Palaumysis bahamensis, Pesce & Iliffe, 2002

Pesce, Giuseppe L. & Iliffe, Thomas M., 2002, New records of cave-dwelling mysids from the Bahamas and Mexico with description of Palaumysis bahamensis n. sp. (Crustacea: Mysidacea), Journal of Natural History 36 (3), pp. 265-278 : 273-275

Palaumysis bahamensis n. sp.

(®gures 7±13)

Material examined. South Andros Island, Bahamas: Atlantis Blue Hole, 2 October 1999; one female (holotype), three females and one male (paratypes) collected with 93 m m mesh plankton net from the water column in 60±70 m depths. Material dissected and preserved on cover slips in the` Crustaceans collection’ at the Dipartimento di Scienze Ambientali, University of L’Aquila, Italy (My-Pa/01±My- Pa/05) .

Description. Body size 1.9±2.5 mm. Alcohol decolourized the specimens which appear white transparent. Live specimens were noted as being bright red. Cephalothorax larger than abdomen. Integument translucent. Anterior part of carapace forming a large triangular area.

Antennule (®gure 13): peduncle short and thick; a prominence (rudiment of male lobe) bears four to ®ve aesthetascs (male) and a very reduced, apomorphic, twosegmented ¯agellum. The main ¯agellum very long, exceeding the length of the body.

Antenna (®gure 9) with a short peduncle and a rudimentary scale.

Eyes large, suboval.

Labrum slightly protruding anteriorly.

Mouthparts not well visible since specimens partially damaged, but seemingly without distinguishing characteristics.

Peraeopods all alike, both in males and females; dactylus as in ®gure 7. Very rudimentary oostegites.

Pleopods (®gures 10, 12) tiny, all alike except the fourth male pleopod which is armed with a very long distal seta (®gure 10).`Pentagonal zones’ on the ventral side of each pleonite, reported in P. simonae Bacescu and IliOEe, 1986, apparently absent.

Telson (®gures 8, 11) slender, subtriangular, about twice shorter than the last pleonite (®gure 11), and bearing two apical spines, small and not articulated.

Uropods (®gure 11): exopod slightly shorter than endopod. Endopod provided with a large statolith and completely devoid of spines on the inner margin; other setation as in ®gure 11, distal setae not ®gured.

Remaining characteristics as in P. simonae .

Remarks. Palaumysis bahamensis n. sp. is similar in most respects to P. simonae , described by Bacescu and IliOEe (1986) from cave waters of Palau ( Micronesia), but diOEers in some important characteristics such as: telson distinctly longer than wide, only half as long the last pleonite (vs one third as long), and bearing two un-articulated spines distally (vs these spines are ®gured as articulated); antennular ¯agellum apomorphic, two-segmented (vs four-segmented); slightly shorter male pleopod IV.

The highly anomalous distribution of this genus, with species occurring in cave waters of Palau (134ssE) in the western Paci®c and Andros (78ssW) in the western Atlantic, is remarkable, but not necessarily unique. The anchialine cave-limited, misophrioid copepod genus Expansophria includes species from Palau and the Galapagos Islands, on opposite sides of the Paci®c, from the Canary Islands in the Eastern Atlantic and from Sardinia in the Mediterranean (Boxshall and IliOEe, 1987, 1990; Jaume and Boxshall, 1996b). Likewise, another anchialine misophrioid, Speleophriopsis , includes species from the Canary Islands, Balearic Islands, Bermuda and Palau (Boxshall and IliOEe, 1990; Jaume and Boxshall, 1996a, 1996b). Such distribution patterns suggest that these fauna are relicts of the once widespread, warm water fauna of the Tethys Sea that colonized anchialine habitats from shallow water/hyperbenthic environments prior to the closure of the Tethys Sea ( Boxshall and Jaume, 1999).

Habitat. Atlantis Blue Hole is an ocean blue hole, or submarine cave, located near Grassy Cay, South Andros Island. The cave entrance consists of a 15 m long by 5 m wide vertical ®ssure, surrounded by living coral heads in 3±4 m water depth. This shaft descends to about 40 m depth, where a vertically orientated ®ssure extends for more than 350 m, reaching depths in excess of 85 m. Such fracture caves parallel the submerged escarpment that marks the edge of the shallow water platform. They are believed to have formed by slumping of the exposed bank margin during glacial periods of lowered sea level in the Pleistocene. Such caves have strong, tidally reversing currents that allow divers to enter only at slack tide when the currents are in the process of changing direction. A thermocline is typically encountered at about 60 m depths with colder water below. This colder water does not ¯ow out of the cave entrance, suggesting that water circulation occurs primarily at shallower depths within the cave system. Other fauna collected from the cave included copepods, cumaceans and amphipods.