These ancient aquatic lizards were warm-blooded, study finds

MAY 9, 2016

by Brett Smith

Paleontologists have debated for years over whether or not ancient lizards called mosasaurs were warm-blooded.

Now, a new paper published in the journal Palaeontology has found that the aquatic lizards were in fact warm-blooded, also known as using “thermoregulation”.

"There was a paper published in Science in 2010 reporting the thermoregulation in marine reptiles at the time of the dinosaurs focusing on the iconic extinct taxa: ichthyosaurs, plesiosaurs and mosasaurs," said author of the new study Alberto Perez-Huerta, an associate professor of geology at the University of Alabama. "This conclusion bothered me a bit because there was not a warm-blooded member organism used for comparison, and we know that size can matter in terms of thermoregulation."

How did the team come to this conclusion?

To reach their conclusion, the study team utilized an oxygen isotope analysis on mosasaur fossils in the University of Alabama's collection and contrasted them to fossils of recognized cold-blooded animals, like fish and turtles, from the same era, as well as the remains of modern warm-blooded organisms like birds.

According to the study, mosasaurs' body-temperatures were similar to the temperatures of contemporary, warm-blooded sea birds, indicating mosasaurs were certainly warm-blooded. The study indicated this tendency toward thermoregulation was regardless of the size of mosasur genus or species. Body size also didn't factor into the results.

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First Warm-Blooded Fish Found

by Stephanie Pappas, Live Science Contributor | May 14, 2015 02:02pm ET

The car-tire-size opah is striking enough thanks to its rotund, silver body. But now, researchers have discovered something surprising about this deep-sea dweller: It's got warm blood.

That makes the opah (Lampris guttatus) the first warm-blooded fish every discovered. Most fish are exotherms, meaning they require heat from the environment to stay toasty. The opah, as an endotherm, keeps its own temperature elevated even as it dives to chilly depths of 1,300feet (396 meters) in temperate and tropical oceans around the world.

Credit: NOAA Fisheries, Southwest Fisheries Science Center

"Increased temperature speeds up physiological processes within the body," study leader Nicholas Wegner, a biologist at the National Oceanic and Atmospheric Administration (NOAA) Fisheries' Southwest Fisheries Science Center in La Jolla, California, told Live Science. "As a result, the muscles can contract faster, the temporal resolution of the eye is increased, and neurological transmissions are sped up. This results in faster swimming speeds, better vision and faster response times." 

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Warm-blooded fish move through water faster, says study

May 7, 2015

Eric Hopton for redOrbit.com – Your Universe Online

Not all fish species are completely cold-blooded. Some have a unique physiological characteristic – a web of arteries and veins that allows them to raise their internal temperatures higher than that of the water surrounding them. This gives them a big ecological advantage over their truly cold-blooded cousins as they can move up to twice as fast and twice the distance. One species, the white shark, has a migration range greater than that of the humpback whale.

An international team of scientists, including UC Santa Barbara research biologist Jenn Caselle, found that species with the ability to warm their core, a process called endothermy, can swim two and a half times faster and have much wider ranges. Some, including certain sharks and tuna species, can travel distances comparable to those of warm-blooded animals such as penguins and other marine mammals.

Transport costs on the rise

“The cost of moving faster and farther is high so there has to be an ecological reason that outweighs the physiological expenditure,” said Caselle. “These endothermic fishes are putting a lot more energy into each unit of movement than their cold-blooded counterparts are.

“In fact, the estimated cost of transport is twice as high, but in return they’re getting benefits from that increased swimming speed and wider range of migration,” she added. “We hypothesize these gains allow these endotherms to be more efficient hunters and to span larger areas in their migration, which probably provides feeding and reproduction benefits.”

The team beefed up existing data with new information by attaching sensors, designed and built by lead author Yuuki Watanabe of Japan’s National Institute of Polar Research, to several sharks in different locations around the world.

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