Speleonectes tulumensis Yager, 1987
Taxonomic Characterization: Body elongate, slender, without eyes or pigment. Cephalic shield small, tapering slightly at anterior end. Trunk segment numbers increasing with age, maximum number examined was 36 segments (Yager, 1987).
Ecological Classification: Stygobitic
Size: Maximum recorded adult length was 27.5 mm
Number of Species in Genus: Nine, all stygobitic
Species Range: Known from Cenote Carwash and Cenote Najaron, Yucatan, Mexico and caves in Belize.
Closest Related Species: S. lucayensis Yager, 1981 from the Bahama Islands.
Habitat: Anchialine limestone caves
Ecology: Associated fauna include several species of hadziid amphipods, thermosbaenaceans, atyid shrimp, mysids, isopods and blind cave fish (Yager, 1987). Schram (1986:40) has noted that remipedes in general, live below a distinct halocline in brackish layers of waters generally deep within the caves. Dissolved oxygen levels in the remipede habitat is very low, around 0.5 parts per billion -virtually anoxic. Yet the animals are moderately active, good swimmers. When collected and maintained in aquaria, the animals take to ceaseless, rather frenetic swimming and literally burn themselves out with a few days. Swimming at any speed is achieved with regular metachronal beats. The robust, prehensile to subchelate mouthparts would seem to imply a carnivorous mode of feeding. Indeed, speleonectids have been observed to feed on Typhlatya garciai, a caridean commonly associated with West Indian nectiopodans. The prey was grasped in the flexed mouthparts and pressed tightly to the mouth. When feeding was completed, an empty cuticle was set afloat.
Life History: Twenty adult and 9 juvenile specimens collected. According to Schram (1986:40), nothing is currently known concerning nectiopodan breeding habits nor details of development. Several of the known species have been found in association with juveniles. In general form, these resemble the adults, but they are smaller, lack gut diverticula and gonopores, and only have from 12 to 17 segments.
Evolutionary Origins: Remipedes are the most primitive of known crustaceans. The combination of a large number of primitive characters in the animals is reminiscent of the ancestral crustacean. The nearest relative to living remipedes is a Carboniferous species, Tesnusocaris goldichi, know only from the fossil record (Schram, 1983, 1986; Yager, 1986).
Conservation Status: Restricted to anchialine caves in Quintana Roo and Belize.
Contributor: Jill Yager, Antioch College, Yellow Springs, OH
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