Moon-fish ( lat. Mola ) - a genus of bead-finned fish of the order Pufferfish . They live in the temperate and tropical zones of the Atlantic, Indian and Pacific Oceans. They reach lengths from 80 cm to 5 m and masses of more than 1 ton. They live in the open sea at a depth of up to 400 m. They feed primarily on jellyfish , as well as plankton , algae , crustaceans and fish. Reproduction by egg production [1] . The largest species of common moon fish ( Mola mola ) can spawn up to 300 million eggs. The strange, "chopped off" appearance of these fish is due to atrophy of the back of the spine and caudal fin [2] .
| Moon fish |
 |
| Scientific classification |
|---|
| No rank : | Bilateral symmetrical |
|
| International scientific name |
|---|
Mola Kölreuter , 1766 |
|
These fish have a huge, strongly laterally compressed body in the form of a disk. The pelvic girdle is reduced [2] . The dorsal and anal fins shifted back and devoid of spiny rays form an elastic cartilaginous plate, which is supported by their branched soft rays [1] . This tail plate acts like a paddle. During individual development, all species of the family undergo a complex metamorphosis . Freshly hatched larvae look like puffer fish . Upon reaching a length of 6-8 mm, the body stage begins - wide bony plates with large triangular protrusions appear, which are then crushed into small teeth with triangular protrusions forming long spikes. At this stage, there is still a larval caudal fin [2] .
Gills in the form of holes, eyes and mouth small, pectoral fins rounded, ventral fins and caudal fin absent. The mouth ends with a well-developed beak formed by fused teeth [1] .
Representatives of this family have the smallest number of vertebrae among fish, ordinary moonfish have only 16. There are completely no caudal fin bones, and the skeleton mainly consists of cartilage . Thick and rather rough skin is devoid of scales and covered with bone protrusions. No swim bladder .
These fish are bad swimmers. They swim with the help of the dorsal and anal fin, pectoral fins act as a stabilizer. To perform a turn, they release a strong stream of water from their mouth or gills [3] . In addition, they are able to maneuver a bit by changing the position of the anal and dorsal fins, similar to the way birds use wings to maneuver [4] .
It is believed that moon fish are able to make grinding sounds with the help of pharyngeal teeth . They have fused teeth that form the characteristic beak of the puffer-bellied squad, which prevents them from closing their mouths tightly. Despite this, the basis of their diet is soft food, although sometimes they eat small fish and crustaceans [3] .
The skin of moon fish is often covered with parasites. To clear them, they sail to the places of gathering of animal cleaners . There they begin to swim, raising their heads almost vertically to the surface of the water. In order to attract the attention of seabirds, for example, gulls, which also peck parasites, moon fish put a fin or beak out of the water [4] .
These fish have tasteless flabby meat. However, in some regions of the western part of the Pacific Ocean and in the south of the Atlantic, specialized fishing for moon fish is carried out. Sometimes they are kept in public aquariums. They are easy to feed, as they reflexively suck in any small feed brought to your mouth. But they often die, breaking on the walls of the tanks [2] . Occasionally, moon fish are found on the shore [5] . The population of moon fish is declining; they are often caught as by- catch [6] .
The name of the family and one of the genera comes from the word lat. mola - millstone. There are 3 types of genus:
- Mola mola - Common Moonfish [7]
- Mola ramsayi - Short Moon Fish
- Mola tecta [8] .
