Caenis hanleyi n. sp.

(Figures 1–5)

LSID urn:lsid:zoobank.org:act: 5A7C1E45-FC7E-414D-9A48-406E787E12EC

Tasmanocoenis sp H (Suter, 1992)

Tasmanocoenis sp H in part (Suter, 1999a)

Type Material (Deposited in the Museum and Art Gallery of Northern Territory). Holotype: 1 Male imago and nymphal exuvium on three slides. Magela Ck at Ranger outlet pipe 12.68S 132.93E 19 May 1988, emerged on 27 May 1988; Identification no. ARR37, ARR38 and ARR39; coll. P. Suter (PS); NTMI011230 . Paratypes: 1 male imago and nymphal exuvium on 4 slides. Same details as holotype; Identification no. ARR33, ARR34, ARR35 and ARR36; coll. PS; NTMI011231 . 1 nymph on 2 slides. Magela Ck at Ranger outlet pipe 12.68S 132.93E 17 Feb 1988; Identification no. ARR28 and ARR29; coll. P. Dostine (PD): NTMI011232 . 1 nymph in ethanol. Magela Ck downstream of pontoon 12.64S 132.90E 9 May 2019 JH; NTMI011233 . 1 nymph in ethanol. Magela Ck upstream pool 12.67S 132.93E 2 Sept 2021 JH; NTMI011234 . 1 nymph in ethanol. Nourlangie Ck 12.856S 132.777E 13 May 2021 JH; NTMI011235 .

Other Material Examined. Northern Territory 3 nymphs, Cooper Ck at Narbalek 12.3S 133.33E 27 May 1988 PS; 20 male imagoes 10 nymphs, Magela Ck at Ranger outlet pipe 12.68S 132.93E 19 May 1988 PS, 17 Feb 1988 PD; 1 nymph, Gulungul Ck at inlet to Gulungul Billabong 12.63S 132.88E 16 May 1988, April 1989 PS; 4 nymphs, Magela Ck at inlet to Mudginberri Billabong 12.60S 132.88E 18 May 1988, April 1989 PS; 2 nymphs, Radon Springs 12.75S 132.92E 18 May 1988 PS; 7 nymphs, Baroalba Springs 12.82S 132.87E April 1989 PS; 2 nymphs, Koolpin Ck 13.48S 132.58E 25 May 1988 PS; 1 nymph, Gulungul Ck at highway crossing 12.65S 132.867E 15 Oct 2006 Identification no. GCH152 CN J. Hanley (JH); 1 nymph, Coomalie Ck at road to Bachelor east of Lichfield National Park 13.0104S 131.1136E 24 Sept 2009 Identification no. JWA1959, PS , J. Webb (JW), J. Hawking (JH), M. Halsey (MH); 5 nymphs, Magela Ck downstream of pontoon 12.64S 132.90E 9 May 2019 JH ; 11 nymphs, Magela Ck upstream pool 12.67S 132.93E 2 Sept 2021 JH; 1 nymph, Nourlangie Ck 12.856S 132.777E 13 May 2021 JH .

Diagnosis. C. hanleyi can be characterised by the following combination of characters. In the male imagoes: body length 1.7–2.2 mm; base of antennal flagellum not dilated (Fig. 1d, 1c); penes with median concavity and rounded lateral lobes (Fig. 1f); styliger plate with apex straight (Fig. 1f); forceps long, broad and straight>7 times longer than terminal spines; apical tuft of four spines on an apical stalk (Fig 1f, 1g). In the nymphs, body length 2.2–2.5 mm; body colour dark brown with antennae, and legs dark (Fig. 2a, 2b, 2c, 4c); body surface covered with distinct short rounded triangular tubercles (Fig. 5b, 5c, 5d); segment II of maxillary palp shorter than segments I and III (Fig. 3b); labial palp with segment II long 1.5–1.6 x longer than segment III (Fig. 3c, 3d); left mandible with three apical teeth and an inner lateral tooth on outer incisors (Fig. 3f, 3h); anterior lateral margin of mesonotum lacking lateral projections (Fig. 4e); coxae of legs without small rounded processes; fore femur transverse row of <10 setae (Fig. 2c, 2i); tarsal claws of fore and mid legs lacking teeth or denticles (Fig. 2d, 2f): hind claw with short microhairs (Fig. 2h); abdominal segment I lacking long setae on posterior margin (Fig. 4a, 4e); segments VII and VIII with long setae on posterior margin (Fig. 4a, 4e); postero-lateral spines on abdominal segment IV–IX (Fig. 4a); posterior margin of sternite IX convex; first gill with segment II 2.5–4.0x longer than segment I (Fig. 4d); operculate gills with Y-shaped ridge reduced (Fig. 2j), outer margin slightly serrated; mesal ridge with approx. eight short bifid setae basally and 3 long pinnate setae (Fig. 2j, 2l), gill dorsal surface covered with short triangular tubercles and net-mesh (Fig. 5f). Submarginal row of microtrichia running closely to lateral margin, ending in middle of hind margin of gill (Fig. 2j, 2k); microtrichia simple fringed apically (Fig. 2k); third to sixth gill oval with>25 tracheal filaments which have multifid (2–4) tracheal branches (Fig. 5).

Description

Male imago (n=3). Body Length 1.7–2.2 mm; wing length 1.4–1.6 mm terminal filament length 3.5–3.8 mm. Head: Base of antennal flagellum not dilated (Fig. 1d, 1e). Antennal pedicel, scape and base of flagellum tinged brown; pedicel 1.7–3.5 x longer than scape, flagellum length 0.47–0.52mm (Fig.1d, e). Prosternum triangular with straight lateral sides, apex broadly rounded (Fig. 5a, 5b). Legs slender and delicate; forelegs longer than mid and hind legs; tarsomeres of foretarsus apically not broadened, foretarsal claws similar, both blunt and ovoid (Fig.1h); mid and hind tarsal claws dissimilar one blunt and one slender, curved and sharp. Tarsal segment formula of foreleg 2, 3=4, 5=1. Femora lacking apical markings. Leg ratios: Foreleg 1.00 (0.39–0.42 mm): 1.10–1.28: 0.79–0.87. Middle leg 1.00 (0.40–0.41 mm): 0.63–0.73: 0.49–0.50. Hind leg 1.00 (0.42–0.44 mm): 0.62–0.73: 0.48–0.52. Scutellum broad, posteriorly broadly rounded. Wings 1.94–2.0 x longer than wide (Fig. 1a), with hind margin lined with long hairs which are longest in anal and cubital region and short in radial region (Fig. 1b). Abdomen: Without markings on sternites, with lateral filaments on abdominal segments IV–VIII (difficult to see or may be dislodged in some specimens) (Fig. 1c). Sternite IX and genitalia (Fig. 1f); styliger plate rectangular length one third width, central sclerite dome shaped, lateral sclerites broad, wider than base of forceps, apophyses short slightly curved inwards; penes with median concavity and rounded lateral lobes. Forceps long, uniformly broad and straight (Fig. 1g), not curved; 7–10 x longer than apical spine length; 3.32–4.00x longer than wide, with tuft of four apical spines and surface covered with long setae/hairs. Three terminal filaments 3.50–3.85 mm long.

Nymph (n=10). Body length: males 2.2–2.5mm; terminal filaments 2.0 mm; females 3.6 mm long. General body colour brown, without mottled markings (Fig. 4e). Head dark brown with light central area in the frontoclypeal region between antennae; antennae with scape, pedicel and base of flagellum brown (Fig. 2a); pedicel 0.06–0.07mm, 2.0–2.3 x length of scape, antennal length 0.76–1.14 mm long. Head covered in small triangular tubercles (Fig. 5b, c), genae not bulged. Mouthparts: Labrum broadly emarginate, width 2.0 x length with long setae along margins, long simple setae posterior to concavity and those along mid row bifid and pinnate (Fig. 3a). Left mandible (Fig. 3e) with long pinnate setae on outer margin, incisors paired, outer incisors with three apical teeth and a single tooth on inner margin, inner incisors with three teeth (Fig. 3h); prostheca robust slightly divided apically with long multifid setae; edge between prostheca and molars lined with short bristles; base of mandible with area of short tuberculate ornamentation. Right mandible (Fig. 3e) with long pinnate setae on outer margin; incisors paired, outer incisors with three teeth; inner incisors with two teeth (Fig. 3g); prostheca robust with multifid apical setae; inner margin of mandible with row of setae; base of mandible with area of short tuberculate ornamentation. Maxilla (Fig. 3b) galeo-lacinia with three apical teeth and row of setae on inner margin; base with a separate row of setae; maxillary palp three segmented, longer than galeo-lacinia, segment ratio 1.00 (0.07–0.08 mm): 0.66–0.78: 1.05–1.22. Labium (Fig. 3c, d) paraglossae longer than glossae; proximal segment of labial palp 1.33–1.70 x longer than broad; lateral margin with 12 short, robust pinnate setae; distal segment short, triangular; segment ratio 1.00 (0.0.07– 0.10 mm): 0.89–1.13: 0.48–0.73. Thorax: Pronotum brown without markings (Fig. 2b), covered with short triangular tubercles (Fig. 5e); antero-lateral margin with 1–2 short spine setae. Mesonotum without distinct markings, with short triangular tubercles on postero-lateral surface and linear rows on surface of wingpads (Fig. 5d). Legs all tinged brown with rows of rounded triangular tubercles, lacking coxal process. Foreleg (Fig. 2a) tinged brown, femur with transverse row of four long bifid setae and four short bifid setae (Fig.2i); tibia with three long setae on transverse surface, three spines on ventral surface, apical spine longest; dorsal surface with long fine hairs; tarsus with five spines on the ventral margin, dorsal and transverse surface with long fine hairs; tarsal claw long and slender, slightly curved and smooth, 0.52–0.61 x tarsus length (Fig. 2d). Mid leg (Fig. 2e) tinged brown; femur with row of 3–4 bifid setae; tibia with long blunt setae on dorsal surface; inner margin with five sharp spines; surface of segment covered with long fine hairs; tarsus with nine sharp spines on inner margin; long fine hairs on surface of segment, tarsal claw long and smooth, 0.56–0.62 x tarsal length (Fig.2f). Hind leg (Fig. 2g) tinged brown; dorsal surface with 2–3 spatulate setae; tibia with long blunt setae on dorsal surface, inner margin with approx. six sharp spines; surface of segment with long fine hairs; tarsus with dual row of spine setae on inner margin and surface with long fine hairs; tarsal claw long, slender, curved with comb of fine, short setae in basal half, 0.51–0.54 x tarsal length (Fig.2h). Ratios of segments: Foreleg 1.00 (0.40–0.42 mm): 0.60–0.70: 0.62–0.67: 0.35–0.38. Middle leg 1.00 (0.37 mm): 0.72: 0.55. Hind leg 1.00 (0.39 mm): 0.80: 0.64. Femur length to width ratios, fore femur 2.5–3.0; mid femur 3.0–3.5; hind femur 2.9–3.4. Abdomen: Tergites brown with light square medial marking on segment VIII, segments VII and X light brown, segment IX dark brown. Posterior margin of abdominal tergite I without setae; tergite II with short triangular process between operculate second gills; hind margins of tergites VII and VIII with numerous long setae; postero-lateral spines on abdominal segment IV–IX (Fig. 4a). Dorsal surface with small triangular tuberculate ornamentation. Sternite of abdominal segment IX with convex posterior margin. Caudal filaments with basal segments with short lateral setae, 0.4 x segment length but with intersegmental setae equal to segment length (Fig. 4b); mid–apical segments of caudal filaments with lateral and intersegmental setae long 0.6 x segment length (Fig. 4c). Gills: First gill two segmented with apical segment 2.0–2.5 x longer than basal segment (Fig. 4d). Second gills operculate 1.3x longer than wide (Fig. 2j), with outer and posterior margins lined with long pinnate setae each separated by short bifid setae (Fig. 2k); inner margin with shorter setae, outer margin slightly serrated; mesal ridge with approx. eight short bifid setae basally and three long pinnate setae (Fig. 2l), and short triangular tubercles along its posterior length; gill dorsal surface covered with short triangular tubercles and netmesh (Fig. 5f). Submarginal row of microtrichia running closely to lateral margin, ending in middle of hind margin of gill (Fig. 2j); microtrichia simple, fringed apically (Fig. 2k). Third to sixth gill oval with>20 filaments each with multifid (2–3) tracheal branches (Fig. 5a).

Etymology. Named in honour of Julie Hanley who has supported our work in the Alligator Rivers region of the Northern Territory with fresh material whenever requested.

Ecological observations. Lotic, in the main streams in slow flowing water where there an accumulation of fine organic material. Specimens were also collected from organic rich, highly coloured, isolated pools at Radon Springs where daytime temperature exceeded 30 oC in May 1988.