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Phylum Arthropoda
Subphylum Crustacea
Class Copepoda
Order Cyclopoida
Family Speleoithonidae

Speleoithona eleutherensis Rocha & Iliffe, 1991

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Speleoithona eleutherensis: habitus, after Rocha & Iliffe, 1991

Taxonomic Characterization: A minute diaphanous anchialine cyclopoid. The genus Speleoithona is distinguished from other cyclopoids by several characteristics. The rostrum is enlarged and notched medially. The inner apical seta on the caudal rami is absent. The mandible has a smooth and quadrangular basal segment 2, and a 2-segmented endopodite with an unarmed proximal segment and 3 setae on the terminal segment. The antennule is 18-segmented, with aesthetascs on segments 8,17, and 18. On the second through fourth legs, the endopodite 3 has a row of pinnules on the caudal face. The fifth legs are 2-segmented, bear long seta, and are joined by an intercoxal plate. In males, the fifth legs also have 2 short setae on the inner side of the distal segment. S. eleutherensis can be distinguished from other Speleoithona by the following characteristics:

  • On the endopodite of the fourth leg the armature is 0-0;0-1;1,2,1.
  • The caudal rami are 2.5 times longer than wide. The slender, outer apical seta and the thickened, smooth, bluntly-pointed median apical setae are both 3.2 times longer than the ramus. The dorsal seta is about 2.7 times as long as caudal ramus and shorter than the median apical setae.
  • The terminal segment of the fifth leg on both sexes bears a long plumose seta on the outer distal corner. The basal segment 1.4 times the length of the terminal segment.
  • In males, the sixth legs have two long slender plumose setae.

Ecological Classification: Stygobitic

Size: Adult females' lengths range from 255 to 290 microns. The adult males' lengths range from 240 to 260 microns.

Number of Species in Genus: Three, all anchialine stygobitic

Genus Range:

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Speleoithona: genus range

Species Range: Known only from Hatchet Bay Cave, Eleuthera, Great Bahama Bank, Bahamas

Closest Related Species: Speleoithona salvadorensis from San Salvador

Habitat: Anchialine limestone cave

Ecology: They were free-swimming, at a depth of 0-3 m and in near fully marine salinity water (32 g/l).

Life History: 122 females, 4 males, and no copepodites were collected. After copulation, females bear a pair of spermatophores that are attached side by side at a ventral position.

Evolutionary Origins: Speleoithonidae is considered to be a sister group of Oithonidae. It is believed that Speleoithona evolved in its restricted habitat, developing very characteristic features, while retaining some primitive traits (Rocha & Iliffe, 1991).

Conservation Status: Restricted to a single cave on the island of Eleuthera, Bahamas


  • Rocha, C.E.F. and T.M. Iliffe. 1991. Speleoithonidae, a new family of Copepoda (Cyclopoida) from anchialine caves on the Bahama Islands. Sarsia, 76:167-175, 28 figures.
  • Rocha, C.E.F. and T.M. Iliffe. 1993. New cyclopoids (Copepoda) from anchialine caves in Bermuda. Sarsia, 78:43-56, 45 figures.


Contributor: Carlos Eduardo F. da Rocha, Universidade de São Paulo, Brazil

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