Speleonectes tanumekes Koenemann, Iliffe & van der Ham, 2003
Taxonomic Characterization: Long and slender species, largest specimens composed of 38-40 trunk segments - the largest number of trunk segments recorded for remipedes to date; pleural tergites weakly developed, with broadly rounded lateral margins in anterior part of trunk, becoming slightly pointed posteriorly; sternal bars sublinear, isomorphic; frontal filaments with short processes; dorsal flagella of antennules short; segment 4 of maxillule subrectangular, with small enditic lobe bearing two long, rasp-like spines and several slender setae; maxilla and maxilliped with distinct tagmosis (i.e., proximal segment is much longer and wider than distal segment), bearing few clusters of long, marginal setae; horseshoe-type claws of maxilla and maxilliped with 17-20 small denticles; anal somite slightly wider than long; caudal rami slightly longer than anal somite (Koenemann et al., 2003).
Speleonectes tanumekes after Koenemann et al., 2003
Ecological Classification: Stygobitic
Size: Adult lengths extend to 27 mm.
Number of Species in Genus: Nine, all stygobitic
Species Range: Know only from Basil Minns Blue Hole, Great Exuma Island,
Exuma Cays, Bahamas.
Closest Related Species: S. tanumekes seems morphologically similar to S. epilimnius from San Salvador.
Habitat: Anchialine limestone caves
Ecology: S. tanumekes was collected from below a hydrogen sulfide layer in 33-43 m depths of an isolated, collapse, dome room located several hundred meters into the cave from the surface entrance. In the depth range in which remipedes were collected, salinity was about 34 ppt, temperature 25oC, pH 7.4 and dissolved oxygen 3 mg/l. Three new species of Speleonectes were collected from this cave including S. tanumekes, S. parabenjamini and S. minnsi. However, the sympatry of these three species is not exceptional for remipedes as several other instances of 2-3 sympatric species have been observed. Sympatric remipedes are likely to be subjected to strong competition, which could lead either to niche differentiation or competitive exclusion. S. tanumekes appears to be the most abundant remipede in this cave. Other stygobitic fauna from this cave includes copepods, ostracods, leptostracans, bochusaceans, amphipods, thermosbaenaceans, mysids, and polychaetes (Koenemann et al., 2003).
Life History: The fact that remipedes are hermaphrodites may point towards an adaptation to small population size (Koenemann et al., 2003).
Evolutionary Origins: Remipedes are an ancient group of crustaceans sharing several well defined features with Tesnusocaris goldichi from the Carboniferous. The current distribution of remipedes consists of a prominent cluster in the northern Caribbean including the Bahamas. Whether this cluster is an ancient center of origin and the disjunct taxa in the Canary Islands and Western Australia are isolated relicts remains to be seen (Koenemann et al., 2003).
Conservation Status: Known only from one anchialine cave on Great Exuma Island.
Contributor: Stefan Koenemann, University of Amsterdam, The Netherlands.
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