Nigrobaetis suma, 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 suma sp. nov.

Figs 21 , 22 , 23 , 24 , 25 , 26 , 27 , 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. 22b ); B) right mandible: incisor with four denticles, kinetodontium with four denticles (Fig. 22c ); C) left mandible: incisor with four denticles, kinetodontium with three denticles; margin between prostheca and mola straight, with row of short, setae-like processes (Fig. 22d ); D) fore femur length ca. 3 × maximum width, dorsal margin with ca. 11 curved, spine-like setae (Fig. 25a ); E) tibia dorsally bare, distally with one stout, apically rounded seta (Fig. 25a, d ); F) claw with 11 or 12 denticles (Fig. 25c ); G) hind protoptera well developed (Fig. 25g ); H) tergalii on abdominal segments I-VII; I) paraproct with six or seven marginal spines (Fig. 26b ); J) posterior margins of abdominal terga: I-IV(V) smooth, without spines; (V-)VI with rudimentary spines; VII-IX with triangular, pointed spines (Fig. 26a ).

Description.

Larva (Figs 21 - 26 ). Body length 3.6-4.9 mm. Cerci ca. ¾ of body length, paracercus ca. ⅔ of cerci length. Antennae ca. 3 × head length.

Colouration (Fig. 21a, b ). Head, thorax, and abdomen dorsally brown, abdominal terga VIII and IX bright beige. Head, thorax, and abdomen ventrally pale brown, abdominal sterna VIII-X ecru. Legs pale brown, femur basally, along margins, and in distal area darker. Caudalii pale brown.

Labrum (Fig. 22a, 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. 22c ). Incisor and kinetodontium fused. Incisor with four denticles; kinetodontium with four 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. 22d ). 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 row of short, setae-like processes. Tuft of setae at apex of mola absent.

Hypopharynx and superlinguae (Fig. 23a ). 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. 23b-d ). Galea-lacinia ventrally with two simple, apical setae under canines. Medially with one spine-like seta and ca. five long, simple setae. Maxillary palp ca. 1.3 × as long as length of galea-lacinia; 2-segmented; segment II bent inwards, distal half sclerotised; palp segment II ca. 1.2 × as long as segment I; setae on maxillary palp fine, simple, scattered over surface of segments I and II; apex of last segment slightly pointed.

Labium (Fig. 24a-f ). Glossa basally broad, narrowing toward apex; slightly shorter than paraglossa; inner margin with ca. eight spine-like setae; apex with two long and one medium, robust setae; outer margin with ca. six 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. three medium, simple setae in medial and anteromedial area; dorsally with two 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. three long, spine-like setae. Segment III subquadrangular; length ca. 0.9 × maximum width; inner apical margin with some setae-like processes (Fig. 24f ); ventrally with short, spine-like, simple setae and short, fine, simple setae.

Hind protoptera (Fig. 25g ) well developed.

Foreleg (Fig. 25a-e ). Ratio of foreleg segments 1.4:1.0:0.8:0.3. Femur. Length ca. 3 × maximum width. Dorsal margin with ca. 11 curved, spine-like setae; length of setae 0.31 × maximum width of femur. Apex rounded, with pair of spine-like setae. Many medium, stout, lanceolate setae along ventral margin; femoral patch absent. Tibia. Dorsal margin bare, 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 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 11 or 12 denticles; distally pointed; subapical setae absent.

Middle and hind legs. As foreleg; femur ventrally with few stout, lanceolate setae; tibia dorsal margin with row of stout setae.

Abdominal terga (Fig. 26a ). Surface with irregular rows of U-shaped scale bases. Posterior margin of terga: I-IV(V) smooth, without spines; (V-)VI with rudimentary spines; VII-IX with triangular, pointed spines.

Abdominal sterna. Posterior margin of sterna smooth, without spines.

Tergalii (Fig. 25f ). Present on segments I-VII. Margin with small denticles intercalating fine simple setae. Tracheae partly extending from main trunk toward inner and outer margins. Tergalius I as long as length of 2/3 of segment II; Tergalius IV as long as length of segments V and 1/3 VI combined; Tergalius VII as long as segments VIII and 1/3 IX combined.

Paraproct (Fig. 26b ). With six or seven stout, marginal spines. Surface scattered with U-shaped scale bases. Cercotractor with numerous small, marginal spines.

Subimaginal gonostyli (Fig. 26c ) developing under cuticle of male last instar larvae folded in Nigrobaetis -type ( Kluge 2004: fig. 29G).

Adult stages. Unknown.

Eggs (Fig. 27 ). Ovoid; surface with numerous polygonal structural elements (surface of the eggs in Fig. 27 could be partly degraded; a central, smaller, rounded, slightly elevated area surrounded by a round trench (as in other species) seems to be absent on the polygonal structural element, or invisible due to degradation).

Etymology.

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

Distribution

(Fig. 40c ). Indonesia, Sumatra.

Biological aspects.

The specimens were collected at altitudes from 10 m to 1300 m, mostly in deforested or agricultural areas. The streams were in average 2-5 m wide, 15-50 cm deep and flowing with 0.5-0.7 m/s. The substrate was always a mix of substantial amounts of boulder, stones, gravel, and sand.

Type-material.

Holotype. Indonesia • larva; Sumatra, volcano Marapi, West; 00°28'29"S, 100°22'08"E; 553 m; 09.iv.2014; leg. M. Gueuning; on slide; GBIFCH00422020; MZL. Paratypes. Indonesia • 28 larvae; same data as holotype; 1 on slide; GBIFCH00592665; MZL; 27 in alcohol; GBIFCH00419696, GBIFCH00421961, GBIFCH00421976, GBIFCH00421985, GBIFCH00421992, GBIFCH00421997, GBIFCH00422012, GBIFCH00422014, GBIFCH00422016, GBIFCH00422017, GBIFCH00422034, GBIFCH00422435, GBIFCH00422704, GBIFCH00422929, GBIFCH00975675; MZL • 1 larva; Sumatra, volcano Marapi; 00°21'58"S, 100°33'18"E; 890 m; 02.iv.2014, leg. M. Gueuning; in alcohol; GBIFCH00422001; MZL • 1 larva; Sumatra, volcano Marapi, East; 00°21'33"S, 100°30'42"E; 1205 m; 03.iv.2014; leg. M. Gueuning; in alcohol; GBIFCH00422041; MZL • 2 larvae; Sumatra, volcano Sago, North, Riv. Simbukan; 00°17'08"S, 100°41'13"E; 880 m; 18.iii.2014; leg. M. Gueuning; in alcohol; GBIFCH00422027, GBIFCH00422037; MZL • 6 larvae; Sumatra, volcano Sago, South, Riv. Kobun; 00°22'33"S, 100°39'33"E; 1095 m; 19.iii.2014; leg. M. Gueuning; in alcohol; GBIFCH00421959, GBIFCH00421966, GBIFCH00422005, GBIFCH00422025, GBIFCH00422040, GBIFCH00423021; MZL • 2 larvae; Sumatra, volcano Sago, South, Riv. Tampo; 00°22'20"S, 100°41'45"E; 960 m; 20.iii.2014; leg. M. Gueuning; 1 on slide; GBIFCH00422032; 1 in alcohol; GBIFCH00421990; MZL • 1 larva; Sumatra, volcano Singgalang, riv. Caruak, 00°22'56"S, 100°22'42"E; 1300 m; 23.iii.2014; leg. M. Gueuning; in alcohol; GBIFCH00421956; MZL • 1 larva; Sumatra, volcano Singgalang, riv. Sianok; 00°19'57"S, 100°19'19"E; 1150 m; 24.iii.2014; leg. M. Gueuning; on slide; GBIFCH00422030; MZL • 10 larvae; Sumatra, volcano Singgalang, riv. Airjernih; 00°24'07"S, 100°16'44"E; 840 m; 25.iii.2014; leg. M. Gueuning; 1 on slide; GBIFCH00592666; 9 in alcohol; GBIFCH00421960, GBIFCH00421970, GBIFCH00422010, GBIFCH00422018, GBIFCH00422028, GBIFCH00422038, GBIFCH00422973; MZL • 6 larvae; Sumatra, volcano Talamau, South, Riv. Pularian; 00°00'60"N, 100°00'01"E; 540 m; 01.iv.2014; leg. M. Gueuning; 1 on slide; GBIFCH00422013; 5 in alcohol; GBIFCH00421981, GBIFCH00421965, GBIFCH00422004, GBIFCH00422021, GBIFCH00423066; MZL • 1 larva; Sumatra Barat, Sawahlunto, stream; 00°41'20"S, 100°46'43"E; 275.m; 10.xi.2011; leg. M. Balke; (UN5); in alcohol; GBIFCH00975705; MZL • 1 larva; Sumatra, upstream Tarusan; 10 m; 24.v.2010; leg. J.-M. Elouard; in alcohol; GBIFCH00975663; MZL • 1 larva; Sumatra, Batusangkar, Riv. Lupuak Tapuak; 440 m; 27.v.2010; leg. J.-M. Elouard; on slide; GBIFCH00975664; MZL.

Figures

Figure 21. Nigrobaetis suma sp. nov., larva habitus a dorsal view b ventral view. Scale bars: 1 mm.

Figure 22. Nigrobaetis suma 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 23. Nigrobaetis suma sp. nov., larva morphology a hypopharynx and Hypopharynx superlinguae b, c maxilla d maxilla, ventrolateral section. Scale bars: 20 µm.

Figure 24. Nigrobaetis suma sp. nov., larva morphology a labium b glossa and paraglossa, ventral focus c glossa and paraglossa, dorsal focus d labial palp, dorsal focus e labial palp, ventral focus f labial palp, inner apical margin of segment III (arrows: setae-like processes). Scale bars: 20 µm.

Figure 25. Nigrobaetis suma sp. nov., larva morphology a foreleg b setae on ventral margin of fore femur c ventral apex of fore tibia and base of fore tarsus d seta on dorsal apex of fore tibia e fore claw f tergalius IV g right hind protopteron. Scale bars: 50 µm.

Figure 26. Nigrobaetis suma sp. nov., larva morphology a posterior margins of abdominal tergites IV-VII b paraproct c subimaginal gonostylus developing under cuticle of male last instar larva. Scale bars: 20 µm.

Figure 27. Nigrobaetis suma sp. nov., eggs. Scale bars: 40 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).