Mortogenesia mesopotamica (Morton, 1921)

Soldán, Tomáš & Godunko, Roman J., 2013, Description of larva, redescription of adults and biology of Mortogenesia mesopotamica (Morton, 1921) (Ephemeroptera: Palingeniidae), Zootaxa 3741 (2), pp. 265-278 : 267-275

Mortogenesia mesopotamica (Morton, 1921)

( Figs 1–17 )

Palingenia mesopotamica Morton, 1921: 177

Mortogenesia mesopotamica: Lestage, 1923: 110 ; Chopra, 1927: 122; Buldovsky, 1935b: 160; Lieftinck, 1949: 311; Demoulin, 1952: 10; Demoulin, 1965: 313; Karim, 1985: 25; Al-Zubaidi et al. 1987: 182; Soldán, 1997: 511

mesopotamica Morton 1921 [ Palingenia ]: Kluge, 2004: 255 (in Mortogenesia /g(1))

Palingenia euphratica: Bodenheimer, 1960: 42 ; Harpaz, 1973: 24 (nomen nudum)

Adult male. Body length 20.6–26.2 mm; length of forewings: 21.5–27.5 mm; length of hind wings 9.6–11.8 mm; length of cerci 25.0– 28.3 mm. Specimens from the Euphrates River and from Iran are evidently smaller in all the measurements than those from the Tigris River.

Head transversal, about twice as broad as long; occiput whitish-yellow, epicranial and ocellar sutures dark brown bordered; fronts and genae dark brown, clypeal area pale with a pair of dark smudges near frontal ocellus. The angle of epicranial suture extremely obtuse (about 120°). Ocelli white, black bordered frontal ocellus smaller by 1/2 than lateral ones; eyes greyish-black, rounded, distance between eyes approximately as long as the eye width. Genae with one bluntly pointed spine at the place of outer genal spine of larva; clypeus straight without any projections. Antennae approximately as long as head; length ratio scape/pedicel—3.3/2.4. Scape yellowish-white, pedicel and base of flagellum as broad as 1/2 of pedicel width, distal part of flagellum colourless, transparent. Atrophied mouthparts whitish, membranous but relatively well preserved. Mandibular tusks with 3–4 rounded projections, glossae, paraglossae and labial and maxillary palps of finger-like shape, well recognizable, sometimes with apparent segmentation.

Pronotum about three times broader than long, brownish-yellow with darker smudges; medial suture blackishdark; posteromedial and anterolateral areas pale. Oblique enterolateral ridges and insertions of endoskeleton behind eyes well apparent. Mesonotum: pleural sclerites and pteralia black (specimens from Iraq, Tigris River) or pitch brown (specimens from Iran, Karkheh River), unicolorous except for narrow white line along the medial suture. Metanotum and base of hind wings black or pitch brown; metanotum with large triangular yellowish spot in middle and medial oblong-shaped projection reaching to the middle of abdominal tergum I. Ventral side of thorax of the same colour, metanotum paler in the middle.

Forewings longer by 1/4 than abdomen, light brown to greyish-brown, unicolorous; longitudinal veins slightly darker, cross veins paler hardly recognizable. Hind wings greyish or milky, costal and subcostal veins and membranes slightly darker, with brownish stipping. Both longitudinal and transversal veins of the same colour as wing. Hind wings reach to the posterior margin of abdominal segment VI. For further detail of venation see the characteristics of the genus. Forelegs whitish-yellow, distal parts of femur, tibia and tarsal segments with brownish rings; middle and hind legs unicolorous whitish. Ratio coxa: trochanter: femur: tibia: tarsus—1: 0.81: 2.06: 2.25: 1.06 for forelegs. Tarsal formula (ratio of segments 1–5) forelegs 1: 1.06: 0.85: 0.67: 0.67; middle legs 1: 1.35: 0.88: 0.88: 2.65; hind legs 1: 1: 1: 1: 1: 3.7. Claws of forelegs similar, paddle-like, about twice longer than wide; those of middle legs similar, more slender, about four times longer than broad pointed at apex; claws of hind legs similar, their shape resembles those of middle legs.

Abdominal terga brown, distal half of terga I, II, VI, VIII and IX whitish-yellow; other terga with paler distal margin, all terga with narrow medial dark brown line and two pairs of divergent elongated spots or strokes (sometime fused) in the middle; tergum X with wide pale medial longitudinal band. Remnants of larval abdominal gills conspicuous, whitish and membranous on terga II–VII. Abdominal sterna whitish-yellow, unicolorous without any markings. In specimens from the Euphrates River, there is a pair of dark brown diffused sublateral smudges on all abdominal sterna especially apparent on sterna II–VI.

Forceps base light brownish, widely arc-shaped, incurred in the middle to about 1/2 of the base, regularly tapering apically. Their inner margins with distinct sclerotized ridge. Segments 2–7 gradually diminishing in the following sequence 1: 0.82: 0.64: 0.50: 0.36: 0.45; last two segments sometimes imperfectly separated. Penis lobes reaching to about 1/3 of the length of forceps segment 1; separated bellow the hind margin of subgenital plate. Their apex rounded (specimens from Iran) ( Fig. 1 ).

Cerci whitish, evenly covered with numerous pointed bristles; these bristles on apical third of cerci are 2–3 times longer than those on basal segments. Apical part of cerci transparent, colourless. Paracercus transparent with 6–8 segments, without any bristles.

Adult female. Body length 22.5–24.7 mm; length of forewing 17.5–18.8 mm; length of hind wings 7.5–8.0 mm; length of cerci 20.0– 22.6 mm.

Head roughly oblong-shaped, about twice broader than long, dark brown, occiput brownish-yellow. Lateral ocelli greyish, conspicuously dark bordered, frontal ocellus very reduced only as long as 1/4 of lateral one with blackish diffuse spots near its base. Eyes greyish-black, ocellar suture dark brown bordered; the distance between eyes twice longer than the eye width; epicranial suture as in males. Genae with two bluntly pointed spines corresponding to those of larvae. Outer spines yellowish, inner spines light brown, clypeal spines strongly reduced or absent. Scape and pedicel unicolorous whitish-yellow (length/width ratio—1/2.4). Flagellum sinuous, transparent. Remnants of mouthparts whitish, much more reduced than in males; mandibular tasks shorter by 1/2 with respect to those in male, without teeth. Other mouthparts not identifiable.

Pronotum light brown with pale sides and large diffuse pale smudge in the middle. Meso- and metanotum and ventral side of thorax of the same colour as in males. Forewings whitish-grey, slightly darker (brownish stippling) near the apex; longitudinal veins of the same colour or slightly paler; cross veins translucent hardly distinguishable; wings only slightly longer than abdomen. Hind wings reaching to the middle of abdominal segment VI, unicolorous whitish-grey. Venation of the same colour, indistinct.

Legs strongly reduced, unicolorous whitish. Foretibiae yellowish-brown. Femora of all legs strongly bowshaped, tibiae bent. The ratio coxa: trochanter: femur: tibia: tarsus: claws—1: 1: 2.16: 1.11: 0.74: 0.26 for forelegs; 1: 0.64: 1.18: 1.43: 0.75: 0.36 for middle ones and 1: 1: 1.85: 2.20: 0.45: 0.35 for hind legs.

Femora of forelegs, tibiae and tarsi of all legs with shrunken cuticle forming irregular ridges and groves. Tibia of foreleg with conspicuous fickler-like projection situated subapically on their outer margin. This blunt or rounded projection is directed forward and most probably represent distal larval tibial spine. Tarsal segments of all legs fused together, with completely eliminated segmentation. Claws simple on all leg pairs, blunt, slightly asymmetrical; those of middle legs longest.

Abdominal terga light brown or yellowish-brown, paler than in males, with the same markings; sterna I, VII and VIII whitish-yellow, markings inconspicuous. Abdominal sterna pale, whitish, without markings, slightly darker on the sides. Cerci whitish, unicolorous, without any signs of segmentation in distal half. Each segment of cerci uniformly covered with pointed bristles. Paracercus with 5–7 distinguishable segments and shrunken distal part, without any segmentation.

Eggs (dissected from female). Eggs lens-shape (i.e. biconvex in lateral view), oval dorsally, measuring 625– 635 to 759–778 Μm. Surface of chorion nearly smooth, with scarce submicroscopic structures resembling tubercles. Eggs provided with adhesive membrane similar to the genus Palingenia Burmeister, 1839 (Gaino & Bongiovanni 1993; Landolt et al. 1995).

Larva. Body length app. 28.5 (max. 31.3) mm; length of cerci app. 12.2 (max. 13.4) mm.

Head and thorax whitish-yellow or dark yellow, abdominal terga stippled with dark brown, imaginal markings very inconspicuous or indistinguishable; ventral side of body pale. Colour patterns described above apparent in 2 young larvae found in the Tigris River. Since only exuviae of mature larvae were studied, their coloration remains unknown.

Epicranial suture as in adults; the distance between compound eyes slightly shorter than the eye width in male larva. Genal spines pointed, dark brown; clypeal spines of irregular shape and position; in one specimen two clypeal spines distally notched. However, there are usually two pairs of clypeal spines, inner ones being by about 1/ 2 lower than outer spines. Both outer genal and clypeal spines with numerous bristles on their outer margins ( Figs 2–4 ).

Antennae about twice longer than head. Scape/pedicel length ratio—1/0.7, flagellum consisting of about 30 segments; most of them with a group of short bristles inserted near the posterior margin. Scape with a single strong bristle situated posteromedially. Labrum with rounded anterior margin and numerous bristles; length/width ratio at base—1/1.7 ( Fig. 6 ). Mandibular tusks about twice longer than wide, with 7 heavily sclerotized teeth; outer incisors regularly triangular, slightly asymmetric, distally notched; inner incisors oblong-shaped as long as outer ones, with

two bluntly pointed teeth ( Figs 7–8 ). Maxillae asymmetric with a single, very long and narrow acutely pointed chitinous spine and three groups of long bristles: ventral, dorsal and lateral ( Fig. 10 ). Segment 1 of maxillary palps oblong-shaped without any bristles; segment 2 oval, symmetric, about twice longer and strongly haired ( Figs 10– 11 ). Hypopharyngeal lingua nearly quadrate with straight interior margin, superlinguae oval with convex margins ( Fig. 9 ). Glossae asymmetric, shorter by 1/3 than paraglossae. Segment 1 of labial palps oval, with conspicuous basal group of very long and strong bristles situated medially. Segment 2 asymmetrical, spoon-shaped, twice longer than broad, with conspicuously convex inner margin ( Fig. 12 ).

Foretibia stout, with 10–13 outer sclerotized spines diminishing proximally; further 3–4 much smaller spines near the base of tibia ( Fig. 13 ). Middle tibiae with 4–5 relatively strong spines pointed apically (at least twice longer than the others). All spines bear conspicuous flat bristles near the basis ( Fig. 14 ). Hind tibiae with one central irregular row of spines and a group of spines along the outer margin ( Fig. 15 ). Fore claws with wide basis, bent, about twice as long as wide; middle and hind claws 3–4 times longer than wide at basis, acutely pointed and strongly hooked at the right angle. The ratio coxa: trochanter: femur: tibia: tarsus: claw—1: 0.40: 1.16: 1.37: 0.40: 0.24 for forelegs; 1: 1: 2.10: 2.60: 1.55: 0.95 for middle one and 1: 1.50: 2.60: 2.80: 1.30: 0.75 for hind legs.

Forewing pads unicolorous yellowish, with straight inner and outer margins. Hind wing pads as long as 1/2 of fore ones, oval, nearly symmetrical.

Gill 1 asymmetric leaf-like, ratio length/width 67/44, colourless, translucent, with distinct simple trachea. Gills 2–7 robust, whitish tracheization of the same colour. Posterior branch of gill 2 bluntly pointed, shorter by 1/3 than the anterior one; posterior branch of gill 6 of the same structure, shorter by 1/2 than the anterior one. Gill 7 with pointed and narrow posterior branch, as long as the anterior one. Marginal fringe of gill 2–7 rich and regular. Gills 2–7 with distinct branched central trachea in both anterior and posterior parts ( Figs 16–17 ).

Abdominal sterna with conspicuous groups of setae near the posterior margin. Forceps in male larva with distinctly separated basal segments (fused with following segment in adults) and 4 or 5 small apical segments; last segments separated imperfectly. Subgenital plate and forceps covered with flat, long and pointed setae. Penis lobes rounded without setae, gonopores well apparent in larval exuviae ( Fig. 5 ). Cerci as long as 1/2 of abdomen, with rich marginal fringe. Paracercus shorter by about 1/5. Cerci and paracercus covered with pointed scales, especially numerous on basal segments.

Material examined. 4 adult males, Iraq, Euphrates River, Hindiya Helia, 14.iii.1970, leg. M. S. Abdul Rassoul; 1 adult male, Iraq, Tigris River, Swaira, March 1984, leg. M. S. Abdul Rassoul; 1 adult male, Iraq, Tigris River, Kut, March 1984, leg. M. S. Salek; 2 male larval exuviae, Iraq, Tigris River, Kut, March 1984, leg. M. S. Abdul Rassoul; 5 adult males, 4 adult females, Iran, Karkheh (or Karkhen) River, Bsaitin, February 1981, leg. Zohair H. Mohsen; 2 young larvae, Tigris River, Huwaish (30 km N of Baghdad), 22.ix.1989, leg. T. Soldán, deposited at the Institute of Entomology, Biology Centre of the Academy of Sciences of the Czech Republic, České Budějovice. Type material was not studied.

Distribution of Mortogenesia mesopotamica

Although Mortogenesia mesopotamica was well-known to peasants and naturalists in the past centuries, the first record of its occurrence was published by Morton (1921) in the original description. Type locality is the Tigris River near Amara. Lestage (1923) and Demoulin (1965) considered the species “distributed in Mesopotamia ”. Chopra (1927) mentioned a single pinned male specimen deposited in the Madras Government Entomologist collection at Coimabatore in India which was collected by Mr. Duraisami at the Tigris River in Karradah, Baghdad on April 1920. As far as we know, further detailed record appeared after more than 70 years. Karim (1985) found adults of Mortogenesia in the vicinity of Basrah City. Since then, the species has been collected from the Tigris River near Kut town in Iraq (Al-Zubaidi et al. 1987). There is no doubt that M. mesopotamica is widely distributed within the lower drainage of the Tigris River. The northernmost occurrence in this river seems to be the locality of Huwaish town (about 40 km N of Baghdad) as undoubtedly documented by the findings of two young larvae and by personal communication of Dr. Nazain A. Ouda. We can suppose the larvae to live in the Tigris River a good distance upstream. However, any mass swarming has not been observed in Mosul City (about 380 km N of Baghdad). The finding of adults in the Euphrates River (see Material examined) represents the first record of M. mesopotamica in this river. Analogously to its distribution in the Tigris River, its mass occurrence in the Euphrates River is very likely.

The question is if species occurs also in the Shatt al-Arab, since the habitat and temperature conditions seem to be quite different from both the above-mentioned rivers. In 1981 Dr. Zohair H. Mohsen discovered M. mesopotamica in Iran (Karkheh River), at a locality somewhat separated from the Euphrates–Tigris basin. To conclude, this species seems to be distributed in lowland rivers of western part of Persian Gulf basin with restriction to respective clayey habitats up to about 100–200 m a.s.l.

Figures

FIGURE 1. Mortogenesia mesopotamica (Morton, 1921), adult male genitalia (ventrally).

FIGURES 2 – 5. Mortogenesia mesopotamica (Morton, 1921), male larval exuvia: 2, head and pronotum (dorsally); 3, head and pronotum (laterally); 4 head, clypeal spines (dorsally); 5, abdominal segments and genitalia (ventrally).

FIGURES 6 – 8. Mortogenesia mesopotamica (Morton, 1921), male larval exuvia: 6, labrum (dorsally; right part without setae); 7, 8, right and left mandibles (ventrally).

FIGURES 9 – 12. Mortogenesia mesopotamica (Morton, 1921), male larval exuvia: 9, hypopharynx (ventrally); 10, maxilla (ventrally); 11, segment 2 of maxillary palp (dorsally); 12, labial palp (ventrally).

FIGURE 13. Mortogenesia mesopotamica (Morton, 1921), male larval exuvia, foreleg (dorsally).

FIGURES 14 – 15. Mortogenesia mesopotamica (Morton, 1921), male larval exuvia: 14, middle leg (dorsally); 15, hind leg (dorsally).

FIGURES 16 – 17. Mortogenesia mesopotamica (Morton, 1921), male larval exuvia: 16, gill 2; 17, gill 6.