Scientific name........Megachasma Pelagios
The Megamouth shark was recently discovered in 1976 off Hawaii and
therefore a new genus, species, and family of vertebrates was
created known as the Megamouth shark. Its scientific name comes from
the Greek to mean "giant yawner of the open sea".
They are a huge shark with a large, wide, long head, short snout and
a huge mouth extending behind the eyes. It has a flabby body, soft
fins, asymmetrical tail, and a lack of keels. It has elongated
pectoral fins, the gill slits are moderately long and are lines with
dense, fingerlike dermal papillae.
The largest size of the megamouth shark reported was 18 feet, the
size of some females have been reported at 12 feet and 16 feet and
males at 6 feet and 13 feet. Size at birth unknown.
For the size of the megamouth shark, their teeth are very small but
plentiful, there are approximately fifty rows of teeth and
relatively numerous on each jaw. The upper and lower jaws have a
symphyseal ( where the two halves of the jaw meet ) is a toothless
space, but it is larger in the upper jaw. A difference between the
upper and lower teeth was recognized on a female specimen. The first
five upper teeth are smaller than the first five lower teeth; the
more distal upper teeth are smaller than the lower teeth; the cusps
of the lower teeth are more acute and longer than those of the upper
These sharks are a gray to blackish brown color on the dorsal
surface ( light margins to blackish pectoral and pelvic fins. ) and
white on the ventral surface. Dark spotting on lower jaw. Mouth roof
on dorsal and lateral parts, and oral membranes, silvery. Tongue
purplish brown with slight silvery tint on both sides, dorsally and
ventrally. Both sexes seem to have a white band on the anterior
surface of the snout. This white band could be considered a feeding
bechacioral characteristic, because it is so contrasted by the dark
coloration of the snout and upper jaw, and becomes very prominent
when the upper jaw is protruded. Probably under low light this white
band may be more visible. This band might also be related to
recognition of other individuals of the same species.
It appears to be a plankton feeder, like the whale shark and the
basking shark. It swims slowly through the open ocean, filtering
small shrimps and other prey from the water as it goes. It spends
the day feeding in deep water and comes up to shallower water at
night. The silvery lining of its mouth cavity is probably
reflective, so that when shrimps and luminous crustaceans enter the
open, cavernous mouth, they may encourage others to enter possibly
This species is presumed to be a verticle migrator on a diel cycle,
( spending the daytime in deep waters and ascending to midwater
depths at night ). This verticle migration may be a response to the
movements of the small animals on which it feeds. The krill that
make up part of megamouth's diet are known to migrate from deep
waters to the surface. Almost all megamouth sharks reported
presented scars in different parts of the body. These scars are
considered bite marks of the cookiecutter shark and with similar
verticle migrator patterns the megamouth combined with its slow
swimming speed it would make it an easy target for the active
Megamouth sharks are found throughout the word's oceans, often at
great depths. From confirmed sightings this species is now known
from India, Pacific and Atlantic Oceans. By tagging some individuals
they were able to demonstrate that this species engages in vertical
migrations on a diel cycle.
Reproduction is unknown, although presumed viviparous with oophagy.
The Megamouth shark is considered to be less active and a poorer
swimmer than that of the basking shark and whale shark. Their poor
mobility likely a reflection of its flabby body, soft fins,
asymmetrical tail, lack of keels and weak calcification.
Due to the lack of information concerning distribution and
population status, the megamouth is considered "Data Deficient" by
the World Conservation Union ( IUCN ).