University of Tasmania, Australia

UTAS Home | UTAS Staff | UTAS Contacts


UTAS Home > IMAS Home > Image Key > Copepoda > Cyclopoida > Corycaeidae >  Agetus flaccus

Agetus flaccus

Giesbrecht (1891)

Download a fact sheet for Agetus flaccus (PDF 438KB)


Phylum Arthropoda
Subphylum Crustacea
Class Maxillopoda
Subclass Copepoda
Order Cyclopoida
Family Corycaeidae
Genus Agetus
Species flaccus


  • Female: 1.20 - 1.89 mm
  • Male: 1.15 - 1.68 mm

Distinguishing characters

  • Proportional length of urosome somites and caudal rami
  • Female genital somite with knob like protuberance
  • Distinct form of female caudal rami


  • Cephalosome fused to 1st pedigerous somite
  • Eye lenses separate
  • Antenna, inner margin of 2nd basal joint has no large tooth, finely serrated
  • Genital somite 1.5 times as long as wide
  • Anal somite wider at proximal than distal margin
  • Caudal rami 7times as long as wide


  • Cephalosome separated from 1st pedigerous somite
  • Cephalosome1.8 times as long as wide
  • Urosome and caudal rami in the proportional lengths 4:3
  • Genital somite 1.5 times as long as wide, with a small rounded protuberance on the mid-dorsal of the somite, lateral margins furnished with short hairs
  • Inner marginal caudal rami seta is the longest and is flanged


  • Epipelagic
  • Coastal and oceanic
  • Widespread in tropics and subtropics of Indian, Pacific and Atlantic


  • Visual predators using raptorial appendages to capture small prey
  • Inhabits the layer below the thermocline in summer


  • Bradford-Grieve, J. M., E. L. Markhaseva, et al. (1999). Copepoda. South Atlantic Zooplankton. D. Boltovskoy. Leiden, The Netherlands, Backhuys Publishers. 1: 869-1098.
  • 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) @
  • Tanaka, O. (1957[1959]). On copepoda of the family Corycaeidae in Japanese waters 1957. Contx Dep Fish Kyushu Univ 3