Nigrobaetis palawus, 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 palawus sp. nov.

Figs 8 , 9 , 10 , 11 , 12 , 13 , 14

Differential diagnosis.

Larva. Following combination of characters: A) dorsal surface of labrum with submedian seta and two long, simple setae in submarginal position (Fig. 10b ); B) right mandible: incisor with four denticles, kinetodontium with four denticles (Fig. 10c ); C) left mandible: incisor with four or five denticles, kinetodontium with three denticles; margin between prostheca and mola smooth, without denticles (Fig. 10d ); D) fore femur length ca. 3 × maximum width, dorsal margin with 8-14 curved, spine-like setae (Fig. 13a ); E) claw with 11 or 12 denticles (Fig. 13b ); F) hind protoptera absent; G) tergalii on abdominal segments I-VII; H) paraproct with ca. 12 marginal spines (Fig. 14b ); I) posterior margins of abdominal terga: I smooth, without spines; II-IX with triangular spines (Fig. 14a ).

Description.

Larva (Figs 9 - 14 ). Body length 2.8-3.9 mm. Caudalii broken. Antennae broken.

Colouration (Fig. 9a, b ). Head dorsally pale brown, basolaterally darker; thorax and abdomen dorsally brown; abdominal terga IV and VIII-X pale brown. Head, thorax, and abdomen ventrally pale brown, abdominal sterna VIII-X brighter. Legs pale brown, femur apically brown, with distomedial spot. Caudalii pale brown.

Labrum (Fig. 10a, 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 anterolateral long, feathered setae and medial long, bifid, pectinate setae.

Right mandible (Fig. 10c ). Incisor and kinetodontium fused. Incisor with four denticles; kinetodontium with four denticles, inner margin of innermost denticle with 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. 10d ). 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, smooth without denticles. Tuft of setae at apex of mola absent.

Hypopharynx and superlinguae (Fig. 11a ). Lingua approx. as long as 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. 11b, c ). Galea-lacinia ventrally with two simple, apical setae under canines. Medially with one spine-like seta and ca. four long, simple setae. Maxillary palp approx. as long as length of galea-lacinia; 2-segmented; palp segment II approx. 1.1 × 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-d ). Glossa basally broad, narrowing toward apex; as long as paraglossa; inner margin with ca. ten spine-like setae; apex with two long and one medium, robust setae; outer margin with ca. four 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 two medium, simple setae in anteromedial area; dorsally with row of three long, spine-like, simple setae near inner margin. Labial palp with segment I 0.9 × 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 three or four long, spine-like setae. Segment III pentagonal; inner apical margin with some setae-like processes; length 1.1 × width; ventrally with short, spine-like, simple setae and short, fine, simple setae.

Hind protoptera: Absent.

Foreleg (Fig. 13a-d ). Ratio of foreleg segments 1.3:1.0:0.8:0.3. Femur. Length ca. 3 × maximum width. Dorsal margin with 8-14 curved, spine-like setae; length of setae 0.27 × maximum width of femur. Apex rounded, with pair of spine-like setae. Stout, lanceolate setae scattered along ventral margin; femoral patch absent. Tibia. Dorsal margin without or with one short, spine-like seta; on apex one stout, apically rounded seta. Ventral margin with row of short, curved, spine-like setae, on apex two longer, spine-like, pectinate setae. Anterior surface with some stout, lanceolate setae near ventral margin. Patellatibial suture present on basal half area. Tarsus. Dorsal margin almost bare. Ventral margin with row of curved, spine-like setae. Claw with one row of 11 or 12 denticles; distally pointed; subapical setae absent.

Middle and hind legs. As foreleg, but tibia at dorsal margin with 1-4 spine-like setae.

Abdominal terga (Fig. 14a ). 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 margins smooth, without spines.

Tergalii (Fig. 13e ). Present on segments I-VII. Margin with small denticles intercalating fine simple setae. Tracheae extending from main trunk to inner and outer margins. Tergalius II as long as length of segments III and ½ IV combined; Tergalius VII as long as length of segments VIII and ½ IX combined.

Paraproct (Fig. 14b ). With 10-12 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 Palawan, where the species was collected.

Distribution

(Fig. 8 ). Philippines: Palawan.

Biological aspects.

The specimens were collected below 100 m in primary and secondary forest, on bottom gravel and on root packs in the run.

Type-material.

Holotype. Philippines • larva; Palawan, San Vincente, waterfall 4km NE Port Barton; 10°23'35"N, 119°09'27"E; 30 m; 18.vi.1997; leg. J. Mendoza; on slide; GBIFCH00975661; PNM. Paratypes. Philippines • 3 larvae; same data as holotype; 3 on slides; GBIFCH00592651; AdMU; GBIFCH0092646, GBIFCH00592647; MZL • 1 larva; Palawan, Roxas, Bgy. Port Barton, mountain river; 10°22'40"N, 119°11'05"E; 90 m; 20.vi.1997; leg. J. Mendoza; in alcohol; GBIFCH00975662; AdMU.

Figures

Figure 8. Distribution of Nigrobaetis species in the Philippines.

Figure 9. Nigrobaetis palawus sp. nov., larva habitus a dorsal view b ventral view. Scale bars: 1 mm.

Figure 10. Nigrobaetis palawus 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 11. Nigrobaetis palawus sp. nov., larva morphology a hypopharynx and Hypopharynx superlinguae b maxilla c maxilla, ventrolateral section. Scale bars: 20 µm.

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 13. Nigrobaetis palawus sp. nov., larva morphology a foreleg b fore claw c ventral apex of tibia d dorsal apex of tibia e tergalius VI. Scale bars: 50 µm.

Figure 14. Nigrobaetis palawus sp. nov., larva morphology a posterior margins of abdominal tergites II-VII b paraproct. Scale bars: 20 µm.