam O'Shanter species Araeosoma coriaceum, supposedly recorded off northern New Zealand by the Challenger Expedition in 1874 and again recorded 100 years later in the Hauraki Gulf.

Examination of old specimens, new material, and original descriptions led to the conclusion that the Challenger specimen had been mis-labelled with its true locality unknown.

The Hauraki Gulf specimen, therefore, had been mis-identified, and is now known as Araeosoma bakeri.

The newly-identified group includes the giant Araeosoma alternatum - which grows up to 23cm in diameter.

It was known from a single specimen, found in the Indian Ocean near Somalia in 1899, and then stored in a Berlin museum where it was destroyed in World War Two.

"The good news is that this species was rediscovered alive and well, relatively rare but widespread around New Zealand," Mr Anderson said.

Around 50 species of Tam O'Shanter sea urchins are known globally, with nearly a third of them found in New Zealand waters.

Some of the newly-found species are now on display next to the giant squid at Te Papa museum in Wellington.