It makes sense that tiny animals are so easy to overlook. A lot of them are so small that you’d be able to brush them off a table without thinking about it, as they’re essentially the size of a crumb.
But why are these animals so small? And how did animals with completely different body plans end up being so minuscule? That’s what we’re going to find out.
A frog that averages 7.7 millimeters long
Paedophryne amauensis is one of the tiniest frogs on Earth. The adults only grow to a size of roughly 7.7mm (0.3 inches) long, so you could fit several of them on top of a penny & still have space left over. These tiny frogs live in damp leaves across Papua New Guinea.
Their calls are just as small as they are, and they sound more like beeps than ribbits. Paedophryne amauensis are some of the smallest vertebrates known to exist. It’s quite incredible when you consider that they have a skeleton & organs inside those tiny bodies.
A fish whose mature females are 7.9 millimeters
Another tiny aquatic creature is Paedocypris progenetica. These fish don’t look like much at first glance, mostly because you can barely see them, and females reach maturity at around 7.9 mm. The majority of the fish are less than a centimeter. Only a few have been known to grow larger than 10mm.
The fish live in Southeast Asia in acidic blackwater swamps. The water is so soft that only the most well-adapted animal species can survive. Part of the Paedocypris progenetica’s skeleton is made of cartilage, not bones, so you can see through it. Shine a light across it & you’ll see the fish’s organs inside.
A mammal that weighs around 1.8 grams
Who would’ve thought a mammal could be so small? That’s exactly how the Etruscan shrew is, since it only weighs around 1.8 grams as an adult & measures between 35 and 48 mm long. These animals are essentially shorter than a golf tee.
But even for such a small animal, the Etruscan shrew is constantly moving & eating, meaning that it continually burns energy. It’s mostly due to the shrew’s high metabolism. You can find them in parts of Europe and North Africa.
A chameleon with a 13.5-millimeter body
You’d be forgiven for thinking that the Brookesia nana looks like a toy chameleon. But it’s a very real animal. The male of the species measures around 13.5 mm from snout to vent & 21.6 mm including the tail. The female is only slightly bigger.
Scientists who captured the species were able to see the developing eggs in the female, using micro-CT scans. Yes, even at such a small size, the female was able to reproduce. She’s small enough to sit on less than half of your thumbnail.
Wasps measured in micrometers
It’s okay to feel insignificant sometimes. Just think about wasps whenever that happens, as some of them aren’t even a full millimeter large. Tinkerbella nana is less than 250 micrometers or 0.25 mm, putting it at a size smaller than a dust speck. They usually live near plants & water surfaces, although you’d never realize it because they’re just so small.
However, they’re not the smallest kind of wasp. Dicopomorpha echmepterygis wins that title. The males of the species can be as small as 139 micrometers & are actually wingless. They’re also smaller than the females.
Entire animals under half a millimeter
Most people have no idea about loriciferans, and that makes sense. These animals live between grains of sand on the sea floor. Most loriciferan species are between 100 and 500 micrometers long, although some of the “larger” ones can be 800 micrometers. But you still wouldn’t be able to see them since several of them could fit on a pinhead.
Loriciferans do have an entire set of body parts, like head, neck, thorax & abdomen. They’re just extremely small. The creatures also have a tough outer casing, known as the lorica. It’s what gives the group its name.
Water bears between 0.05 & 1.2 millimeters
You might’ve heard that tardigrades can survive all sorts of extremes. But that’s not the only interesting thing about them. A typical tardigrade, or water bear, is around 0.05 mm to 1.2 mm. The larger members of the species are barely big enough to see without a microscope. That’s right, all the images online of tardigrades are massively magnified.
These water bears walk on eight legs and move quite slowly compared to the animals that live near them. Still, they do have a knack for surviving. They can live in practically any moist environment, like moss or soil, freshwater or saltwater.
The following sources were consulted in the preparation of this article:
- Ecological Guild Evolution and the Discovery of the World’s Smallest Vertebrate
- Paedocypris, a new genus of Southeast Asian cyprinid fish with a remarkable sexual dimorphism, comprises the world’s smallest vertebrate
- First Data on the Helminth Community of the Smallest Living Mammal on Earth, the Etruscan Pygmy Shrew, Suncus etruscus (Savi, 1822) (Eulipotyphla: Soricidae)
- Extreme miniaturization of a new amniote vertebrate and insights into the evolution of genital size in chameleons
- A new genus and species of fairyfly, Tinkerbella nana (Hymenoptera, Mymaridae), with comments on its sister genus Kikiki, and discussion on small size limits in arthropods
- A complete three-dimensional reconstruction of the myoanatomy of Loricifera: comparative morphology of an adult and a Higgins larva stage
- Tardigrades: Facts about one of the hardiest animals on Earth, and beyond
