Triops longicaudatus

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.

• Biogeographic Regions
• nearctic nearctic
  • native native
• oriental oriental
  • introduced introduced
• neotropical neotropical
  • native native

Habitat

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.

• Habitat Regions
• temperate temperate
• tropical tropical
• freshwater freshwater

• Aquatic Biomes
• benthic benthic
• lakes and ponds
• temporary pools

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.

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger
• sexes shaped differently

Development

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.

• Development - Life Cycle
• metamorphosis metamorphosis

Reproduction

Sexual reproduction is rare for Triops longicaudatus , and there is no information available on the mating habits of this species.

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.

• Key Reproductive Features
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• simultaneous hermaphrodite
• parthenogenic parthenogenic
• sexual sexual
• asexual asexual
• fertilization fertilization
  • external external
• oviparous oviparous

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.

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

Lifespan/Longevity

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.

Behavior

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.

• Key Behaviors
• natatorial natatorial
• diurnal diurnal
• motile motile
• sedentary sedentary
• solitary solitary

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.

• Communication Channels
• visual visual

• Perception Channels
• visual visual
• chemical chemical

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.

• Primary Diet
• omnivore omnivore

• Animal Foods
• insects
• aquatic crustaceans
• zooplankton zooplankton

• Plant Foods
• roots and tubers
• algae
• phytoplankton phytoplankton

• Other Foods
• detritus detritus

• Foraging Behavior
• filter-feeding filter-feeding

Predation

Many species of bird, particularly water fowl, feed on Triops longicaudatus , both eggs and adults. Also, wood frogs, Rana sylvatica , 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.

• Anti-predator Adaptations
• cryptic 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.

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.

• 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.

Additional Links

Encyclopedia of Life

BioKIDS Critter Catalog

Contributors

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

References

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.