Crassabwa flava ( Crass 1947 )

Kluge, Nikita J., Gattolliat, Jean-Luc & Salles, Frederico F., 2017, Redescription of the Afrotropical genus Crassabwa Lugo-Ortiz & McCafferty 1996 (Ephemeroptera: Baetidae: Protopatellata), Zootaxa 4350 (3), pp. 401-435 : 408-419

Crassabwa flava ( Crass 1947)

( Figs 1–52 )

Centroptilum flavum Crass 1947: 78 (♀ and ♂ imago, larva; not subimago). Afroptilum flavum: Gillies 1990: 99 .

Crassabwa flava: Lugo-Ortiz & McCafferty 1996b: 238 (larva).

Material examined. TANZANIA: Iringa Region , Little Ruaha river 10 km upstream Iringa, 7°47'S / 35°48'E, 22– 26.VII.2016, coll. N. Kluge and L. Sheyko: 1 L-S/I ♂ , 16 larvae (ZIN); Iringa Region, Msosa river (tributary of Great Ruaha) in Msosa Camp (9 km S Mbuyuni), 7°33'S / 36°32'E, 5–10.VIII.2017, coll. N. Kluge & L. Sheyko: 8 larvae ( ZIN) ; border of Mbeya Region and Njombe Region, Great Ruaha river upstream Mfumbi ( 8 km E Chimala ), 8°52'S / 34°05'E, 26.VII–3.VIII.2016, coll. N. Kluge and L. Sheyko: 3 L-S-I ♂ , 1 L-S-I♀, 63 larvae (including L/S) (ZIN); the same date and collectors, 13–16.VIII.2017: 1 L-S-I♂, 1 L-S/I♂, 13 larvae (ZIN); Mbeya Region, Chimala river near Chimala, 12.VIII.2017, coll. N. Kluge: 3 larvae ( ZIN) ; Mbeya Region, Lufurio river near Tapio Bridge, 15 km NW Matema, 9°24'S / 33°55'E, 14–15.VIII.2016, coll. N. Kluge: 2 L-S-I ♀ , 15 larvae (ZIN); Tanga Region, Usambara Mountains, Sigi river near bridge 5 km upstream Amani , 5°08'02''S / 38°37'16''E, 19.VIII–2.IX.2016, coll. N. Kluge and L. Sheyko: 5 young larvae ( ZIN) . ZAMBIA: Luangwa river near Luangwa Bridge, 15°00'S / 30°13'E, 2–8.VIII.2014, coll. N. Kluge & L. Sheyko: 2 L-S-I ♂ , 1 L-S♂, 6 L-S-I♀, 2 L-S♀, 1 I ♀, 42 larvae (including L/S) (ZIN); West Lunga river near Mwinilunga , 11°45'S / 24°26'E, 14–17.VIII.2014, coll. N. Kluge & L. Sheyko: 1 larva ( ZIN) ; Maramba river in Livingstone, 17°51'S / 25°53'E, 24.VIII.2014, coll. N. Kluge and L. Sheyko: 2 larvae ( ZIN). SOUTH AFRICA , Limpopo basin, Kruger NP: near Malelane, Crocodile river , 25°24'S / 31°37'E, 17.V.2003, coll. J.- L. Gattolliat: 30 L ( MZL) ; near Skukuza Camp, Sabie river , 25°10'S / 31°60'E, 18.V.2003, coll. J.- L. Gattolliat: 6 L ( MZL) ; near Olifants Camp, Olifants river, 24°01'S / 31°40'E, 20.V.2003, coll. J.- L. Gattolliat: 48 larvae ( MZL); near Pafuri gate, Luvuvhu river , 22°25'S / 31°13'E - 22°26'S / 31°04'E, 22- 23.05.2003, coll. J.- L. Gattolliat: 3 L. Limpopo basin, Near Louis Trichardt, Mutshindudi river , 22°56'S / 30°23'E, 24.V.2003, coll. J.-L. Gattolliat: 2 L (MZL).

Descriptions. Larva. CUTICULAR COLORATION. As characterized above [see Crassabwa (1)]. Cuticle of fore protoptera with lines darker than background along convex longitudinal veins and lines lighter than background along concave longitudinal veins; crossveins without cuticular markings ( Figs 1–4 ).

HYPODERMAL COLORATION As characterized above [see Crassabwa (2)]. Before molt to subimago larva gets hypodermal coloration as in imago, including contrastingly dark brown marking on patella, sigmoid markings on sides of abdominal sterna and red coloration of proximal parts of cerci (see below).

STRUCTURE. Head and mouth parts as characterized above [see Crassabwa (3)–(10)]. Left mandible without setae between prostheca and mola; mola proximad of distal molar projection without large ridges, with straight row of fine processes ( Fig. 8 ; Crass 1947: 21g; Lugo-Ortiz & McCafferty 1996b: Fig. 3 ). Right mandible with dense setae between prostheca and mola; mola with 2 semicircular protuberances in distal part ( Fig. 9 ; Crass 1947: 21f; Lugo-Ortiz & McCafferty 1996b: Fig. 4 ). Inner-apical projection of 2nd segment of labial palp moderately large ( Fig. 5 ; Crass 1947: Fig. 21c ; Lugo-Ortiz & McCafferty 1996b: Fig. 6 ).

Legs as characterized above [see Crassabwa (12)–(16), (19)]. Fine colorless setae forming cross row near base of tibia and dispersed along posterior side of tibia and tarsus [see Crassabwa (14)] bifurcate; oblique part of this row on anterior side of tibia consists of 6–8 setae ( Figs 13–14 ). Claw relatively short, with distal portion (from distal denticle to apex) shorter than remainder part (from base to distal denticle); denticles unequal in two rows [see Crassabwa (19)]: two enlarged distal denticles in posterior row much smaller than two enlarged distal denticles in anterior row ( Figs 15 , 18–19 ).

Abdomen as characterized above [see Crassabwa (22)–(24)]; terga with various scales, from wide, short and blunt to narrow, long and pointed ( Figs 20–21 ); sterna I–IV without denticles, sternum V with vestigial denticles, sterna VI–IX with regular row of pointed denticles (as in Fig. 104 ). Tergalius of first pair lanceolate, nearly symmetric ( Fig. 24 ); in last larval instar its anal-proximal part narrowly bent down [see Crassabwa (25)] ( Fig. 23 ). Tergalii II–V subequal ( Fig. 25 ), tergalii VI–VII gradually smaller, with anterior margin more convex ( Figs 27–28 ). Most part of thick tracheae of tergalii pigmented by dark brown granules; tracheal branches arising from main trachea in costal direction poorly developed or absent. Brown band on dorsal cuticle of tergalius [see Crassabwa (26)] wider than main trachea and gradually narrowing distally, that makes wrong allusion that main trachea is abnormally wide and wedge-like ( Figs 1–3 , 25, 27–30 ). Tenth abdominal segment and caudalii as described above [see Crassabwa (28), (29)].

Subimago. CUTICULAR COLORATION. Head ocher with brown. Pronotum light brown. Mesonotum light brownish with colorless areas, with sutures in antero-lateral part contrastingly dark brown, parascutellum with contrasting dark brown macula on latero-posterior corner ( Fig. 35 ). Pleura and sterna of thorax light brownish with colorless membranes and certain sclerites dark brown ( Fig. 36 ). Legs light brown, fore tibiae and tarsi darker brown. Abdominal terga and sterna light brownish. Sternum IX of male subimago lighter than others, with darkened latero-anterior areas and median longitudinal stripe; styliger darkened; gonostyli dark brown ( Fig. 42 ). Cerci dark brown.

HYPODERMAL COLORATION. As in imago, but poorly visible through brown subimaginal cuticle.

TEXTURE. Tarsi covered by pointed microlepides [see Crassabwa (18)].

Imago, male ( Figs 31–32 ). Head, thorax and abdomen with hypodermal coloration forming ocher, orange, red or reddish-brownish areas [see Crassabwa (2)]. Turbinate eyes wide; facetted surface orange, sometimes bordered by thin brown line; stem whitish. Thorax varies from ocher ( Figs 31–34 ) to brown, equally dark on dorsal and ventral sides. Wings with membrane and veins colorless. Hind wing [see Crassabwa (21)] with or without cross veins ( Figs 51–53 ). Legs [see Crassabwa (17)] with hypodermal coloration varying from ocher to red-brown, either unicolor, or with more or less contrasting red band on middle of ocher femur; in all cases short proximal portion of tibia (on outer side limited by patella-tibial impression) contrastingly colored by very dark brown (hypodermal coloration probably caused by the same red pigment as other body parts). Abdominal terga either nearly unicolor orange, or with various orange and ocher maculation. Abdominal sterna lighter, mainly ocher; sterna II–IX always with pair of contrasting dark brown lateral sigmoid marks. Cerci in proximal part intensively colored by deep red to dark brown, in distal part colorless [see Crassabwa (2)]. Genitals ( Figs 37–41 ) poorly colored, ocher. Shape of unistyligers variable, their median projections [see Crassabwa (31)] vary from small to very long ( Figs 37–39 ). First segment of gonostylus varies from rectangular, with prominent inner-apical angle ( Fig. 39 ) to nearly conic; its median side with longitudinal concavity; distal part of median side covered by small spines. Before molt from subimago to imago, base of 2nd segment of future imaginal gonostylus is inserted into 1 st segment ( Fig. 44 ). Penial bridge [see Crassabwa (32)] with median part flexible and shallowly convex; gonovectes slender ( Figs 40–41 ).

Imago, female ( Figs 33–34 ). Head ocher. Thorax ventrally lighter than dorsally. Coloration of legs, abdomen and cerci as in male.

Eggs ( Figs 45–50 ). Elongate-oval, 0.17 mm length; chorion with relief characterized above [see Crassabwa (33)].

Dimension. Fore wing length of male and female 6–8.5 mm (up to 10 mm, according to Crass 1947).

Discussion. Originally, Centroptilum flavum was described as male and female imagoes, subimagoes and presumably associated larvae from «Mooi, Lions and Umgeni Rivers; Yarrow and Furth streams; Jackson's spruit, Curry's Post» in South Africa. According to the personal communication by Helen James (Albany Museum, South Africa), all syntypes are probably lost. So identification of this species can be based only on its original description. Identification of our specimens from Zambia and Tanzania as C. flava is based on the shape of hind wing ( Crass 1947: Fig. 20f ) and statements that female imago has «Abdomen ... ventrally pale buff yellow, with small purple sigmoid markings on each segment, laterally» and «Cerci distally pale yellow, proximally tinged with crimson» ( Crass 1947: 78). Crass did not report these characters for male imago, probably because they are the same as in female.

However, cerci of subimago were characterized as «whitish grey» ( Crass 1947: 78). In the specimens examined, red (or crimson) pigment of the proximal part of cerci locates in hypoderm; it appears during development of last instar larva, being retained both in subimago and imago; if subimaginal cuticle is very dark, this red pigmentation is invisible in subimaginal stage, but it is impossible to overlook this red pigmentation if subimaginal cuticle is light («whitish grey»). That means that subimagoes, ascribed by Crass (1947) to Centroptilum flavum , possibly belong to another species.

Male imaginal genitals were figured without projection of unistyliger ( Crass 1947: Fig. 21e ). In our specimens, this projection varies from large and prominent to rather small; if it is small and directed by its apex ventrally, it is poorly visible from ventral view and can be overlooked.

Larva, described by Crass (1947) was «assigned to the imago on its structural characters, especially the hindwing bud, on its size, and on the fact that it has been taken in the same localities as the imago». Rearing imagoes from larvae in Zambia and Tanzania confirms correctness of this association of larvae with imagoes. Larvae examined by us, agree with the Crass's description in coloration, shape of labium, mandibles, labrum, tergalii and claws ( Crass 1947: Figs 21a–c, f–i ).

However, larval claw was characterized as «elongate with two large and about four small denticulations» and figured with one row of such denticles ( Crass 1947: 80, Fig. 21i ); the same error was made by Lugo-Ortiz & McCafferty (1996b). All specimens examined by us have two rows of denticles; the second (posterior) row of denticles can be overlooked, because its two enlarged distal denticles are much smaller than two enlarged distal denticles of the anterior row ( Figs 15 , 18–19 ) [see Crassabwa (19)].

Maxillary palp was originally figured with thin second segment ( Crass 1947: Fig. 21d ). On the figure by Lugo- Ortiz & McCafferty (1996b: Fig. 5 ), which is based on material from South Africa, this segment is shown as wide with apical projection, that is in agreement with the specimens examined by us [see Crassabwa (8)].

Kimmins (1960) reported Centroptilum flavum from Jinja on Lake Victoria in Uganda, but did not give morphological comments. Among mayflies collected by N. Kluge at the same place in 2007, this species is absent.

Chutter (1963, 1970) reported Centroptilum flavum in the papers on hydrobiology of Vaal River basin in South Africa. Correctness of this species determination seems doubtful, because larvae were said to be found in the «stony backwaters» ( Chutter 1963: Table 17) and in the biotope «3», which is «stones out of current» ( Chutter 1970), while larvae of C. flavum cannot live in stagnant water.

Description of larvae from South Africa, attributed by Lugo-Ortiz & McCafferty (1996b) to Crassabwa flava , is in agreement with the specimens examined by us, if take in account corrections concerning tibial setation [see Crassabwa (14)] and structure of claws [see Crassabwa (19)].

Figures

FIGURES 1 – 4. Crassabwa flava, last instar larvae. 1 – 3, dorsal view; 4, exuviae of half of pronotum and mesonotum.

FIGURES 5 – 9. Crassabwa flava. 5, labium (at left ventral view, with muscles of glossa, paraglossa and palp shown by interrupted lines; at right dorsal view); 6, apex of maxilla, dorsal view; 7, dentisetae and setae of inner-dorsal row of another individual; 8 and 9, left and right mandible of penultimolarva with developing ultimolarval mandibles inside. Abbreviations: ds 1, ds 2, ds 3, dentisetae.

FIGURES 10 – 15. Crassabwa flava, larval legs. 10 – 12, fore, middle and hind legs, anterior view; 13, apex of femur and base of tibia of middle leg, anterior view (bifurcate setae on opposite side shown by interrupted lines); 14, outer side of fore tibia with cross row of bifurcate setae (arrows show three setae of this row); 15, claw (inner-posterior view).

FIGURES 16 – 19. Crassabwa flava, larval legs. 16, apex of fore tibia and base of tarsus (posterior view); 17, same, enlarged; 18, apex of claw; 19, claw.

FIGURES 20 – 22. Crassabwa flava, exuviae of larval abdomen. 20, submedian part of tergum III; 21, its part, enlarged; 22, anterior-lateral part of sternum III with lateral rugose convexity and bifurcate setae laterad and posteriad of it (scale as on Fig. 20).

FIGURES 23 – 30. Crassabwa flava. 23, tergalius I of last instar larva in natural condition; 24, tergalius I spread on slide; 25, tergalius II; 26, costal rib of tergalius of penultimolarva (developing compressed ultimolarval denticles shown by interrupted line); 27 and 28, tergalii VI and VII; 29, tergalii II (in normal condition) and III (with dorsal cuticle partly separated from tissues); 30, enlarged fragment of this separated cuticle.

FIGURES 31 – 36. Crassabwa flava. 31 – 32, male imagoes; 33 – 34, female imagoes; 35, half of exuviae of subimaginal mesonotum; 36, postsubalar sclerite of subimaginal exuviae (arrow shows concavity of dorsal margin of posterior-dorsal process).

FIGURES 37 – 39. Crassabwa flava, genitals of male imago, ventral view (internal sclerites and muscles shown by interrupted lines; on right side of Fig. 37 and on Figs 38 – 39 gonostylar muscles not shown; on Fig 38 gonoducts shown by dotted lines). 37, specimen from Luangwa; 38 – 39, specimens from Great Ruaha. Arrow shows median projection of dorsal wall of unistyliger. Abbreviations: gs 1, gs 2, gs 3, segments of gonostylus; mIX-X, places of attachment of muscles running to common base of paraprocts.

FIGURES 40 – 44. Crassabwa flava. 40, cuticle of penis after treating by alkali (at left dorsal view, at right ventral view); 41, the same, apical view (at right hidden under unistyliger, gonostylus removed); 42, subimaginal exuviae of sternum IX and genitals; 43, subimaginal gonostyli; 44, imaginal gonostylus developing under subimaginal cuticle. Large arrow shows median projection of dorsal wall of unistyliger. Abbreviations: gs 1, gs 2, gs 3, segments of gonostylus; gv, gonovectis; m. gv, apodemes of gonovectal muscle; pb, paired internal projection of penial bridge.

FIGURES 45 – 50. Crassabwa flava, eggs.

FIGURES 51 – 55. Wings. 51 – 53, Crassabwa flava, hind wings of three individuals; 54 – 55, Crassabwa ludmilae sp. n., fore and hind wings on one scale.

FIGURES 104 – 107. Crassabwa ludmilae sp. n., male genitals. 104, subimaginal genitals developing under larval cuticle; 105, exuviae of subimaginal genitals; 106, genitals of male imago, ventral view (unistyligers and gonostyli unnaturally brought together because of wrong fixation; internal sclerites and muscles shown by interrupted lines, right gonostylar muscle not shown; large arrow shows median projection of dorsal wall of unistyliger); 107, penis enlarged, ventral view (gonoducts shown by dotted lines). Abbreviations: gs 1, gs 2, gs 3, segments of gonostylus; gv, gonovectis; mIX-X, places of attachment of muscles running to common base of paraprocts; pb, paired internal projection of penial bridge; usg, unistyliger.