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Ditrichicorycaeus dahli

Tanaka (1957)

Download a fact sheet for Ditrichocorycaeus dahli (PDF 470KB)


Phylum Arthropoda
Subphylum Crustacea
Class Maxillopoda
Subclass Copepoda
Order Cyclopoida
Family Corycaeidae
Genus Ditrichocorycaeus
Species dahli


  • Female: 0.85 - 1.21 mm
  • Male: 0.68 - 0.99 mm

Distinguishing characters

  • Peg like endopod of P4 with 2 setae and a small posterior projection
  • Proportional length of urosome somites and caudal rami
  • Female genital somite with pronounced dorsal lump or folding and ventral hook
  • Male has oval genital somite with small ventral hook


  • Antenna terminal claw longer than 2nd basal joint
  • Prosome 1.4 times as long as urosome
  • Prosome 1.5 times as long as wide
  • Apical spines on first 3 legs are straight
  • Genital somite oval, 1.6 times as long as wide
  • Small ventral hook on genital somite
  • Caudal rami nearly 2 times as long as anal somite
  • Caudal rami 8 times as long as wide
  • Longest caudal rami setae longer than rami
  • Urosome somites and caudal rami in the proportional lengths 50:18:32


  • Basal spine on antenna 2 times as long as spine on next segment
  • Prosome 1.7 times as long as urosome
  • Prosome points extend beyond middle of genital somite
  • Apical spine of exopodite of P2 curved, with ~6 teeth on inner, anterior side
  • Genital somite 1.3 times as long as wide, vaulted on dorsal surface or a folding on the distal 2/3 of somite, ventral surface flat
  • Anal somite wider at proximal than distal margin
  • Caudal rami divergent, 16 times as long as wide, nearly 2 times as long as anal somite
  • Urosome somites and caudal rami in the proportional lengths 35:23:42


  • Epipelagic
  • Coastal and oceanic
  • Subtropical and tropical
  • Indian and Pacific Oceans


  • Visual predators using raptorial appendages to capture small prey
  • Undertakes diel vertical migration, where it spends most of its time near the bottom and ascends to the upper layers close to midnight


  • Bradford-Grieve, J. M., E. L. Markhaseva, et al. (1999). Copepoda. South Atlantic Zooplankton. D. Boltovskoy. Leiden, The Netherlands, Backhuys Publishers. 1: 869-1098.
  • Tanaka, O. (1957[1959]). On copepoda of the family Corycaeidae in Japanese waters 1957. Contx Dep Fish Kyushu Univ 3
  • Chen Q.-c. & Zhang S.-z. , 1974.  The pelagic copepods of the South China Sea. I.. Studia mar. sin., 9: 101-124.
  • Dahl, M. (1912). Die Copepoden der Plankton-Expedition. I. Die Corycaeinen. Mit Berucksichtigung aller bekannten Arten bearb. (Ergebnisse der Plankton-Exp. Bd II. G. f. 1.).  Pages: (iv + 136)
  • Owens, L. Rothlisberg, P.C. 1991. Vertical migration and advection of bopyrid isopod cryptoniscid larvae in the Gulf of Carpentaria, Australia, Journla of plankton research, 13:4:279