Labiobaetis glaucus (Agnew, 1961)

Gattolliat, Jean-Luc, Kondratieff, Boris C., Kaltenbach, Thomas & Dhafer, Hathal M. Al, 2018, Labiobaetis from the Kingdom of Saudi Arabia (Insecta, Ephemeroptera, Baetidae), ZooKeys 774, pp. 77-104 : 77

Labiobaetis glaucus (Agnew, 1961) Figs 34-39, 40-44, 45-47

Baetis glaucus Agnew, 1961: 14.

Pseudocloeon glaucum , Lugo-Ortiz et al. 2000: 281.

Labiobaetis glaucus , Kluge and Novikova 2016: 32-33.

Specimens examined.

18 larvae (GBIFCH00235711 + 4 slides GBIFCH00235741 (Genetics), GBIFCH00235746, GBIFCH00235750 (Genetics), GBIFCH00235756: Saudi Arabia (AR01); Al Jiwah, Thee Aine; 19°55'32"/ 41°26'17"; Alt. 752m; 13.X.2010; Coll. B. Kondratieff.

3 larvae (GBIFCH00235708): Saudi Arabia (AR19); Wadi Khat; 19°05'22"/ 41°58'16"; Alt. 490m; 13.III.2012; Coll. Al Dhafer, H.

1 larva (GBIFCH00235712): Saudi Arabia (AR28); Thee Ain, Al-Baha; 19°55'43"/ 41°26'34"; Alt. 760m; 3.VI.2012; Coll. Al Dhafer, H. & Kondratieff, B.

3 larvae (GBIFCH00235713): Saudi Arabia (AR31); Thee Ain, Al-Baha; 19°55'43"/ 41°26'34"; Alt. 760m; 8.XI.2012; Coll. J-L Gattolliat.

1 larva (GBIFCH00235707): Saudi Arabia (AR43a); Wadi Shahadan; 17°28'36"/ 42°51'25"; Alt. 460m; 12.XI.2012; Coll. J-L Gattolliat.

2 larvae GBIFCH00465151 (Genetics): Saudi Arabia (AR43b); Wadi Shahadan; 17°28'17"/ 42°51'14"; Alt. 440m; 12.XI.2012; Coll. J-L Gattolliat.

7 larvae (GBIFCH00235723 + 1 slide GBIFCH00235738), 3 male imagos (GBIFCH00235724 + 1 slide GBIFCH00235731 (Genetics)): Saudi Arabia (AR44); Wadi Shahadan; 17°28'36"/ 42°42'50"; Alt. 190m; 13.XI.2012; Coll. J-L Gattolliat.

Differential diagnosis.

Larva: abdominal pattern (Fig. 47) with tergites I, VI and X lighter (in some specimens tergites V and IX also lighter). Scape of antenna without distolateral process (Fig. 41). Segment II of the maxillary palp without a distomedial concavity (Fig. 38). Segment II of labial palp with a broad apically rounded triangular distomedial projection (Fig. 39). Dorsal margin of femur (Fig. 40) with numerous setae proximally and rarely any distally; ventral margin with a few scattered setae. Dorsal margin of tibia with a few minute setae. Paraproct with approx. ten stout, pointed spines increasing in length towards apex (Fig. 44). Male imago: Genitalia with inner margin at the apex of segment I and base of segment II with a triangular well-marked expansion; segment III almost globular (Fig. 46).

Description.

Larva. Length: fully grown female: Body 6.2-8.0 mm, cerci 3.6-4.0 mm, terminal filament 2.4-2.8 mm. Fully grown male: Body 4.8-7.3 mm, cerci 3.3-3.6 mm, terminal filament 1.7-1.9 mm.

Colouration (Fig. 47): head almost uniformly medium brown, with darker, faint vermiform marking on vertex and frons, border of sclerites yellow. Prothorax medium brown with poorly marked yellowish pattern; mesothorax medium brown with a V-shaped yellow pattern; metathorax medium brown. Legs ecru except femora with a central brown spot and apex of femora, tibiae and tarsi brown. Tergites medium brown with small ecru spot except tergites I, V, VI, IX and X yellow, tergites V and VI generally with a dark M-shaped mark. Abdominal sternites ecru. Cerci ecru without dark stripe.

Head: scape of antenna without distolateral process (Fig. 41).

Labrum (Fig. 34) rounded, with a small anteromedial emargination, dorsally with one feathered submedian seta, and a distolateral row of approx. eight feathered setae; short, thin, simple setae scattered on dorsal surface of labrum; distal margin bordered with feathered setae.

Right mandible (Fig. 35): canine with two almost fused incisivi each with four denticles, outer denticle much shorter than others, inner margin of inner incisive with a row of very thin setae; stout prostheca apically with small rounded denticles; margin between prostheca and mola straight, smooth, without setae; tuft of setae at apex of mola reduced to two small setae.

Left mandible (Fig. 36): canine with two almost fused incisivi each with four denticles, outer denticle much shorter than others; stout prostheca apically with small denticles and a comb-shaped structure; margin between prostheca and mola straight, distally with crenulations; tuft of setae at apex of mola reduced to a single seta.

Hypopharynx as in Fig. 37.

Maxilla (Fig. 38) with a medioapical row of relatively short setae, basal end of row with approx. seven long setae; posterior side of lacinia mediobasally with a row of three medium-sized setae, a single small seta close to the medial margin of lacinia; palp 2-segmented, segment II without distomedial concavity.

Labium (Fig. 39) with glossae slightly shorter than paraglossae; glossae inner margin with two rows of approx. six long setae, apically with a few setae feathered on one side; paraglossae stout, apically rounded, with three rows of long setae, part of them feathered on one side; labial palp with segment I slender, shorter than segments II and III combined; segment II with a broad apically rounded triangular distomedial projection covered with thin setae, on posterior side with a row of three long setae; segment III subconical, inner margin apically slightly concave, with scattered short thin setae and a few stouter setae.

Thorax: hind wing pads present.

Legs (Fig. 40): Forefemur dorsally with a row of medium-sized, apically rounded setae, numerous proximally and rare distally; apex with two short flattened setae; ventral margin with a well-developed villopore and scarce, short, stout setae. Foretibia dorsally with a row of scarce tiny, stout setae; ventrally with a few short setae, not longer apically, apex with a patch of numerous flattened short setae. Foretarsus almost bare dorsally; ventral margin with a row of pointed setae slightly increasing in length toward apex; tarsal claw with a single row of approx. twelve pointed teeth; subapical setae absent. Middle and hind legs similar to foreleg but with reduced setation.

Abdomen: tergites (Fig. 43) with numerous scale bases, with a few setae; posterior margin with short and broad triangular spination. Sternites with a few setae, without scales and scale bases; sternites I-VII with posterior margin smooth without spines, sternites VIII and IX with small triangular spines.

Gills present on abdominal segments I–VII, distally serrated, tracheation brown, poorly developed (Fig. 42).

Paraproct (Fig. 44) with scale bases and a few setae, margin with approx. ten stout, pointed spines increasing in length; posterolateral extension with a few scale bases, minute spines along the margin.

Male imago.Length. Body 4.4-4.5 mm; forewing 4.2-4.3 mm; hindwing 0.8 mm.

Colouration: head dark brown; antenna ecru. Facetted surface of turbinate eyes orange brown, shaft orange brown (Fig. 45). Thorax yellowish brown with margin of sclerites generally dark brown. Legs: yellowish without marks or pattern. Wings hyaline except costal and subcostal area apically white, with brown venation. Abdomen: tergites I to X light brown without mark or pattern. Sternites I and II light brown; sternites III to VII uniformly ecru without marks or pattern; sternites VIII and IX light brown. Cerci ecru. Genitalia (Fig. 46) ecru except inner margin of segment I medium brown. Forewing (Fig. 45): pterostigma with approx. four cross-veins not reaching subcostal vein; double intercalary veins shorter to almost equal to distance between corresponding main veins. Hindwing similar to Fig. 17 except two longitudinal veins reaching margin. Genitalia (Fig. 46): basal segment with inner margin not expanded apically; segment I and II almost completely fused; inner margin at the apex of segment I and base of segment II with a triangular well-marked expansion; segment III almost globular.

Distribution and habitat.

This species was collected in three different wadis at altitudes between 200 m and 750 m. Larvae occur in small streams, generally very shallow (a few centimeters to 20 cm) with moderate current. The substrate was a mix of sand, cobbles and rocks (Figs 50, 51, 52). This species was sympatric with the two other species of Labiobaetis and C. cf. soldani , but generally less abundant than other species.

Molecular results

The mitochondrial reconstruction clearly recovers L. potamoticus and L. alahmadii as monophyletic clades (BS (Bootstrap support) of 83% and 100% respectively), with intraspecific K2P distances below 1% (Table 2). Labiobaetis glaucus is also highly supported as a monophyletic clade (BS of 100%), with the three populations (KSU, Mayotte, and South Africa) supported as monophyletic sister-clades (BS of 87%, 81% and 90% respectively). The sister group of Labiobaetis potamoticus is an undescribed species from South Africa; the distance between the two taxa is slightly higher than intraspecific distance (between 4.2 and 5.1%). Labiobaetis potamoticus possesses high distances to all the other species included in the study (16.2 to 25.5%). The relationships of L. alahmadii and L. glaucus with other species of Afrotropical and Palaearctic origins also are unclear and have no molecular support (Fig. 11). Both species are highly distant from any other taxa (Table 2).