The sunfish (Mola mola) is a bony fish that is part of the Molidae family. It is known worldwide for being the heaviest of fish, due to the fact that in the adult state it could weigh 2.3 tons. Another notable feature is its rapid growth, which can be around 0.82 kg / day. This allows it to quickly reach its large body size.
It also eats sponges, small fish, flounder, cathenophores, snake starfish, Portuguese frigatebirds, and eel larvae found in deep water. As for plant species, it eats various types of eelgrass, plankton, algae and eel grass.
The wide range of foods it consumes indicates that the Mola mola forages at different levels of the ocean. Thus, they do so on the surface, among floating weeds, in deep water and on the seabed.
Research works, based on the study of stomach content in young and adult species, indicate that there are differences in their diet. The adult sunfish diet is composed mainly of gelatinous zooplankton, while the young mostly are benthic feeders.
Eating methods
In general, the foods of this species are poor in nutrients. Due to this, the animal is forced to consume large amounts of food daily to meet its metabolic needs.
Sunfish have special adaptations for eating jellyfish. Among these, its thick skin stands out, which provides protection against the numerous stingers or nematocysts that jellyfish have.
In temperate regions, cleaner fish exist, generally located in those areas where drifting algae are found. These are responsible for removing the parasites that live on the skin of the Mola mola. When the sunfish lives in the tropics, it receives the help of those fish that are in the coral reefs.
In Bali, this species frequently approaches cleaning stations on the reefs, where groups of school banner fish (Heniochus diphreutes) are found. These eat the organisms that live on the skin of the sunfish.
When this fish emerges to the surface, it positions itself on its side or projects its dorsal fin above the water, allowing seabirds to feed on the ectoparasites on its skin. In southern California, gulls often fulfill that role.
I swim
Mola mola has a short spine and lacks a tail fin. Due to these morphological changes that it has suffered evolutionarily, it has a particular way of swimming. Their swimming method is different from that based on dragging, typical of the vast majority of bony fish.
The push required to move is caused by the synchronous movement of the anal fin and the dorsal fins. This force is based on elevation and resembles the flight of birds.
This way of swimming could involve adaptations in the nervous system, related to the locomotor system. In this sense, studies of the anatomy of this fish show that its peripheral nervous system presents differences with other fish of the order Tetraodontiformes.
References
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- Hailin Pan, Hao Yu, Vydianathan Ravi, Cai Li, Alison P. Lee, Michelle M. Lian, Boon-Hui Tay, Sydney Brenner, Jian Wang, Huanming Yang, Guojie Zhang (2016). The genome of the largest bony fish, ocean sunfish (Mola mola), provides insights into its fast growth rate. Recovered from ncbi.nlm.nih.gov.
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