Branchiobaetis aduncus, Kaltenbach & Kluge & Gattolliat, 2022

Kaltenbach, Thomas, Kluge, Nikita J. & Gattolliat, Jean-Luc, 2022, A widespread new genus of Baetidae (Baetidae, Ephemeroptera) from Southeast Asia, ZooKeys 1135, pp. 1-59 : 1

3. Branchiobaetis aduncus sp. nov.

Figs 14 , 15 , 24a , 26a , 28a

Type material.

Holotype. Indonesia • Sumatra, volcano Singgalang, River Caruak; 00°23'03"S, 100°21'24"E; 1640 m; 23.III.2014, leg. M. Gueuning; larva on slide; GBIFCH00422219; MZL. Paratypes. Same data as holotype; 1 larva on slide; GBIFCH00422126; MZL; 4 larvae in alcohol; GBIFCH00422185, GBIFCH00422194, GBIFCH00422203, GBIFCH00422209; MZL. Indonesia • Aceh, Mt. Leuser area, Kedah rainforest lodge; 03°58'36"S, 97°15'17"E; 1300 m, 3.-12.X.2013, leg. M. Balke; larva on slide; GBIFCH00515622; MZB (temporarily housed in MZL) • Sumatra Barat, Talang, 20 km south of Solok; 00°52'52"S, 100°37'23"E; 650 m; 25.V.2010; leg. J.-M. Elouard; larva on slide; GBIFCH00592486; MZL.

Differential diagnosis.

Larva. Following combination of characters distinguish B. aduncus sp. nov. from other species of Branchiobaetis gen. nov.: A) labial palp segment II with medium triangular protuberance, segment III apically rounded (Fig. 14j ); B) incisor of right mandible with ventral denticle (Fig. 14b, d ); C) dorsal margin of femur with row of medium, spine-like setae, basally longer and clavate; additional row of short, hook-like setae along margin (Fig. 15a-c ); D) dorsal margin of tibia and tarsus with row of short, hook-like setae (Fig. 15a, c ); E) posterior margin of tergites: I smooth, without spines; II-V rounded, wider than long; VI partly rounded, partly triangular; VII-IX triangular, narrower and longer towards last segment (Fig. 15f ); posterior margins of sternites: I-VI smooth, without spines; VII-IX with small, spaced, triangular spines; F) paraproct with short, stout, apically rounded setae along posterior margin (Fig. 15h ).

Description.

Larva (Figs 14 , 15 , 24a , 26a ). Body length 7.0-8.1 mm. Caudalii broken. Antenna: ca. 2.5 × as long as head length.

Colouration (Fig. 24a ). Head, thorax, and abdomen dorsally brown, ventrally light brown. Femur light brown, apically and dorsally along margin dark brown, with large, distomedial, dark brown spot; tibia light brown, basally along patella-tibial suture darker, tarsus dark brown. Caudalii light brown, primary swimming setae dark brown.

Antenna (Fig. 15i ). Scape distally and outside distolaterally with short, stout, apically rounded setae.

Labrum (Fig. 14a ). Length 0.6 × maximum width. Submarginal arc of setae composed of nine or ten long, simple setae.

Right mandible (Fig. 14b-d ). Incisor blade-like with three denticles and a ventral denticle; kinetodontium with four denticles. Margin between prostheca and mola straight.

Left mandible (Fig. 14e-g ). Incisor blade-like with four denticles; kinetodontium with three denticles. Margin between prostheca and mola straight, with minute denticles towards subtriangular process.

Both mandibles with lateral margins slightly convex.

Hypopharynx and superlinguae (Fig. 14h ). Lingua as long as superlinguae. Lingua longer than broad; medial tuft of stout setae well developed. Superlinguae distally rounded; lateral margins rounded; fine, long, simple setae along distal margin.

Maxilla (Fig. 14i ). Galea-lacinia ventrally with two simple, apical setae under canines. Medially with one pectinate, spine-like seta and six or seven medium, simple setae. Maxillary palp approx. as long as galea-lacinia; palp segment II approx. as long as segment I; setae on maxillary palp fine, simple, scattered over surface of segments I and II.

Labium (Fig. 14j, k ). Inner margin of glossa with ca. nine spine-like setae, increasing in length distally; apex with one long, one medium and one short, robust setae; outer margin with ca. nine spine-like setae; Paraglossa with three short, simple setae in anteromedial area and one in posterolateral area; dorsally with three long, spine-like setae near inner margin. Labial palp with segment I 1.1 × length of segments II and III combined. Segment I ventrally with short, fine, simple setae. Segment II with medium, triangular, distomedial protuberance; distomedial protuberance 0.5 × width of base of segment III; ventral surface with short, fine, simple setae; dorsally with five or six spine-like setae near outer margin. Segment III apically rounded; length 0.8 × maximum width; ventrally covered with short, spine-like, simple setae and short, fine, simple setae.

Foreleg (Fig. 15a-e ). Ratio of foreleg segments 1.3:1.0:0.5:0.2. Femur. Length ca. 3 × maximum width. Dorsal margin with row of 6-9 medium, curved, spine-like setae and basally 10-12 longer, clavate setae. Additional row of short, stout, hook-like setae along dorsal margin. Apex rounded, with pair of spine-like setae; short, stout, hook-like setae on anterior and posterior side. Short, stout, apically rounded setae scattered along ventral margin. Tibia. Dorsal margin with two irregular rows of short, stout, hook-like setae. Surface with short, stout, hook-like setae along patella-tibial suture. Ventral margin with row of short, curved, spine-like setae, on apex a tuft of fine, simple setae. Tarsus. Dorsal margin with row of short, stout, hook-like setae and row of fine, simple setae. Claw with one row of ten or eleven denticles, distal denticle much longer than other denticles.

Terga (Fig. 15f ). Surface with irregular rows of U-shaped scale bases and scattered fine, simple setae. Posterior margin of tergites: I smooth, without spines; II-V rounded, wider than long; VI partly rounded, partly triangular; VII-IX triangular, narrower and longer towards last segment. Posterior margins of sternites: I-VI smooth, without spines; VII-IX with small, spaced, triangular spines.

Tergalii (Figs 15g , 26a ). Tracheae extending from main trunk to inner and outer margins; with light brown band along main trunk of tracheae on anal side. Tergalius I 2/3 as long as segment II, tergalius IV as long as length of segments V and 1/3 VI combined, tergalius VII as long as length of segment VIII.

Paraproct (Fig. 15h ). Posterior margin with 12-16 stout spines. Short, stout, apically rounded setae near posterior margin. Surface scattered with scale bases, micropores and fine, simple setae.

Etymology.

Based on the Latin word aduncus, meaning hooked, with reference to the hook-like setae on the legs.

Distribution.

Indonesia: Sumatra (Fig. 28a ).

Biological aspects.

The species was found at altitudes from 650 m to 1640 m, most specimens were collected in a forest stream with the following parameters: slope below 5%, width 1-3 m, depth 15-30 cm, velocity 0.2 m/s, water temperature 17 °C, pH 7, stream bed dominated by boulder, stones, and gravel.

Figures

Figure 14. Branchiobaetis aduncus sp. nov., larva a labrum (left: ventral view, right: dorsal view) b right mandible c right prostheca d apex of right mandible e left mandible f left prostheca g apex of left mandible h hypopharynx and superlinguae i maxilla j labium (left: ventral view, right: dorsal view) k apex of paraglossa.

Figure 15. Branchiobaetis aduncus sp. nov., larva a foreleg b seta of femur basal dorsal margin c hook-like seta of leg dorsal margins d fore femur apex, posterior view e fore claw f tergum IV g tergalius IV h paraproct i base of antenna.

Figure 24. Habitus, larvae, dorsal view a Branchiobaetis aduncus sp. nov. b Branchiobaetis hamatus sp. nov. c Branchiobaetis joachimi sp. nov. (Sumatra, volcano Sago) d Branchiobaetis joachimi sp. nov. (Sumatra, Bukit Barisan, above Padang).

Figure 26. Larva, tergalii IV a Branchiobaetis aduncus sp. nov. b Branchiobaetis hamatus sp. nov. c Branchiobaetis joachimi sp. nov. d Branchiobaetis minangkabau sp. nov. e Branchiobaetis jhoanae sp. nov.

Figure 28. Distribution maps a, b new species of Branchiobaetis gen. nov. in Sumatra.