#Fantastic Animals #Rising Knowledge: The 6 Strangest Hearts in the Animal Kingdom, Which One Do You Like! 》
The heart shape has become an iconic symbol of Valentine's Day, but when it comes to heart shapes in the real world, one size isn't for everyone – especially in the animal kingdom. At rest, the human heart beats 60 to 80 times a minute for days, but at the same time, the heart of a hibernating groundhog beats tightly for 5 days, while the heart of a hummingbird beats 1,260 times per minute during a powered flight. The human heart weighs about 0.6 pounds (0.3 kg), but the giraffe weighs about 25 pounds (11 kg) because the organ needs to be strong enough to pump blood into the long neck of the animal. There are other creatures with strange hearts here.
1. Frogs. Daniel Markahi, a vertebrate research collaborator at the Smithsonian Institution's Natural History Museum in Washington that specializes in amphibians and reptiles, says that the hearts of mammals and birds are four-chamber, while frogs have only three chambers, with two atriums and one ventricle.
In general, he said, the heart absorbs deoxygenated blood from the body, transports it to the lungs for oxygen, and then pumps it into organs throughout the body for oxygen. In humans, a four-chamber heart preserves oxygenated and deoxygenated blood in different chambers. But in frogs, grooves called trabeculars separate oxygenated blood from deoxygenated blood in one ventricle.
2. Whales. This life-size model shows the huge heart of a blue whale. (Image: © AMNH/D. Finnin)
The heart of the blue whale is the largest of all animals today. "It's only the size of a small car and weighs about 950 pounds (430 kilograms)," said James Mead, emeritus curator of marine mammals in the Department of Vertebrate Zoology at the Smithsonian Institution's National Museum of Natural History. Like other mammals, whales have four chambers in their hearts.
When blue whales dive deep into the sea, their heart rate slows down to four times per minute, which helps them extend their dives and even alleviate decompression sickness known as bends. A 2021 study published in Comparative Biochemistry and Physiology Part A: Journal of Molecular and Integrated Physiology suggests that this lower heartbeat reduces the passage of blood into the pressurized lungs, while a reduction in nitrogen uptake may reduce curvature.
3. Cephalopods
Cheer for the three hearts of Aonius borealis squid. (Image: Michael Vecchione)
Cephalopods have no place for half-heartedness. These tentacled and armed sea creatures, including octopus, squid and cuttlefish, each have three hearts.
Michael Vecchione said the two humeral hearts on either side of the cephalopod's body oxygenate the blood by pumping blood into the gills' blood vessels, while the whole-body heart in the body center pumps oxygenated blood from the gills into the rest of the organism, an invertebrate at the Smithsonian's National Museum of Natural History.
Cephalopods are actually blue-blooded animals because they contain copper in their blood. Human blood is red because of the iron in hemoglobin. "Just as rust is red, the iron in our hemoglobin is red when oxidized," Vecchione said. But in cephalopods, oxygenated blood turns blue.
4. Cockroaches
Cockroaches beat their hearts at about the same rate as human hearts. (Image: Paul Starosta via Getty Images)
Like other insects, cockroaches have an open circulatory system, which means its blood doesn't fill up with blood vessels. Don Moore III, a senior scientist at the Smithsonian's National Zoo in Washington, D.C., said that instead, blood flows through a structure with 12 to 13 chambers.
Moore said the heart of a wingless cockroach is usually smaller than that of a flying cockroach. He added that the heart of a cockroach beats at about the same rate as a human heart.
5. Earthworms
Earthworms have five five false hearts. (Image: Gayle Shortland, by Getty Images)
The earthworm can't cheer up because it doesn't have one. Instead, the worm has five pseudo-hearts around its esophagus. Instead of pumping blood, Moore said, these fake hearts squeeze blood vessels to help blood circulate through the worm's body.
It also does not have lungs, but absorbs oxygen through its moist skin. "The air trapped in the soil, or the worms remain moist on the ground after the rain, dissolve in the mucus of the skin, oxygen is sucked into cells and blood it is pumped to the system around the body,"
Earthworms have red blood that contains hemoglobin, a protein that carries oxygen, but unlike humans, earthworms have an open circulatory system. "So hemoglobin just floats in other fluids," Moore said.
6. Fish
Zebrafish can regenerate the heart. (Image: Mirko_Rosenau via Getty Images)
Humans can regenerate livers, amphibians and some lizards can regenerate tails, and in a 2022 study published in the journal Science Advances, frogs given a special drug cocktail can even re-grow legs, but the regenerative ability of zebrafish makes it the primary model for studying heart growth, Moore said.
However, fish have a unique heart. In addition to an atrium and an ventricle, fish have two structures that are not seen in humans. The "sinus" is the sac located in front of the atrium, and the "arterial bulb" is the tube located behind the ventricle.
Like other animals, the heart drives blood throughout the body. Deoxygenated blood enters the sinuses and flows into the atrium, Moore said. The atrium then pumps blood into the ventricles.
The ventricular walls are thicker and more muscular, pumping blood into the arterial bulb. As blood flows through the capillaries around the gills of the fish, the arterial bulb regulates the pressure of the blood. It is in the gills that oxygen is exchanged through cell membranes into the bloodstream, Moore said.
Which of these 6 hearts do you like the most? #科普 #
