A London aquarium announced Tuesday that its popular same-sex penguin couple had adopted a Gentoo penguin chick that will be raised gender-neutral in a “world’s first.”

Sea Life London Aquarium said the 4-month-old Gentoo penguin chick will not be named or characterized as male or female and will be raised by females Rocky and Marama, which the aquarium described as a “same-sex” penguin couple.

It will be “the world’s first penguin to not have its gender assigned,” the aquarium said, CNN reported.

“While the decision may ruffle a few feathers, gender neutrality in humans has only recently become a widespread topic of conversation, however, it is completely natural for penguins to develop genderless identities as they grow into mature adults,” Graham McGrath, the aquarium’s general manager, said in a news release.

“What makes us really proud at the aquarium is the success of Sea Life London’s Gentoo breeding program and the amazing job of same-sex penguins Rocky and Marama who took the chick under their wing and raised it as their own,” he said.

The aquarium said Rocky and Marama had proven over the course of six breeding seasons that they were a “close couple” and could create nesting conditions to raise a chick, CNN reported.

Same-sex penguin couples are not uncommon in zoos across the world.

“The two sexes in penguins behave very similarly to one another,” one expert told CNN. “They look almost identical to one another. Behaviorally, they act very similarly as well, particularly in terms of reproduction — both males and females invest pretty equally in raising their chicks.”

The London aquarium said the genderless chick may later join its breeding program depending on the “gender its biology determines.”