Nigrobaetis (Margobaetis) klugei Sivaruban et al. 2022

Kluge, Nikita, Sivaruban, T., Srinivasan, Pandiarajan, Barathy, S. & Isack, Rajasekaran, 2024, Redescriptions of Indian species of Nigrobaetis Kazlauskas (in Novikova & Kluge) 1987 (Ephemeroptera, Baetidae), Zootaxa 5418 (5), pp. 528-550 : 542-548

Nigrobaetis (Margobaetis) klugei Sivaruban et al. 2022

( Figs 44–89 )

Nigrobaetis klugei Sivaruban, Srinivasan, Barathy & Isack 2022: 183 (larva).

Nigrobaetis (Margobaetis) klugei : Kluge 2022: 163, 164 (subimago).

Material examined. INDIA: state Tamil Nadu: Rajapalayam district, Sastha falls , 9°41′50″N & 77°40′15″E; 195 m a.s.l., 24.I.2021, coll. P. Srinivasan & R. Isack.: 13 larvae (holotype and paratypes); Theni district, Suruli Falls, 24–26.I.2016, coll. L. Sheyko & N. Kluge : 10 L-S-I♂, 9 L-S-I♀, 1 L-S♀, 13 larvae ( ZIN); Theni district , Veerapandi river , 31.VIII.2022, coll. P. Srinivasan & R. Isack: 1 I ♂ ( AMC); Madurai district, Vaigai river , 14.XII.2022, coll. P. Srinivasan & R. Isack: 3 L-S-I♂ ( AMC); Tirunelveli district, Courtallam, Chittar river near Peraruvi (= Main Falls ), 3–7.II.2013, coll. N. Kluge & L. Sheyko: L-S-I♀, 4 larvae ( ZIN); state Karnataka: border of Shivamogga and Udupi districts near Agumbe and Someswar, 11.I–1.II.2013, coll. N. Kluge & L. Sheyko: 3 larvae ( ZIN) .

Additional descriptions

Larva. CUTICULAR COLORATION: Pronotum and mesonotum mostly brown, with variable paired blanks ( Figs 48, 50, 52 ). Leg of each pair mostly colorless, with more or less expressed brown transverse band on femur and brown femur-tibia articulation ( Figs 45–46 ); sometimes femur mostly brown, with two colorless blanks ( Figs 58–60 ; Sivaruban et al. 2022: figs 3A–E). Abdominal terga II– III, V –VII and X mostly brown, sometimes with lighter submedian sigilla; terga I, IV and VIII –IX more or less lighter ( Figs 47, 49, 51 ; Sivaruban et al. 2022: figs 1A–B, 3H). Caudalii proximally brown, distally colorless ( Figs 49, 51 ).

HYPODERMAL COLORATION: Not expressed.

SHAPE AND SETATION: Labrum semicircular ( Fig. 53 ; Sivaruban et al. 2022: fig. 2A). Other mouthparts as in drawings and photos ( Fig. 54 ; Sivaruban et al. 2022: figs 2B–G).

Hind protoptera present ( Fig. 46 ; Sivaruban et al. 2022: fig. 3H).

Each tibia with one stout, parallel-sided, blunt seta on outer side near apex (subapical seta); middle and hind tibiae, besides subapical seta, with several (2–10) setae of same kind forming longitudinal row on outer side ( Figs 56–57 ); outer side of fore tibia with no more than one stout seta other than subapical one ( Fig. 55 ).

Posterior margins of abdominal terga I–X or II–X with triangular denticles, shorter and blunter on anterior segments, longer and more pointed on posterior segments ( Sivaruban et al. 2022: fig. 3G). Posterior margins of all abdominal sterna smooth, without denticles ( Figs 61, 62 ). Paraproct with few especially long and pointed denticles ( Figs 61–63 ; Sivaruban et al. 2022: fig. 3K). All 7 pairs of tergalii present; tergalii of 1st pair much smaller than others, twice shorter than tergalii of next pair ( Figs 64–68 ). Cercus with several prominent, pointed denticles on outer (lateral) side of each 4th segment; paracercus with 2 such denticles on dorsal side of each 4th segment, sometimes with one such denticle on segment between them ( Figs 69–71 ).

Subimago. CUTICULAR COLORATION: Head colorless, antennae light brown. Pronotum light brown.

Mesonotum light brown, with darker sutures ( Fig. 73 ). Thoracic pleura and sterna mostly ochre, with certain sclerites brown ( Fig. 72 ). Legs mostly colorless, with brown marking proximad of patella-tibial suture ( Fig. 81 ) or its place (on fore leg of male). Abdomen light brownish. Caudalii colorless.

HYPODERMAL COLORATION: As in imago.

TEXTURE: On all legs of both sexes, last tarsal segment covered with pointed microlepides; other tarsomeres covered mostly with blunt microlepides, with few pointed microlepides on distal margin ( Kluge 2022).

Imago, male ( Fig. 74 ). Head ochre-brownish. Turbinate eyes dark reddish-brown. Thorax ochre-brownish, equally colored dorsally, laterally and ventrally. Wings colorless, veins ochre-brownish, C and Sc+ R proximad of costal brace darker. Pterostigma with simple, oblique crossveins. Hind wing with costal projection and two veins, second vein asymmetrically forked ( Fig. 75 ). Legs of all pairs uniformly light ochre. On middle and hind legs, tarsus with 2 apical spines, on 1st+2nd and 3rd tarsomeres. Abdominal terga and sterna I– VI colorless, translucent, with brown spots on spiracles; terga VII–X ochre-brownish. Cerci ochre.

Male genitalia ( Figs 82–85 ): Styliger without median sclerite (in contrast to N. minutus ). 1st segment of gonostylus narrowing from base to apex, angulate apically-medially. 3rd (terminal) segment of gonostylus elongate. Penial bridge non-sclerotized medially. Gonovectes with apices greatly thicken and darkened, so that well visible through styliger even in living specimens and specimens in alcohol ( Fig. 80 ).

Imago, female ( Figs 78–79 ). All abdominal terga ochre-brownish, sterna ochre with pair of brownish stripes laterally. Hind wing narrower than in male ( Figs 76–77 ). On fore leg, tarsus with 2 apical spines, on 2nd and 3rd tarsomeres.

Egg ( Figs 86–89 ). Asymmetric: one side bluntly cone-like pointed, opposite side evenly convex, hemi-ellipsoid. Convex surface evenly and regularly covered with relief consisting of round papillae surrounded by concentric folds. Conic surface partly with less expressed papillae, partly smooth. Micropyle wide, located on any part of egg.

Dimension. Fore wing length (and approximate body length): male 3.5 mm, female 4 mm.

Distribution. Oriental Region (known from India, Thailand and Java).

Comparison with N. gracilis . The species currently known as Nigrobaetis (Margobaetis) gracilis , was originally described by Bogoescu & Tabacaru (1957) based on larvae from Romania as « Baetis sp. nympha gracilis ». Sowa (1962) described imagines and larvae of B. gracilis from Poland, based on 2 male imaginal specimens (which he wrongly called «syntypy») and 3 larval specimens. Müller-Liebenau (1969) redescribed male imago and larva of B. gracilis based on imagines collected by Sowa in Poland and larvae collected by Tabacaru in Romania.

Nigrobaetis (Margobaetis) gracilis is closely related to N. (M.) klugei . Denticles on its larval cerci and paracercus have not been described. To reveal their features, we examined a last-instar male larva with label « Ukraine, Vyshkiv: Tysa (Visk: Tisza), 29.06.2004, Tibor Kovács»; it was kindly sent by T. Kovács and currently is deposited in ZIN. This larva differs from N. (M.) klugei by smaller lateral denticles on cerci and by absence of two long denticles on dorsal side of each 4th segment of paracercus.

Egg surface N. gracilis is covered by wide protuberances separated by narrow rings of threads ( Kopelke & Müller-Liebenau 1981: Abb. 20), in contrast to eggs of N. kluge , which bear small papillae surrounded by wide fields of fused threads ( Figs 86–89 ).

Comparison with N. tatuensis . The species currently known as Nigrobaetis (Margobaetis) tatuensis , was originally described based on two larvae from Taiwan as Baetis tatuensis Müller-Liebenau 1985 . However, figures in the original description were mismatched, so that the drawings of larval parts belonging to B. tatuensis were indicated as belonging to Baetis taiwanensis Müller-Liebenau 1985 (which is described in the same paper), and the drawings of larval parts belonging to B. taiwanensis were indicated as belonging to B. tatuensis . The photos of abdominal terga belonging to B. taiwanensis and B. tatuensis (Müller-Liebenau 1985: figs 14–15) are arranged in such a way that it is unclear which legend belongs to which figure. Because of this, Kang, Chang & Yang (1994) redescribed larva of B. taiwanensis under the wrong name « Baetis (Tatubaetis) tatuensis » and designated it as the type species of the subgenus Tatubaetis Kang, Chang & Yang 1994 ; they redescribed B. tatuensis under the wrong name « Baetis (Margobaetis) taiwanensis » and wrongly placed it in the newly established subgenus Margobaetis Kang, Chang & Yang 1994 . This confusion was revealed by Fujitani, Hirowatari, Kobajashi & Tanida (2004).

Nigrobaetis (Margobaetis) tatuensis is closely related to N. (M.) gracilis and N. (M.) klugei . Denticles on its larval cerci and paracercus have not been described neither by Müller-Liebenau (1985), nor by Kang et al. 1994. To reveal their features, we examined a mature male larva ready to molt to subimago with the label « Taiwan, Shanherchiaur, Linkuei, Kooshiung Hsien, 27.VII.1993, S.C. Kang»; it was used by Kang et al. 1994 for their description of « Baetis (Margobaetis) taiwanensis » and currently is deposited in ZIN. It differs from N. (M.) klugei by smaller lateral denticles on cerci and by absence of two long denticles on dorsal side of each 4th segment of paracercus. Difference between N. (M.) tatuensis and N. (M.) gracilis is not revealed yet.

Figures

FIGURES 44–52. Nigrobaetis (Margobaetis) klugei, larval exuviae. 44, head; 45, prosternum with fore leg; 46, mesosternum, metasternum and metanotum with hind protoptera, middle and hind legs; 47, 49, 51, abdomen; 48, 50, 52, half of pronotum and mesonotum.

FIGURES 53–54. Nigrobaetis (Margobaetis) klugei, larval exuviae. 53, labrum; 54, labium.

FIGURES 55–57. Nigrobaetis (Margobaetis) klugei, larval exuviae of tibia and tarsus. 55, fore leg; 56, middle leg; 57, hind leg.

FIGURES 58–68. Nigrobaetis (Margobaetis) klugei, larval exuviae. 58–60, fore, middle and hind legs; 61–63, paraprocts; 64–68, fragments of abdomen with tergalii I–VII.

FIGURES 69–71. Nigrobaetis (Margobaetis) klugei, larval exuviae of caudalii (dorsal view). 69, caudalii; 70, fragment of paracercus; 71, fragment of right cercus.

FIGURES 72–81. Nigrobaetis (Margobaetis) klugei. 72, subimaginal exuviae of meso- and metapleura; 73, subimaginal exuviae of mesonotum; 74, male imago; 75, hind wing of male imago; 76–77, hind wings of female imago (one and the same specimen); 78–79, female imago; 80, genitalia of male imago; 81, subimaginal exuviae of hind leg.

FIGURES 82–85. Nigrobaetis (Margobaetis) klugei, genitalia of male imago, ventral view. 82, with gonovectes retracted; 83–85, with gonovectes protracted (84, with focus on surface and sterno-styligeral muscle; 85, with focus on gonovectes and intersegmental sternal muscles). Abbreviations: m.IX-X, paired intersegmental muscles going to paraprocts base; m.s, median sterno-styligeral muscle.

FIGURES 86–89. Nigrobaetis (Margobaetis) klugei, eggs.