The Mola mola (sunfish), which lives in tropical and temperate waters, has a flattened body with a rounded shape – almost disc-shaped – and, instead of a tail fin, it has a rounded tail similar to a rudder, it was considered so far the heaviest bony fish in the world . In fact, it is listed in the Guinness Book of Records as such. It is true that there are sharks larger than this fish crossing the oceans, but the skeletons of shark are not made of bone, but of cartilage.
It had been established that this species – you can see a specimen in the image of this article – had the world record for the heaviest bony fish considering the characteristics of a specimen caught in 1996 off the Japanese coast of Kamogawa, Chiba.
The specimen in question had a mass of 2,300 kilograms and was about 2.72 meters long. However, after a more exhaustive and recent examination of the characteristics of the different species of sunfish through photographs and specimens, as well as the analysis of more than a thousand documents – among them, there were half a millennium old -, has come to the conclusion that that fish, deserving of the first place in the mentioned ranking , was not actually a Mola mola , but a Mola alexandrini .
Two type specimens of ‘Mola alexandrini’ (left) and ‘Mola mola’ (right).
The Mola alexandrini specimens are distinguished from those of the other species of sunfish – the Mola mola and the Mola tecta – by certain specific morphological characteristics that can be observed in adults, such as, for example, a bulge on the head – peculiarity due to the one that has also been called the ragged-headed sunfish – and a different chin and tail.
The study was carried out by a team of Japanese researchers led by Etsuro Sawai, who is an expert on sunfish and works at the University of Hiroshima, and their results have recently appeared in the journal Ichthyological Research , published by Springer.
There must be bigger ones
Sawai is convinced that we will see how this record is broken in the future, as he is sure that there must be larger living Mola alexandrini specimens in the oceans. In this way, back in 2004, a female measuring 3.32 meters in length was already captured on the Japanese island of Aji (Miyagi). However, it cannot be considered the heaviest in the world because the mass of this marine giant was not measured.
It is not easy to have a specimen of this type to carry out a scientific study because, due to their enormous dimensions, they are difficult to catch and also to transport to undergo the morphological and genetic tests that researchers need to carry out. . But if there is something that this research makes clear, it is that we still have much to discover and rediscover the mysteries that our planet’s oceans hold.
Referencia: ‘Redescription of the bump-head sunfish Mola alexandrini (Ranzani 1839), senior synonym of Mola ramsayi (Giglioli 1883), with designation of a neotype for Mola mola (Linnaeus 1758) (Tetraodontiformes: Molidae)’. Ichthyological Research (2017). DOI:10.1007/s10228-017-0603-6
Imagen: Mola alexandrini bump-head sunfish ©Hasama Underwater Park
