Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Chondrichthyes
Order: Orectolobiformes
Family: Rhiniodontidae
Genus: Rhincodon
Species: Rhincodon typus
The sole living member of its family, the whale shark is the world's largest living fish. Its massive, fusiform body reaches lengths in excess of
46' (14m). It has alternating thin white vertical bars and columns of spots on a dark background, with long ridges along the upper side of the
body and a prominent lateral keel. The narrow mouth extends across the full width of its flattened head. The eyes are small and far forward on
the head. Each nostril has a small barbel and the gill slits are long and extend above the pectoral fins. Above the relatively small pelvic fins
are the first of two dorsal fins. The powerful caudal fin is semicircular.
Its well-developed internal spongy filters at the gill arches help to retain small prey within its huge mouth. This mechanism may impede the
flow of water through the mouth during swimming, which limits the amount of plankton the shark can strain. So, as well as filter feeding, it
can also pump water into its mouth to feed on concentrated patches of plankton.
Size:
This shark is 45 cm (17.7 inches) at birth and attains a maximum length 14 m (46 feet),
and possibly larger.
The whale shark is aptly named to express the magnitude of their size. It is estimated that whale sharks have a
maximum life span of around 100-150 years.
Distribution:
The whale shark ranges
circumglobally near the equator, from 35 degrees south to 30 degrees south
Habitat:
The whale shark is found in all tropical and subtropical oceans, along coastal regions,
and enters lagoons on tropical islands. It is mostly seen on the surface were divers and snorkelers can swim with this gentle, curious creature. Read more.
Reproduction:
It appears as though whale sharks take part in copulation, but details beyond that
are scarce. This ovoviviparous species whose egg cases hatch in utero just before birth. Recently, a female whale shark (10.6 m [34 feet] long
and 16 metric tons) was examined from Taiwan that had about 300 embryos in the uteri. Some of the embryos were still in the leathery egg cases
and had yolk sacs, while most had emerged from the egg case and were lacking the yolk sac.
Feeding:
The whale shark will purge indigestible objects from the alimentary tract by inverting its
gut out its mouth. They occasionally associate with other sharks, dolphins, and pilot whales. It is a filter feeder that sucks squid, planktonic
crustaceans, and sardines into its capacious mouth. Tuna and jacks are also eaten as they feed on the sardines, while shark suckers may be
accidentally ingested. Whale sharks have been observed to adopt a vertical orientation at the water's surface when feeding. The sharks hang
in a tail-down position and thrust themselves up through schools of feeding tuna and baitfish until their heads break the water's surface.
Frenzied tuna have been observed to leap into the mouths of whale sharks feeding in this manner. Whale sharks have also been observed to adopt
this vertical orientation to ingest air bubbles emitted from scuba tanks! Juvenile whale sharks will employ a surface, suction feeding when
preying upon patches of planktonic copepods. They will lift their heads partway out of the water, turn their heads from side to side and gulp
down copepods swarming near the water's surface.
Behavior:
Usually solitary or in small loose groups, but has been observed in large aggregations,
numbering over 100 individuals. Whale sharks regularly associate with schools of scombrid fishes (i.e., mackerel and tuna).
These sharks are mild
mannered and usually indifferent or cautious when encountering humans. The whale shark is also a favorite host of remoras and shark suckers. These
commensals have been observed entering the mouth, spiracles and gill slits of the whale shark. They will feed on parasitic crustaceans, on food
scraps and the zooplankton (e.g., copepods) that their hosts eat. Other whale shark associates include requiem sharks, cobia, jacks, barracuda.
Distinguishing Characteristics:
Unmistakable! This species has light stripes and spots on a dark
background. The whale shark has a terminal mouth, ridges or keels on the side of its body and caudal peduncle, a broad head and a semilunate tail.
The jaws are lined with 300 rows of minute teeth and the inside of the gill slits support a spongy connective tissue. This shark is a filter
feeder and the spongy material associated with the gill arches helps sieve food items from the water.
