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Phylum Arthropoda
Subphylum Crustacea
Class Copepoda
Order Cyclopoida
Family Cyclopidae

Diacyclops chakan Fiers & Reid, 1996

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Diacyclops chakan: after Fiers et al., 1996

Taxonomic Characterization: Spinule ornamentation on the caudal side of the basipodite is very reduced. All rami of the swimming legs 3-segmented. Female has an 11-segmented antennule, though it is suggested that some populations could have antennule with 12, 14 or 15 segments. The modified ornamentation of the setae of the leg 3 endopodite and the different length of the terminal leg 2 endopodal spine in the male are unique features (Fiers et al., 1996).

Disposition of Specimens: National Museum of Natural History, Smithsonian Institution, catalog numbers USNM 259839-42, 264231, 271850, 274313, 278028-31; and Invertebrate Collection of the Royal Belgian Institute of Natural Sciences, catalog numbers COP 3863-8, 3870-1, 3874, 3876, 3880-3, 3920.

Ecological Classification: Stygobitic

Size: The largest female measured 0.727 mm; the largest male 0.544 mm.

Number of Species in Genus: More than 100.

Genus Range: This genus has a world-wide distribution with numerous species inhabiting subterranean waters. In Italy, the genus Diacyclops is the most diversified and widespread with more than 30 subterranean species/subspecies.

  • Yucatan Peninsula: D. chakan Fiers & Reid, 1996; D. puuc Fiers, 1996 and D. bernardi (Petkovski, 1986) reported in Reid, 1993

Species Range: Found in Cenote Chen-Ha, Cenote Mucuych, Cenote Yuncu, Aguada, Cenote Ponderosa (Fiers et al., 1996), Cenote Chan-Hoch (Rocha et al., 2000) and six wells in Yucatan and Quintana Roo, Mexico.

Closest Related Species: D. puuc Fiers, 1996

Habitat: Anchialine and freshwater limestone caves and wells

Ecology: Benthic crevicular species. Found in depths as shallow as 1 meter and as deep as 30 meters. Within the wells, the bottom sediments consisted of fine, brilliant white sand, while at greater depths within the cenotes, the bottom substrate was mud. Additional fauna include harpacticoid and cyclopoid copepods, amphipods, thermosbaenaceans, mysids, isopods, and ostracods.

Life History: More than 390 specimens have been collected. This is a female dominated species with more than 185 specimens being female, approximately 14 were male and 93 were copepodids. Two paratype specimens had egg sacs that contained two relatively large eggs (Fiers et al., 1996).

Evolutionary Origins: The reduced antennule supports the hypothesis that Diacyclops are derived from some benthic ancestor resembling D. bernardi and D. hispidus. However, two arguments indicate that D. chakan and D. puuc may share a common ancestor with a planktonic species. First, it is thought that the 11-segmented antennule was derived directly from a 16 or 17-segmented antennule. The second indication may be the relatively long antennule of both species, which reaches the middle of the second thoracic somite (Fiers et al., 1996).

Conservation Status: Found in a number of caves and groundwater habitats in the states of Yucatan and Quintana Roo.


  • Fiers, F., J.W. Reid, T.M. Iliffe and E. Suárez-Morales. 1996. New hypogean cyclopoid copepods (Crustacea) from the Yucatan Peninsula, Mexico. Contributions to Zoology, 66(2):65-102, 21 figures, 1 table.
  • Reid, J.W. 1988. Cyclopoid and harpacticoid copepods (Crustacea) from Mexico, Guatemala, and Colombia. Transactions of the American Microscopical Society, 107:190-202.
  • Reid, J.W. 1993. New records and redescriptions of American species of Mesocyclops and of Diacyclops bernardi (Petkovski, 1986) (Copepoda: Cyclopoida). Bijdragen tot de Dierkunde, 63(3):173-191.
  • Rocha, C.E.F., T.M. Iliffe, J.W. Reid, and E. Suárez-Morales. 2000. Prehendocyclops a new genus of the subfamily Halicyclopinae (Copepoda: Cyclopoida, Cyclopidae) from cenotes of the Yucatan Peninsula, Mexico. Sarsia, 85:119-140, 57 figures, 2 tables.


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