Branchiobaetis hamatus, 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

publication ID	https://dx.doi.org/10.3897/zookeys.1135.93800
publication LSID	lsid:zoobank.org:pub:0915A6D8-A8C5-4C7A-9560-1D6EF9E14B0F
persistent identifier	https://treatment.plazi.org/id/4C505602-E896-4CA6-99BE-EFF79C82DBDF
taxon LSID	lsid:zoobank.org:act:4C505602-E896-4CA6-99BE-EFF79C82DBDF
treatment provided by	ZooKeys by Pensoft
scientific name	Branchiobaetis hamatus
status	sp. nov.

Treatment

4. Branchiobaetis hamatus sp. nov.

Figs 16 View Figure 16 , 17 View Figure 17 , 24b View Figure 24 , 26b View Figure 26 , 28a View Figure 28

Type material.

Holotype. Indonesia • Sumatra, volcano Talamau; River Pularian; 00°00'60"N, 100°00'01"E; 960 m; 01.IV.2014; leg. M. Gueuning: larva on slide; GBIFCH00422261; MZL. Paratypes. Same data as holotype; 2 larvae on slides; GBIFCH00422231, GBIFCH00422242; 20 larvae in alcohol; GBIFCH00422233, GBIFCH00422252, GBIFCH00422267, GBIFCH00422276, GBIFCH00422355, GBIFCH00422359, GBIFCH00422445, GBIFCH00422748, GBIFCH00422753, GBIFCH00422798, GBIFCH00422843, GBIFCH00423022, GBIFCH00975634, GBIFCH00975635; MZL. Indonesia • Sumatra, volcano Singgalang, River Sianok; 00°19'57"S, 100°19'19"E; 1150 m; 24.III.2014; leg. M. Gueuning; 2 larvae on slides; GBIFCH00422184, GBIFCH00423074; 13 larvae in alcohol; GBIFCH00422123, GBIFCH00422167, GBIFCH00422206, GBIFCH004208, GBIFCH00422215, GBIFCH00422216, GBIFCH00422224, GBIFCH00422797, GBIFCH00422889, GBIFCH00422938, GBIFCH01115975, GBIFCH01116020; MZL.

Differential diagnosis.

Larva. Following combination of characters distinguish B. hamatus sp. nov. from other species of Branchiobaetis gen. nov.: A) labial palp segment II with medium, rounded protuberance, segment III apically slightly pointed (Fig. 16h View Figure 16 ); B) incisor of right mandible with ventral denticle (Fig. 16b View Figure 16 ); 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. 17a, b View Figure 17 ); D) dorsal margin of tibia and tarsus with row of short, hook-like setae (Fig. 17a, b View Figure 17 ); E) posterior margin of tergites: I smooth, without spines; II-IX triangular, narrower and longer towards last segment (Fig. 17e View Figure 17 ); posterior margin of sternites: I-VII smooth, without spines; VIII-IX with small, spaced, triangular spines; F) tergalius IV apically slightly concave (Fig. 17f View Figure 17 ); G) paraproct with short, stout, apically rounded setae along posterior margin (Fig. 17g View Figure 17 ).

Description.

Larva (Figs 16 View Figure 16 , 17 View Figure 17 , 24b View Figure 24 , 26b View Figure 26 ). Body length 6.8-8.5 mm. Cerci: broken. Paracercus: ca. 0.4 × body length. Antenna: ca. 2.5 × as long as head length.

Colouration (Fig. 24b View Figure 24 ). Head, thorax and abdomen dorsally brown, abdominal segment X light brown; head, thorax and abdomen ventrally light brown, scape with dark brown spot at inner lateral side. Femur light brown, apically and dorsally along margin dark brown, with large, medial, dark brown spot; tibia light brown, tarsus dark brown in distal half. Caudalii light brown, cerci darker brown in area of ca. ½ of length, paracercus darker brown parallel to cerci; primary swimming setae dark brown.

Precursors of turbinate eyes (Fig. 25c View Figure 25 ) in male last instar larvae representing a pair of subtriangular maculae; in the middle of this macula, a smaller, round, elevated area with well-expressed facets, approx. ten facets in diameter; peripheral area of the macula with indistinct facets.

Antenna (Fig. 17h View Figure 17 ). Scape distally and outside distolaterally with short, stout, apically rounded setae.

Labrum (Fig. 16a View Figure 16 ). Length 0.6 × maximum width. Submarginal arc of setae composed of 7-10 long, simple setae.

Right mandible (Fig. 16b, c View Figure 16 ). Incisor blade-like with three denticles and a ventral denticle; kinetodontium with four denticles. Margin between prostheca and mola straight, with minute denticles.

Left mandible (Fig. 16d, e View Figure 16 ). 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. 16f View Figure 16 ). 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. 16g View Figure 16 ). Galea-lacinia ventrally with two simple, apical setae under canines. Medially with one pectinate, spine-like seta and five or six 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. 16h View Figure 16 ). Inner margin of glossa with 10-12 spine-like setae, increasing in length distally; apex with two long and one medium, robust setae; outer margin with six or seven spine-like setae; Paraglossa with two 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 approx. as long as length of segments II and III combined. Segment I ventrally with short, fine, simple setae. Segment II with medium, rounded, distomedial protuberance; distomedial protuberance 0.3 × width of base of segment III; ventral surface with short, fine, simple setae; dorsally with 4-8 spine-like setae near outer margin. Segment III apically slightly pointed; length 0.8 × maximum width; ventrally covered with short, spine-like, simple setae and short, fine, simple setae.

Foreleg (Fig. 17a-d View Figure 17 ). Ratio of foreleg segments 1.3:1.0:0.5:0.2. Femur. Length ca. 3 × maximum width. Dorsal margin with row of 7-9 medium, curved, spine-like setae and basally 10-15 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. On surface 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. 17e View Figure 17 ). Surface with irregular rows of U-shaped scale bases and scattered fine, simple setae. Posterior margin of tergites: I smooth, without spines; II-IX triangular, narrower and longer towards last segment. Posterior margin of sternites: I-VII smooth, without spines; VIII-IX with small, spaced, triangular spines.

Tergalii (Figs 17f View Figure 17 , 26b View Figure 26 ). 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 1/2 VI combined, tergalius VII as long as length of segment VIII.

Paraproct (Fig. 17g View Figure 17 ). Posterior margin with 11-16 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 hamatus, meaning hooked, with reference to the hook-like setae on the legs.

Distribution.

Indonesia: Sumatra (Fig. 28a View Figure 28 ).

Biological aspects.

The specimens were collected in two sites at altitudes of 940 m and 1150 m, with following physical conditions: slope 5-10%, width of stream 3-8 m, depth 1-50 cm, velocity 0.5 m/s-0.7 m/s, pH 8, stream bed dominated by boulder, stones and gravel or stones and sand respectively. One of the sites was strongly influenced by human activities, with lot of waste and brown water.