Labiobaetis excavatus, Kaltenbach & Gattolliat, 2021

Kaltenbach, Thomas & Gattolliat, Jean-Luc, 2021, Labiobaetis Novikova & Kluge in Ethiopia (Ephemeroptera, Baetidae), with description of a new species, African Invertebrates 62 (1), pp. 231-255 : 231

2. Labiobaetis excavatus sp. nov. Figures 2a , 3 , 4 , 5

Differential diagnosis.

Nymph. Following combination of characters: A) colouration: abdomen dorsally uniform brown; B) scape with well-developed distolateral process; C) labial palp segment II with broad, thumb-like distomedial protuberance; segment III oblong; D) maxillary palp segment II with strong excavation at inner distolateral margin; E) fore femur rather slender, length 3.6 × maximum width; dorsal margin with 18-27 curved, spine-like setae, and a partial row of spine-like setae near margin; femoral patch absent; F) hind protoptera well developed; G) seven pairs of gills; H) paraproct with 15-20 stout marginal spines.

Description.

Nymph (Figs 3 - 5 ). Body length 7.3-8.5 mm. Cerci: ca. 2/3 of body length. Paracercus: ca. 2/3 of cerci length. Antenna: approx. twice as long as head length.

Colouration (Fig. 3a, b ). Head, thorax and abdomen dorsally brown, fore protoptera brown. Head, thorax and abdomen ventrally ecru, frons brown. Legs ecru, femora and tarsi apically brown. Caudalii brown.

Antenna (Fig. 4g ) with scape and pedicel subcylindrical, with well-developed distolateral process at scape.

Labrum (Fig. 5a ). Subrectangular, 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 setae composed of one plus ca. 17 long, feathered setae. Ventrally with marginal row of setae composed of lateral and anterolateral long, feathered setae and medial long, bifid setae; ventral surface with ca. nine short, spine-like setae near lateral and anterolateral margin.

Right mandible (Fig. 5b, c ). Incisor and kinetodontium fused. Incisor with four 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. Tuft of setae at apex of mola present.

Left mandible (Fig. 5d, e ). 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 slightly convex, with minute denticles towards subtriangular process. Subtriangular process long and slender, above level of area between prostheca and mola. Denticles of mola apically constricted. Tuft of setae at apex of mola absent.

Both mandibles with lateral margins almost straight. Basal half with fine, simple setae scattered over dorsal surface.

Hypopharynx and superlinguae (Fig. 5f ). Lingua longer than superlinguae. Lingua longer than broad; medial tuft of stout setae well developed, short; distal half laterally not expanded. Superlinguae distally rounded; lateral margins rounded; fine, long, simple setae along distal margin.

Maxilla (Fig. 5g, h ). Galea-lacinia ventrally with two simple, apical setae under canines. Inner dorsal row of setae with three denti-setae, distal denti-seta tooth-like, middle and proximal denti-setae slender, bifid and pectinate. Medially with one pectinate, spine-like seta and six simple setae increasing in length distally. Maxillary palp slightly longer than length of galea-lacinia; 2-segmented; palp segment II 1.4 × length of segment I; setae on maxillary palp fine, simple, scattered over surface of segments I and II; apex of last segment rounded, with strong excavation at inner distolateral margin.

Labium (Fig. 5i, j ). Glossa basally broad, narrowing toward apex; shorter than paraglossa; inner margin with ca. seven spine-like setae, distalmost seta much longer than other setae; apex with one long, one medium and one short, robust seta; outer margin with 5-7 spine-like setae increasing in length distally; ventral surface with fine, simple, scattered setae. Paraglossa sub-rectangular, curved inward; apex rounded; with three rows of long, robust, distally pectinate setae in apical area and three or four medium, simple setae in anteromedial area; dorsally with row of five 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 with broad thumb-like distomedial protuberance; distomedial protuberance 0.9 × width of base of segment III; ventral surface with short, fine, simple setae; dorsally with two or three long, spine-like setae near outer margin. Segment III oblong; apex slightly pointed; length 1.2 × width; ventrally covered with short, spine-like, simple setae and short, fine, simple setae.

Hind protoptera (Fig. 4h ) well developed.

Foreleg (Fig. 4a, b ). Ratio of foreleg segments 1.1:1.0:0.4:0.1. Femur. Length 3.6 × maximum width. Dorsal margin with 18-27 curved, spine-like setae and partial second row near margin in basal area; length of setae 0.14 × maximum width of femur. Apex rounded, with pair of spine-like setae and some short, stout setae. Many stout, lanceolate setae scattered along ventral margin; femoral patch absent. Tibia. Dorsal margin with row of short, stout setae and fine simple setae, and row of short, stout setae near margin. Ventral margin with row of short, curved, spine-like setae, distally of patellotibial suture one longer, curved, spine-like seta, on apex some longer setae and tuft of fine, simple setae. Anterior surface scattered with stout, lanceolate setae. Patellotibial suture present on basal half area. Tarsus. Dorsal margin with row of short, stout setae and fine, simple setae. Ventral margin with row of curved, spine-like setae. Claw with one row of 10-13 denticles; distally pointed; with ca. five stripes; subapical setae absent.

Terga (Fig. 4c ). Surface with irregular rows of U-shaped scale bases and scattered fine, simple setae. Posterior margin of tergum IV with triangular spines, ca. as long as wide.

Gills (Fig. 4d, e ). Present on segments I-VII. Margin with small denticles intercalating fine simple setae. Tracheae extending from main trunk to inner and outer margins. Gill I ca. 2/3 length of segment II; gill IV as long as length of segments V and half VI combined; gill VII slightly longer than length of segment VIII.

Paraproct (Fig. 4f ). Distally not expanded, with 15-20 stout, marginal spines. Surface scattered with U-shaped scale bases, fine, simple setae and micropores. Cercotractor with small, marginal spines, partly split at apex.

Etymology.

Referring to the strongly developed excavation at inner, distolateral margin of maxillary palp segment II.

Biological aspects.

The specimens were collected at an altitude of 2400 m in relatively cold water (15.9 °C; see Englmaier et al. 2020: table 1). The sampling site lies in a protected area (S1, National Forest Priority Area), unlike all other sampling sites in this study ( Englmaier et al. 2020).

Distribution.

Ethiopia (Fig. 2a ).

Type-material.

Holotype. Ethiopia • nymph; Upper Awash River, Chilimo Forest ; 09°04'01"N, 38°08'09"E; 2390 m; 06.11.2017; leg. W. Graf; on slide; GBIFCH00592380 ; MZL. Paratypes. Ethiopia • 9 nymphs; same data as holotype; 4 on slides; GenBank MW307229 , MW307228 ; GBIFCH00763725 , GBIFCH00674636 , GBIFCH00592390 , GBIFCH00592423 ; MZL; 5 in alcohol; GBIFCH00515502 , GBIFCH00515552 ; MZL .

Figures

Figure 2. Distribution of Labiobaetis in Ethiopia.

Figure 3. Labiobaetis excavatus sp. nov., habitus, nymph a dorsal view b ventral view. Scale bars: 1.0 mm.

Figure 4. Labiobaetis excavatus sp. nov., nymph morphology a foreleg b fore claw c tergum IV d gill IV e margin of gill IV f paraproct g antennal scape h metanotum. Scale bars: 0.1 mm.

Figure 5. Labiobaetis excavatus sp. nov., nymph morphology: a labrum b right mandible c right prostheca d left mandible e left prostheca f hypopharynx and superlinguae g maxilla h apex of maxillary palp (left: dorsal view, right: inner lateral view) i labium j apex of paraglossa. Scale bar: 0.1 mm.