Nigrobaetis sumbensis, Kaltenbach & Gattolliat, 2023

Kaltenbach, Thomas & Gattolliat, Jean-Luc, 2023, New species of Nigrobaetis from Southeast Asia (Ephemeroptera, Baetidae), ZooKeys 1166, pp. 175-234 : 175

Nigrobaetis sumbensis sp. nov.

Figs 15 , 16 , 17 , 18 , 19 , 20 , 40c

Differential diagnosis.

Larva. Following combination of characters: A) dorsal surface of labrum with submedian seta and two long, simple setae in submarginal position (Fig. 16b ); B) right mandible: incisor with four denticles, kinetodontium with three denticles (Fig. 16c ); C) left mandible: incisor with four denticles, kinetodontium with three denticles; margin between prostheca and mola straight, with four or five long, setae-like processes (Fig. 16d ); D) fore femur very slender, length ca. 4.8 × maximum width, dorsal margin with eight or nine curved, spine-like setae (Fig. 19a ); E) tibia dorsally with row of spine-like setae; F) claw with 14-17 relatively long denticles (Fig. 19c ); G) hind protoptera absent; H) tergalii on abdominal segments I-VII; I) paraproct with 10-14 marginal spines (Fig. 20b ); J) posterior margins of abdominal terga: I smooth, without spines; II-IX with triangular, pointed spines (Fig. 20a ).

Description.

Larva (Figs 15 - 20 ). Body length 3.7-4.6 mm. Caudalii broken. Antennae broken.

Colouration (Fig. 15a, b ). Head, thorax, and abdomen dorsally brown, with lively bright pattern as in Fig. 15a . Noticeable are the bright beige abdominal terga I, IV (with brown marks), and VIII-X. Head, thorax, and abdomen ventrally pale brown, abdominal sterna VIII-X brighter. Legs pale brown, femur darker in distal 2/3. Caudalii bright beige.

Labrum (Fig. 16a, b ). Length 0.7 × maximum width. Distal margin with medial emargination and a small process. Dorsally with medium, fine, simple setae scattered over surface; submedian seta and two long, simple, submarginal setae. Ventrally with marginal row of setae composed of lateral and anterolateral long, feathered setae and medial long, bifid, pectinate setae.

Right mandible (Fig. 16c ). Incisor and kinetodontium fused. Incisor with four denticles; kinetodontium with three denticles, inner margin of innermost denticle without row of thin setae. Prostheca stick-like, apicolaterally denticulate. Margin between prostheca and mola straight, with row of setae-like processes. Tuft of setae at apex of mola present.

Left mandible (Fig. 16d ). Incisor and kinetodontium fused. Incisor with four denticles; kinetodontium with three denticles. Prostheca robust, apically with small denticles and comb-shaped structure. Margin between prostheca and mola straight, with four or five long, setae-like processes. Tuft of setae at apex of mola absent.

Hypopharynx and superlinguae (Fig. 17a ). Lingua shorter than Hypopharynx superlinguae . Lingua longer than broad; medial tuft of stout setae poorly developed, broad; distal half laterally not expanded. Superlinguae distally straight; lateral margins rounded; fine, long, simple setae along distal margin.

Maxilla (Fig. 17b-d ). Galea-lacinia ventrally with two simple, apical setae under canines. Medially with one spine-like seta and ca. four long, simple setae. Maxillary palp ca. 1.3 × as long as length of galea-lacinia; 2-segmented; palp segment II ca. 1.3 × as long as segment I; setae on maxillary palp fine, simple, scattered over surface of segments I and II; apex of last segment pointed.

Labium (Fig. 12a-e ). Glossa basally broad, narrowing toward apex; slightly shorter than paraglossa; inner margin with nine or ten spine-like setae; apex with two long and one medium, robust setae; outer margin with ca. eight spine-like setae; ventral surface with fine, simple, scattered setae. Paraglossa curved inward; apex rounded; with three rows of long, robust, distally pectinate setae in apical area and ca. four medium, simple setae in anteromedial area; dorsally with row of four long, spine-like, simple setae near inner margin. Labial palp with segment I 0.7 × length of segments II and III combined. Segment I ventrally with short, fine, simple setae. Segment II without protuberance; ventral surface with short, fine, simple setae; dorsally with row of ca. five long, spine-like setae. Segment III slightly pentagonal, inner distal margin slightly concave, with few setae-like processes; length ca. 1.2 × maximum width; ventrally with short, spine-like, simple setae and short, fine, simple setae.

Hind protoptera: Absent.

Foreleg (Fig. 19a-c ). Ratio of foreleg segments 1.3:1.0:0.6:0.2. Femur. Very slender, length ca. 4.8 × maximum width. Dorsal margin slightly concave, with eight or nine curved, spine-like setae; length of setae 0.29 × maximum width of femur. Apex rounded, with pair of spine-like setae and medium, fine, simple setae. Row of stout, lanceolate setae on ventral margin; femoral patch absent. Tibia. Dorsal margin with row of medium, spine-like setae, on apex one seta somewhat longer and with rounded apex. Ventral margin with row of short to medium curved, spine-like setae, on apex two longer, spine-like, pectinate setae. Anterior surface with stout, lanceolate setae along ventral margin. Patellatibial suture present on basal half. Tarsus. Dorsal margin bare. Ventral margin with row of curved, spine-like setae. Claw with one row of 14-17 relatively long denticles; distally pointed; subapical setae absent.

Middle and hind legs. As foreleg.

Abdominal terga (Fig. 20a ). Surface with irregular rows of U-shaped scale bases. Posterior margin of terga: I smooth, without spines; II-IX with triangular, pointed spines.

Abdominal sterna. Posterior margin of sterna: I-V smooth, without spines; VI with rudimentary spines; VII-IX with triangular spines.

Tergalii (Fig. 19d, e ). Present on segments I-VII. Margin with small denticles intercalating fine simple setae. Tracheae extending from main trunk to inner and outer margins. Tergalius I as long as length of segments II and ⅓ III combined; Tergalius IV as long as length of segments V and VI combined; Tergalius VII reaching beginning of segment X.

Paraproct (Fig. 20b ). With 10-14 stout, marginal spines. Surface scattered with U-shaped scale bases. Cercotractor with numerous small, marginal spines.

Adult stages. Unknown.

Etymology.

Referring to the island of Sumba, where the species was collected.

Distribution

(Fig. 40c ). Indonesia, Sumba.

Biological aspects.

The specimens were collected at an altitude of 400 m.

Type-material.

Holotype. Indonesia • larva; Sumba, Waikelo. Stream; 09°35'45"S, 119°20'25"E; 400 m; 27.ix.2011; leg. M. Balke; (SUA04); on slide; GBIFCH00592616; MZB. Paratypes. Indonesia • 2 larvae; same data as holotype; 2 on slides; GBIFCH00592660, GBIFCH00975677; MZL.

Figures

Figure 12. Nigrobaetis palawus sp. nov., larva morphology a labium b glossae and paraglossae, ventral focus c labial palp, ventral focus (arrows: setae-like processes) d labial palp, dorsal focus. Scale bars: 20 µm.

Figure 15. Nigrobaetis sumbensis sp. nov., larva habitus a dorsal view b ventral view. Scale bars: 1 mm.

Figure 16. Nigrobaetis sumbensis sp. nov., larva morphology a labrum, ventral focus b labrum, dorsal focus (arrows: submedian and submarginal setae) c right mandible d left mandible. Scale bars: 20 µm.

Figure 17. Nigrobaetis sumbensis sp. nov., larva morphology a hypopharynx and Hypopharynx superlinguae b, c maxilla d maxilla, ventrolateral section. Scale bars: 20 µm.

Figure 18. Nigrobaetis sumbensis sp. nov., larva morphology a labium b glossae and paraglossae, ventral focus c labial palp, ventral focus d labial palp, dorsal focus e apex of glossa and paraglossa, dorsal focus. Scale bars: 20 µm.

Figure 19. Nigrobaetis sumbensis sp. nov., larva morphology a foreleg b fore femur apex c fore claw d tergalius I e tergalius IV. Scale bars: 50 µm.

Figure 20. Nigrobaetis sumbensis sp. nov., larva morphology a posterior margins of abdominal tergites II-VII b paraproct. Scale bars: 20 µm.

Figure 40. a Nigrobaetis kaliman sp. nov., egg b Nigrobaetis kaliman sp. nov., pack of developing eggs (extracted from same larva than a) c distribution of Nigrobaetis species in Indonesia. Scale bars: 40 µm (a, b).