Researchers have for the first time identified the larva of a giant self-headed

Australian and New Zealand scientists have made a significant discovery and for the first time successfully identified the tiny larva of a giant self-headed larva.

The identification of the self-headed larva is the result of a team that worked under the guidance of an expert on these unusual fish, Dr Marianne Nyegaard of Auckland War Museum. Together with Kerryn Parkinson and Andrew King from the Australian Museum, Nyegaard used available ichthyological collections and support from the world-leading Genomics Laboratory in Sydney.

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The self-headed mola is one of only three species of mola fish found in Australian waters. These landmark discoveries have provided important information that will help scientists understand the entire life cycle of these marine giants. It will also contribute to the conservation of an entire unique species.

For the first time, we have been able to genetically identify a specimen of the larvae of the self-headed larvae (Mola alexandrini) anywhere in the world – Dr Nygaard said.

Special specimens

Several specimens of larvae collected off the coast of New South Wales in 2017 by CSIRO researchers caught the attention of Dr Nyegaard. She decided to conduct research and identify the species.

As Dr Nygaard explained, fish larvae often look nothing like their adult form. In the case of larvae, none of the features used to identify adult larvae are visible in the smallest larval specimens. This makes their identification particularly difficult.

Despite this, using the resources of the Australian Museum’s Genomics Laboratory, we were able to carry out a DNA analysis of one of the specimens – Nyegaard said.

To minimise damage to the extremely rare larval specimen (about 5mm long), Kerryn Parkinson meticulously removed a single eyeball from the unidentified specimen. In turn, Andrew King, a genomics specialist, carried out DNA extraction and analysis.

We compared the DNA sequence from an existing specimen with reference data generated by our international collaborators. Differences in the genetic code are statistically analysed to distinguish between species – Andrew King explained.

These beautiful sea giants can be found all over the world. They live in the open waters of tropical and temperate seas. The classification of species in the genus Mola has long been confused, despite the great interest that these fish generate. No doubt this is mainly due to their rarity and the difficulty in preserving them for research.

Photo: Kerryn Parkinson / Australian Museum