Scientific detective work uncovers historic sunfish mix up

December 6, 2017

Marianne Nyegaard securing a small genetic sample from a Mola alexandrini off Bali, Indonesia Photo credits: Jonathan Anderson

An investigation by a Murdoch University PhD student has resulted in Australia losing its 130 year claim to its unique sunfish species.

During her PhD research, Marianne Nyegaard collaborated with a Japanese research team, led by Dr Etsuro Sawai from Hiroshima University ,to clear up inaccuracies in sunfish taxonomy (species classification) dating back more than a century.

The researchers reviewed more than 1,000 accounts from 500 years of museum records.

“We combined genetic analysis with a review of historic records in natural history museums around the world,” Ms Nyegaard said.

“To our surprise, results showed that Australia’s sunfish species, Mola ramsayi, had already been discovered and described in 1839 in the Mediterranean Sea.”

The breakthrough discovery came in 2013, when Dr Sawai and Ms Nyegaard visited the University Zoology Museum in Bologna, Italy, where they recognised a familiar shape hanging on the wall of a staircase; a huge and distinct sunfish.

“Despite the dust, skin ruptures, fin damage, and someone’s old, discarded chewing gum in its mouth, there was no mistaking the identity of the stuffed fish,” Ms Nyegaard said.

“This specimen was unequivocally a ‘Mola ramsayi’ far away from what was thought to be its home in Australia.”

Ms Nyegaard explained that after such a discovery, the taxonomic code stipulates that the species name reverts back to the oldest description. This has forced Australia’s Mola ramsayi to now be known as Mola alexandrini, the species described by researchers in Italy many years before.

These findings come only months after a new species of sunfish, Mola tecta, was described from New Zealand and Australia by Ms Nyegaard and collaborators.

“All this finicky sunfish taxonomy work will ultimately help us to determine which species of sunfish occur where, and if any of them are at risk from human

A “Mola ramsayi” from Sydney ca. 1883, now re-identified as Mola alexandrini. The fish was too large for the doors at the Australian Museum, and was pulled in through an upstairs window. Photo credits: Australian Museum Archives

activities,” Ms Nyegaard said.

“This project has shown that Mola alexandrini has been widely mistaken for its close relative Mola mola across the world, and in fact has earned the title of the world’s heaviest bony fish in the next edition of the Guinness Book of World Records.”

The findings were published in Ichthyological Research.

The research involved collaboration between the Australian Fisheries Management Authority (AFMA), the Australian Commonwealth longline fishing industry and NZ fisheries. In Australia, the AFMA on-board observers collected genetic samples from all sunfish incidentally caught during long line fishing operations.

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