Labiobaetis ranongensis, Kaltenbach & Gattolliat & Boonsoong & Suttinun, 2025

Kaltenbach, Thomas, Gattolliat, Jean-Luc, Boonsoong, Boonsatien & Suttinun, Chanaporn, 2025, New species of Labiobaetis Novikova & Kluge from Thailand (Ephemeroptera, Baetidae), ZooKeys 1258, pp. 213-276 : 213-276

Labiobaetis ranongensis sp. nov.

Figs 28 , 29 , 30

Type material.

Holotype. Thailand • larva; Ranong Prov., Mueang Distr., Huai Nam Sai ; 09°43'25"N, 98°36'29"E; 50 m; 20.vi.2018; leg. C. Suttinun; on slide; GBIFCH 00980864 ; VMCMU . Paratypes. Thailand • 4 larvae; Ranong Prov., Mueang Distr., Punyaban Waterfall ; 10°03'54"N, 98°40'13"E; 52 m; 19.vi.2018; leg. C. Suttinun; 1 on slide; GBIFCH 01223077 ; MZL; 3 in alcohol; GBIFCH 00763828 ; VMCMU • 14 larvae; Ranong Prov., Mueang Distr., Huai Por Ta Hin Rao ; 09°52'08"N, 98°37'32"E; 20 m; 20.vi.2018; leg. C. Suttinun; 1 on slide; GBIFCH 00980860 ; MZL; 13 in alcohol; GBIFCH 00763826 , GBIFCH 00763834 ; VMCMU; GBIFCH 00975850 ; MZL • 1 larva; Ranong Prov., Mueang Distr., Klong Nok Ngang ; 09°42'22"N, 98°34'39"E; 11 m; 21.vi.2018; leg. C. Suttinun; on slide; GBIFCH 00975861 ; MZL • 5 larvae; Ranong Prov., Mueang Distr., Huai Por Ta ; 10°02'03"N, 98°39'29"E; 22 m; 19.iv.2018; leg. C. Suttinun; in alcohol; GBIFCH 00763835 ; VMCMU .

Diagnosis.

Larva. Following combination of characters differentiate L. ranongensis sp. nov. from other species of the group sumigarensis : abdomen dorsally yellow-brown, basal parts of terga paler, posterior parts with a darker, slightly crown-like marking; labial palp segment III subrectangular, segment II with thumb-like protuberance with straight distal margin and rounded lateral margin; maxillary palp longer than galea-lacinia, terminal segment with well-developed, distolateral excavation; left mandible with margin between prostheca and mola straight, with minute marginal and submarginal denticles; abdominal tergites II – IX with triangular, sharply pointed spines on posterior margins; paraproct distally not expanded, with ~ 28 spines.

Description.

Larva (Figs 28 – 30 ). Body length 3.3–4.9 mm. Cerci ~ 1 / 2 body length, paracercus ~ 0.4 × body length. Antenna: ~ 2 × as long as head length.

Colouration (Fig. 28 a – c ). Head and thorax dorsally yellow-brown, with dark brown markings; abdomen dorsally yellow-brown, anterior parts of abdominal segments paler, posterior parts with a darker, slightly crown-like marking; Fore protoptera yellow-brown. Thorax ventrally off-white; abdomen ventrally pale grey-brown. Legs with femur off-white, with distomedial, triangular grey-brown marking, apex grey-brown; tibia and tarsus yellow-brown. Caudalii yellow-brown.

Antenna (Fig. 30 e ) with scape and pedicel sub cylindrical, distolateral process at scape absent.

Labrum (Fig. 29 a, b ). Sub-rectangular, length 0.7 × maximum width. Distal margin with medial emargination and small process. Dorsally with medium, fine, simple setae scattered over surface; submarginal arc of ~ 18 long, clavate setae on each side. Ventrally with marginal row of setae composed of anterolateral long, feathered setae and medial long, bifid setae.

Right mandible (Fig. 29 i ). Incisor and kinetodontium fused. Incisor with five denticles; kinetodontium with three denticles, inner margin of innermost denticle with row of thin setae. Prostheca robust, apically denticulate. Margin between prostheca and mola slightly convex, with minute denticles. Tuft of setae on proximal corner of mola present.

Left mandible (Fig. 29 h ). Incisor and kinetodontium fused. Incisor with five denticles, kinetodontium with three denticles. Prostheca robust, apicolaterally with small denticles and comb-shaped structure. Margin between prostheca and mola straight, with marginal and submarginal, minute denticles. Tuft of setae on proximal corner of mola absent.

Both mandibles with lateral margins almost straight.

Hypopharynx and superlinguae (Fig. 29 e ). Lingua longer than superlinguae, longer than broad, subdistally slightly expanded; medial tuft of stout setae well developed. Superlinguae with lateral margins rounded; fine, long, simple setae along distal margin.

Maxilla (Fig. 29 f, g ). Galea-lacinia ventrally with two simple, apical setae below canines. Medially with one feathered, spine-like seta and three medium to long, simple setae. Maxillary palp longer than length of galea-lacinia; 2 - segmented; palp segment II ~ 1.2 × length of segment I; setae on maxillary palp fine, simple, scattered over surface of segments I and II; apex of last segment with well-developed distolateral excavation, apically rounded.

Labium (Fig. 29 c, d ). Glossa basally broad, narrowing toward apex; shorter than paraglossa; inner margin with ~ 7 robust, spine-like setae, increasing in length distally; apex with two long and one medium, robust, apically pectinate setae; outer margin with ~ 4 spine-like setae; ventral surface with fine, simple, scattered setae. Paraglossa sub-rectangular, slightly curved inward; apex rounded; with three rows of long, robust, distally pectinate setae in apical area and four medium, simple setae in anteromedial area; dorsally with three or four long, spine-like setae near inner margin. Labial palp with segment I approx. as long as segments II and III combined. Segment II with thumb-like protuberance with straight distal margin and rounded lateral margin; distomedial protuberance ~ 0.9 × width of base of segment III; dorsally with two spine-like setae near outer margin. Segment III subrectangular; length approx. as maximal width; ventrally covered with short, spine-like, simple setae and short, fine, simple setae. Mentum distally with dark grey-brown marking.

Hind protoptera absent.

Legs (Fig. 30 a – d ). Ratio of foreleg segments 1.1: 1.0: 0.4: 0.1, middle leg 1.1: 1.0: 0.4: 0.1, hind leg 1.2: 1.0: 0.4: 0.1. Femur. Femur length ~ 3.7 × maximum width. Outer margin with row of 9–15 spine-like setae; length of setae ~ 0.30 × maximum width of femur. Apex rounded, with pair of spine-like setae and usually few short, apically blunt setae. Stout, lanceolate, pointed setae scattered along inner margin; femoral patch absent on fore and middle legs, rudimentary on hind leg. Tibia. Outer margin with row of short, apically blunt setae, distalmost seta larger. Inner margin with two rows of medium spine-like setae; on apex tuft of fine, simple setae. Patella-tibial suture present on basal 1 / 3. Tarsus. Outer margin almost bare. Inner margin with row of curved, spine-like setae. Claw with one row of 7–14 denticles; distally pointed.

Abdominal terga (Fig. 30 f, g ). Surface with irregular rows of U-shaped scale bases and fine, simple, scattered setae. Posterior margin of terga: I smooth, without spines, II – IX with triangular, sharply pointed spines, becoming longer, narrower and sharper toward end of abdomen.

Abdominal sterna (Fig. 30 g ). Posterior margin of sterna: I – VI smooth, without spines; VII – IX with triangular spines, spines on segment IX not continuous.

Tergalii (Fig. 30 i, j ). Present on segments II – VII. Margin with small denticles intercalating fine, simple setae. Tracheae partly extending from main trunk to inner and outer margins. Tergalius IV somewhat longer than segment V; tergalius VII as long as 3 / 4 length of segment VIII.

Paraproct (Fig. 30 h ). Distally not expanded, with ~ 30 stout, marginal spines. Surface scattered with U-shaped scale bases and fine, simple setae. Cercotractor with numerous small, marginal spines.

Imago.

Unknown.

Etymology.

The species name refers to Ranong Prov., where the type locality is located.

Distribution.

Thailand (Fig. 32 d ).

Figures

Figure 28. Labiobaetis ranongensis sp. nov., larva: a. Habitus, dorsal view; b. Habitus, ventral view; c. Abdomen, dorsal view. Scale bars: 1 mm (a, b); 100 µm (c).

Figure 29. Labiobaetis ranongensis sp. nov., larva morphology: a. Labrum; b. Section of labrum, dorsal focus; c. Labium; d. Labial palp; e. Hypopharynx and superlinguae; f. Maxilla; g. Maxillary palp; h. Left mandible; i. Right mandible. Scale bars: 20 µm (c, e, f, h, i); 10 µm (a, b, d, g).

Figure 30. Labiobaetis ranongensis sp. nov., larva morphology: a. Hind leg; b. Section of hind femur; c. Section of hind tibia; d. Hind tarsus and claw; e. Antennal base; f. Posterior margins of abdominal terga; g. Posterior margins of abdominal segment IX; h. Paraprocts; i, j. Tergalius V. Scale bars: 50 µm (a); 20 µm (g); 10 µm (b – f, h – j).

Figure 32. Distribution maps: a. Labiobaetis batakorum species group; b. Labiobaetis numeratus species group; c. Labiobaetis operosus species group; d. Labiobaetis sumigarensis species group.