The largemouth, megamouth or widemouth shark (Megachasma pelagios), is a shark that was identified as a new species relatively recently in 1983. Further studies are still needed to find out more details about this animal, since various aspects related to its biology, behavior and habitat are unknown. As of December 2018, just over 120 individuals had been documented, which has undoubtedly limited studies on the species.[1]
However, different characteristics of this cartilaginous fish have been discovered, which turn out to be peculiar and different from the traits commonly shared by chondrichthyans. We invite you to continue reading this file on our site and discover some of the characteristics of the largemouth shark.
Characteristics of the Greatmouth Shark
The most prominent feature of this shark, which gives rise to its common name, is its large mouth, which is broadly rounded. As for the parts of the largemouth shark, the head is large, the eyes are small, and the snout is extremely short and round. The jaws correspond to this last aspect, managing to open widely but without distending much laterally. This animal has many small hook-shaped teeth, but they are not functional.
Due to the presence of a rather conspicuous white stripe, which is present on its upper lip, it was thought that this animal produced bioluminescence, which was used as a feeding decoy. However, recent studies [2] have discarded this idea and establish that it is most likely that thanks to the denticles that are located in this strip, the animal reflects the light of luminescent plankton.
The body of the widemouth shark is cylindrical and robust, but it tapers towards the posterior region, giving a tadpole-like shape. It has a flaccid build and dark brown coloration The largemouth shark reaches reach a size of about 5 meters long and a weight of 750 kg
As for the fins, it has two dorsal fins, which are located low and are angular. The anal is small in size, while the pectorals are elongated and narrow. For its part, the pelvic is of medium size and the caudal is asymmetrical.
Bigmouth shark habitat
The widemouth shark has a wide distribution range in the tropical and temperate waters of the main oceans. Although there is limited data on its populations, it is known to occur in greater abundance in regions such as Taiwan, Japan, and the Philippines, as well as in the central and western Pacific Ocean. Reports indicate [3] that the first specimen captured was in 1976 in Hawái
The habitat in which it is located corresponds to waters of the continental shelf and the oceanic ones. It manages to be present at different depths, to 5 m near the coast, 40 m on the continental shelf and in much greater depths in the pelagic zone, about 1000 m.
Customs of the Greatmouth Shark
The widemouth shark is not considered a dangerous species for humans because no aggressive behavior has been identified. It used to swim slowly and until now it is considered a kind of vertical migration It That is, it makes continuous movements in this direction. The monitoring of some individuals showed that during the day they moved to depths between 120-160 m and at night they ascended between 12-25 m approximately.
These vertical mobilizations seem to be linked to the light levels that affect the food of these animals. It is also estimated that it dives deeper to escape disturbances, which could be related to why the species had not been previously known.
Occasionally, some individuals have been seen swimming in the surface waters.
Food of the Greatmouth Shark
This animal is one of the few shark species that exclusively filter feedsDespite having a large number of rows of teeth in both jaws, nonfunctional. It moves at low speeds with its mouth open to allow water to enter, which it will then expel. But, thanks to the cartilaginous lining of the gills, the food is trapped and can be consumed.
The widemouth shark feeds mainly on plankton, krill, copepods, a kind of luminescent jellyfish (Atolla vanhoeffeni) and small fish.
Reproduction of the largemouth shark
Until now it is only known that male largemouth sharks mature when they are approximately 4 meters long. It is a species with internal fertilization and due to its reproductive mode it is classified as ovoviviparous or lecithrotrophic viviparous After absorbing the yolk sac, the embryo resorts to oophagy or uterine cannibalism, that is, it consumes other eggs produced by the mother.
In some areas the species can reproduce between October and November and at birth they are smaller than 177 cm.
Conservation status of the widemouth shark
The main threat to the widemouth shark is its bycatch by large fisheries,so that this animal gets caught in various types of nets used by the aforementioned industry. Until now, the International Union for Conservation of Nature (IUCN) has classified it as in the category of least concern and its population trend is unknown. In Asia and Brazil it is a species that is marketed for consumption.
Among conservation actions, the retention of these individuals in the United States has been prohibited, unless they are captured incidentally and in these cases they are donated or sold for scientific, educational or exhibition purposes. In countries like Taiwan, there is the obligation to report captures of this animal
Due to the lack of information on the global population and the habits of the largemouth shark that indicate a tendency to be caught incidentally with some ease, it is necessary to develop protection actions to avoid future risks leading to possible extinction of the species.
