Torix (genus)

Two members of the genus, T. tagoi and T. tukubana, show high percentages of Rickettsia infection in the wild; 96% and 83% respectively, according to a 2003 study.[8] Eggs of T. tagoi were found to all contain the bacteria, indicating the bacteria is almost always passed on to the next generation (vertical transmission).[8] It was found that infected leeches grew far larger than those uninfected with the bacteria.[8] Another paper concluded that the Rickettsia that acted as endosymbionts in the leeches represented a separate clade of Rickettsia, named the torix clade.[9][10] As T. tagoi feeds on the blood of amphibians such as frogs and newts, it is possible that those amphibians were the route of horizontal transmission.[9]

Photo of a leech, probably a member of the genus Torix on a frog of the Rana genus uploaded from iNaturalist.

The number of species the genus contains is disputed between taxonomic databases. Given below is a complete list; the text in superscript indicates which papers or taxonomic databases support the validity of that species.

• Torix baicalensis Shegolev, 1922 ^{(Sasaki, 2015, Light & Siddall, 1999 Biolib)}
• Torix cotylifer Blanchard, 1898 ^{(Sasaki, 2015, Moore, 1930, Lukin & Ephstein, 1960, Biolib)}
• Torix mirus Blanchard, 1893 ^{(Sasaki, 2015, Kambayashi et al., 2020, Biolib, GBIF, WoRMS)}
• Torix novaezealandiae (Dendy & Olliver, 1900) ^{(Biolib, ADW)}
• Torix orientalis (Oka, 1925) ^{(Sasaki, 2015, Biolib)}
• Torix tagoi (Oka, 1925) ^{(Sasaki, 2015, Biolib)}
• Torix tukubana (Oka, 1935) ^{(Sasaki, 2015, Kambayashi et al., 2020, Biolib, GBIF, WoRMS, NCBI)}