To date, there's only one species that has been called 'biologically immortal': the jellyfish Turritopsis dohrnii. These small, transparent animals hang out in oceans around the world and can turn back time by reverting to an earlier stage of their life cycle.
Sturdy turtles. Slow and steady really does win the race. Turtles have been known to live for centuries, and researches have found that their organs don't seem to break down over time. The New York Times reports that turtles might even be able to live indefinitely if they are able to avoid predators and disease.
Sharks never stop growing and will continue to expand as long as their environment allows them. The largest fish in the sea, the whale shark, can measure up to 40 feet long and weigh 60 tons.
Flatworms, nematodes, and cnidarians (jellyfish, sea anemones, and corals) do not have a circulatory system and thus do not have blood. Their body cavity has no lining or fluid within it.
Tardigrades are practically unkillable. The microscopic creatures, commonly known as "water bears," can tolerate stress that would end most other organisms.
Can you guess what animals might have blue blood? Lobsters, crabs, pillbugs, shrimp, octopus, crayfish, scallops, barnacles, snails, small worms (except earthworms), clams, squid, slugs, mussels, horseshoe crabs, most spiders. None of these animals have backbones. Some of these animals are Mollusks, like the snails.
To many, leeches are horrifying creatures. To a few, they're impressive and miraculous. They have 32 brains, 2 hearts, 300 teeth grouped in 3 jaws, five pairs of eyes...
Explanation: Black milk is the slimmest milk containing very little amount of fat (0.2%) is produced by Black rhinoceros.
Snails have more teeth than any animal.
A snail's mouth is no larger than the head of a pin, but can have over 25,000 teeth (but these aren't like regular teeth, they are on its tongue).
Spiders usually have eight eyes but few have good eyesight.
Some spiders have median eyes that can detect polarised light and they use this ability to navigate while hunting.
It's red because of the red blood cells (hemoglobin). Blood does change color somewhat as oxygen is absorbed and replenished. But it doesn't change from red to blue. It changes from red to dark red.
Giraffes have no vocal cords.
Snails, spiders and octopi have something in common- they all have blue blood! We're not talking in the sense of royalty, these creatures literally have blue blood. So why is their blood blue and ours red? One of the purposes of blood is to carry oxygen around the body.
What is a tardigrade? Tardigrades are microscopic eight-legged animals that have been to outer space and would likely survive the apocalypse. Bonus: They look like adorable miniature bears. Around 1,300 species of tardigrades are found worldwide.
Tardigrades are among the most resilient animals known, with individual species able to survive extreme conditions – such as exposure to extreme temperatures, extreme pressures (both high and low), air deprivation, radiation, dehydration, and starvation – that would quickly kill most other known forms of life.
The ocean quahog is a fist-size clam that can live to be 500 years or older. Some researchers believe the sturdy quahog's secret to a long life is its ability to protect its proteins from damage.
Interestingly enough, in our versatile animal kingdom, there are multiple animals that are born blind. One of them is the eyeless shrimp, which only has light perception. Another one is the star-nosed mole, the fastest-eating mammal in the world, who uses touch as their main sensory organ.
It comes from the coleoid cephalopods, the squids, cuttlefishes, and octopuses. These animals seem to be deaf. Their deafness is so remarkable that it needs to be explained in functional and evolutionary terms.
Hydras are the relatives of jellyfish with tentacles. You must have studied how hydras move using their tentacles. They use their tentacles to sting and hunt other smaller invertebrates in an aquatic environment. They do not have eyes but have the capability of responding to light.
Without red color in the sunlight, only green light reflects from the blood. This fact can be startling to divers who get a cut while diving. Again, the blood does not change when in the deep ocean. Rather, the green color of blood that is always there becomes obvious once the brighter red color is no longer present.
Blood in the human body is red regardless of how oxygen-rich it is, but the shade of red may vary.
Sometimes blood can look blue through our skin. Maybe you've heard that blood is blue in our veins because when headed back to the lungs, it lacks oxygen. But this is wrong; human blood is never blue. The bluish color of veins is only an optical illusion.
Although chitons look very simple, these mollusks have a very sophisticated shell. Its outer layer contains up to 1000 tiny eyes, each a bit smaller than the period at the end of this sentence.
The mantis shrimp's visual system is unique in the animal kingdom. Mantis shrimps, scientifically known as stomatopods, have compound eyes, a bit like a bee or a fly, made up of 10,000 small photoreceptive units.