Prosopistoma alaini, 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 : 116-120

Prosopistoma alaini sp. n.

Larva. Notal shield (carapace) length along median suture 3.1 mm and total length of body 4.7 mm. Carapace slightly wider than long, width 1.1 x length; head width 2.1 x length and 0.6 times carapace width ( Figs 1 B, 8).

Head: Head yellowish-brown unicoloured, antennae lighter. Compound eyes oval, blackish, slightly smaller than roughly oval lateral ocelli ( Fig. 8). Epicranial suture well-visible, passing through posterior margin of lateral ocelli, and between compound eyes and antennal bases ( Fig. 8 A). Antennae 7-segmented, third segment markedly shorter (0.6 x times) than total length of segments IV–VII; antennae not reaching anterior margin of head ( Fig. 9 A).

Mouthparts: Fore margin of labrum markedly convex in medial part and straight laterally, lateral parts fringed with long fine setae ( Fig. 9 A). Dorsal surface of labrum pitted.

Outer canine of right mandible with three apical teeth equal in size; inner margin of outer canine with five teeth increasing in size towards apex and outer margin of outer canine with 5–7 wide teeth closely adjoining below ( Fig. 9 B). Inner canine of right mandible shorter and narrower than outer, with two short and wide apical teeth of similar size, four long acute teeth in outer margin of canine below apex and three long acute teeth in inner margin of canine below apex. Eight or nine long and serrated setae arise from base of inner canine, first anterior setae shorter than remaining setae. A field of rich setae and/or setal sockets medially to basally on mandible.

Maxillae crowned by rigid canine and four subequal moveable dentisetae; three stout and mildly serrated setae near base of dentisetae, one long reaching length of dentisetae and two shorter of about one fifth of length of longer setae ( Fig. 9 C). Maxillary palps 3-segmented, segment II very narrow and long, distinctly longer than segment I (about 1.8–1.9 times).

Labium typical of Prosopistomatidae ( Fig. 9 D). Labial palps 3-segmented, reaching front margin of labium. Labial palp segment II 0.8 times length of segment I, segment III 0.4 times length of segment II.

Thorax: Carapace yellowish-brown, without any distinct markings, abdominal segments slightly brownish tinted ( Fig. 1 G). Wing pads and their basis of teneral subimago well-recognisable in mature larva ( Fig. 1 B). Carapace flange transparent but not apparently translucent, relatively wide. Posteromedial part of carapace weakly concave, almost straight ( Figs 1 G, 6B).

Fore femora and coxa with ornamentation on dorsal surface consisting of scale-like structures; dorsal margin of femora with numerous fine and simple setae ( Fig. 10 ). Ventral margin of fore tibiae with 8 large and pointed spines, with pectinate inner margins (with about 4–5 acute teeth) proximally following by 6–7 thin pointed spines (probably also pectinate), and with one long rounded seta on distal margin of tibiae; dorsal surface of tibia with about 20 double setae; ventral surface of tibia with about 10 long, stout pointed setae along entire length of tibia. Foretarsus with several long pointed setae along both dorsal and ventral margins and on dorsal surface.

Lamella of gill I apically extended into a lobe; mature larva with about 8–9 major filaments branching of gill I ( Fig. 5 B). Gill II rectangular (ratio width/length 0.8), posterior margin and outer lateral margin concave, inner lateral margin distinctly convex.

Abdomen: Anterior part of abdominal segment VII covered by carapace; abdominal segments VII–IX apparently angular with straight posterior margins; posterolateral projections nearly symmetric, with straight inner margins and relatively wide apices ( Figs 1 G, 6B). Segment X rectangular, wider than long. Cerci retracted, not visible in dorsal view.

Diagnosis. Larvae of P. alaini sp. n. can be told apart from other Palaearctic species by the combination of characters and comparative ratios shown in Table 1 . Carapace of Prosopistoma alaini sp. n. is wider than long like in P. orhanelicum , P. oronti and P. helenae sp. n., but with weakly concave, almost straight, medial part of posterior margin and posterior margin of carapace gently slopes rearwards covering anterior half of abdominal segment VII ( Figs 1 , 6 ). Unlike P. oronti and P. pennigerum , it has no distinct ornamentation. The number of antennal segments is higher than in P. pennigerum , P. helenae sp. n. and P. oronti and despite high number of antennal segments, antennae do not reach anterior margin of head ( Fig. 7 A). Further, P. alaini sp. n. differs in the number of setae on right mandible and pectinate spines on foretibiae ( Table 1 ).

Larvae of P. alaini sp. n. are the most similar to those of P. orhanelicum ; common features include the number of antennal segments not reaching anterior margin of head, no distinct ornamentation on carapace and angular abdominal segments VII–IX ( Table 1 ). P. alaini sp. n. has more setae on right mandible, different shape of inner canine of mandible (short and wide apical teeth) and gill I (lamella with extended apex and much less rich branching; Fig. 5 ), and almost straight posterior margin of carapace (comparing to convex carapace of P. orhanelicum , Fig. 6 ). The number of spines on foretibiae is high in both species, but probably higher in P. alaini sp. n. Mature larva of P. alaini sp. n. has eight thick pectinate spines that are followed by six or seven thin setae in the proximal third of foretibiae ( Fig. 9 ). Mature larva of P. orhanelicum has up to nine, rarely ten, spines which are both pectinate and simple according to Dalkıran (2009) (six thick pectinate spines followed by several simple thin spines were depicted).

Type material. Holotype: mature larva (parts on slides); Oued Isser, Sidi Abdelli; 300 m a.s.l., 16. vi. 1982; J. Gagneur leg. Grid reference of the type locality is not available.

Paratypes: 1 mature larva and 1 mature larva on slides from the same locality as holotype.

Deposited in the collection of Institute of Entomology, Biology Centre, Czech Academy of Sciences, České Budějovice, Czech Republic.

Etymology. The species is named after Alain G.B. Thomas (Toulouse, France), an outstanding expert on the North African aquatic fauna and mayflies in general.

Remarks. Prosopistoma alaini sp. n. is known only from Oued Isser in Algeria. Material collected in Oued Tizguid near Ifrane in the Middle Atlas Mountains in Morocco ( Touabay et al. 2002) could belong to this species as well. We visited Oued Tizguid below Ifrane in May 2014, however, we did not find any specimen of Prosopistoma there. The species could be extirpated due to strong water pollution there.

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 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).

FIGURE 9. Prosopistoma alaini 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 10. Prosopistoma alaini sp. n., foreleg of larva with enlargement of scales covering the surface of coxa and femur and pectinate setae on tibia.