A group of marine biologists led by Murdoch University researcher Marianne Nyegaard has identified and described an elusive new species of ocean sunfish.
The Hoodwinker Sunfish (Mola tecta) in Reserva Marina Isla Chanaral, Chile, 2015. Image credit: Cesar Villarroel, https://vimeo.com/129499857.
Ocean sunfishes (family Molidae) are the heaviest and most distinctive of all bony fishes, with some specimens weighing in excess of 2 tons (4,400 lb) and growing to 9-15 feet (3-4.6 m) in length.
The newly discovered sunfish species, named the Hoodwinker Sunfish (Mola tecta), is thought to approach a similar size.
In 2009, a genetic study by a team of Japanese researchers from Hiroshima University and the University of Tokyo revealed an unknown sunfish species, dubbed Mola species C, in Southeast Australian waters, “but the fish kept eluding the scientific community because we didn’t know what it looked like,” Nyegaard said.
“Finding these fish and storing specimens for studies is a logistical nightmare due to their elusive nature and enormous size, so sunfish research is difficult at the best of times.”
Over a three-year period Nyegaard and co-authors collected data from 27 specimens of the Hoodwinker Sunfish, at times traveling thousands of miles or relying on the kindness of strangers to take samples of sunfish found stranded on remote beaches.
“The new species managed to evade discovery for nearly three centuries by ‘hiding’ in a messy history of sunfish taxonomy, partially because they are so difficult to preserve and study, even for natural history museums,” Nyegaard said.
According to the team, the Hoodwinker Sunfish is the first addition to the genus Mola in 125 years.
“The process we had to go through to confirm its new species status included consulting publications from as far back as the 1500s, some of which also included descriptions of mermen and fantastical sea monsters,” Nyegaard explained.
“We retraced the steps of early naturalists and taxonomists to understand how such a large fish could have evaded discovery all this time.”
“Overall we felt science had been repeatedly tricked by this cheeky species, which is why we named it the Hoodwinker.”
Similar to its two sister species, the Ocean Sunfish (Mola mola) and the Southern Ocean Sunfish (Mola ramsayi), the new species has the characteristic truncated appearance of half a fish, but the differences between the three species become clear with growth.
The Hoodwinker Sunfish remains sleek and slender even in larger sizes, differing from the other species by not developing a protruding snout, or huge lumps and bumps.
“We suspect that, as with other sunfish species, feeding takes place during deep dives. The digestive tract contents of three specimens we sampled consisted mostly of salps, a gelatinous sea creature loosely resembling a jellyfish,” Nyegaard said.
The Hoodwinker Sunfish appears to prefer cold water. Its core distribution is likely in the waters of the Southern Hemisphere. It has so far been found around New Zealand, along the south-east coast of Australia, off South Africa and southern Chile.
The new species is described in a paper in the Zoological Journal of the Linnean Society.
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Marianne Nyegaard et al. Hiding in broad daylight: molecular and morphological data reveal a new ocean sunfish species (Tetraodontiformes: Molidae) that has eluded recognition. Zool J Linn Soc, published online July 19, 2017; doi: 10.1093/zoolinnean/zlx040
