If you have ever wondered what is the smallest animal on earth then the answer is probably one that lives in the ocean, here with this list of tiny animals we will show you why.
Sometimes, being a small fish in a big pond really does have its advantages. Especially when the big pond we are referring to is the ocean. The big blue is home to some awesome small sea creatures and different types of small fish, however, the tiny sea creatures can be very very difficult to find and cannot even be measured in inches. The world seems a lot bigger when you are only 4 mm small!
What is the Smallest Animal in the Ocean?
The ocean is not only home to the biggest animal in the world, the Blue Whale, but also home to probably the smallest animal in the world. Many scuba divers do not notice many of these teeny sea creatures when diving.
What are the smallest creatures in the ocean called?: Many of the small ocean animals that are in the oceans of the world are viruses & bacteria, making them all but invisible to the naked eye. But once you get beyond the microscopic level you’ll find that some of the smallest sea creatures are quite adorable!
They may be the smallest animals on earth, but don’t let that fool you, these tiny sea animals are just as important to the ocean and its ecosystems any of the scientists that study them will tell you.
In no particular order, below we have put together our top 10 list of the smallest animals in the ocean. From marine viruses and the smallest organism in the ocean to the super cool Irukandji jellyfish.
1. Marine Viruses
Let’s start minuscule – like, microscopic small. Marine viruses exist similarly as they do on land and the smallest of those that live there measures just 40 nanometers (nm) that’s right not mm or even inches. What the heck is a nanometre right?!
In today’s society, you probably associate nano as a SIM card for an iPhone for example, to put this into perspective for you a nanometre is one-billionth of a meter! So, technically are the smallest known.
The biggest marine viruses can grow up to 400 nm in diameter and are yet still invisible to the human eye without using an intensified microscope. Marine viruses come in all sorts of sizes and with destructive capabilities and there are literally millions of different types of them!
The existence of marine viruses was actually discovered through epifluorescence and electron microscopy of ecological water samples by scientists, following the metagenomics sampling of uncultured viral samples. Cool eh!?
2. Marine Bacteria
Just like the marine viruses, marine bacteria exist just as on dry land, and the ocean is home to infinite marine bacteria. The marine bacteria are the second smallest organisms found in the sea.
Although bigger than the marine viruses, many of these bacteria are still very tiny in size, with some measuring only 1,000 nm in length. Although they may seem a lot larger than the marine viruses, these organisms remain invisible to the naked human eye.
Studies of the marine bacteria that live in the ocean are becoming a quickly growing field within ocean research. In fact, did you know that in just one milliliter of seawater, you can find up to a million living microscopic organisms? Tiny but mighty, these bacteria play critical roles in the ocean’s environment. Yay for bacteria!
The sea is home to some of the planet’s smallest plant organisms. Many of these are single-celled green algae specimens. Around five times larger than the marine bacteria, they measure from 5,000 nm (5 micrometers).
These teeny tiny algae tend to become prey for the larger, yet still tiny, little sea creatures. Algae really do vary when it comes down to size, ranging from the smallest known microscopic mircomonas species to the gigantic kelps that are known to tower the ocean seabed by growing up to 60 meters (200 feet) tall.
As well as their ecological roles played both by producing oxygen and providing food for most aquatic life, algae are also a source of crude oil that is used in some foods and numerous pharmaceutical and industrial products used by humans.
Due to the popularity of the scrummy kelp and the oil it produces, giant kelp forests have now been granted an endangered status.
4. Dwarf Lantern Shark
What is the smallest sea creature? Yes, that’s right, a shark and it has made our top 10 smallest animals found in the ocean! The smallest shark and therefore possibly the smallest fish in the ocean is the dwarf lantern shark and is probably the smallest animal in the world of sharks, and quite clearly one of the cutest!
The largest specimen ever to be recorded measures only 7.8 inches (20 cm) in body length. That’s tiny! These small aquatic animals are found around the upper continental slopes off of Venezuela and Colombia and lives at a depth of about 283 – 439 meters (928 – 1,440 ft).
The lantern shark can be identified not only by its teeny size even at maturity, but by its long flattened head, it’s a mid-dorsal line and also by the black ventral markings.
This awesome small sea creature is actually capable of producing light from an extraordinary array of photophores and although the dwarf lantern shark isn’t targeted by commercial fisheries, its species could become threatened as a result of by-catch just like a lot of other endangered shark species. The impact of human activity on this the smallest creature in the ocean is currently unknown.
5. Sexy Shrimp
Swit Swoo!! I know what you’re thinking, not your type of sexy? Think again! There is a reason the Thor Amboinensis species is also known as the sexy shrimp, and that is down to its unusual body movements.
They get this flamboyant nickname from the way they sway their abdomen back and forth with an exotic like flair. The sexy shrimp can grow up to about 1-¼ inches in body length but on average the adult is usually smaller, truly one of the small marine animals.
Most often found within the reefs of the Indo-Pacific, the sexy shrimp is generally found hiding amongst the tentacles of an anemone. These flirtatious fellas are very popular amongst the macro photographers and although these are small ocean creatures they make up for in color as they boast a vibrant orange colored body that is decorated with white polka dot. Making it the cutest small water animal in the ocean possibly, as far as we are concerned.
6. Juvenile Frogfish
Frogfish tend to be a favorite for divers to look for underwater and attract a lot of attention, especially to the underwater photographers. Their popularity is clear amongst the variety of small sea animals, due to them being very well camouflaged and being able to adapt to their surroundings makes it difficult to spot them.
Ranging in all kinds of sizes and different colors, these tiny saltwater fish are so ugly, it makes them cute but we do have a tendency to think that about them all!
Adult frogfish are known to grow from anything from an inch up to almost 22 inches. However, it is the baby frogfish that have made a spot on our smallest critter list.
Dependent on the type, some juvenile frogfish can be smaller than an inch long in size, or even grow to just a few millimeters!! The small size makes it extremely difficult to find these little guys, but believe us, the search is truly worth it when you find this species!
For the non-divers, the idea of a slug-like bottom-dweller may seem a little boring or uninteresting, but they would be mistaken!! For us divers, the picture is painted very differently. Nudibranchs are little wonders of the ocean that many experienced scuba divers love to see.
This tiny species is a colorful critter that can grow up to about 12 inches (30 cm) long with the smallest being less than ¼-inch long (4 mm) and is therefore on our list for being another smallest sea animal and is known for its colors.
Ranging in extraordinary colors and striking forms, nudibranchs tend to give off a little and helpless vibe, but studies show them to be quite the contrary. Over 3,000 different species of these tiny creatures have been discovered to date with more being found and identified worldwide every single day.
8. Pygmy Seahorse
Another favorite that is known to scuba divers and number eight on our list of tiny animals is the beautiful pygmy seahorse. This tiny saltwater fish spends their whole adult life living on soft corals and beautifully colored sea fans and are found in warm tropical waters.
Growing to the average size of a fingernail they tend not to grow any bigger than an inch (2.4 cm) long. Juvenile pygmy seahorses are usually so tiny (measures but a few millimeters), they are basically invisible to the diver’s eye, especially as they are almost perfectly camouflaged to the surroundings in which they live.
Pygmy seahorses are not only the smallest known of all seahorses but are one of the most popular subjects for the macro photographers. Because of this animals’ small size, they are extremely hard to see, but if you are lucky enough to be able to find them and get a picture, please be aware that they do not actually have eyelids and are therefore very sensitive to light!
9. Octopus Wolfi
The Octopus wolfi is the world’s smallest known octopus. And boy is it adorable! Found most commonly in the shallow waters of the western Pacific Ocean, they are a delight for divers to spot!
The octopus wolfi is characterized by a pattern formed by papillate fringes around the edges of its suckers. It makes our list for measuring around 2.5 cm (1 inch) in length and normally weighs less than 1g (0.04 oz). Are you a fan of the octopus? Make sure to check out our best gifts for octopus lovers!
10. Irukandji Jellyfish
Remember the cute little guy Squishy, that Dory found in the film Finding Nemo? For those of you who haven’t seen the film (watch it, it’s great!), Dory finds a teeny tiny jellyfish and names it “Squishy”, blinded by its cuteness, she touches it and gets a nasty sting! We have all been fooled by this kind of way before, but when it comes to the Irukandji jellyfish don’t be like Dory and let this cute little thing deceive you.
The Irukandji jellyfish is a deadly venomous type of box jellyfish. Growing to an adult size that only measures about 1 cm long, they not only hold the claim to being one of the smallest known jellyfish in the oceans, but also the most venomous. Like most venomous animals in the world, they can be found in Australia.
The Irukandji jellyfish are able to fire their stingers into their victim, and unlike most jellyfish, its stingers are found in the bell as well as its tentacle. As small water animals go this certainly packs a punch if you encounter one. Check out our blog to find out more jellyfish facts or if you are looking for a gift for a jellyfish fan why not pop over and check out some of our gift ideas for jellyfish lovers.
Frequently Asked Questions
There you have it, the world’s smallest ocean animals. To fill your head with even more facts and knowledge, we have also answered some of the most frequently asked questions about the smallest animals found in the world.
What is the smallest animal on earth today?
The smallest animal on earth is probably the Brookesia Micra chameleon that grows to about 1 inch, which is endemic to Madagascar and only discovered in early 2012.
A very close second place for the smallest creatures in the world is also the smallest mammal and is Kitti’s hog-nosed bat that measures an average of 1.1 inches
What is the smallest living thing in the world?
If you are looking to find the smallest living thing in the world you would need a powerful microscope. As it would be a bacteria, organism, or virus. Which is the smallest known though is often hotly debated as the Irukandji jellyfish and a parasitic jellyfish called Myxozoa could also be known as the smallest species.
What is the biggest and smallest animal in the world?
When comparing the biggest and smallest animal in the world the difference is beyond words. In our opinion, because the smallest is debated, we would say that they are both mammals, the biggest being the blue whale and the smallest mammal being Kitti’s hog-nosed bat.
The largest animal, the Blue Whale is without doubt, but for the smallest, we would also like to mention the Irukandji jellyfish and a parasitic jellyfish called Myxozoa as they could also be the smallest known species.