The world’s biggest fishes are the mola, or sunfish. An adult sunfish are the heaviest bony fish in the world, measuring up to 10 feet long and weighing more than 2,000 kilograms. They have bizarre shape. adults resemble enormous, flattened pancakes topped by a massive dorsal fin like a shark’s. Their bodies are unusually short and have no tail fin, as most fish do. Instead, sunfish have a long structure at their rear end known as a clavus, which extends downward and resembles a boat’s rudder.
The baby molas as larvae are just a few millimetres in length and they do not look like their parents. So it is difficult for the scientists to match larvae with the correct species of mola. For the first time DNA sequencing identified the larvae of the bump-head sunfish ((Mola alexandrini)). Sunfish larvae are so tiny that they are extremely difficult to find. In 2017, researchers working off the coast of New South Wales in south eastern Australia managed to collect tiny sunfish larva measuring about 0.2 inches (5 mm) long. By removing one of a larva’s eyeballs for genetic sequencing, the scientists were able to minimize damage to the specimen and extract usable DNA. They compared the DNA to genetic samples collected from adult sunfish, and found a match to (Mola alexandrini). This will help the scientists to compare the larva to unidentified Mola larvae in the collections of the Australian Museum and the Commonwealth Scientific and Industrial Research Organisation in Hobart, Australia
For protecting these marine giants understanding the life history is required and that includes knowing what the larvae look like and where they occur.