Mictocaris halope Bowman & Iliffe, 1985
Mictocaris halope: after Bowman & Iliffe, 1985
Taxonomic Characterization: Mictocaris halope is a blind, unpigmented, small and slender peracarid crustacean. The first thoracic sement is fused with the head, while the remaining 7 are free. The carapace is not developed posteriorly, but there are small lateral carapace folds above which is a thin-walled inflated area apparently respiratory in function. A down-curved rostrum is present on the head between the pyriform eyestalks, which lack visual elements. Swimming is accomplished by setose exopods on thoracopods 2-6. The spines and setae of the mandibular palp appear to be designed for grooming;
those of the exopod of maxilla 1 for gnawing, and those of maxilla 2 and the maxilliped for confining food particles and moving them to the mouth. The robustness of the spines of the posterior margin of the telson and of the medial margin of the uropodal endopod suggests their use in prehension or defense (Bowman & Iliffe, 1985; Bowman, 1986).
Disposition of Specimens: All specimens were deposited in the United States Museum of Natural History; male holotype (USNM 213227), 19 male, 33 female, 1 manca and 2 juvenile paratypes from several caves (USNM 213228 - 213235).
Ecological Classification: Stygobitic
Size: Total body length of adult ranges from 3.0-3.5 mm.
Number of Species in Genus: One
Species Range: Known from the following caves in Bermuda: Crystal, Green Bay (South Harrington Sound Passage and North Shore Passage), Roadside and Tucker's Town Caves (Bowman & Iliffe, 1985).
Mictocaris halope - Photo by Peter Parks
Closest Related Species: Mictocaris halope, although differing on the family level, has affinities with Hirsutia (Sanders et al., 1985). However, Mictocaris differs from Hirsutia in possessing eyestalks and a rostrum, an anteriorly rounded labium, marginal setae on the mandibular palp, nonsetose oostegites arising medially, and a pereiopod 2 that is not enlarged (Bowman & Iliffe, 1985).
Habitat: Anchialine limestone caves
Mictocaris halope - photo by Peter Parks
Ecology: Mictocaris halope inhabits a number of anchialine caves on Bermuda. Specimens were collected at depths of 0-20 m using a suction bottle in some locations and with a fine mesh dip net in other locations. Divers used a bright underwater light to scan the clear cave waters for the animals which reflected the light. Mictocaris was observed only in those parts of the underwater caves well isolated from the sea and away from daylight. Mictocaris has been primarily observed swimming in midwater, while seen only rarely resting on or walking over rocks or bottom sediments. Several specimens kept in small aquaria in the laboratory, spending a large amount of time on the walls or bottom of the aquarium. An attempt was made to feed the mictaceans freeze-dried tubifex worms, but they showed no interest in them. Feeding habits are unknown but the well developed grinding molar and powerful muscles of the mandible adapt it for chewing, and the dense complex setation of the 2nd maxilla suggests filter feeding.
Mictocaris halope - Photo by Peter Parks
Life History: Collected specimens included 20 males, 33 females, 1 manca and 2 juveniles. Eggs are carried in a marsupium formed by nonsetose oostegites, and the hatchling is a manca, lacking the posterior pair of thoracopods (Bowman, 1986).
Evolutionary Origins: The relatively great abundance and wide distribution of Mictocaris in Bermuda indicates that this species is well adapted to the cave habitat and has probably been resident there for a considerable period of time (Bowman & Iliffe, 1985). In general appearance, the Mictacea are most similar to the Mysidacea, Spelaeogriphacea, and Thermosbaenacea, but these orders differ from the Mictacea in ways thar are far from trivial. The Mysidacea differ in lacking a manca, in different articulation of the pereiopods, and in the 1-segmented rami of the uropods. In Spelaeogriphus, the exopods of pereiopods 4-6 are large and natatory with paddle-shaped rami bearing marginal setae; no pleopods are modified in the male; and the uropods have 2-segmented exopods and 1-segmented endopods. The Thermosbaenacea have a dorsal marsupium, lack eyestalks, and a scale on antenna 2, and the pereiopods have 1 less segment (Bowman et al., 1985).
Conservation Status: This species is considered to be critically endangered (IUCN, 1996).
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