SUPERFAMILY TACHIDIOIDEA Boeck, 1865

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Data from the literature suggest that the family is confined to the northern hemisphere; however, unpublished records from Brazil (T. Kihara, pers.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


TACHIDIUS Giesbrecht, 1881 (syn. Rhyncoceras Labbé, 1927 )


  • Tachidius abrau Krichagin, 1877 (= Ectinosoma abrau (Krichagin, 1877)
  • Tachidius acutifrons (Dana, 1847) (= Euterpe gracilis Claus, 1863)
  • Tachidius berberus Monard, 1935 (= Microarthridion berberum (Monard, 1935)
  • Tachidius discipes Giesbrecht, 1881
  • Tachidius arcticus Olofsson, 1917
  • Tachidius brevicornis Lilljeborg, 1853
  • Tachidius convergens Labbé, 1927
  • Tachidius crassicornis Scott T., 1892 (= Microarthridion littorale (Poppe, 1881)
  • Tachidius elongatus (Labbé, 1926)
  • Tachidius fonticula Lang, 1948
  • Tachidius hydrobiologicus Oliveira, 1945
  • Tachidius incisipes Klie, 1913(=Geeopsis incisipes (Klie, 1913)
  • Tachidius laurenticus Nicholls, 1939 (= Microarthridion laurenticum (Nicholls, 1939)
  • Tachidius littoralis Poppe, 1881 (= Microarthridion littorale (Poppe, 1881)
  • Tachidius longicornis Olofsson, 1917
  • Tachidius minutus Claus, 1866
  • Tachidius pygmaeus Krichagin, 1873
  • Tachidius reductus Monard, 1935 (= Microarthridion reductum (Monard, 1935)
  • Tachidius rotus (Labbé, 1926)
  • Tachidius spitzbergensis Olofsson, 1917
  • Tachidius triangularis Shen & Tai, 1963 (=Tachidius (Neotachidius) triangularis Shen & Tai, 1963
  • Tachidius vicinospinalis Shen & Tai, 1964 (= Sinotachidius vicinospinalis (Shen & Tai, 1964)


    NEOTACHIDIUS Shen & Tai , 1963 Grad. Nov.

  • Neotachidius coreanus Huys, Ohtsuka & Conroy-Dalton, 2005 [Korea, brackish waters]
  • Neotachidius parvus Huys, Ohtsuka & Conroy-Dalton, 2005 [Korea, brackish waters]
  • Neotachidius triangularis (Shen & Tai 1963)


    SINOTACHIDIUS Huys, Ohtsuka & Conroy-Dalton, 2005


  • Sinothachidius vicinospinalis (Shen & Tai, 1964) [Korea, brackish waters]


    GEEOPSIS Klie, 1913

  • Geeopsis incisipes (Klie ,1913)


    MICROARTHRIDION Monard, 1936


  • Microarthridion berberum (Petkovski ,1964)
  • Microarthridion corbisierae Kihara & Rocha 2007
  • Microarthridion fallax Perkins. 1956
  • Microarthridion laurenticum (Nicholls, 1940)
  • Microarthridion litospinatus Shen & Tai, 1973
  • Microarthridion littorale (Klie , 1913)
  • Microarthridion paralittorale Apostolov, 2021 [Korea] (Syn. Microarthridion littorale (Poppe, 1881) - sensu Kim, Choi & Yoon, 2016
  • Microarthridion perkinsi Bodin, 1970
  • Microarthridion reductum (Monard, 1935)
  • Microarthridion thanhi Tran et al., 2011 [North Vietnam]


    EUTERPINA Norman, 1903 (syn. Euterpe Claus, 1863 )

  • Euterpina acutifrons (Dana, 1848) [cosmopolitan, except Australia?; marine coastal waters]
  • Euterpina armata (Scott T., 1894)
  • Euterpina gracilis gracilis (Claus, 1863)


    CITHADIUS Bowman, 1972

  • Cithadius cyathurae Bowman, 1972


    PSEUDONEOTACHIDIUS Nazari et al., 2020

  • Pseudoneotachidius sinuspersici Nazari et al., 2020 [Iran]



    | OTHER SPECIES AND REVIEW OF THE GENERA IN: HUYS, OHTSUKA & CONROY-DALTON, 2005 |





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