Episode 140 – Mako Shark: Hot-Blooded Hotrod

Sharks are a primordial design. A torpedo built to catch and shred prey. These cold black eyes, like a doll’s eyes, are nothing but dark pools of basic, rudimentary instinct, right? Well some sharks are built differently than their kin. The mako shark is one of a few fish with an interesting adaptation that is foreign among fish. These hot-blooded predators of the temperate ocean have an ability that gives them an edge against their most elusive food sources. Sometimes the only way to survive is chase down and catch Life, Death, and Taxonomy…

Description of the Mako Shark

  • Pretty typical shark
  • Slim, tubular body
  • Sharp, pointed snout
  • Large, black eyes (Like a doll’s eyes)
  • Extremely janky thornbush of teeth
  • Countershaded: silver back and sides with white belly

Measure Up

Welcome to the beloved Measure Up segment. The official listener’s favorite part of the show! The part of the show when we present the animal’s size and dimension in relatable terms through a quiz that’s fun for the whole family. It’s also the part of the show that’s introduced by you when you send in audio of yourself saying, singing, or chittering the words “measure up” into ldtaxonomy at gmail dot com. We have a new Measure Up intro, again from the Wizard Gandalf. He wrote, “My apologies for my previous submission. Saruman hacked my account. Go in peace!”

Length

  • 3.2 m (10 ft)
  • How many mako sharks go into the length of a square acre of land?
  • Hint: In the UK in the 19th century, the Swing Riots broke out over poor wages and unemployment of farmworkers. Between 1770 and 1830, 6 million acres of formerly common land was enclosed, which means it was absorbed into larger owned farms. The riots also had to do with the new use of threshing machines which made it so fewer workers were needed to complete a harvest. The Swing Riots were named after the fictitious Captain Swing, who would sign threatening letters sent to officials and farmers. Ironically, the riots ended with 19 hangings, 644 imprisonments, and sending 481 to Australia. Also, an acre is traditionally a rectangle that’s equal to one chain by one furlong. 
  • 20.8 sharks. A square acre is about 208.71 feet × 208.71. 

Weight

  • 60–135 kg (132–298 lb)
  • How many mako sharks go into the weight of the Titanic’s center anchor?
  • Hint: The anchor was the largest hand-forged anchor at the time. It measured 15 feet in length. The anchor was produced in pieces by three different companies.
  • 53.6 sharks. The anchor was nearly 8 tons.

Fast Facts About Mako Sharks

  • Range: All over the world’s oceans except for the arctic and Antarctic zones.
  • Diet: cephalopods, mackerels, tunas, bonitos, swordfish, other sharks, porpoises, sea turtles, seabirds. Swordfish are particularly dangerous.
  • Behavior: 
    • Voracious predator that ambushes prey from below.
    • They use smell and vision to hunt rather than electroreception like the great white
    • Like most sharks, mako sharks are ovoviviparous – meaning they give birth to live young
    • They can live to be about 29-32 years old
    • Has a high brain-to-body ratio (like the manta ray), so makos are relatively intelligent and are fast learners
    • I always thought they were responsible for a large number of fatal shark attacks, but there have only been 9 attacks recorded and only one was lethal.

Mako Shark Major Fact: Hot-Blooded Hot Rod

Most sharks are ectotherms, which means they’re cold-blooded like other fish, reptiles, and amphibians. Ectotherms depend on their environments to regulate their body temperatures, so they are found in the greeted diversity in warm regions. 

That’s why you’ll find most sharks in tropical and subtropical waters. There are arctic sharks like the Greenland shark, which survive by adapting to an extremely slow metabolism. But they are also some of the slowest swimming fish in the ocean.

A few sharks, including Great Whites, are endothermic, which means warm-blooded. This allows them to self-regulate their body temperature, which allows them to enjoy cooler climates. The Great White can be found all over the ocean, from Alaska to southern Argentina.

Our friend the mako shark has a somewhat bigger range than other ectothermic sharks, but it still prefers warm and temperate water. However, it’s warm blood may lend itself to something else: high-performance swimming. 

Mammal vs. Fish Breathing and Cardio

Humans, and other mammals and birds with warm blood, have different bodily systems to cold-blooded fish. Your blood flows from your heart to your organs, and back again. Then it’s sent to the lungs to be oxygenated, then back to the heart to be distributed. The cardiovascular and respiratory systems are two separated but connected systems.

In fish, it’s all one system where the heart pumps blood to the body, then through the gills and directly back to the body. Cold-blooded sharks do generate their own heat in their swimming muscles, but these muscles are on the outside of their flanks and close to the skin where most of the heat is lost to the ocean, like Wilson the volleyball.

Warm-blooded sharks have swimming muscles that are buried in their bodies which keeps them warmer longer. Makos also have more red-muscle, which is more powerful and requires more oxygen than white muscle. To supply this type of muscle, endothermic sharks have wider arteries that direct blood inwards to their swimming muscles. Their special network of arteries is called the Rete mirabile.

This vein and artery network involves a close net of tubes that carries blood to and from the muscles and heart. Arteries carry oxygenated blood to warm swimming muscles where it’s heated. Then veins carry oxygen-depleted blood close to the counterflowing arteries. The heated blood in the veins transfers heat to the blood in the arteries, which sends that heat back to muscles that produced the heat in the first place. This allows the shark to reach a heat equilibrium, where blood in the arteries and veins are around the same warm temperature. Since sharks need to continually swim to respirate, the shark maintains its own heat system. 

What Does This Have to Do With Speed?

The Mako shark is the fastest shark in the ocean. They can reach speeds of up to 35 mph, which is 10 mph faster than the speed of their fastest prey, the tuna. That’s 51 feet per second, so if you’re one and a half school buses away from him, he could reach you and give you a kiss on the cheek in the time it takes you to say, “Hey, it’s a mako.” The mako shark wins the title for several reasons. 

For one, it swims more efficiently than other sharks. If you look at similar-sized sharks, they’re bodies sway back so that their head counters their tail movement. Mako shark’s heads and front half remain still and straight while their powerful tails propel them forward. This helps them take better advantage of their perfectly conical and aerodynamic heads and body to reduce drag. 

Their muscles are also adapted to take in oxygen quickly which helps them recover from bursts of speed. Finally, their warm-blooded nature keeps their swimming muscles warm, which aids in performance. 

A study in 2003 examined metabolic enzyme activity in the muscles of a variety of sharks, including endothermic sharks like mako sharks and thresher sharks and cold-blooded sharks. Do you know what they found? 

They said, “Adjustment of enzyme activities to in vivo red muscle and white muscle temperatures in the endothermic lamnids elevates citrate synthase and lactate dehydrogenase in both tissues relative to the ectothermic sharks.”

In other words, hot muscles enhance enzyme activity which helps with aerobic and anaerobic performance. A hot muscle is a fast muscle. 

Episode 139 – Giant Manta Ray: A Focused Fish

“…and today we’re talking about a buccal pumping pup sucking histotroph in huge chunks. That sentence will only get grosser when you know what those words mean. But more on that later…”

Sometimes the biggest giants are the gentlest giants. But this gentle giant is also a genius giant. While the oceanic manta ray might not be smarter than a fifth-grader, it does use its brain in ways that would make other fish extremely sad and jealous if they had any feelings. In fact, it’s those feelings that make the manta ray a prime candidate for smartest swimming blanket. But when you’re the biggest fish in the pond, you can afford a little self-awareness here in Life, Death, and Taxonomy.