Prosopistoma helenae, Bojková, Jindřiška & Soldán, Tomáš, 2015

Bojková, Jindřiška & Soldán, Tomáš, 2015, Two new species of the genus Prosopistoma (Ephemeroptera: Prosopistomatidae) from Iraq and Algeria, Zootaxa 4018 (1), pp. 109-123 : 110-116

Prosopistoma helenae sp. n.

Larva. Notal shield (carapace) length along median suture 2.5 mm and total length of body 4.0 mm. Carapace wider than long, width 1.2–1.3 x length; head width 3 x length and 0.6 times carapace width. Carapace flange relatively wide ( Figs 1 A, 2).

Head: Head yellowish-brown unicoloured, antennae lighter. Compound eyes oval, blackish, slightly smaller than oval lateral ocelli ( Figs 1 A, 2). Epicranial suture weakly visible, passing through middle part of lateral ocelli, and between compound eyes and antennal bases ( Fig. 3 A). Antennae 6-segmented, third segment shorter (0.8 x times) than total length of segments IV–VI; antennae reaching anterior margin of head ( Fig. 3 A).

Mouthparts: Fore margin of labrum convex in medial part and straight laterally, with short fringe of thin setae ( Fig. 3 A). Dorsal surface of labrum densely covered with articulated tiny hair-like setae, without any apparent microstructures.

Outer canine of mandible with three apical teeth of approximately same length, inner one slightly longer ( Fig. 3 B). Outer margin of outer canine with 4–6 teeth, inner margin of outer canine with 3–5 teeth; first distal tooth large, conspicuous, more than twice as long and wider than others. Inner canine of mandible shorter by one third than outer one, rod-like, apically bifurcate, with a pair of elongate and narrow pointed teeth, with three subapical sharply pointed teeth (first tooth markedly longer than following teeth). Five serrated long setae arising from base of inner canine, first anterior seta shorter than remaining setae, and one long simple seta in the middle of outer margin of mandible. A field of setae and setal sockets medially to basally on mandible.

Maxilla with four dentisetae, three long and mildly serrated setae near base of dentisetae and one simple seta near base of galeolacinia ( Fig. 3 C). Maxillary palp 3-segmented, segment II long, distinctly longer than segment I (1.7–1.8 times).

Labium typical of Prosopistomatidae ( Fig. 3 D). Labial palps 3-segmented, reaching front margin of labium. Labial palp segment II 0.8 times length of segment I, segment III 0.5 times length of segment II.

Thorax: Carapace yellowish-brown, without any markings, carapace flange and distal part of carapace transparent ( Fig. 1 A). Posteromedial part of carapace distinctly concave ( Fig. 6 A).

Fore femora and coxa with reticulate pattern on dorsal surface consisting of scale-like hexagonal or pentagonal structures; dorsal margin of femora with over 20 fine and simple setae ( Fig. 4 ). Ventral margin of fore tibiae with six or seven large and pointed spines with pectinate inner margins (with about 6–7 acute teeth) and one long rounded seta on distal margin of tibiae; dorsal margin of tibiae with two simple setae submarginally; dorsal surface of tibia with several double (V-shaped) setae; ventral surface of tibia with 4–5 stout pointed setae ( Fig. 4 ). Fore tarsus with several long pointed setae along both dorsal and ventral margins and on dorsal surface.

Lamella of gill I apically not extended, but slightly asymmetric and rounded; fully-grown larva with about 8–9 major filaments branching of gill I ( Fig. 5 A). Gill II rectangular (ratio width/length 0.75), posterior margin evidently concave, outer lateral margin straight, inner lateral margin distinctly convex ( Fig. 5 A).

Abdomen: Abdominal segments VII–IX apparently round or even semi-circular with posterolateral projections asymmetric, with concave posterior margin and relatively narrow apex ( Fig. 6 A). Segment X oblong-shaped, distinctly longer than wide. Cerci retracted, hardly visible in dorsal view.

Imago. Not known.

Diagnosis. Larvae of P. helenae sp. n. can be separated from other Palaearctic species by the combination of characters and comparative ratios shown in Table 1 . Prosopistoma helenae sp. n. clearly differs from P. oronti and P. orhanelicum by the different number of antennal segments and the number of setae on right mandible ( Table 1 ). The shape of carapace is similar in these species ( Fig. 1 ), wider than long. However, the median part of posterior margin of carapace is convex in P. orhanelicum comparing to concave margin in P. helenae sp. n. and P. oronti and the ornamentation of the carapace is indistinct in P. helenae and P. orhanelicum comparing to distinct four-spotted dark brown ornamentation on anterior half of the carapace in P. oronti ( Fig. 1 ). Absence of ornamentation on the carapace of P. helenae was apparent also on fresh material in 1989, when it was examined for the first time. The number of pectinate spines on foretibiae in older larvae is similar in P. helenae sp. n. and P. oronti and higher in P. orhanelicum .

based on material described in Thomas et al. (1988): 23 larvae and parts on slides; Liban, l'Aouali au pont (Jisr) Bisri, v.–ix. 1979 –1980; A. Dia leg., coll. T. Soldán based on literature data ( Dalkıran 2009)

Larvae of P. helenae sp. n. have the same number of antennal segments reaching anterior margin of head as those of P. pennigerum , although antennal segment III is shorter in P. helenae sp. n. ( Table 1 ). At a glance, they differed by the shape and ornamentation of carapace and abdominal segments VII–X. Carapace of P. helenae sp. n. is distinctly wider than long, with wide flange and apparently concave medial part of posterior margin, and without ornamentation ( Figs 1 , 2). Abdominal segments VII–IX have clearly round posterior margins and narrow apical parts of their lateral processes ( Figs 1 F, 6A). In contrast, the carapace of P. pennigerum is longer than wide, with narrower flange and only shallowly concave medial part of posterior margin ( Figs 1 C, 6D). Its ornamentation is typical, with darker orange-brown lateral parts of carapace and darker parts above wing pads forming two lobes forwards ( Fig. 1 C). This pattern is apparent also on younger larvae. Abdominal segments VII–IX have angular posterior margins and wide apical parts of their lateral processes ( Fig. 6 D). Further, they have different shape of the apical part of gill I, rounded in P. helenae sp. n. and extended to a lobe in P. pennigerum , and slightly different shape of gill II ( Fig. 5 ). P. helenae sp. n. has fewer pectinate spines on foretibiae than P. pennigerum .

Type material. Holotype: older larva (parts on slides); Iraq, Mosul Province, Tigris River in Mosul; 36°19'54.3"N, 43°09'04.6"E, 190 m a.s.l.; 29.–30. ix. 1989; T. Soldán leg.

Paratypes: 12 larvae and parts on slides from the same locality as holotype.

The material is deposited in the collection of Institute of Entomology, Biology Centre, Czech Academy of Sciences, České Budějovice, Czech Republic.

Type locality. Prosopistoma helenae sp. n. was collected in the Tigris River in Mosul near the bridge where the river channel was relatively wide (150–200 m) and formed islands, lagoons and short lateral channels ( Fig. 7 A). Larvae were not collected in the habitats with slow and uniform flow prevailing in the main channel of the river, but only in riffles and swift flow below an impoundment on lateral channel ( Fig. 7 B). The lateral channel was about 15–20 m wide and about 20–40 cm deep (max. depth about 1 m) with medium current velocity and turbid water. Larvae lived predominantly under cobbles sparsely overgrown with green algae, accompanied by larvae of Labiobaetis sp., Baetis gr. fuscatus, Serratella ignita and Caenis cf. luctuosa (no Heptageniidae or Leptophlebiidae were found).

Etymology. The species is named after Helen Barber-James (Grahamstown, South Africa), an expert and enthusiast on the family Prosopistomatidae .

Figures

FIGURE 1. A— Prosopistoma helenae sp. n. (paratype), B— Prosopistoma alaini sp. n. (paratype, mature larva), C— Prosopistoma pennigerum (mature larva), D— Prosopistoma oronti (immature larva), E— Prosopistoma oronti (carapace and abdomen of mature larva), F— Prosopistoma helenae sp. n. (detail of abdomen), G— Prosopistoma alaini sp. n. (detail of abdomen).

FIGURE 3. Prosopistoma helenae sp. n., A—head of larva as seen flattened under a compound microscope preparation, Bright mandible, C—right maxilla, D—labium, left ventral view, right dorsal view.

FIGURE 4. Prosopistoma helenae sp. n., foreleg of larva with enlargement of scales covering the surface of coxa and femur and pectinate setae on tibia.

FIGURE 5. Gill I (left) and gill II (right) of larva. A— Prosopistoma helenae sp. n., B— Prosopistoma alaini sp. n., C— Prosopistoma pennigerum, D— Prosopistoma oronti, E— Prosopistoma orhanelicum (according to Dalkıran 2009).

FIGURE 6. Detail of posterior part of carapace and abdominal segments VII – X. A— Prosopistoma helenae sp. n., B— Prosopistoma alaini sp. n., C— Prosopistoma orhanelicum (according to Dalkıran 2009), D— Prosopistoma pennigerum, E— Prosopistoma oronti.

FIGURE 7. Tigris River, the type locality of Prosopistoma helenae sp. n. A—stream channel at the type locality, B—habitat where the type material was collected. (photos T. Soldán).

Tables

TABLE 1. Comparison of the West Palaearctic species of the genus Prosopistoma.

	Prosopistoma pennigerum	Prosopistoma helenae sp. n.	Prosopistoma oronti *	Prosopistoma orhanelicum **	Prosopistoma alaini sp. n.
Total body length	4–6 mm	4 mm	3.5–4 mm	5.5 mm	4.1–4.7 mm
Ornamentation of carapace	distinct	indistinct	distinct	indistinct	indistinct
Ratio head width/length	2	3	2.3	2.3 (variability: 2–2.5)	2.1
No. of antennal segments incl. scape and pedicel Antenna reaching / not reaching anterior margin of head Length ratio antenna seg. III / remaining segments of flagellum No. of setae on right mandible	6 5 (Vayssière 1890) reaching equal (1.05) 7–8	6 reaching shorter (0.8) 5	5 not reaching longer (1.3) 7–9	7 not reaching shorter 7	7 not reaching shorter (0.6) 8–9
No. of subapical teeth on outer margin of outer canine No. of subapical teeth on inner margin of outer canine No. of subapical teeth on inner canine Ratio length of seg. I / seg. II of maxillary palps Ratio length of seg. II / seg. I of labial palps Shape of distal medial margin of carapace Ratio carapace width / length	6–8 6–7 3 0.6–0.7 0.8–0.9 shallowly concave 0.8–0.9	4–6 4–5 3 0.6–0.7 0.7–0.9 distinctly concave 1.2–1.3	6–9 4–5 3 0.6–0.7 0.8–0.9 distinctly concave 1.1–1.2	7–8 6–7 3–4 0.5–0.7 0.7–0.9 convex 1.1–1.4	5 5–7 3–4 0.5–0.6 0.8–0.9 weakly concave, almost straight 1.1
Apex of lamella of gill I	extended lobe	rounded asymmetrically	rounded symmetrically	rounded symmetrically	extended lobe
Lateral outer margin of gill II	concave	straight	concave	concave	concave
No. of major filaments branching of gill I No. of pectinate spines on inner margin of foretibia Abdominal segments VII-IX	8–9 10–11 angular	8–9 6–7 round	8–9 6–7 angular	11–12 9–10 angular	8–9 10–14 angular