Triops longicaudatussummer tadpole shrimp

Geographic Range

Triops longicaudatus is the most widely distributed notostracan crustacean. It can be found in various freshwater bodies, especially vernal pools, in North America, South America, the Caribbean, Japan and some Pacific Islands. This tadpole shrimp is widespread in the contiguous 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 speculated that these crustaceans were introduced to Japan and the Pacific Islands and were natively found throughout the Western Hemisphere. (Sassaman, et al., 1997)


Triops longicaudatus is found at the bottom of warm (average 21 to 31 °C), freshwater ephemeral pools that are on average 4 ft deep and are 30 ft by 60 feet long. These tadpole shrimp also prefer to live in highly alkaline waters, and cannot tolerate a pH below 6. The pools they inhabit retain water for about a month, and do not experience large changes in temperature. During the day, these tadpole shrimp can be found in the benthic region of the pool digging and scavenging for food. At night, T. longicaudatus tends to bury itself in the pool bed. (Hamasaki and Ohbayashi, 2000; Weeks, 1990)

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

Physical Description

Triops longicaudatus is commonly known as a tadpole shrimp, because the body superficially resembles a frog larva. 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 of T. longicaudatus tends to be a brown or grayish-yellow color, and is segmented into a head, thorax, and abdomen. It has many small, hair-like appendages (around 60) on the proximal side of its abdomen that beat rhythmically and allow the individual to channel food (via current) toward its mouth. This species of tadpole shrimp is unique in that it possesses a medial eye, in addition to its two compound eyes. It also differs from other tadpole shrimp by lacking secondary maxillae, and the ability to turn pink when a large amount of hemoglobin is present in its blood. The sexes differ in both size and morphology. Males tend to have a slightly larger carapace length and possess larger secondary antennae, which can be used as claspers during reproduction. Further, 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


A female keeps her eggs in the egg sac for several hours after fertilization. If conditions are favorable, the female then lays the eggs/cysts, which tend to be white, on various substrates present in the pool. If conditions are not favorable, the female will modify the eggs so that they enter a state of dormancy, and will not hatch until conditions improve. In either case, the first larval stage post-hatching is the metanauplius. In this early stage, they are orange in color and possesses three pairs of limbs and a single eye. Several hours later, they shed their exoskeleton and the telson begins to form. At this stage, the larvae are considered planktonic. After another 15 hours, the larva sheds its exoskeleton again and begins to resemble a miniature adult. The juvenile will continue to molt and grow to its full adult size within the next several days. After a total of seven days, the crustacean turns a brownish color, and it can lay its own eggs because it has reached full sexual maturity. Like many tadpole shrimp, growth is strongly dependent on density and will be slowed at high densities. (Erickson and Brown, 1980; Fry, et al., 1994)


Sexual reproduction 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 can exhibit several different reproductive methods. While T. longicaudatus may reproduce sexually, it is very rare, and the majority of populations are female-dominated. As such, parthenogenesis is the most common method of reproduction. A third reproductive strategy is selfing (self-fertilization), which can exist in a population that is largely composed of hermaphrodites. In all cases, fertilization is external. Males and females tend to breed at the beginning of spring when the vernal pools start to fill. 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 substrates that are present in the pool or release the eggs into the water column. 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 provisioning in her eggs, which she lays on various substrates or in the water column and then departs. There are no further interactions. (Sassaman, et al., 1997)

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


Triops longicaudatus has a relatively short lifespan both in the wild and in captivity. Its average lifespan in the wild is 40 to 70 days if the temporary pool does not dry up. It 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


Triops longicaudatus is a relatively solitary species of tadpole shrimp, and individuals are found separated in the different areas of a vernal pool. This is due to the higher level of predation that occurs when the tadpole shrimp are present in large groups. These small crustaceans use appendages called phyllopods to push themselves forward in the water. They are constantly moving during the day and are found swimming in the water column. These crustaceans possess exopods which allow them to dig in the mud in search for food. They are more active during the day, and can be found embedded in the pond bed at night. Studies have shown that these tadpole shrimp can reduce their basal metabolic rate in times where food is scarce or when other environmental conditions are unfavorable. (Fryer, 1988; Scholnick, 1995)

Communication and Perception

Triops longicaudatus has three eyes that are most likely used to identify food and potential partners (if reproduction for the population is sexual). Posterior to the eyes is a dorsal, nuchal organ that is most likely used for chemoreception. (Erickson and Brown, 1980; Fryer, 1988)

  • Communication Channels
  • visual

Food Habits

This species of tadpole shrimp is omnivorous. Individuals tend to prefer animal detritus over plant detritus but will eat both if available on the pool floor. Insect larvae as well as various zooplankton are also common prey items for T. longicaudatus. These tadpole shrimp seem to show a preference toward eating mosquito larvae over other insect larvae. In times when food is scarce, some individuals will resort to cannibalizing juvenile tadpole shrimp or use their thoracic appendages to filter food toward their mouth. Triops longicaudatus is especially adept at chewing off the roots and leaves of seedling plants such as rice plants. (Erickson and Brown, 1980; Fryer, 1988)


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 predation, 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 sediment at the bottom of their pools. (Fry, et al., 1994; Fryer, 1988; Scholnick, 1995)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

These small crustaceans are a major source of food for water fowl. Certain parasitic bacteria of the genus Echinostoma have been known to use T. longicaudatus as a host organism. Also, more food is provided for filter feeders as a result of this crustacean's constant digging in the pond substrate which stirs up the sediment. These tadpole shrimp have been known to greatly reduce the population sizes of mosquitoes, such as Culex quinquefasciatus, by consuming their larvae. (Fry, et al., 1994)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Triops longicaudatus helps control pest populations, such as mosquitoes, by consuming their larvae which are sometimes deposited into vernal pools. (Tietze and Mulla, 1991)

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

There are no known adverse effects of Triops longicaudatus on humans.

Conservation Status

Triops longicaudatus has no special conservation status.


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



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map


living in the southern part of the New World. In other words, Central and South America.

World Map


reproduction that is not sexual; that is, reproduction that does not include recombining the genotypes of two parents


Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


uses smells or other chemicals to communicate


having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.


particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).

  1. active during the day, 2. lasting for one day.

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body


union of egg and spermatozoan


a method of feeding where small food particles are filtered from the surrounding water by various mechanisms. Used mainly by aquatic invertebrates, especially plankton, but also by baleen whales.


mainly lives in water that is not salty.


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.


referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.


A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.


having the capacity to move from one place to another.


specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.


an animal that mainly eats all kinds of things, including plants and animals


found in the oriental region of the world. In other words, India and southeast Asia.

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reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


development takes place in an unfertilized egg


photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)

seasonal breeding

breeding is confined to a particular season


remains in the same area


reproduction that includes combining the genetic contribution of two individuals, a male and a female


lives alone


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.


uses sight to communicate


animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)


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.