Perlodes thomasi Vinçon, Dia & Kovács, 2013

Vinçon, Gilles, Dia, Aref, Kovács, Tibor & Murányi, Dávid, 2013, A New Stonefly From Lebanon, Perlodes Thomasi Sp. N. (Plecoptera: Perlodidae), Illiesia 9 (3), pp. 18-27 : 20-23

Perlodes thomasi Vinçon, Dia & Kovács sp. n.

( Figs. 2 a-e, 3a-d, 4a-d, 5 right)

Material examined. Holotype male: northern Lebanon, western slope of Lebanon Mount, Ouâdi Qâdîcha torrent , 1500 m a.s.l., about 500 m above the village of Bcherré, Abou Aali water basin, 18.05.1996, deposited in the Zoology Museum of Lausanne ( ZML) ( Fig. 1 , station 1b). One female paratype, same location and date, in the ZML. One larva, 24.04.1996, same location, also in the ZML . Other material from the same locality: 1♂, 1♀, 30.05.1995, 1 larva, 24.04.1996 (in the collection of G. Vinçon); 25 larvae, 24.4.1996; 18♂, 7♀, 8 larvae, 2 exuviae, 18.05.1996; 2♂, 6♀, 15 larvae, 6.05.1999; 7♂, 5♀, 30.05.1999. Qâdîcha spring, resurgence of the Abou Aali stream, 1760 m a.s.l. ( Fig. 1 , station 1a), 8♀, 30.05.1995; 10♀, 15.06.1996; 4♀, 9.07.1995.

Description. Medium sized Perlodes species : ♂ body length 1.5-1.6 cm, ♀ 2.0- 2.2 cm. ♂ micropterous with relative wing length (RWL) between 1.1 and 1.3 (RWL = wing length / head width at the position of eyes). ♀ normal winged (wing length: 2.4-2.6 cm). General colour brown. Head dark brown except yellowish occiput and oval yellow spot in the ocellar triangle ( Fig. 2a ); two dark spots on each side of the occiput, behind the compound eyes. Antennae dark brown. Median part of pro- and mesonotum with lateral dark brown patterns and contrasting median yellowish strip. Legs brownish.

Male genitalia. The paraprocts are nearly pyramidal, mostly membranous on their inner side and protected by a wide outer sclerite that narrows progressively towards the tip of the paraproct. This expansion of the sclerite ends in a thin blade, extending around the tip of the paraproct; it is more visible in ¾ view ( Fig. 2c ) than in lateral view ( Fig. 2d ). The membranous part of the paraprocts is of very variable size, from hardly turgescent ( Figs. 2 c-d) to strongly turgescent ( Fig. 2e : male with everted penis). The penis is often not visible since it is retracted in the abdomen; in some specimens it could be reverted (perhaps during mating or due to finger pressure of the collector); it is fully membranous and of complicated structure comprising two wide lateral lobes extending on each side of the abdomen tip, two upper lobes with a median depression and two less developed posterior lobes ( Fig. 2e ).

Female genitalia. Subgenital plate wide, semicircular, with rounded edges and shallow median depression on the outer edge. The plate sides nearly reach the lateral edges of the abdomen. Two lateral dark spots occur near the anterior edge of the plate ( Fig. 2b ).

Larva ( Figs. 3 a-c). Head brownish, with a wide yellow marking covering the occiput and an oval median yellow spot between the three ocelli ( Fig. 3a ). M-line yellowish, sinuous and poorly visible. The lacinia is typical of the genus Perlodes , with a very strong outer tooth, gently curved over its length, and one inner tooth which is about twice as long as the smaller. Two strong bristles are visible, one on the inner edge of the lacinia, proximally to the smaller tooth, and the other between the two teeth ( Fig. 3b ). Paraprocts triangular, well sclerotized, and covered with only few scattered short spine-like bristles ( Fig. 3c ).

Egg ( Figs. 4 a-d). Exceptionally large (about 0.5 mm length and 0.4 mm width), bullet-shaped. The ridges of the egg are clearly visible, rather thick and bulged (not flat). The hatching line is strong, bulged, well delimiting the operculum. The attachment disc is flanked by several concentric rows of peripheral cells similar to the petals of a flower. These cells are placed on the anterior surface of the attachment disc (surface of the disc connected to the base of the egg). Therefore, the cells are more visible in lateral view ( Fig. 4a ) than in basal view ( Fig. 4b ). The cells of the inner rows are rounded and smaller than those of the outer rows that are more oval or even quadrangular ( Figs. 4c ). Numerous mushroom-like globules are gathered on the surface of the attachment disc near its outer edge ( Fig. 4 b-c). The chorionic surface is covered by a conspicuous polygonal network of follicular cell impressions (FCIs) ( Figs. 4a, d ). The surface of each polygon is covered by several rounded granulations ( Fig. 4d ).

Affinities. In the genus Perlodes , P. thomasi sp. n. shares a very distinct position together with P. floridus floridus from the Balkan Peninsula and P. floridus peloponnesiacus from the Greek Peloponnes. Both species have bullet-shaped eggs with a distinctive flower-like attachment disc ( Figs. 4 b-c, 4fg). Nevertheless, the eggs of P. thomasi sp. n. are about one third wider and longer than those of P. floridus floridus and P. floridus peloponnesiacus ( Figs 4a, 4e , 5 ). The chorion is covered by a network of conspicuous convex polygonal cells FCIs ( Fig. 4d ), while that of P. floridus floridus just shows hardly visible depressions and is densely covered with numerous rounded globules ( Fig. 4h ). In P. floridus peloponnesiacus the polygonal cells of the chorion are concave instead of convex ( Kovács et al. 2012, Figs 12, 13, 15). The male paraproctal sclerite is also different: in P. thomasi the sclerite expansion is short, narrowing quickly toward the tip ( Fig. 2c ), while in P. floridus it is more elongated and slender ( Kovács et al. 2012, Fig. 3a ). In both species the apex of the sclerite of the paraproct turns around the tip of the paraproct, just as in P. jurassicus and to a lesser degree for P. intricatus ( Lubini et al. 2012, Vinçon, Murányi & Kovács in prep.). In P. microcephalus the sclerite of the paraproct ends in a rather long thin expansion that is just slightly curved at the tip, and in P. dispar the sclerite of the paraproct is very short with a rounded apex ( Marten 1991, Lubini et al. 2012).

Etymology. This species is named in honor of Prof. Alain Thomas (Toulouse) for his important contributions to the knowledge of Mediterranean aquatic Insects, especially Ephemeroptera.

Figures

Fig. 2. P. thomasi sp. n. a: male head (2 mm), b: female subgenital plate (2 mm), c: male paraproct in ¾ view (0.5 mm), d: male paraproct in side view (same scale), e: male everted penis (2 mm).

Fig. 1. Map of Lebanon, with the two collecting sites for Perlodes thomasi sp. n.

Fig. 3. P. thomasi sp. n. larva. a: head (5 mm), b: maxilla (1 mm), c: paraprocts (1 mm).

Fig. 4. Comparison of the eggs of P. thomasi sp. n. (a-d) and P. floridus (e-h). a, e: egg in side view; b, f: attachment disc; c, g: peripheral cells of the attachment disc; d, h: chorion ornamentation; a, b, f, e same scale.

Fig. 5. Perlodes eggs, from left to right: P. floridus floridus, P. floridus peloponnesiacus and P. thomasi sp. n.