Manta rays may not be warm and cuddly, but they’re not your typical cold-blooded creatures either. These graceful giants don’t fit neatly into a single category: while technically cold-blooded, they evolved to warm up certain parts of their body, giving them an edge in speed, smarts, and survival.
The Basic Science: Cold-Blooded vs. Warm-Blooded
Before diving deeper, let’s clarify what these terms mean in the scientific world:
Cold-blooded (ectothermic) animals don’t maintain a constant body temperature. Their internal temperature fluctuates based on their surroundings. In simple words, when the air/water is cold, the animal is cold. Most fish, reptiles, and amphibians fall into this category.
Warm-blooded (endothermic) animals maintain a relatively constant internal body temperature regardless of their environment. The heat is generated inside the body. Mammals and birds are classic examples, typically maintaining high internal temperatures, around 35–37°C (96–99°F), even when external temperatures fluctuate.
Manta Rays: Cold-blooded With a Twist
According to Dr. Robert Rubin, Director of the Pacific Manta Research Group and a leading expert on manta physiology, the question of whether manta rays are cold or warm-blooded is more complex than it seems.
Recent research suggests that manta rays might be regionally endothermic. This means that while most of their body stays at the same temperature as the ocean, certain parts, like the brain or swimming muscles, can be warmer, thanks to a clever system of blood vessels called the rete mirabile (Latin for “wonderful net”).
This network of blood vessels works like a heat exchanger: when manta rays swim, their powerful pectoral fins generate heat. The rete helps retain that heat and direct it to the brain, where warmer temperatures can support higher function and quicker responses, even potentially increasing their intelligence level.
When the muscles warm up, their power output also increases, which is one reason why manta rays can reach speeds of up to 22 miles (35 km) per hour.
Not everything is clear-cut yet, though. In our correspondence, Dr. Rubin specified that researchers still don’t have exact measurements of the temperatures inside a manta ray’s brain, muscles, or eyes. However, their brain anatomy and the muscle structure near the base of their fins strongly suggest these areas stay warmer than the surrounding water.
Because of the manta’s large size and wide-ranging ocean lifestyle, collecting this kind of data for scientific research is challenging.
More Marine Animals That Generate Their Own Heat
Manta rays are not the only marine animals with this unique ability to warm specific parts of their bodies.
Like manta rays, tuna are known for their nonstop swimming. They can also maintain high speeds for long periods because their powerful swimming muscles generate heat, which is then retained and circulated through their bodies using the rete mirabile system. This allows them to keep their core muscles warmer than the surrounding water, improving performance and endurance.
Salmon sharks, which belong to the same family as great white sharks, take it further. They live in the cold waters of the Gulf of Alaska, where ocean temperatures are frigid. Despite this, their muscle temperatures can run 10 to 15 degrees Celsius warmer than the surrounding water. This helps them remain fast and agile in conditions where most other fish would slow down.
Even swordfish have adapted to life in deep, dark waters: instead of warming their muscles, they focus heat on their eyes and brain. This localized warmth likely helps them see better and process information faster during high-speed hunts.
This energy-efficient biology allows these animals to perform without the high metabolic demands of being fully warm-blooded.
There’s So Much More to Manta Rays Than You’d Think
Manta rays are a perfect example of how nature defies simple categories. While they are technically cold-blooded fish, their ability to warm specific parts of their bodies helps them swim faster, react quicker, and move efficiently – a clear evolutionary advantage for such large, ocean-roaming creatures.
This is just one of the many reasons manta rays are so fascinating. Their speed and agility make them among the most maneuverable animals in the ocean. They’ve even inspired engineers to rethink how underwater robots are designed – learn more about that here.
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