The Megamouth Shark: Habitat and Characteristics
Written and verified by the biologist Cesar Paul Gonzalez Gonzalez
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 sharks stranded on the beach or through accidental fishing. One of the main characteristics is its giant mouth, which is why it is called the “megamouth shark”.
This cartilaginous fish is a close relative of the whale shark, so it’s quite big, but isn’t a dangerous species. If you want to find out more about this animal, keep reading.
Habitat of the megamouth shark
Despite the lack of information that exists about the animal, some of its characteristics have been recorded. The records of the localities where this species has been found have shown that it’s distributed in seas with tropical temperatures and climate.
This shark is able to live in three of the five oceans of the world: the Pacific, the Atlantic, and the Indian. Specimens have even been identified in places such as Japan, Taiwan and the Philippines, where encounters with this animal have increased.
Its habits are comparable to pelagic species, as this animal shows constant movements to the surface. In addition, it lives in average depths of 20 meters at night and 150 meters (65 to 500 feet)during the day.
Origin and classification
In 1976, while the United States Navy was lifting its floating anchor, a 4.46 meter long (nearly 1 5 feet) entangled shark was found. The specimen weighed 750 kilograms (1650 pounds) and appeared to be a filter species, as its stomach was full of krill. From that moment on, theur captors referred to it as megamouth.
The second encounter with this animal wasn’t until 1984, in California, where, in the same way, a megamouth shark was caught in a fishing net. On this occasion, the shark was still alive when they found it and weighed 700 kilograms and measured 4.5 meters. In fact, the specimen is preserved and available to view at the Los Angeles County Museum of Natural History.
In 1983, Taylor, Compagno and Struhsaker described and named the broadmouth shark. Since then, it has been placed in the order of the Lamniformes, as a close cousin of species such as the whale shark or the basking shark.
Due to the scarcity of information, its evolutionary origin hasn’t 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 capable of inhabiting the waters 36 million years ago. The theory is founded on the multiple fossil records that resemble the species.
The second hypothesis is based on molecular analysis, in which, through its DNA, its origin is estimated to be from 100 million years ago.
These discrepancies don’t mean that either one or the other is wrong, but, rather, that it’s impossible to define their origin with the current information. Both hypotheses have their foundations, so it’s just a matter of time before this puzzle is solved.
Global distribution
Although this organism has a wide distribution, it is likely to be affected by patterns of seasonality. In other words, its presence in various oceans may increase or decrease, depending on the time of year. This is because their movement patterns seem to be linked to the availability of food.
Characteristics of the megamouth shark
One of the main characteristics of the megamouth shark is its length, as it can reach more than 5 meters (16 feet) in length. In fact, females can reach up to 7 meters (23 feet) in length, this being a clear example of sexual dimorphism of the species.
Its body is soft and flabby to the touch, while its shape is similar to that of a tadpole, with a large head and a body that tapers as it reaches the tail. Its mouth is very large, with rounded edges and it extends 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, in addition to having 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, since at night it only reaches between 12 and 25 meters deep (40 – 80 feet). Its movement appears to follow the vertical migration of zooplankton, which is a large part of their diet.
The characteristics of the megamouth shark make it a slow species when swimming, since it reaches a speed of less than 1 meter (3.3 feet) 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 the diet of this organism is krill, however, it also consumes some copepods and zooplankton. This classifies it as a filter 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 its physiology is weak – it has to suck rather than actively chase 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 tropical regions.
The type of fertilization that this cartilaginous fish uses is internal and they have copulatory encounters that can leave scars. This shark is an ovoviviparous species, so its children feed on yolk inside their mothers.
Protection and conservation status
This organism is listed as a species of least concern, however, this is due to the lack of information on its populations. It’s likely that, despite this, the species has a stable population, as since its discovery, encounters with this animal have increased slowly.
The planet is covered by almost three-quarters of water, so the number of aquatic species is unbelievably high. It’s likely that, in the future, we’ll continue to discover more and more marine animals that may surprise us, such as this shark. It isn’t necessary to fear them, but, rather, to get to know and understand them.
All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.
- Martin, A. P., Pardini, A. T., Noble, L. R., & Jones, C. S. (2002). Conservation of a dinucleotide simple sequence repeat locus in sharks. Molecular Phylogenetics and Evolution, 23(2), 205-213.
- Shimada, K., & Ward, D. J. (2016). The oldest fossil record of the megamouth shark from the late Eocene of Denmark and comments on the enigmatic megachasmid origin. Acta Palaeontologica Polonica, 61(4), 839-845.
- Watanabe, Y. Y., & Papastamatiou, Y. P. (2019). Distribution, body size and biology of the megamouth shark Megachasma pelagios. Journal of fish biology, 95(4), 992-998.
- Nakaya, K. (2010). Biology of the megamouth shark, Megachasma pelagios (Lamniformes: Megachasmidae). In Proceedings of an international symposium—into the unknown, researching mysterious deep-sea animals. Okinawa: Okinawa Churaumi Aquarium (pp. 69-83).
- Castillo-Géniz, J. L., Ocampo-Torres, A. I., Shimada, K., Rigsby, C. K., & Nicholas, A. C. (2012). Tiburón bocudo juvenil, Megachasma pelagios, capturado en la costa del Pacífico de México, y su relevancia para la diversidad de los peces condrictios en México. Ciencias marinas, 38(2), 467-474.
This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.