For the next few months we’re going to share some facts about the whale sharks every week with you. In this third episode we’re talking about the physiology & anatomy of the whale sharks!
The largest whale shark that has been directly measured was reported to be 12.65 meters (41.50 ft) long and weighed more than 21.5 tons.
The body surface is mostly grey (above) and white (below). Three prominent ridges run along the sides and the skin is marked with a checkerboard of spots and stripes which may function as camouflage. The patterns of spots are used to identify sharks from photographs, a method that assumes that they are unique to an individual and that they do not change with age.
The skin of whale sharks is relatively thin, a couple of millimeters, and is covered in tiny teeth-like scales called denticles, which provide a tough, hydrodynamic surface layer. Below the skin is a layer of fatty tissue that can be 10-15 cm thick and is probably important for insulating the shark’s muscles and vital organs.
Whale sharks have two dorsal fins and two lateral pectoral fins. The upper lobe of the tail (caudal) fin of juvenile sharks is larger than the lower lobe compared with adults which have a more crescent-shaped tail.
Spiracles are the small circular openings just behind the whale shark’s eyes. The function of the spiracles of whale sharks is not known. It might be intermediate as whale sharks are more closely related to bottom-dwelling sharks though they also spend substantial time swimming throughout the water column. Consequently the spiracles might function when whale sharks are occasionally stationary but not feeding (when water is passing over the gills).
The mouth of this large filter feeder can be up to 1.5 meters wide. It contains between 300 and 350 rows of tiny scale-like teeth which look like a rasp close-up and account for the species original latin name Rhinodonte, which means rasp-tooth. These teeth do not appear to have function in feeding.
Whale sharks have five large pairs of gills which serve two functions. They extract oxygen from the water to support metabolism and also filter out small prey from seawater.
There are two small eyes located near the front of the wide, flat head. The forward, lateral placement of the eyes allows the sharks to see forward, backward, above and below.
The nostrils are in the front of the head above the mouth and they may have an important function in detection of substances in the water. The large, well developed internal sensory structures connected to the nostrils support this suggestion.
If you are interested in facts about the whale sharks, make sure you read this blog every week. If you want more information and want to get the latest news from EcoColors subscribe to our monthly newsletter!
Even though Monday was the official national holiday of el Día de la revolución (3rd Monday of November), today is el veinte de noviembre (20th of November) so the historical date of the Revolution.
At this day, the Mexicans remember and celebrate the Revolution of 1910 to 1920. But why is it celebrated at the 20th of November? I will try to explain what happened that day…
Francisco I. Madero was one of many people in mexico who were tired of Díaz’ (President) authoritarian rule. Madero formed the Anti-Reelectionist Party and ran against Diaz, but the elections were rigged and Díaz won. Diaz set Madero in jail, but upon his release he fled to Texas and wrote a plan which urged the people to rise up in arms against the government. The date of November 20th was set for the revolt to begin.
The first shots of the revolution were fired on November 18 at the home of Aquiles Serdán, which is now the Museo de la Revolución. This is because the authorities discovered that Aquiles Serdán and his family were planning to participate in the revolution. The rest of the revolutionaries joined the fight on November 20th as planned, and that is still considered the official beginning of the Mexican Revolution.
Nowadays they celebrate el veinte de noviembre (20th of November) with parades and civic ceremonies throughout the enitre country. There is a large parade in Mexico City’s Zocalo, as well as speeches and official ceremonies. In cities and towns throughout Mexico schoolchildren dress themselves as revolutionaries to participate in local parades.
If you like to know more about the Mexican traditions and holidays, read my other blog about the celebration of el Día de los Muertos (Day of the dead), at the 2nd of November!
– Chantal van den Boogaert