Brevisomabathynella uramurdahensis, Cho & Humphreys, 2010

Cho, Joo-Lae & Humphreys, W. F., 2010, Ten new species of the genus Brevisomabathynella Cho, Park and Ranga Reddy, 2006 (Malacostraca, Bathynellacea, Parabathynellidae) from Western Australia, Journal of Natural History 44 (17 - 18), pp. 993-1079 : 1015-1022

Brevisomabathynella uramurdahensis sp. nov.

( Figures 13–18 )

Material examined

Holotype (adult male), allotype (adult female), paratypes (two adult males and one adult female). Holotype dissected on seven slides ( WAM C 40079) . Allotype dissected on seven slides ( WAM C 40080) . Paratypes: one adult male and one adult female each dissected on six slides, one adult male as a whole specimen on a slide ( WAM C 40081–C 40083) .

Type locality

Australia, Western Australia, Carey Palaeodrainage, Millbillillie Station, Uramurdah Lake , MEB site 264 (26°41′15″ S, 120°20′18″ E), BES 10515, 3 June 2004, leg. W.F. Humphreys, C.H.S. Watts and C. Clay.

Other locality

One adult male and one adult female each dissected on five slides, two adult males and two adult females each as a whole specimen on separate slides, MEB site 262 (26°41′15″ S, 120°21′11″ E), BES 6449, 5 September 2004, leg. W.F. Humphreys and C.H.S. Watts, ( WAM C 40084) .

Description of adult male (holotype)

Body. Length 3.62 mm, fat-bellied, width of body at first segment 0.31 mm, increasing posteriorly to 0.70 mm at 10th segment and then decreasing ( Figure 13A,B ). Head as long as anterior three thoracic segments 1–3 combined.

Antennule ( Figure 14A ). Seven-segmented. First segment with one seta on inner margin, with four simple dorsal setae and with one dorsal, one ventromedial and two lateral plumose setae. Second segment with one group of four plumose setae and with six simple setae on inner margin. Two openings on inner margin. Third segment with three lateral setae including one plumose seta and six setae on inner margin. Inner flagellum of third segment with three simple setae. Fourth segment with one stub seta and one plumose seta on dorsal margin, and with two stub setae and two plumose setae on outer distal apophysis. Fifth segment with five setae on inner margin, and with one simple seta and one aesthetasc dorsally. Sixth segment with four setae on inner margin and with dorsal group of two aesthetascs, one simple seta and one additional aesthetasc lateral to simple seta. Seventh segment with three subterminal aesthetascs and four simple setae.

Antenna ( Figure 14B ). Five-segmented, as long as antennular segments 1–3 combined. Fourth segment as long as fifth segment. Setal formula: 0+0/0+0/1+1/2+2/4(1). Plumose seta of distal segment shorter than longest simple seta.

Labrum ( Figure 14C ). Flat with 14 median teeth of more or less similar size flanked by six (left) or seven (right) teeth decreasing in size laterally on each sides. Ventral surface with numerous combs of ctenidia and teats.

Mandible ( Figure 14D,E ). Incisor process of five teeth. Tooth of ventral edge triangular. Spine row consisting of 20 spines. Palp of one segment, with one apical seta.

Maxillule ( Figure 14F ). Two-segmented. Proximal segment with four setae on inner margin. Distal segment with two terminal spines, with five spines with denticles on inner edge, and with three simple setae on outer margin.

Maxilla ( Figure 14G,H ). Four-segmented, setal formula 6-7-22-24.

Thoracopods I–VII ( Figures 16 A–C, 17A–D, 18A,B). Thoracopods I–IV increasing in size posteriorly. Thoracopods IV–VII similar in size. Thoracopods I–VII each bearing one epipod on protopod. Basipod of thoracopod I with two setae, while that of thoracopods II–VII with one seta. Number of exopodal segments of thoracopods I–VII: 9-11-12-11-11-11-11. Endopod of thoracopods I–VII four-segmented, setal formulae:

Th. I 5+1/8+1/6+1/4(2)

Th. II, III 3+1/9+2/5+1/6(4)

Th. IV 3+1/8+2/5+1/6(4), 5(3)

Th. V 3+1/8+2/5+2/6(4)

Th. VI 2+1/8+2/5+1/5(3)

Th. VII 2+1/6+2/4+1/4(2)

Thoracopod VIII ( Figure 15 A–C). More or less rectangular in frontal view, twice as long as wide. Protopod massive, with prominent penial region with terminal opening. Epipod large, triangular, distal part covering penial region of protopod. Basipod without setae, inner margin of basipod drawn out into sharp projection. Exopod one third size of basipod, triangular, bearing five terminal teeth and three subterminal setae. Endopod as long as exopod, with three terminal setae.

First pleopod ( Figure 15E ). In form of two stubs attached to each other basally. Each stub bearing two terminal setae.

Uropod ( Figure 15G,H ). Twenty spines on inner margin of sympod. Four distal spines significantly thicker than others. Exopod 32 % as long as sympod, with ten setae on outer and terminal margin, without basiventral setae. Endopod 19% as long as sympod, with two dorsal plumose setae near base, with two terminal setae and one subterminal plumose seta on outer margin, and with one terminal, one subterminal and two inner-marginal spines. Terminal spine somewhat longer than subterminal spine. Two inner-marginal spines spike-like, half as long as terminal spine and thin.

Pleotelson ( Figure 15F,G ). One seta near base of each furcal ramus on both sides. Anal operculum flat.

Furcal rami ( Figure 15F,G ). Twice as long as wide, with two large terminal spines, and nine (right) or ten (left) spines on inner margin, and with two dorsal setae.

Description of adult female (allotype)

Body. Length 3.60 mm. Identical to male except for following characters:

Antennule. Second segment with eight simple setae on inner margin. Third segment with five setae on inner margin. Fifth segment with five setae on inner margin.

Antenna. Setal formula: 0+0/0+0/1+1/2+2/5(1).

Thoracopods I – VII. Number of exopodal segments of thoracopods I – VII: 8-9-10- 11-11-10-10. Setal formulae of endopods:

Th. I 4+1/8+1/4+1/5(3)

Th. II 3+1/7+2/4+1/5(3)

Th. III 3+1/8+2/4+1/5(3)

Th. IV, V 3+1/7+2/5+1/5(3)

Th. VI 2+1/7+2/5+1/5(3)

Th. VII 2+1/5+2/4+1/5(3)

Thoracopod VIII ( Figure 15D ). Conical, half as long as endopod of male thoracopod VIII.

Uropod. Sympod with 18 spines. Exopod with 11 setae.

Intraspecific variation

Range of body length: male 3.30–3.62 mm; female 3.20–3.60 mm. Variation in number of setae, spines or segments as listed in Table 3.

Etymology

The specific name refers to Lake Uramurdah.

Figures

Figure 13. General habitus of Brevisomabathynella uramurdahensis sp. nov. (Ƌ, paratype): (A) dorsal; (B) lateral. Scale bar 2 mm.

Figure 14. Brevisomabathynella uramurdahensis sp. nov. (Ƌ, holotype): (A) left antennules (dorsal); (B) left antenna (dorsal); (C) labrum (ventral); (D) right mandible (dorsal); (E) spine row of right mandible (dorsal); (F) right maxillule (dorsal); (G) right maxilla (inner lateral); (H) fourth segment of right maxilla (outer lateral). Scale bars 0.1 mm.

Figure 15. Brevisomabathynella uramurdahensis sp. nov. (Ƌ, holotype; ♀, allotype): (A) right thoracopod VIII Ƌ (inner lateral); (B) right thoracopod VIII Ƌ (ventral); (C) right thoracopod VIII Ƌ (frontal); (D) right and left thoracopods VIII ♀ (ventral); (E) right and left pleopods I Ƌ; (F) pleotelson and furcal rami (dorsal); (G) pleotelson, furcal rami and uropod (lateral); (H) right uropod Ƌ. Scale bars 0.1 mm.

Figure 16. Brevisomabathynella uramurdahensis sp. nov. (Ƌ, holotype): (A) right thoracopod I (frontal); (B) right thoracopod II (frontal); (C) left thoracopod III (frontal). Scale bar 0.1 mm.

Figure 17. Brevisomabathynella uramurdahensis sp. nov. (Ƌ, holotype): (A) right thoracopod IV (frontal); (B) distal segment of exopod of left thoracopod IV (frontal); (C) distal segment of endopod of left thoracopod IV (frontal); (D) right thoracopod V (frontal). Scale bar 0.1 mm.

Figure 18. Brevisomabathynella uramurdahensis sp. nov. (Ƌ, holotype): (A) left thoracopod VI (frontal); (B) right thoracopod VII (frontal). Scale bar 0.1 mm.