Australian Museum | Kerryn Parkinson

Biologists Only Just Discovered What Sunfish Larva Look Like And They're Adorable

Ryan Ford 22 Jul 2020

If you've watched any number of nature documentaries, you know very well how much biologists love to track animals from birth to death. They just can't resist exploring every little bit of an animal's life cycle and capturing it all in stark detail.

That's why it's so surprising to learn that so little was known about one of the ocean's largest residents, the giant bump-head sunfish.

The bump-head sunfish isn't exactly easy to overlook.

Giphy

It's a cousin to the slightly more famous Mola Mola, and they're both among the largest fish in the ocean, with an upper limit of about 4,400 pounds.

They're also gentle giants and completely harmless to humans, so it's not at all uncommon to see footage of divers enjoying their company.

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So, why had biologists never identified their larvae before?

Wikimedia | https://commons.wikimedia.org/wiki/File:Bump_head_sunfish.jpg

It's an excellent question, especially considering that female sunfish are among the most fertile fish around - a female can carry up to 300 million ova at a time.

But that appears to be part of the problem - it's all been quite confusing for scientists because the three species of sunfish off Australia are all so fertile, yet their larval young are rare to find, and when they have been found, well, it hasn't been easy to tell what kind of sunfish they'll grow into.

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To sort out the mystery, scientists at the Australian Museum didn't even try to find one of the rare specimens out in the wild.

Giphy | Monterey Bay Aquarium

Instead, they turned to the Museum's own archives to see what was on hand that hadn't been identified.

The museum's sunfish expert, Dr Marianne Nyegaard, along with Kerryn Parkinson and Andrew King, had to examine the specimens on hand and found a promising candidate in a larva found near New Zealand in 2015. To confirm it, they had to sequence its DNA, and obtaining a sample proved problematic because the larva was a mere five millimeters in size.

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Nevertheless, they did manage to get their DNA sample without doing much damage to the specimen.

Australian Museum | Kerryn Parkinson

The DNA confirmed that they indeed had a bump-head sunfish larva in their collection.

And just look at it! Would you ever think this adorable customer would grow up to become that huge, hulking sunfish? Maybe, going by the shape. Mayyyybe.

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The scientists don't seem overly concerned with how cute the larva is right now, however.

Wikimedia | https://commons.wikimedia.org/wiki/File:Mola_alexandrini_(Bump-head_Mola).jpg

They're looking more at the discovery as a starting point to look further into the mysterious early life cycle of the giant sunfish, with the promise of possibly not having to search beyond what's already in their collection.

"A genetic ID of one of these larvae is incredibly important but only one step on the long journey towards describing the early ontogeny of all three Mola species - an endeavour which will require global collaboration. If we want to protect these marine giants we need to understand their whole life history and that includes knowing what the larvae look like and where they occur," Nygaard said in a statement.

h/t: scimex

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