The Megamouth shark (Megachasma pelagios) is one of the rarest and least known species in the world. Since it was discovered in 1976, only 117 sightings have been reported, and most of them come from organisms stranded on the beach or accidental fishing. One of its main characteristics is its giant mouth, which is why it is called “Megamouth shark”.
This cartilaginous fish is a close relative of the whale shark, so it has a rather showy size, but it is not a dangerous species. If you want to find out more about this organism, read on.
Megamouth shark habitat
Despite the lack of information on the animal – due to the fact that it is not easy to encounter this shark – it has been possible to date some of its characteristics. The records of the localities where this species has been found have shown that it is cosmopolitan, as it is distributed in seas with tropical temperatures and climate.
It has been established that this shark is capable of living in at least 3 of the 5 oceans of the world: the Pacific, the Atlantic and the Indian Ocean. Specimens have even been identified in places such as Japan, Taiwan and the Philippines, where encounters with this animal have increased.
Its habits are similar to those of pelagic species, as this animal is constantly moving to the surface. In addition, it lives at average depths of 20 meters during the night and 150 meters during the day.
Origin and classification
In 1976, while the U.S. Navy was raising its floating anchor, a 4.46-meter-long entangled shark was found. The specimen weighed 750 kilograms and appeared to be a filter-feeder species, as its stomach was full of krill. From that moment on, its captors referred to it as megamouth, due to its huge mouth.
The second encounter with this animal was not until 1984, in California, where a Megamouth shark was caught in a fishing net. On this occasion, the shark was still alive when it was found and weighed 700 kilograms and measured 4.5 meters. In fact, the specimen is preserved and available for viewing at the Natural History Museum of Los Angeles County.
In 1983, Taylor, Compagno and Struhsaker described and named the Megamouth shark. Since then, it has been placed in the order Lamniformes, as a close cousin of species such as the whale shark or basking shark.
Due to the scarcity of information, its evolutionary origin has not been determined, but there are two hypotheses. The first is based on the morphology of its crown-shaped teeth, which would place this organism as being able to inhabit the waters of 36 million years ago. The theory is based on the multiple fossil records that resemble the species.
The second hypothesis is based on molecular analysis, in which, by means of its DNA, its origin is estimated at 100 million years ago. These discrepancies do not mean that one or the other postulation is wrong, but that it is impossible to define its origin with the current information. Both hypotheses have their foundations, so it is only a matter of time before this puzzle is solved.
Although this organism has a wide distribution, it is likely to be affected by seasonality patterns. That is, its presence in various oceans may increase or decrease, depending on the time of year. This is because its movement patterns appear to be linked to the availability of food.
Megamouth shark characteristics
One of the main characteristics of the Megamouth shark is its large size, as it is capable of reaching more than 5 meters in length. In fact, females can reach up to 7 meters in length, being this a clear example of sexual dimorphism of the species.
Its body is soft and flaccid to the touch, while its shape is similar to that of a tadpole, with a large head and a body that narrows as it reaches the tail. Its mouth is very large, with rounded edges that extend to behind the eyes. In addition, it has small crown-shaped teeth, with rows of 85 to 100 in each jaw.
The gill slits are quite long, and it has two small dorsal fins and an anal fin. Its color is typical of these elasmobranchs, with shades between black-blue and gray, with white bellies.
Character and behavior
This organism usually prefers to swim shallow, as during the night it only reaches 12 to 25 meters deep. However, it can move to 120 to 166 meters depth during the day, in constant locomotion in order to feed. This behavior seems to follow the vertical migration of zooplankton, which is a large part of its diet.
The characteristics of the Megamouth shark make it a slow swimming species, reaching a speed of less than 1 meter per second. This is understandable, since its musculature is quite weak, its fins are too soft and it lacks a keel.
Diet and feeding
The basis of this organism’s diet is krill, however, it also consumes some copepods and zooplankton. This classifies it as a filter-feeding species, which also sucks part of the water in order to catch its food.
The Megamouth shark takes advantage of its large mouth to be able to absorb as much food as possible. Although, contrary to others – and because of its weak physiology – it has to suck in instead of actively chasing its prey, as the basking shark does.
Reproduction of the Megamouth shark
This species seems to reach maturity when it reaches 4 meters in length in males or 5 meters in females. It has reproductive activities throughout the year and gives birth near the tropic regions.
The type of fertilization used by these cartilaginous fish is internal and they have copulatory encounters that can leave scars. This shark is an ovoviviparous species, so their offspring feed on yolk inside the mothers.
Protection and conservation status
This organism is listed as a species of the least concern, however, this is due to the lack of information on its populations. It is likely that despite this, the species has a stable population, as encounters with this animal have slowly increased since its discovery.
The planet is covered by almost 3 quarters of water, so the amount of aquatic species that exist can be very high. It is possible that in the future we will continue to discover more and more marine animals that can amaze us, as is the case of this shark. It is not necessary to fear them, but to know and understand them.