Mola alexandrini, the enormous bump-head sunfish, has been harboring a small secret. The larval form of one of the world’s largest fish had previously been unknown to ocean experts, but thanks to the combined efforts of scientists from Australia and New Zealand, the early life stage of one of the world’s largest fish has finally been discovered. The larva of the huge bump-head sunfish is absurdly tiny and resembles something between a cinnamon crunch and a snowflake, much to the delight of those who prefer things that are smol and squishy. The Australian Museum, whose collections were crucial to the investigation, announced the discovery.
The bump-head sunfish is one of three Mola species found in Australian seas, with only the ocean sunfish, commonly known as the Mola mola, weighing more. It can reach a height of more than 3 meters (9.8 ft) and weigh more than 2,000 kilos (4,400 pounds). It spends its life travelling between the ocean depths and the sea surface, where it can be spotted basking on its side to heat up and be groomed with parasiticide by gulls.
Female sunfish have the largest fertility potential of any vertebrate, with adult Mola mola containing 300 million ova. Given their massive ovulatory output, experts were mystified as to why their eggs had never been found in the wild and larval sightings were so rare.
To make things easier, Auckland War Museum sunfish expert Dr Marianne Nyegaard chose to look for answers in conserved museum specimens rather than attempting to find the bump-larva head’s in the open water. Nyegaard sifted through materials with Australian Museum scientists Kerryn Parkinson and Andrew King in search of a plausible candidate. Unfortunately, sunfish larvae rarely match their adult forms, making species identification much more challenging.
The winning sample was collected off the coast of New South Wales in 2017, but doing DNA analysis on the fragile, microscopic specimen, which was only 5 millimeters in size, created its own set of obstacles. Kerryn Parkinson of the AM’s Ichthyology section delicately removed a single eyeball that Andrew King, a genomics specialist, utilized for DNA extraction and analysis to avoid damage to the material.
According to King, “the DNA sequence from the current AM specimen was matched to reference data supplied by our international researchers.” “A clear match from the sequencing was identified with adult Bump-head Sunfish (Mola alexandrini) samples.”
The researchers want to utilize their findings to discover other mola larvae sunfish collections kept in museums, thereby providing a more complete picture of the life cycle of these marine giants. Their achievement emphasizes the relevance of museum collections and their role in ongoing study as new technology open up new avenues for investigation.
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