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summer tadpole shrimp

Triops longicaudatus

What do they look like?

Triops longicaudatus is commonly known as a tadpole shrimp, because it looks like a frog tadpole. Triops longicaudatus is a fairly large tadpole shrimp, with a length of 10 to 40 mm long, a width of 3 to 8 mm, and a mass of 2 to 2.5 g. The body tends to be a brown or grayish-yellow color, and has three parts: a head, thorax, and abdomen. It has many small, hair-like appendages (around 60) near the center of its abdomen that beat rhythmically and move food toward its mouth. This species of tadpole shrimp is unique in that it has a third, middle eye, in addition to its two compound eyes. It also has the ability to turn pink when a large amount of hemoglobin is present in its blood. The sexes differ in both size and shape. Males tend to have a slightly larger body length and have larger secondary antennae, which can be used to hold the female during reproduction. Also, females have an egg sac whereas males do not. (Fryer, 1988; Weeks, 1990)

  • Sexual Dimorphism
  • male larger
  • sexes shaped differently
  • Range length
    10 to 40 mm
    0.39 to 1.57 in

Where do they live?

Triops longicaudatus, a crustacean often referred to as a type of tadpole shrimp, is found in various freshwater bodies, especially temporary pools, in North America, South America, the Caribbean, Japan and some Pacific Islands. This tadpole shrimp is common throughout the United States and in Hawaii but not Alaska. Unlike many tadpole shrimp, Triops longicaudatus is not found in the Great Lakes. In Canada, T. longicaudatus is found only in the provinces of Manitoba, Alberta, and Saskatchewan. It is thought that these crustaceans are native to the western hemisphere, and were introduced to Japan and the Pacific Islands. (Sassaman, et al., 1997)

What kind of habitat do they need?

This tadpole shrimp is found at the bottom of warm (average 21 to 31 °C), freshwater pools that are on average 4 ft deep and are 30 ft by 60 ft long. The pools they live in stay filled with water for about a month, and do not experience large changes in temperature. During the day, these tadpole shrimp can be found in the bottom of the pool digging and searching for food. At night, T. longicaudatus tends to bury itself in the sediment at the bottom of the pool. (Hamasaki and Ohbayashi, 2000; Weeks, 1990)

  • Aquatic Biomes
  • benthic
  • lakes and ponds
  • temporary pools
  • Average depth
    1.2 m
    3.94 ft

How do they grow?

A female keeps her eggs in the egg sac for several hours after fertilization. If conditions are good, the female then lays the eggs, which tend to be white, on various surfaces present in the pool. If conditions are not good for survival, the female will change the eggs so that they become dormant, and will not hatch until conditions improve. When the eggs do hatch, they hatch into the larvae. The first larval stage is called the metanauplius. In this stage, the metanauplius is orange in color, has 3 pairs of limbs, and one eye. After several hours, the metanauplius sheds its exoskeleton, and the tail (called the telson) begins to develop. After another 15 hours, the larvae sheds its exoskeleton again, and looks like a small adult. It continues to shed its exoskeleton (called molting), and grows to its full adult size within the next several days. After 7 total days, the tadpole shrimp becomes a brownish color, and is able to lay eggs. (Erickson and Brown, 1980; Fry, et al., 1994)

How do they reproduce?

Mating between males and females is rare for Triops longicaudatus, and there is no information available on the mating habits of this species. (Sassaman, et al., 1997; Scholnick, 1995)

Triops longicaudatus has several 3 different ways of reproducing. While these tadpole shrimp may reproduce sexually, with males and females mating, it is very rare, and most populations are primarily female. Parthenogenesis is the most common method of reproduction, where the females do not mate, but produce offspring from unfertilized eggs. The third method is called selfing, which occurs in a population of hermaphrodites. A hermaphrodite has both male and female reproductive parts, and selfing occurs when they are able to fertilize their own eggs. In all cases, fertilization of the eggs takes place outside of the body. Males and females tend to breed at the beginning of spring when the temporary pools start to fill with water. Reproduction takes place only during the warmer months and little to no reproduction occurs during the winter. Females or hermaphrodites will lay eggs in the morning on various surfaces that are present in the pool or release the eggs into the water. Eggs are released in batches that can vary from 10 to 100 in number. (Sassaman, et al., 1997; Scholnick, 1995)

  • Breeding season
    Mating takes place from spring to summer.
  • Average age at sexual or reproductive maturity (female)
    7 days
  • Average age at sexual or reproductive maturity (male)
    7 days

The female likely provides nutrients in her eggs for the offspring to grow and develop. She lays the eggs on various surfaces or in the water column and then leaves. There are no more parental care. (Sassaman, et al., 1997)

  • Parental Investment
  • pre-hatching/birth
    • provisioning
      • female

How long do they live?

These tadpole shrimp have a relatively short lifespan both in the wild and in captivity. Their average lifespan in the wild is 40 to 70 days if the temporary pool they live in does not dry up. They can live an average of 70 to 90 days in captivity. (Fry, et al., 1994; Scholnick, 1995)

  • Typical lifespan
    Status: wild
    40 to 70 days
  • Typical lifespan
    Status: captivity
    70 to 90 days

How do they behave?

Triops longicaudatus is a relatively solitary species of tadpole shrimp, and individuals are found separated in the different areas of a pond or pool. This is due to the higher level of predation that occurs when the tadpole shrimp are present in large groups; by separating they draw less attention to predators. These small crustaceans use body parts called phyllopods to push themselves forward in the water. They are constantly moving during the day and are often found swimming in the water. The tadpole shrimp have appendages which allow them to dig in the mud in search for food. They are more active during the day, and can be found buried in the pond bed at night. (Fryer, 1988; Scholnick, 1995)

How do they communicate with each other?

Triops longicaudatus has three eyes that are most likely used to identify food, and potential mates if the population reproduces by males and females mating. Behind the eyes is an organ that is most likely used to detect chemicals. (Erickson and Brown, 1980; Fryer, 1988)

  • Communication Channels
  • visual

What do they eat?

This species of tadpole shrimp is omnivorous. They eat a large variety of food, including detritus (small bits of organic material from decomposing plants and animals), zooplankton, algae, phytoplankton, and insect larvae. Mosquito larvae are a common prey item. When other food is unavailable, some individuals will cannibalize smaller tadpole shrimp, or will use their appendages to filter food towards their mouth. Triops longicaudatus will also chew off the roots and leaves of seedling plants such as rice plants. (Erickson and Brown, 1980; Fryer, 1988)

What eats them and how do they avoid being eaten?

Many species of bird, particularly water fowl, feed on Triops longicaudatus, both eggs and adults. Also, wood frogs, Lithobates sylvaticus, have been known to prey on T. longicaudatus. In times when food is scarce, these crustaceans may resort to cannibalism. To decrease the chances of being eaten, tadpole shrimp tend to be solitary, making themselves smaller targets and less noticeable than a large group would be. Their brown coloration also functions as camouflage, blending into the soil at the bottom of their pools. (Fry, et al., 1994; Fryer, 1988; Scholnick, 1995)

  • These animal colors help protect them
  • cryptic

What roles do they have in the ecosystem?

These small crustaceans are a major source of food for birds. Certain parasitic bacteria of the genus Echinostoma have been known to infect Triops longicaudatus. Also, this crustacean's constant digging in the bottom of their ponds and pools stirs up the dirt and nutrients into the water, providing food for other organisms living there. These tadpole shrimp have also been known to greatly decrease the population sizes of mosquitoes, such as Culex quinquefasciatus, by eating their larvae. (Fry, et al., 1994)

Commensal or parasitic species (or larger taxonomic groups) that use this species as a host

Do they cause problems?

There are no known negative effects of this tadpole shrimp on humans.

How do they interact with us?

Triops longicaudatus helps control populations of insects that can be harmful to humans, such as mosquitoes, by eating the mosquito larvae which sometimes live in the same pools and ponds. (Tietze and Mulla, 1991)

  • Ways that people benefit from these animals:
  • controls pest population

Are they endangered?

This species of tadpole shrimp is not an endangered species.


Eric Hasbun (author), The College of New Jersey, Keith Pecor (editor), The College of New Jersey, Angela Miner (editor), Animal Diversity Web Staff.


Erickson, C., R. Brown. 1980. Comparative respiratory physiology and ecology of phyllopod Crustacea. Crustaceana, 55: 1-10.

Fry, L., M. Mulla, C. Adams. 1994. Field introductions and establishment of the tadpole shrimp, Triops longicaudatus (Notostraca: Triopsidae), a biological control agent of mosquitoes. Biological Control, 2: 113-124.

Fryer, G. 1988. Studies on the functional morphology and biology of the Notostraca (Crustacea: Branchiopoda). Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 321: 27-124.

Hamasaki, K., N. Ohbayashi. 2000. Effect of water pH on the survival rate of larvae of the American tadpole shrimp, Triops longicaudatus (Notostraca: Triopsidae). Applied Entomology and Zoology, 35: 225-230.

Sassaman, C., M. Simovich, M. Fugate. 1997. Reproductive isolation and genetic differentiation in North American species of Triops (Crustacea: Branchiopoda: Notostraca). Hydrobiologia, 359: 125-147.

Scholnick, D. 1995. Sensitivity of metabolic rate, growth, and fecundity of tadpole shrimp Triops longicaudatus to environmental variation. Biological Bulletin, 189: 22-28.

Tietze, N., M. Mulla. 1991. Biological control of Culex mosquitoes (Diptera: Culicidae) by the tadpole shrimp, Triops longicaudatus (Notostraca: Triopsidae). Journal of Medical Entomology, 28: 24-31.

Weeks, S. 1990. Life-history variation under varying degrees of intraspecific competition in the tadpole shrimp Triops longicaudatus (LeConte). Journal of Crustacean Biology, 92: 498-503.

University of Michigan Museum of ZoologyNational Science Foundation

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Hasbun, E. 2014. "Triops longicaudatus" (On-line), Animal Diversity Web. Accessed March 25, 2019 at

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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