Girardia


Girardia is a genus of freshwater planarians belonging to the family Dugesiidae.

Distribution

The genus Girardia is endemic to the Americas, from Argentina to Canada, although most species occur in South America. The only two species known to occur naturally in North America, Girardia tigrina and Girardia dorotocephala, have been introduced in other continents and islands.

Description

Species of Girardia are very similar to species of other genera of Dugesiidae and few apomorphies that clearly define the genus are known. One of the few exclusive characteristics is the presence of pigment granules in the outer pharyngeal wall.
Until 1991 Girardia was considered a subgenus of Dugesia, then it was upgraded to the genus rank. However, some works continued to use the old genus for some Girardia species, mainly for Girardia dorotocephala and Girardia tigrina.

Species

Phylogeny

Phylogenetic tree including five dugesiid genera after Álvarez-Presas et al., 2008: