This article explores some of the extremes in the animal world, including the largest animal (blue whale), smallest animal (parasitic wasp), most durable animal (tardigrades), and longest animal (snare worm). Much of the planet’s biodiversity is represented by arthropods that have not been studied yet.
With an estimated 3-30 million animal species, this planet is teeming with biodiversity. Much of this diversity is represented by arthropods that have not even been studied yet.
Of all the animals we know, the range of features is staggering. But it’s the extremes in the animal world that capture our imaginations and keep us interested in learning more about life on our planet. This article will look at some of the more fascinating extremes of the animal world.
Of all the extremes in the animal world, the most obvious is size. The largest living animal – perhaps the largest that ever lived – is the blue whale, with an individual weighing 190 tonnes (209 tons) with a length of 30m (100ft). Others were measured at 33.3 m (110 ft) in length but not weighed. This makes the blue whale about as long as a ten-story building.
As for the smallest animal, there are numerous microscopic animals that consist of only about a hundred cells, including rotifers, gastrotrichans, and the smallest nematodes. These simple animals are so small that you can see their individual cells in a microscope image. Sure, there are numerous unicellular organisms around us, but since these contain only one cell, they are not classified as animals, which must be multicellular.
Among the phyla we would consider most familiar, one of the smallest animals is the parasitic wasp Dicopomorpha echmepterygis, measuring just 0.139 mm in length, smaller than some amoebae. Its internal organs are tightly packed in the correct arrangement with very little space left for an internal body cavity.
Another of the interesting extremes in the animal world is durability. This record is likely held by tardigrades, or “water bears,” small segmented animals that superficially resemble bears because of their fat bodies and tiny appendages. Tardigrades are one of the very few animals capable of temporarily suspending their metabolism and entering a state called cryptobiosis. In this state, they can withstand temperatures down to absolute zero, up to 151°C (303°F), 1,000 times more radiation than any other animal, more than a decade without water, and pressures down to vacuum. Because of these characteristics, tardigrades are thought to be the only animals that could survive exposure for long periods in space.
Another of the extremes in the animal world is not size but length. Although the blue whale is the largest and heaviest extant animal, it is not the longest. That title is held by a snare worm, Lineus longissimus, which has been measured at 55 m (180 ft). These invertebrate predators burrow along the ocean floor, catching prey with their proboscis. They superficially resemble snakes.
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