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Kidadl Team

AUGUST 05, 2021

Ostracod Facts You'll Never Forget

Check out Ostracod facts about an interesting marine species.

Have you ever come across small aquatic animals that look like mussels but are not exactly mussels? Then you must have encountered Ostracod. The ocean is a home for millions of creatures, and here we bring you some exciting facts about Ostracod, sometimes referred to as seed shrimp.

Ranging from the size of poppy seed to meatball, these tiny creatures are often found crawling at the bottom of the ocean, sea or lakes, or mosses. Ostracod's scientific name is Ostracoda and it belongs to the class of the Crustacea. Interestingly they are tiny organisms that, in their appearance, are merely more than a head with eight pairs of appendages (an external body part). The outer shell (carapace) is bivalved; hence common name Mussel shrimp was derived. Ostracoda looks like a tiny dot floating on the water's surface with very few externally visible characteristics with naked eyes. If you like to look at Ostracods' features in detail, you would need a microscope of at least 40x magnification.

If you have a keen interest in learning about weird creatures, read on, and also check out our latest articles on water strider and apple snail.


Ostracod Interesting Facts

What type of animal is an ostracod?

Ostracods are tiny small crustaceans (Ostracoda). They are widespread in aquatic and non-aquatic environments.

What class of animal does an ostracod belong to?

Ostracods belong to the small Crustaceans, whereas non-marine Ostracods belong to the order Podocopida. There are around 70,000 identified species of Ostracod Crustaceans grouped into several orders.

How many ostracods are there in the world?

There could be limitless Ostracoda globally; imagine how many can these small creatures be present in the water sources with thousands of species they are classified into. Some species are so small that identifying species itself requires tedious efforts and definitely a powerful microscope. They are considered as the most speciose groups of living Crustacea. When it comes to Ostracod classification, it is estimated that there are more than 70,000 species of Ostracod, taxonomy has 8000 identified species, of which 2000 are non-marine.

Where does an ostracod live?

The Ostracods are found in almost all aquatic habitats from deep oceans, shallow water of the seashore, freshwater rivers, lakes and ponds, wet marshy areas, or wetlands. They are often overlooked due to their diminutive appearance. You can find uncountable Ostracoda species on the ocean floors and different waters, and some are planktonic. Family of freshwater Ostracod species are found in streams, pools, lakes, and groundwater. Terrestrial and semi-terrestrial species are seen in damp leaf litter, soil in forests in New Zealand, South America, western Pacific Islands, Australia, and Africa.

What is an ostracod's habitat?

Ostracods are found in every aquatic habitat, from tiny pools to the deep sea. Some live in semi-terrestrial habitats like damp mosses, soil, and leaf litter.

Who do ostracods live with?

Most species of Ostracods live in groups. Myodocopid Ostracods attack the prey in groups that are much larger than themselves. They are considered ferocious predators and bring down worms and fishes.

How long does an ostracod live?

Ostracod can survive for more than two years and molt (shedding the shells) several times during their lifetime; every molt appendage is usually added each time.

How do they reproduce?

Ostracod, as said, has thousands of species, of which most of them reproduce sexually, for some reproduction happens asexually by Parthenogenesis.

Males have two sexual organs, and females have two genital openings. Sperms are six times the length of the male Ostracod, and they are coiled up within. During the reproduction phase, large numbers of females swim to join the males. Luminescent male Ostracods use light for courtship display. So there is a better chance for males getting spotted. Ostracod mating results in multiple broods. The males transfer the sperms in the female's posterior of the carapace. The eggs are brooded inside the shell before they leave the female. In contrast, some species release the eggs onto suitable surfaces.

We can observe different kinds of reproduction mechanisms happening in Ostracods; some are partially or wholly Parthenogenetic (egg develop into an embryo without being fertilized by a sperm.)

Can you imagine an egg hatching after several years? Ostracod eggs survive extreme environments. Maybe this is why these species can survive for millions of years. Freshwater Ostracods, when they happen to lay eggs in temporary water sources, the eggs (dormant eggs) are viable for several years even after they are dried up. They get carried away by the wind, get attached to birds' feet or toads, and thus get transported to faraway places. Young ones develop once they reach a suitable environment. Surprising, isn't it?

What is their conservation status?

The conservation status is Not Extinct. These species are available in abundant numbers in marine or non-marine environments. The ability of Ostracods to adapt to any new environment, their ecological flexibility and tolerance, the boon of having dormant eggs, light enough to be carried away to faraway places let Ostracods dispersed to entirely new places, be it aquatic, subterranean, and epigean aquatic habitats.

Ostracod Fun Facts

What do ostracods look like?

Ostracods are seen in varied, elongated, spheroidal, compressed, or inflated shapes. In general, Ostracods are seed-shaped. Due to their bivalved carapace, don't mistake them for clams or mussels. If you carefully observe one, we can figure out that it is an Ostracod by its size and appendages.

The Ostracod carapace has two valves that cover its entire body. They can tightly close the carapace when needed. An Ostracod has thorax, head, and multiple pairs of appendages, five on their head but only one to three pairs on the rest of the body and a simple eye. Ostracods are available in different colors ranging from white to amber, reddish-brown to black; the colors are formed due to progressive carbon fixation on Ostracod shells.

Ostracoda found in almost all waters.

How cute are they?

Cuteness is perceived differently by different people. Due to their small size, we can term them as cute, but few may not like the bug-like appearance of this tiny animal.

How do they communicate?

The exact mode of communication of Ostracods is not known. Few Ostracods possess luminance property, which is used as a decoy or communication.

How big is an ostracod?

Most species of Ostracods are typically tiny; they are 0.019-0.079 in (0.5–2.0 mm) long. Some species are much smaller, say  0.0079 in (0.2 mm), and some attain 0.31 in (8 mm). On average, they are five times smaller than a mosquito.

How fast can an ostracod move?

These small organisms do not have limbs; they move slowly through the water using antennae. The movement appendages also aid Ostracod to move. The exact speed of Ostracods is not yet determined.

How much does an ostracod weigh?

The weight of Ostracods could be no more than a few milligrams. The exact weight is not known. Female Ostracods are 3-10 times more rounders than males due to their brood pouches that carry eggs.

What are their male and female names of the species?

There is no specific name given to Ostracod males and females. We can simply term them as female Ostracods and male Ostracods. In some species, only females exist, and reproduction happens through Parthenogenesis.

What would you call a baby ostracod?

Baby Ostracods are called young Ostracods. Juvelliene Ostrocods has a hard shell and molts eight times before it becomes an adult. It takes around 30 days to three years for some marine species to become adults. Once adults, they attain reproduction capability.

What do they eat?

Different Ostracods species exhibit different eating patterns and fall under many rungs of the trophic level. Some are herbivores, carnivores/predators, detritivores, scavengers. They are, in general, omnivorous scavengers (third trophic level). The Ostracod diet consists of bacteria, algae, molds, diatoms.

Most Ostracods play a crucial role as filter feeders. It means they consume edible particles in the water but letting the water in through the carapace anteriorly and letting out through the carapace posteriorly.

Are they dangerous?

Of course not; they don't pose any danger to humans or other animals.

Sometimes we end up having freshwater Ostracods in aquariums and tanks; as they are incredibly resilient to any environment, it is a little hard to get rid of them. Even if the female dies, it preserves the eggs in the valves or shells and waits for a suitable environment for young ones to grow again. So, how can we get rid of Ostracods? It requires at least three years of effort to say goodbye to Ostracods. We need to place a fish or other predators who eat away Ostracods and their offspring with them. Another way is to thoroughly clean and re-silicone the tank regularly.

Would they make a good pet?

No one wants to have an Ostracod as a pet as they are not appealing, and ironically, they are too small to locate and are not social animals. Why would someone want to pet Ostracod when it can't identify or recognize us?

Did you know...

The Ostracoda is as old as Dinosaurs; the first Ostracod fossil was found around 500 million years ago, from the rocks of the Ordovician period.

With around 8000 living species, Ostracoda is one of the most successful aquatic Crustacean groups. And by far, they are the most complex organisms studied in the field of micropalaeontology.

Marine Ostracods glow blue at night in sand and water (bioluminescent). The Ostracod's bright cloud of luminescence is much larger than the Ostracod itself, thus helping them to scare the predators away. The male Ostracod uses luminescence to attract females. Hence, the Japanese named these glowing Ostracod bioluminescence creatures as fireflies.

The biggest deep-sea Ostracods - Gigantocypris, are the size of a pea. Don't be fooled by its appearance like a shrimp. Also, it would be harder than a shrimp due to its carapace.

When threatened, they close the antennae, seal the valves and reach the bottom of the water to protect themselves.

Ostracods specialize in adapting to any habitat; the environment controls the types of Ostracods species.

In the North Atlantic Ocean, there exists a giant Ostracod at depths of roughly 2,000 m. The Gigantocypris is found in the San Clemente trench, California, and is 1.2 inches in diameter.

How old are ostracods?

It is surprising to know that these tiny animals have been living on the earth and surviving through varying climatic conditions for almost 500 million years. Ostracods are one such animal that provides the most complete and consistent fossil record. The first fossils of Ostracods (the earliest Ostracod) were observed on the rocks of the Ordovician Period, which was estimated to be 485-443 million years old. Within the arthropod, Ostracod fossils are the most abundantly preserved.

These fossil records provide abundant information about the depth of water, sedimentation, salinity, temperature, and other paleoecological factors. The fossil record also gives data about the environment in which the sediments were accumulated as different Ostracod lived in different types of environments.

Can ostracods survive being eaten?

Cypridopsis vidua is a specific species of Ostracods that were found alive even after being eaten by small Bluegill sunfish, thanks to the shell of Ostracod. Even though the fish eat it up, the Ostracod can tightly close the shell and pass the gut of the fish.

Another exciting feature about Ostracods is that they escape from being eaten by fishes due to their ability to lighten up. Cardinalfish are happy to eat these tiny animals. Still, when a certain Ostracod species emit light, the Cardinalfish is bound to omit as the light in the belly can attract predators that feed on Cardinalfish. It is an excellent site to watch fish omit Ostracod; it resembles a firework display.

Here at Kidadl, we have carefully created lots of interesting family-friendly animal facts for everyone to discover! Learn more about some other arthropods including peacock mantis shrimp, or sea snake.

You can even occupy yourself at home by drawing one on our Ostracod coloring pages.

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