Fall Asleep While Learning About Whale Sharks

In this episode of the I Can't Sleep Podcast, fall asleep while learning about whale sharks. These beautiful creatures have been on my I'm-totally-not-afraid-of-the-deep-ocean bucket list to see and interact with up close. Thanks to Madison for recommending this topic. Happy sleeping!

Transcript

Welcome back,

Or welcome to the I Can't Sleep Podcast,

Where I read random articles from across the web to bore you to sleep with my soothing voice.

I'm your host,

Benjamin Boster.

Today's episode is from a Wikipedia article titled Whale Shark,

As recommended by Madison from Spotify.

The whale shark is a slow-moving,

Filter-feeding carpet shark,

And the largest known extant fish species.

The largest confirmed individual had a length of 18.

8 meters,

Or 61.

7 feet.

The whale shark holds many records for size in the animal kingdom,

Most notably being by far the most massive living non-cetacean animal.

It is the sole member of the genus Rhincodon,

And the only extant member of the family Rhinodontidae,

Which belongs to the subclass Elasmobronchii in the class Chondrichthyes,

Before 1984 was classified as Rhiniodon into Rhinodontidae.

Whale sharks inhabit the open waters of all tropical oceans.

They are rarely found in water below 70 degrees Fahrenheit.

Whale sharks' lifespans are estimated to be between 80 and 130 years,

Based on studies of their vertebral growth spans and the growth rates of free-swimming sharks.

Whale sharks have very large mouths and are filter feeders,

Which is a feeding mode that occurs in only two other sharks,

The megamouth shark and the basking shark.

They feed almost exclusively on plankton and small fishes and pose no threat to humans.

The species was distinguished in April 1828 after the harpooning of a 4.

6 meter specimen in Table Bay,

South Africa.

Andrew Smith,

The military doctor associated with British troops stationed in Cape Town,

Described it the following year.

The name whale shark refers to the animal's appearance and large size.

It is a fish,

Not a mammal,

And,

Like all sharks,

Is not closely related to whales.

In addition,

Its filter feeding habits are similar to baling whales.

Whale sharks possess a broad flattened head with a large mouth and two small eyes located at the front corners.

Unlike many other sharks,

Whale shark mouths are located at the front of the head rather than on the underside of the head.

A 12.

1 meter whale shark was reported to have a mouth 1.

55 meters across.

Whale shark mouths can contain over 300 rows of tiny teeth and 20 filter pads which it uses to filter feed.

The spiracles are located just behind the eyes.

Whale sharks have five large pairs of gills.

Their skin is dark gray with a white belly marked with an arrangement of pale gray or white spots and stripes that is unique to each individual.

The skin can be up to 15 centimeters thick and is very hard and rough to the touch.

The whale shark has three prominent ridges along its sides which start above and behind the head and end at the caudal peduncle.

The shark has two dorsal fins set relatively far back on the body,

A pair of pectoral fins,

A pair of pelvic fins,

And a single medial anal fin.

The caudal fin has a larger upper lobe than the lower lobe.

Whale sharks have been found to possess dermal denticles on the surface of their eyeballs that are structured differently from their body denticles.

The dermal denticles,

As well as the whale shark's ability to retract its eye deep into their sockets,

Serve to protect the eyes from damage.

Evidence suggests that whale sharks can recover from major injuries and may be able to regenerate small sections of their fins.

Their spot markings have also been shown to reform over a previously wounded area.

The complete and annotated genome of the whale shark was published in 2017.

Rhodopsin,

The light-sensing pigment in the rod cells of the retina,

Is normally sensitive to green and used to see in dim light,

But the whale shark and the bottom-dwelling cloudy cat shark,

Two amino acid substitutions,

Make the pigment more sensitive to blue light instead,

The light that dominates the deep ocean.

One of these mutations also makes rhodopsin vulnerable to higher temperatures.

In humans,

A similar mutation leads to congenital stationary night blindness,

As the human body temperature makes the pigment decay.

This pigment becomes unstable in shallow water,

Where the temperature is higher and the full spectrum of light is present.

To protect from this instability,

The whale shark deactivates the pigment when in shallow water,

As otherwise the pigment would hinder full color vision.

In the colder environment,

At 2,

000 meters below the surface where the shark dives,

It is activated again.

The mutations thus allow the shark to see well at both ends of its great vertical range.

The eyes have also lost all cone opsins except LWS.

The whale shark is the largest non-cetacean animal in the world.

Evidence suggests that whale sharks exhibit sexual dimorphism with regards to size,

With females growing larger than males.

A 2020 study looked at the growth of whale shark individuals over a 10-year period.

It concluded that males,

On average,

Reach 8 to 9 meters in length.

The same study predicted females to reach a length of around 14.

5 meters on average,

Based on more limited data.

However,

These are averages and do not represent the maximum possible sizes.

The study also found that females were larger than males,

However,

These are averages and do not represent the maximum possible sizes.

Previous studies estimating the growth and longevity of whale sharks have produced estimates ranging from 14 to 21.

9 meters in length.

Limited evidence,

Mostly from males,

Suggests that sexual maturity occurs around 8 to 9 meters in length,

With females possibly maturing at a similar size or larger.

The maximum length of the species is uncertain due to a lack of detailed documentation of the largest reported individuals.

Several whale sharks around 18 meters in length have been reported.

Large whale sharks are difficult to measure accurately,

Both on the land and in the water.

When on land,

The total length measurement can be affected by how the tail is positioned,

Either angled,

As it would be on life,

Or stretched as far as possible.

Historically,

Techniques such as comparisons to objects of known size and knotted robes have been used for in-water measurements,

But these techniques may be inaccurate.

In 2011,

Laser photogrammetry was proposed to improve the accuracy of in-water measurements.

Since the 1800s,

There have been accounts of very large whale sharks.

Some of these are as follows.

In 1868,

The Irish natural scientist Edward Percival Wright obtained several small whale shark specimens in the Seychelles.

Wright was informed of one whale shark that was measured as exceeding 45 feet.

Wright claimed to have observed specimens over 50 feet and was told of specimens upwards of 70 feet.

Hugh M.

Smith described a huge animal caught in a bamboo fish trap in Thailand in 1919.

The shark was too heavy to pull ashore,

And no measurements were taken.

Smith learned through independent sources that it was at least 10 wa,

A Thai unit of length measuring between a person's outstretched arms.

Smith noted that 1 wa could be interpreted as either 2 meters,

Or the approximate average of 1.

7 to 1.

8 meters,

Based on the local fishermen.

Later sources have stated this whale shark as approximately 18 meters,

Or 59 feet,

But the accuracy of the estimate has been questioned.

Scott A.

Eckert and Brent S.

Stewart reported on satellite tracking of whale sharks from between 1994 and 1996.

Out of the 15 individuals tracked,

Two females were reported as measuring 15 feet.

A 20.

75 meter long whale shark was reported as being stranded along the Ratnagiri coast in 1995.

A female individual with a standard length of 15 meters,

And an estimated total length of 18.

8 meters,

Was reported from the Arabian Sea in 2001.

In a 2015 study looking into the size of marine megafauna,

McClain and colleagues considered this female as being the most reliable and accurately measured.

On the 7th of February 2012,

A large whale shark was found floating 150 kilometers off the coast of Karachi,

Pakistan.

The length of the specimen was said to be between 11 and 12 meters,

With a weight of around 15,

000 kilograms.

The whale shark inhabits all tropical and warm temperate seas.

The fish is primarily pelagic and can be found in both coastal and oceanic habitats.

Tracking devices have shown that the whale shark displays dynamic patterns of habitat utilization,

Likely in response to availability of prey.

Whale sharks observed off the northeast Yucatan Peninsula tend to engage in inshore surface swimming between sunrise and mid-afternoon,

Followed by regular vertical oscillations in oceanic waters during the afternoon and overnight.

About 95% of the oscillating period was spent in the epipelagic depths,

But whale sharks also took regular deep dives,

Often descending in brief stutter steps,

Perhaps for foraging.

The deepest recorded dive was 1,

928 meters,

Making the whale shark the deepest diving fish to be recorded.

Whale sharks were also observed to remain continuously at depths of greater than 50 meters for three days or more.

The whale shark is migratory and has two distinct sub-populations,

An Atlantic sub-population from Maine and the Azores to Cape Agulhas,

South Africa,

And an Atlantic sub-population from the Atlantic coast to Cape Agulhas,

South Africa.

And an Indo-Pacific population,

Which holds 75% of the entire whale shark population.

It usually roams between 30 degrees north and 35 degrees south,

Where water temperatures are higher than 70 degrees Fahrenheit,

But have been spotted as far north as the Bay of Fundy,

Canada,

And the Sea of Okhotsk north of Japan,

And as far south as Victoria,

Australia.

Seasonal feeding aggregations occur at several coastal sites,

Such as the Persian Gulf and Gulf of Oman,

Ningaloo Reef in Western Australia,

Darwin Island in the Galapagos,

Quintana Roo in Mexico,

Mafia Island of Pawnee region in Tanzania,

And Yemeneh province in Mozambique,

The Philippines,

Around Mahe and the Seychelles,

The Gujarat and Kerala coasts of India,

Taiwan,

Southern China,

And Qatar.

In 2011,

More than 400 whale sharks gathered off the Yucatan coast.

It was one of the largest gatherings of whale sharks recorded.

Aggregations in that area are among the most reliable seasonal gatherings known for whale sharks,

With large numbers occurring in most years between May and September.

Associated ecotourism has grown rapidly to unsustainable levels.

The whale shark is a filter feeder,

One of only three known filter feeding shark species,

Along with the basking shark and the megamouth shark.

It feeds on plankton,

Including copepods,

Krill,

Fish eggs,

Christmas island red crab larvae,

And small nektonic life,

Such as small squid or fish.

It also feeds on clouds of eggs during mass spawning of fish and corals.

The many rows of vestigial teeth play no role in feeding.

Feeding occurs either by ramming filtration,

In which the animal opens its mouth and swims forward,

Pushing water and food into the mouth,

Or by active suction feeding,

In which the animal opens and closes its mouth,

Sucking in volumes of water that are then expelled through the gills.

In both cases,

The filter pads serve to separate food from water.

These unique black sieve-like structures are presumed to be modified gill rakers.

Food separation in whale sharks is by cross-flow filtration,

In which the water travels nearly parallel to the filter pad surface,

Not perpendicularly through it.

This is an extremely efficient filtration method that minimizes fouling of the filter pad surface.

Whale sharks have been observed coughing,

Presumably to clear a buildup of particles from the filter pads.

The water is then sucked into the gills of the whale shark,

And the gills of the whale shark are filled with water.

The whale shark is an active feeder,

Targeting concentrations of plankton or fish.

It is able to ram filter feed,

Or can gulp in a stationary position.

This is in contrast to the passive feeding of the whale shark.

The active feeding of the whale shark is the feeding of plankton or fish.

It is able to ram filter feed,

Or can gulp in a stationary position.

This is in contrast to the passive feeding basking shark,

Which does not pump water.

Instead,

It swims to force water across the gills.

A juvenile whale shark is estimated to eat 21 kilograms of plankton per day.

The BBC program Planet Earth filmed a whale shark feeding on a school of small fish.

The same documentary showed footage of a whale shark timing its arrival to coincide with the mass spawning of fish shoals,

And feeding on the resultant clouds of eggs and sperm.

Whale sharks are known to prey on a range of planktonic and small fish.

Whale sharks are known to prey on a range of planktonic and small nektonic organisms that are spatiotemporally patchy.

These include krill,

Crab larvae,

Jellyfish,

Sardines,

Anchovies,

Mackerels,

Small tunas,

And squid.

In ram filter feeding,

The fish swims forward at constant speed with its mouth fully open,

Straining prey particles from the water by forward propulsion.

This is also called passive feeding,

Which usually occurs when prey is present at low density.

Due to their model of feeding,

Whale sharks are susceptible to the ingestion of microplastics.

As such,

The presence of microplastics in whale shark scad was recently confirmed.

Despite its size,

The whale shark does not pose any danger to humans.

Younger whale sharks are gentle and can play with divers.

Underwater photographers,

Such as Fiona Eyrst,

Have photographed them swimming close to humans without any danger.

Although whale sharks are docile fish,

Touching or riding the sharks is strictly forbidden and finable in most countries as it can cause serious harm to the animal.

The megamouth shark is a species of deep water shark.

Rarely seen by humans,

It measures about 5.

2 meters long and is the smallest of the three extant filter feeding sharks alongside the relatively larger whale shark and basking shark.

According to Sharkman's World Organization,

A total of 286 specimens have been observed or caught since its discovery in 1976.

Like the other two planktivorous sharks,

It swims with its mouth wide open,

Filtering water for plankton and jellyfish.

It is recognizable from its large head with rubbery lips.

The megamouth is so unlike any other type of shark that it is usually considered to be the sole extant species in that family,

Though some scientists have suggested it may belong to another family.

As of the 5th of March 2018,

Only 99 megamouth specimens have been caught or sighted.

They have been found in the Pacific,

Atlantic,

And Indian Oceans.

Japan,

The Philippines,

And Taiwan have each yielded at least 10 specimens,

The most of any single area,

Amounting to more than half the worldwide total.

Specimens have also been sighted in or come out of the waters near Hawaii,

California,

Mexico,

Indonesia,

Australia,

Brazil,

Senegal,

South Africa,

Puerto Rico,

Ecuador,

And possibly Vietnam.

Researchers have predicted the feeding patterns of megamouth sharks in relation to the other two planktivorous sharks.

The three planktivorous sharks have ram feeding in common,

As it evolved from ram feeding swimming type ancestors that developed their filtering mechanism to capture small prey like plankton.

The appearance of the megamouth is distinctive,

But little else is known about it.

It has a brownish-black color on top,

Is white underneath,

And has an asymmetrical tail with a long upper lobe,

Similar to that of the thresher shark.

The interior of its gill slits are lined with finger-like gill rakers that capture its food.

A relatively poor swimmer,

The megamouth has a soft flabby body and lacks caudal keels.

The megamouth is considerably less active than the other filter-feeding sharks,

The basking shark and the whale shark.

The megamouth has a stout body and a long,

Wide bulbous head.

Megamouths are large sharks,

Able to grow to 5.

49 meters in length.

Mature males average at 4 meters and females at 5 meters.

Weights of up to 1,

215 kilograms have been reported.

A 2019 study suggested that it would have reached 6 meters in maximum length.

Megamouth sharks can be found as far northward as northern Japan,

Southern California,

LACM 43745-1,

And near Punta Eugenia,

Baja California and Hawaii.

Megamouth sharks are dark blue,

Brownish-black,

Or gray above,

Lighter below,

With a white band along the upper jaw,

While the posterior margin of its fins are white.

As their name implies,

Megamouths have a large mouth with small teeth and a broad,

Rounded snout,

Causing observers to occasionally mistake the megamouth for a young orca.

The protruding inside of the upper lip is a brilliant,

Silvery white,

Which is very visible when the mouth is open.

This lip was initially thought to be possibly embedded by luminous photophores when the first shark was examined in the early 1980s,

Which may act as a lure for plankton,

While the team examining the second shark in the mid-1980s instead proposed that the lower lip might glow while the white band used as a reflector of sorts,

But neither theory has been proven.

In 2020,

A study concluded that this species of shark does not,

In fact,

Produce any light.

The white band was found to merely be highly reflective of light.

This white band is present in both sexes and could be either a feeding mechanism,

Or possibly be used as a means of identifying other individuals of megamouth sharks.

Their mouths can reach up to 1.

3 meters in width.

Megamouth sharks have up to 50 rows of teeth in their upper jaw,

And up to 75 rows of teeth in their lower jaw.

Reviews

Love these sleep stories. They always put me back to sleep in the middle of the night.

I never heard of whale sharks, how interesting! Although I did fall asleep after 5 minutes so it was either your voice or the topic (I’m going with your voice!)