Girardia tigrina, known as the brown planarian or the immigrant triclad flatworm, is a species of dugesiid native to the Americas.Ball, I. R.: A contribution to the phylogeny and biogeography of the freshwater triclads (Platyhelminthes: Turbellaria). Biology of the Turbellaria (Edited by: Riser NW and Morse MP). New York: McGraw-Hill New York 1974 , 339-401. It has been accidentally introduced into Europe and Japan.Sluys, R., Kawakatsu, M., Yamamoto, K., 2010. "Exotic freshwater planarians currently known from Japan". Belgian Journal of Zoology, 140 (Suppl.). p. 103-109
Description G. tigrina individuals are around 10 mm in length. They have a head with two broad and short auricles. The two eyes are in two pigment-free patches. The dorsal surface of the body has numerous pigment spots.
Distribution and ecology Originally from the Americas, Girardia tigrina has become an invasive species in Europe and Japan. Since being first recorded in France in 1925, this species has been reported from many other European countries, including Germany,Meinken (H.)., 1925. Ein verkannter Laichraùher — Wochenschrift fur Aquarien und Terrarienkunde, 22 S : 94-96.Meinken (H.)., 1927. Planaria maculata, ein aus Nordamerika eingeschleffter Laichriiber und seine Vertilgung — Blatter fiir Aquarien und Terrarienkunde, 38 S : 131-133. Italy,Benazzi M., 1970. Karyological research on the American planarians Dugesia dorotocephala and Dugesia tigrina. J. Biol. Psychol. / Worm Runner's Digest, XII (1): 81-82. the Netherlands, Romania,An der Lan (H.)., 1962. Zur Turbellarien Fauna der Danau. Arch. Hydrobiol., suppl., 2 7 : 3-27. and Wales.Gee, H., 1990. The biology of the immigrant triclad Dugesia tigrina, (Girard): a comparative study with native triclad species. Unpublished Ph.D. Thesis, University of Liverpool, England.
In North Wales, this species has displaced the native triclad species Polycelis nigra and Polycelis tenuis due to its superior exploitation of food.
Diet G. tigrina is a carnivorous species that feeds on invertebrates such as oligochaetes, isopods, chironomids, snails, caddisflies, and mayflies.
Karyology The haploid number is n=8. There are diploid (2n=16) and triploid (3n=24) specimens.
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