New Zealand scientists say they have discovered a new species of crustacean, which provides an important insight into the little known lives of creatures in the deep sea.

The previously unknown species of sand-hopper was found living inside another deep sea organism on the Chatham Rise, an area of ocean floor to the east of New Zealand, said scientists from the National Institute of Water and Atmospheric Research (NIWA) on Wednesday.

The sand-hopper, an amphipod species, was found living inside a see-through layer on a bryozoan, also known as a moss animal, which lives between 500 and 1,500 meters deep, said NIWA marine biologist Dr Dennis Gordon.

It was probably the only example of a relationship between these two types of organisms known anywhere in the world, he said in a statement.

"It is a significant find as much less is known about relationships among organisms in the deep sea, compared to those in shallower water," Gordon said.

Males, females and juvenile hoppers up to 1 centimeter long were living inside a species of bryozoan that grew to about 5 cm in length.

The scientists believed the hoppers reproduced in the bryozoan and when the bryozoan died, the hoppers left to colonize another.

They were unsure whether both the amphipods and the bryozoa benefited from the arrangement or whether the hoppers were the sole beneficiaries, deriving nutrients and protection from their host.

The scientists have named the new species tutus (meaning "safe") and the new amphipod genus bryoconversor ("living in Bryozoa").