Dugesia tigrina

Geographic Range

Dugesia tigrina is a triclad turbellarian found across North America. Human activities have extended the range of D. tigrina to parts of northwestern Europe and eastern Asia, with notable population densities in Great Britain and Japan.

• Biogeographic Regions
• nearctic nearctic
  • native native
• palearctic palearctic
  • introduced introduced

• Other Geographic Terms
• holarctic holarctic

Habitat

Dugesia tigrina is typically present in lakes, ponds, and streams in temperate regions. It shows negative phototaxis and dwells in the benthic zones of freshwater biomes as a result. The microhabitats for this organism include the undersides of rocks, plant material, and other types of debris found on lake and stream beds. The existing literature does not specify a depth range for the organism, but studies indicate the presence of D. tigrina in lakes at maximum depths of 25 to 40 cm. Dugesia tigrina shows a preference for water temperatures between 13 and 25°C.

• Habitat Regions
• temperate temperate
• freshwater freshwater

• Aquatic Biomes
• benthic benthic
• lakes and ponds
• rivers and streams

Physical Description

Dugesia tigrina is colloquially known as a flatworm, and it has a body that is flattened dorsoventrally. Additionally, the body plan exhibits cephalization, and the body surface is covered with cilia used to facilitate gliding locomotion. Sensory lobes known as auricles make the head region look triangular, and eyespots called ocelli are found on the head. In terms of coloration, the body is typically brown with white and yellow spots. The average length of Dugesia tigrina is 9 to 15 mm, but body dimensions can vary due to the organism's ability to regenerate lost parts.

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

Development

Individuals of Dugesia tigrina that are produced sexually hatch from a cocoon, and are typically 2.0 to 4.5 mm in length when first hatched. They are transparent, and have visible yellow yolk cells. As they grow, they use up the yolk, and the spots of pigment grow and darken. Individuals are considered mature after reaching a mean length of 9 mm.

Reproduction

Dugesia tigrina is hermaphroditic, and only some populations reproduce sexually. There is no courtship process, and when one individual encounters another, it glides on top of it. They either both face the same direction or opposite directions, and the top flatworm moves its head back and forth over either the head or dorsal side of the bottom flatworm, stimulating it. After several minutes, both lift their tail ends, maneuvering so that both ventral sides meet, and the penes are mutually inserted. Copulation can last 1 minute to 1.5 hours, and ends when the pair separates and leaves. Individuals can mate many times in their lives.

Dugesia tigrina reproduces both sexually and asexually. Some populations reproduce solely sexually, while others reproduce only by fission, and still other populations reproduce both ways. High temperatures (at approximately 26°C) permit asexual transverse fission, whereas lower temperatures (approximately 20°C) yield a preference for sexual reproduction. Some populations therefore switch from asexual fission to mating seasonally. Reproduction for Dugesia tigrina reaches its peak during the summer months. An adult delivers a cocoon that attaches to surfaces by means of a short stalk. The cocoons have mean diameter of 1.30 mm and give rise to a mean of about 4 newborns upon hatching. An individual can produce multiple cocoons during its lifetime.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• simultaneous hermaphrodite
• sexual sexual
• asexual asexual
• fertilization fertilization
  • internal internal
• oviparous oviparous

Dugensia tigrina produces a cocoon for every group of offspring produced, and provides provisioning. Otherwise, there is no parental care.

• Parental Investment
• no parental involvement
• pre-hatching/birth
  • provisioning

Lifespan/Longevity

There is no current record of the highest, lowest, and average lifespans of Dugesia tigrina . Current literature comments that populations of Dugesia tigrina do not show any signs of degenerative aging due to their regenerative capabilities. It is reported that the mortality rates of fed individuals are negligible because they are solely due to experimental accidents. It is also presented in the literature that Dugesia tigrina is able to reabsorb its body tissues and shrink in size to prevent death from famine.

Behavior

Dugesia tigrina is free-swimming and exhibits gliding locomotion with the help of mucus secretions as well as cilia that cover the body surface. Individuals can be found both independently or in groups. Group foraging has been observed to increase rates of daily per capita ingestion, which drives increased rates of asexual fission.

• Key Behaviors
• natatorial natatorial
• motile motile
• sedentary sedentary
• solitary solitary
• social social

Communication and Perception

Dugesia tigrina is considered one of the most primitive animal forms known to possess a central nervous system for higher order perception and integration. These flatworms are equipped with two eyespots called ocelli that appear as dark pigment cups on the anterior dorsal surface. Dugesia tigrina also has two earlike lobes as part of its anterior head region that function in tactile and chemical sensation. These structures, called auricles, have receptors and cilia on them to facilitate such sensation and perception. Gliding mobility is facilitated by cilia covering the body surface, and the organism shows negative phototaxis upon exposure to light.

• Perception Channels
• visual visual
• tactile tactile
• chemical chemical

Food Habits

Being an opportunistic predator, Dugesia tigrina primarily forages on small crustaceans, insect larvae (particularly those of chironomids and mosquitoes ), small round worms , and the soft structures of some freshwater sponges . Dugesia tigrina uses its mucus secretions not only for gliding locomotion but also for capturing prey items. It has been observed that D. tigrina exhibits a threshold temperature for feeding. Feeding is significantly reduced or completely stops below a critical temperature of 6°C.

• Primary Diet
• carnivore carnivore
  • insectivore insectivore
  • eats non-insect arthropods
  • vermivore

• Animal Foods
• insects
• aquatic or marine worms
• aquatic crustaceans

Predation

Common predators of Dugesia tigrina include freshwater fish, amphibians such as newts, and some insect larvae, including Odonata larvae. Mucus secreted from Dugesia tigrina functions to inhibit being captured by these organisms. Group foraging is reported to increase survival rates.

Ecosystem Roles

Dugesia tigrina serves as prey to a variety of animals, including fish, amphibians, and insects. It is also a predator itself of insects, aquatic worms, and crustaceans. As a significant predator of insect larvae, particularly mosquitoes, Dugesia tigrina has been introduced to catch basins in Ontario to successfully limit the population growth of immature mosquitoes. However, mosquito populations were not observed to be effectively controlled after introducing these flatworms to vernal pools in North Dakota.

Economic Importance for Humans: Positive

Despite its simple physical structure, Dugesia tigrina is equipped with a central nervous system (CNS) for integrative neuronal communication and has regenerative abilities. Consequently, this flatworm has been increasingly used as a model organism for educational and research purposes to better understand both tissue regeneration as a result of wear and tear and brain development as the main neural processing center in animals. Genetic research at the molecular level is currently underway for these organisms to attempt to shed light on human growth, development, and tissue turnover. Additionally, Dugesia tigrina has been introduced to some bodies of water in an attempt to control mosquito populations through larval predation by these flatworms, to varying degrees of success.

• Positive Impacts
• research and education
• controls pest population

Economic Importance for Humans: Negative

There are no known adverse effects of Dugesia tigrina on humans.

Conservation Status

Dugesia tigrina has no special conservation status.

Other Comments

Dugesia tigrina is also referred to as Girardia tigrina in the current literature.

It is suggested that feeding populations of this species do not age and are therefore considered immortal due to their regenerative capabilities.

Mitotic activity for Dugesia tigrina in terms of its growth and regenerative patterns are regulated by a temporal pattern. The rate of mitosis is observed to have an initial maximum 4 to 12 hours after injury, fall to a minimum at 1 day, and then rebound to attain a second maximum after 2 to 3 days. Anterior and posterior regenerative patterns show the most rapid rate of mitotic activity residing near the site of a wound and diminishing at body sections away from an injured body section.

Additional Links

Encyclopedia of Life

BioKIDS Critter Catalog

Contributors

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

References

Cash, K., M. McKee, F. Wrona. 1993. Short- and long-term consequences of grouping and group foraging in the free-living flatworm Dugesia tigrina . Journal of Animal Ecology , 62: 529-535.

Davies, R., T. Reynoldson. 1969. The incidence and intensity of predation on lake-dwelling triclads in the laboratory. Ecology , 50: 845-853.

Folsom, T., H. Clifford. 1978. The population biology of Dugesia tigrina ( Platyhelminthes : Tubellaria ) in a thermally enriched Alberta, Canada lake. Ecology , 59: 966-975.

Gee, H., J. Pickavance, J. Young. 1998. A comparative study of the population biology of the American immigrant triclad Dugesia tigrina (Girard) in two British lakes. Hydrobiologia , 361: 135-143.

Meyer, H., L. Learned. 1981. A field test of the potential of a local flatworm, Dugesia tigrina , for biological control of mosquitoes in temporary pools. North Dakota Farm Research , 39: 19-21.

Pickavance, J. 1971. The diet of the immigrant planarian Dugesia tigrina (Girard): I. Feeding in the laboratory. Journal of Animal Ecology , 40: 623-635.

Salo, E., J. Baguna. 1984. Regeneration and pattern formation in planarians. I. The pattern of mitosis in anterior and posterior regeneration in Dugesia tigrina , and a new proposal for blastema formation. Journal of Embryology and Experimental Morphology , 83: 63-80.

Sinko, J., W. Streifer. 1971. A model for population reproducing by fission. Ecology , 52: 330-335.

Sluys, R., M. Kawakatsu, K. Yamamoto. 2010. Exotic freshwater planarians currently known from Japan. Belgian Journal of Zoology , 140: 103-109.

Smales, L., H. Blankespoor. 1978. The epidermis and sensory organs of Dugesia tigrina ( Turbellaria : Tricladida ). Cell and Tissue Research , 193: 35-40.

Stokely, P., T. Brown, F. Kuchan, T. Slaga. 1965. The distribution of fresh-water triclad planarians in Jefferson County, Ohio. The Ohio Journal of Science , 65: 305-318.

Takano, T., J. Pulvers, T. Inoue, H. Tarui, H. Sakamoto, K. Agata, Y. Umesono. 2007. Regeneration-dependent conditional gene knockdown (Readyknock) in planarian: demonstration of requirement for Djsnap-25 expression in the brain for negative phototactic behavior. Development, Growth and Differentiation , 49: 383-394.

Vowinckel, C., J. Marsden. 1971. Reproduction of Dugesia tigrina under short-day and long-day conditions at different temperatures. II. Asexually derived individuals. Journal of Embryology and Experimental Morphology , 26: 599-609.

Vreys, C., J. Crain, S. Hamilton, S. Williamson, N. Steffanie. 2002. Evidence for unconditional sperm transfer and sperm-dependent parthenogenesis in a hermaphroditic flatworm ( Girardia tigrina ) with fissipary. Journal of Zoology , 257/1: 43-52.