Halosbaena daitoensis Shimomura & Fujita, 2009, sp. nov.
Creators: name: Shimomura, Michitaka
name: Fujita, Yoshihisa
Publisher: name: Zenodo
Year: 2009
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Thermosbaenacea
Halosbaenidae
Halosbaena
Halosbaena daitoensis

description: Halosbaena daitoensis sp. nov.
Figs 1–5
Material examined. Holotype. Male, 2.01 mm (KMNH IvR 500,239), appendages dissected and mounted on glass slides, body proper in vial, anchialine cave located at southwestern part of Minamidaito-jima Island, plankton net, 2 December, 2007, collected by Y. Fujita.
Paratypes. 9 females, 2.21 mm (KMNH IvR 500,240), 2.08 mm (KMNH IvR 500,241), 2.05 mm (KMNH IvR 500,242), appendages dissected and mounted on glass slides, body proper in vial, 1.98 mm (KMNH IvR 500,243), 1.70 mm (KMNH IvR 500,244), 1.65 mm (KMNH IvR 500,245), 1.63 mm (KMNH IvR 500,246), 1.43 mm (KMNH IvR 500,247, 500,248), whole specimens, locality and collection date same as in holotype.
Description of the holotype male. Body (Fig. 1 A): carapace 0.24 times as long as body; thoracomeres 7 and 8 with a pair of simple macrosetae laterally; pleonite 2 with a pair of simple macrosetae laterally; pleonites 3–6 with a pair of simple macrosetae ventrally and two pairs of simple macrosetae laterally.
Antenna 1 (Fig. 1 E) about 0.8 times as long as body length: peduncle segment 1 with 4 subplumose macrosetae and 7 simple macrosetae; peduncle segment 2 1.25 times as long as segment 1, with 4 subplumose macrosetae and 5 simple macrosetae; peduncle segment 3 as long as segment 2, with 4 subplumose macrosetae and 4 simple macrosetae; main flagellum 13-segmented; accessory flagellum 4-segmented.
Antenna 2 (Fig. 2 A): peduncle segment 1 without setae; peduncle segment 2 1.91 times as long as segment 1, with 2 teazel macrosetae and 2 simple macrosetae; peduncle segment 3 0.87 times as long as segment 2, with 1 teazel macroseta and 3 simple macrosetae; peduncle segment 4 as long as segment 3, with 2 teazel macrosetae and 3 simple macrosetae; peduncle segment 5 0.9 times as long as segment 4, with 4 simple macrosetae; flagellum 5-segmented; flagellum segments 1 and 2 with 3 simple macrosetae mediodistally and 1 simple macroseta laterodistally; segment 3 with 2 simple macrosetae mediodistally and 1 simple macrosetae laterodistally; segment 4 with 2 simple macrosetae mediodistally; segment 5 with 4 simple macrosetae apically.
Ocular scales (Fig. 1 C) with 2 pairs of simple setae dorsally: anteriorly evenly rounded; mediodistal angle broadly rounded.
Labrum (Fig. 3 A) 0.55 times as long as wide, with ciliate microsetae (type 2b) laterally to apically, and with ovate microsetae (type 2a) subapically.
Left mandible (Fig. 2 B): incisor with 3 cusps; molar process with many fine setae apically; lacinia mobilis with 5 cusps; setal row with 5 stout plumose macrosetae (type IB1); segment 1 of palp without setae; segment 2 with 4 plumidenticulate macrosetae; segment 3 with 3 short and 1 long plumidenticulate macrosetae, and 1 long serrulate macroseta; corpus mandibula with row of 5 serrate macrosetae. Right mandible (Fig. 2 C): incisor with 6 cusps; molar process with many setae apically; setal row with 6 stout plumose macrosetae (type IB1); segment 1 of palp without setae; segment 2 with 4 plumidenticulate macrosetae; segment 3 with 4 plumidenticulate macrosetae; corpus mandibula with row of 6 serrate macrosetae.
Labium (Fig. 3 B): deeply cleft, its two lobes with rounded converging tips, ventrally and marginally with many ciliate microsetae (type 2b).
Maxilla 1 (Fig. 2 D): differentiated into precoxopodal endite with a mediodistal armature of 12 stout plumose macrosetae (type IB1); basipodal endite with distal armature of 7 toothed macrosetae (type III) and 1 stout lateral seta with broad base; row of about 6 short setae medially. Endopodite forming slender 2-segmented palp: segment 1 with 1 long simple macroseta (type IIA1); segment 2 with 1 long macroseta laterally, 3 simple macrosetae (type IIA1) subapically and 2 bisetulate macrosetae (type IB3(b)) apically.
Maxilla 2 (Fig. 2 E): coxopodal endite with 23 long plumose macrosetae (type IA1), 6 simple macrosetae, 1 simple seta and 2 stout plumose macrosetae (type IB1). Basipodal endites: endite 1 with 6 stout plumidenticulate macrosetae, 1 long plumidenticulate macroseta, 2 simple macrosetae and 5 obscurely serrate plumidenticulate macrosetae apically and 14 simple setae laterally; endite 2 with two transverse rows of 29 small and 16 large rake-like serrate subterminal macrosetae; endite 3 with 70 rake-like serrate macrosetae increasing in size and dentation towards the medial margin of the appendage. Palp (Fig. 2 F) 2-segmented; segment 1 without setae; segment 2 with 1 long simple macroseta (type IIA1) laterally and 2 long simple macrosetae (type IIA1) apically.
Maxilliped (Fig. 3 C): coxopodal endite a tapering lobe with 1 subterminal, 2 terminal and 1 lateral pappose macrosetae; basipodal endite with three rows of plumidenticulate macrosetae, ventral row of 8 curved macrosetae, central row of 6 bifid macrosetae, and dorsal row of 9 tall and finely setulate macrosetae, submarginally an additional large modified plumidenticulate macroseta with 6 short stiff setules on basal portion; endopodite with many fine setae laterally; exopodite with 2 simple setae apically and many fine setae laterally; epipodite lobate.
Gnathopod (Fig. 3 D): baso-ischium longest segment, widened dorsally, with 1 simple macroseta on ventral margin; merus 0.57 times as long as baso-ischium, with 1 teazel macroseta (type IIB3) dorsodistally and ventrodistally, respectively; carpus 0.63 times as long as merus, with 2 teazel macrosetae ventrodistally; propodus as long as carpus, with 1 teazel macroseta dorsodistally and 4 teazel macrosetae ventrodistally; dactylus 0.88 times as long as propodus, with 1 subterminal and 1 terminal teasel macrosetae, and with 2 terminal serrulate macrosetae (type IIB1).
Pereiopod 2 (Fig. 3 E): basis without setae; ischiomerus of endopodite with 4 tiny teazel macrosetae proximally and 1 teazel macroseta (type II3 B) dorsodistally; carpus 0.68 as long as ischiomerus, with 1 simple macroseta ventrodistally and 2 teazel macrosetae (type II3 B) ventrally; propodus 1.61 times as long as carpus, with 1 subplumose macroseta (type IB2) dorsodistally and 2 teazel macrosetae (type II3 B) ventrally; dactylus 0.38 times as long as propodus, with 2 teazel macrosetae (type II3 B) ventrally and a well-developed serrulate macroseta (type IIB1(b)) forming terminal “unguis”; segment 1 of exopodite with 1 plumose macroseta (type IB1) dorsally; segment 2 with 3 medial, 3 lateral and 2 terminal plumose macrosetae (type IB1). Pereiopod 3 (Fig. 3 F) longer than pereiopod 2: basis without setae; ischiomerus of endopodite with 2 teazel macrosetae dorsally and 2 teazel macroseta (type II3 B) dorsodistally; carpus 0.67 as long as ischiomerus, with 1 simple macroseta ventrodistally and 2 teazel macrosetae (type II3 B) ventrally; propodus 1.83 times as long as carpus, with 1 subplumose macroseta (type IB2) dorsodistally and 2 teazel macrosetae (type II3 B) ventrally; dactylus 0.36 times as long as propodus, with 2 teazel macrosetae (type II3 B) ventrally and a well-developed serrulate macroseta (type IIB1(b)) forming terminal “unguis”; segment 1 of exopodite with 1 plumose macroseta (type IB1) dorsally; segment 2 with 3 medial, 3 lateral and 2 terminal plumose macrosetae (type IB1). Pereiopods 4 and 5 (Figs. 4 A, B) similar to pereiopod 3 in shape, size and chaetotaxy excluding ischiomerus of endopodite. Pereiopod 4 (Fig. 4 A): ischiomerus of endopodite with 1 teazel macrosetae dorsally and 3 teazel macroseta (type II3 B) ventrally. Pereiopod 5 (Fig. 4 B): ischiomerus of endopodite with 1 teazel macrosetae dorsally and 4 teazel macrosetae ventrally (type II3 B). Pereiopod 6 (Fig. 4 C) similar to pereiopod 3 in chaetotaxy excluding ischiomerus and propodus of endopodite: ischiomerus of endopodite with 3 teazel macrosetae (type II3 B) ventrally; propodus with 1 simple macroseta and 1 subplumose macroseta (type IB2) dorsodistally and 2 teazel macrosetae (type II3 B) ventrally; exopodite shorter and narrower than those of pereiopods 2–5; segment 1 of exopodite with 1 plumose macroseta (type IB1) dorsally; segment 2 with 2 medial, 2 lateral and 2 terminal plumose macrosetae (type IB1). Pereiopod 7 (Fig. 4 D): endopodite similar to that of pereiopod 6 in chaetotaxy excluding ischiomerus; ischiomerus with 1 teazel macroseta dorsally and 2 teazel macrosetae (type II3 B) ventrally; exopodite shorter and narrower than that of pereiopod 6; segment 1 of exopodite with 1 plumose macroseta (type IB1) dorsally; segment 2 with 1 medial, 1 lateral and 2 terminal plumose macrosetae (type IB1).
Male penial lobe (Fig. 4 D) 1.3 times as long as ischiomerus of pereiopod 7 endopodite, laterally with short projection near at base, distally tapering, truncate, slightly bend at middle, medially associated with coxopodite.
Pleopod 1 (Fig. 5 A) with 2 processes: one subtriangulate with 4 subplumose macrosetae and one tapering with 1 subplumose macroseta.
Pleopod 2 (Fig. 5 A) with 3 subplumose macrosetae medially and 1 subplumose macroseta apically.
Uropod (Fig. 5 B) 1.51 times as long as telson: propodite with 3 medial and 5 lateral simple macrosetae; segment 1 of exopodite 1.28 times as long as propodite, with 6 cuspidate macrosetae and 5 subplumose macrosetae laterally, and with 1 cuspidate macroseta and 4 subplumose macrosetae medially; segment 2 of exopodite 0.52 times as long as segment 1, with 1 short simple macroseta and 4 subplumose macrosetae laterally, and with 5 subplumose macrosetae medially and 1 long subplumose macroseta apically; endopodite 1.6 times as long as propodite, with 3 simple macrosetae and 6 subplumose macrosetae laterally, 6 cuspidate macrosetae and 5 subplumose macrosetae medially, 2 subplumose macrosetae apically, and with 1 cuspidate macroseta and 5 subplumose macrosetae dorsally.
Telson (Fig. 5 B) 0.56 times as width as length, with two pairs of cuspidate macrosetae laterally and five pairs of serrate macrosetae on posterior margin; medial pair of serrate macrosetae short; 3 pairs longer and stout.
Description of the paratype female. Body (Fig. 1 B): carapace 0.29 times as long as body. Antenna 1 (Fig. 1 B): main flagellum 14-segmented. Ocular scales (Fig. 1 D) with 3 pairs of simple setae dorsally. Pereiopod 7 (Fig. 4 E): ischiomerus of endopodite with 1 teazel macroseta (type II3 B) dorsodistally; carpus with 1 simple macroseta dorsodistally and 1 teazel macrosetae (type II3 B) ventrally; propodus with 1 teazel macroseta (type II3 B) dorsally and 1 subplumose macroseta (type IB2) dorsodistally, and with 2 teazel macrosetae (type II3 B) ventrally; dactylus with 2 teazel macrosetae (type II3 B) ventrally and a well-developed serrulate macroseta (type IIB1(b)) forming terminal “unguis”; segment 1 of exopodite with 1 plumose macroseta (type IB1) dorsally; segment 2 with 1 medial, 1 lateral and 2 terminal plumose macrosetae (type IB1).
Variation. Some variations (N=8) were recognized in the number of flagellum segments of antennae 1 and 2, dorsal seta on eye scales. Antenna 1: main flagellum 12- to 14-segmented. Antenna 2: flagellum 4- or 5-segmented. Ocular scales with 2 or 3 pairs of simple setae dorsally.
Remarks. Halosbaena daitoensis sp. nov. resembles H. tulki Poore & Humphreys, 1992 from an almost fresh water in a cave on the semi-arid North West Cape peninsula of Western Australia, in having rounded mediodistal angle of ocular scales, uropodal endopodite with 4–6 cuspidate macrosetae and segment 2 of exopodite with 7–9 plumose macrosetae. The two species, however, differ from one another in the following combination of characters (those of H. tulki in parentheses): main flagellum of antenna 1 12–14 segmented (7–9 segmented); exopodite of pereiopods 2–5 with 8 plumose macrosetae (6 plumose macrosetae); segment 2 of uropodal exopodite with 9 plumose macrosetae (7 plumose macrosetae); telson about 0.6 times as width as length (about 0.9 times as width as length); male penial lobe distally tapering, with a short projection on its base (distal portion slightly broadened, without projection on its base).
Habitat and biological implication. The water of the anchialine pool where Halosbaena daitoensis sp. nov. was collected is clear, salinity: 2.0‰, temperature: 21. 0°C. The pool lies in dim light. Its greatest depth is about 1 m. The pool seems to have an underground connection with the sea as the water level falls and rises with the tides.
The other crustaceans collected from this cave include: one alpheid, Metabetaeus minutus (Whitelegge, 1897), one atyid, Antecaridina lauensis (Edmondson, 1935), and unidentified copepods.
Etymology. The new species is named after the type locality.
description: Published as part of Shimomura, Michitaka & Fujita, Yoshihisa, 2009, First record of the thermosbaenacean genus Halosbaena from Asia: H. daitoensis sp. nov. (Peracarida: Thermosbaenacea: Halosbaenidae) from an anchialine cave of Minamidaito-jima Is., in Okinawa, southern Japan, pp. 55-64 in Zootaxa 1990 on pages 56-63, DOI: 10.5281/zenodo.185528