TACHIDIIDAE Boeck 1865

(syn. EUTERPINIDAE Brian, 1921)

"The family Tachidiidae was one of the first to be recognized in the Harpacticoida. Boeck (1865) introduced the higher taxon name Tachidina but it is conceivable that he meant to attribute full family status to this taxon".

Data from the literature suggest that the family is confined to the northern hemisphere; however, unpublished records from Brazil (T. Kihara, pers. comm.) and New Zealand (G. R. F. Hicks, pers. comm.) indicate a worldwide distribution ranging from high latitudes (e.g. Olofsson, 1917; Mielke, 1974) to tropical waters. Huys et al . (1996) recognized four genera in the family: Tachidius Lilljeborg, 1853, Microarthridion Lang, 1944, Cithadius Bowman, 1972 and Geeopsis Huys, 1996.

Shen & Tai (1963) subdivided the genus Tachidius into two subgenera, Tachidius and Neotachidius , based on differences in the P1 endopod and the P5 armature in both sexes. The latter subgenus was established to accommodate a new freshwater species, T. (N.) triangularis , originally described from the Pearl River estuary in southern China (Shen & Tai, 1963), and subsequently recorded from south-western British Columbia by Kask, Sibert & Windecker (1982) and Korea by Song & Chang (1995).

According to the latter authors the species is commonly found in brackish estuarine waters and littoral localities all around the Korean peninsula. Some Tachidiidae, such as Microarthridion littorale (Poppe, 1881) and Tachidius discipes Giesbrecht, 1881, have occasionally been recorded from coastal plankton (El-Maghraby & Perkins, 1956; Hauspie & Polk, 1973; J. R. Cordell, pers. comm.), as they can get entrained in the water column. However, the great majority of the species are benthic, occurring over a wide spectrum of salinity regimes and sediment grain sizes" (from: Huys, Ohtsuka & Conroy-Dalton, 2005). The Euterpinidae Brian, 1921 was synonymized with Tachidiidae Sars, 1909 (Seifried, 2003)

Key to genera of Tachidiidae Boeck, 1865

To date the family includes 16 species of six genera (Tran and Chang, 2012). They are mainly characterized by nuchal organs, reduced