Discover the Incredible 3-Eyed Dinosaur Shrimp That Can Lay Eggs That Don’t Hatch for 27 Years

Written by Jennifer Gaeng
Published: September 27, 2022
© IrinaK/
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Today we are going to explore the Triops longicaudatus (also known as the American tadpole shrimp and the longtail tadpole shrimp), and their process of putting off egg hatching called “diapause.” You may be curious about what this process is and about this creature in general. In this article, you will learn some interesting facts about the Triop, a shrimp with three eyes and a body like a dinosaur! We will also explore the process in which it delays its eggs from hatching for as long as 27 years! So read on to discover the incredible 3-eyed dinosaur shrimp!

About the Triop

Triops longicaudatus is a freshwater crustacean


This shrimp, Triops longicaudatus, has been given the nickname “tadpole” due to its resemblance to the larval stage of a frog. The tadpole shrimp, Triops longicaudatus, is relatively large, measuring 10–40 mm in length, 3–8 mm in breadth, and weighing 2–2.5 g. The body is usually a brown or grayish-yellow tint, and it consists of a head, a thorax, and an abdomen. Near the middle of its belly, it possesses a cluster of tiny, hairlike appendages (about 60 in all). In combination with its two compound eyes, this tadpole shrimp species also has a third, middle eye, making it one of a kind!

This tadpole shrimp lives at the base of freshwater ponds that are typically 4 feet deep and 30 feet by 60 feet in size, and that are heated to a comfortable 21 to 31 degrees Celsius. The water in the pools they inhabit remains at a constant temperature for around a month. These tadpole shrimp spend their days at the pool’s bottom, where they dig and look for food. T. longicaudatus is nocturnal, and it prefers to spend the night buried in the pool’s silt.

They can be found across North America, South America, the Caribbean, Japan, and some of the Pacific Islands. This tadpole shrimp can be found in the continental United States, Hawaii, and Puerto Rico, but not in Alaska.

The Triops Process of Diapause

After fertilization, a female protects her eggs for several hours while they develop inside the egg sac. The female will subsequently lay her eggs, which are typically white in color, on various surfaces in the pool if the conditions are favorable. A female will alter her eggs thus they go dormant if she senses that survival conditions are not optimal.

A triops egg has an alveolar layer composed of hundreds of tiny chambers linked by a spongy matrix and is less than 0.5 mm in diameter. Liquid enters the alveolar layer as soon as the egg is laid. The egg will now sink because of this. Here, amid the silt, the eggs can wait to hatch. There is less danger of being devoured by adult triops here. After the water dries, air replaces the fluid in the alveolar layer. When the eggs are wet, if they aren’t buried in silt, they float to the surface, which the sun can warm them. When an egg is exposed to light, it knows it is no longer concealed and may begin the hatching process. They are reburied if they do not however hatch, protecting them from being eaten by their siblings.

Did you know that scientists believe these eggs can continue to “survive” for considerably longer than 27 years? The eggs are resistant to extremes of cold and heat (although not boiling). This is because the wind blows the eggs in just the right direction, and the eggs will land in a puddle in a ditch, in which this process will begin all over again. A few key conditions, which we’ll cover today, will determine how well this works.

The Hatching Process

The larvae develop from the eggs after they hatch. Meta nauplius describes the initial stage of larval development. The orange meta nauplius has three sets of legs and a single eye at this stage in its development. The meta nauplius starts developing its tail (called the telson) and shedding its exoskeleton after many hours. At the end of another 15 hours, the larval has lost its exoskeleton once more and resembles a little adult. Over the next few days, it will reach its full adult size as it continues to molt. When the tadpole shrimp has developed for 7 days, it turns a brownish color and is ready to reproduce.

The Importance of Specific Conditions

Triops longicaudatus live in freshwater habitats


In the case of triops eggs, they can endure years of full dehydration and lack of metabolic activity until being exposed to optimum conditions for hatching. The triops eggs also have other ways to keep them from hatching in the wrong conditions. Not only does the right type of water cause the egg to hatch, but so does its osmotic pressure, temperature, and exposure to light. In the right setting, the pool quickly fills up with water from rain or seasonal flooding. In this case, the water is mostly pure, has few minerals or organics dissolved in it, and has an exceptionally low osmotic pressure.

Specifics vary depending on the species, but in general, only a tiny proportion of eggs have a chance to hatch shortly after being laid. The remaining eggs must be dried for at least one period before they can hatch. Some of these eggs will hatch after just one drying, while others won’t hatch until two or more drying and wetting cycles have taken place!

Why are the right circumstances so important? Triops are too small, slow, and don’t have the natural defenses they need to stay away from predators their size or bigger, especially when they are young. A body of water that has been there for a long time may be home to fish, amphibians, aquatic insects, and other creatures that will kill the hatchlings quickly. Also, a body of water that has been there for a long time could be an old pool that is about to dry up. The eggs won’t hatch until the conditions of the water show that there is a new body of fresh water. Two especially crucial factors play into the proper conditions for diapause which include ideal temperatures and water type.


Typically, the ideal temperature range for hatching Triops eggs is between 59 and 86 degrees Fahrenheit. If the temperature is lower than optimal, growth will slow, and the hatchlings might not be able to reach maturity before the pool dries up. There’s a risk that the hatchlings won’t survive if the pool temperature hits its peak, and the surrounding air is too hot for them. Accordingly, the hatch rate is indicative of how near the eggs are to this optimum range.

Water Type

Second, the characteristics of the temporary bodies of water in which they live are critical. The shrimp family triops includes common names like a clam, fairy, and tadpole due to its specialized adaptations for life in temporary freshwater or brackish water pools. Almost nothing else can live in the extremely salty environments where these shrimps make their temporary home. Finally, the attrition caused by active predators in a constant body of water is not something their reproductive systems can manage.

In Conclusion

Triops have adapted to temporary pools where there aren’t usually any predators bigger than them. Many have gotten even better at living in places with vastly different pH levels, like alkaline pools and acidic peat bogs. The triops have made their own special paradise in these unpredictable and changing specialized habitats, where it seems like nothing bigger than freshwater plankton should live.

Another type of adaptation is a fast metabolism and rate of growth, which lets them live their whole lives in a few liters of rainwater that may only last a few weeks. Even though the eggs may have been dormant for ten years or more, once the right conditions are back, they hatch very quickly. Some species need anywhere from a few hours to a day to hatch.

Given how much Earth has changed, it’s hard to believe that a living thing that came into being so long ago is still doing pretty much the same thing. Their plan has worked well for them so far! They might still be around after 300 million years if people don’t mess up their homes. One must wonder if the same could be said about us!

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Triops longicaudatus is a freshwater crustacean
© IrinaK/

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About the Author

A substantial part of my life has been spent as a writer and artist, with great respect to observing nature with an analytical and metaphysical eye. Upon close investigation, the natural world exposes truths far beyond the obvious. For me, the source of all that we are is embodied in our planet; and the process of writing and creating art around this topic is an attempt to communicate its wonders.

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