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Phylum Arthropoda
Subphylum Crustacea
Class Remipedia
Order Nectiopoda
Family Speleonectidae

Lasionectes entrichoma Yager & Schram, 1986


Taxonomic Characterization:
Remipedes are "free-swimming, troglobitic crustaceans characterized by a short head followed by an elongate trunk. The head is covered by a cephalic shield. All species have a pair of slender, cylindrical pre-antennal frontal processes. The trunk lacks tagmosis and is composed of numerous segments each bearing a pair of biramous, paddlelike swimming appendages.
Remipedes lack eyes and body pigmentation. Their appendages have a vast array of very diverse setae and sensilla which enable them to sense an environment devoid of light" (Yager, 1994).
L. entrichoma is distinguished by second maxilla and maxilliped subchelate and distinctly more robust than first maxilla; terminal segments bearing trifid claw with comb-like row of spinules between large central spine and two flanking spines; both appendages with short setae along entire medial margin.

Ecological Classification: Stygobitic

Size: Adult holotype measured 31.5 mm in length.

Number of Species in Genus: Two

Genus Range:

  • Australia: L. exleyi Yager & Humphreys, 1996
  • Caicos Islands:
    • Middle Caicos Island: L. entrichoma Yager & Schram, 1986
      • Cottage Pond (Yager & Schram, 1986)
    • Providenciales Island: L. entrichoma Yager & Schram, 1986
      • Old Blue Hill Cave & Airport Cave (Yager & Schram, 1986)

Species Range: Found in caves located on both Middle Caicos Island and Providenciales Island, Caicos Islands, B.W.I.

Closest Related Species: The only other species from this genus is L. exleyi from Western Australia

Habitat: Anchialine limestone caves

Ecology: Found free-swimming in brackish waters at depths of 5-20 m.

Life History: According to Yager (1994): "Remipedes are simultaneous hermaphrodites. The ovary originates in the posterior portion of the head and lies dorsal to the midgut. The oviducts extend ventrally to the 7th swimming or trunk appendages where the female gonopores are located. The female gonopore is a semicircular structure on the posterior base of the protopod.
The testes are paired organs which originate in the 7th trunk segment and extend posteriorly until about the 10th trunk segment. At this position there is a transition from testes to vas deferens. The vas deferens extends to the male gonopores located at the base of the 14th swimming or trunk appendages. Spermatids are flagellate with a 9 + 2 microtubular arrangement. As they mature and move posteriorly they are packages into spermatophores.
To date, nothing is known about remipede development. Small juveniles have been collected which resemble adults. They are about one-third or less the length of adults."

Evolutionary Origins: The large number of trunk segments, each with similar, laterally directed, biramous, swimming appendages, plus a combination of the other characteristics necessitated the erection of a new crustacean class, the Remipedia (Yager, 1981). Remipedes are believed to be the most primitive of living crustaceans. The fossil species Tesnusocaris goldichi Brooks from Late Mississippian deposits in Texas has been placed in this class. The recent discovery of remipedes from anchialine caves in Western Australia is further evidence for a Tethyan distribution (Yager & Humphreys, 1996).

Conservation Status: Restricted to three anchialine caves in the Caicos Islands

References:

  • Yager, J. 1994 Remipedia. Pp. 87-90 in: Encyclopaedia Biospeologica, Vol. 1, V. Decu and C. Juberthie, eds., Society of Biospeleology, Paris, 880 pp., 3 figures, 1 plate, 1 table.
  • Yager, J. and F. Humphreys. 1996. Lasionectes exleyi sp. nov., the first remipede crustacean recorded from Australia and the Indian Ocean, with a key to the world species. Invertebrate Taxonomy, 10:171
  • Yager, J. and F. Schram. 1986. Lasionectes entrichoma, new genus, new species, (Crustacea: Remipedia) from anchialine caves in the Turks and Caicos, British West Indies. Proceedings of the Biological Society of Washington, 99(1):65-70, 3 figures.

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Contributor: Jill Yager, Antioch College, Yellow Springs, OH


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