Synorthocladius federicoi, Lencioni & Moubayed, 2021

Lencioni, Valeria & Moubayed, Joel, 2021, Synorthocladius federicoi sp. nov., a new species occurring in the middle basin of the Adige River, northern Italy (Diptera, Chironomidae, Orthocladiinae), ZooKeys 1057, pp. 105-116 : 105

Synorthocladius federicoi sp. nov.

Material examined.

Holotype: adult male, leg. L. Latella; Adige River in the city of Verona, Veneto Region, Italy (altitude = 61 m a.s.l.; 45°26'58.68"N, 10°58'52.81"E); 13 April 2020.

The holotype (on one slide and abdomen in one tube) is deposited in the entomological collection of MUSE-Museo delle Scienze , Trento, Italy (Accession number: cINV0017_s61v73) .

Etymology.

The new species is named ' Synorthocladius federicoi ' after Federico, the first author’s son, who has an inherited passion for insects and contributed to the collection of chironomids with the light trap.

Diagnostic characters.

Head: Frontal tubercles broadly semi-circular, coronal triangle and coronal suture reduced, coronal setae absent; temporals 6; last flagellomere of antenna bilobed apically, with numerous curved sensilla chaetica; AR 0.90. Palpomere 3 without sensilla coeloconica. Clypeus inverted safety helmet shaped, with 5 setae. Thorax: Lobes of antepronotum not gaping, thinner basally; acrostichals 2; dorsocentrals 7-8, uniserial; prealars 4; humeral pit absent; scutellars 6; squama with 4-5 setae. Legs. Sensilla chaetica on tibiae and tarsomeres ta1-ta5 of PI-PII, only on tarsomeres ta1-ta5 of PIII. Abdomen: Tergites II-VI with a unique distribution of setae in two longitudinal rows. Tergite IX broadly semicircular, bearing a hump, postero-median and caudal areas with 15 setae mostly located close to base of anal point. Anal point triangular, short and sharply pointed, distinctly curving upwards distally. Sternapodeme orally projecting; phallapodeme unusual comma-like. Virga present, branched apically. Gonocoxite with dorsal distal half parallel-sided; ventral side broadly expanded, bearing several stout setae placed in 2 arched rows. Superior volsella swollen. Inferior volsella subtriangular, inwardly projecting into a spherical lobe, which is hyaline and bare. Gonostylus atypically shaped; globular when viewed dorsally, bean-like in ventral view; crista dorsalis absent; megaseta well developed, tongs-like, visible only in dorsal view.

Description.

Adult male (n = 1; Figs 1A, C-D, F, H, J, L ; 2A, C-I ). Medium- to large-sized Synorthocladius species. Total length 2.35 mm. Wing length 1.85 mm. TL/WL = 1.27.

Colouration. Blackish species with greenish to brownish legs. Head dark brown including eyes and pedicel; antenna brownish. Thorax with contrasting blackish to dark green mesonotal stripes, area between thoracic stripes greenish; scutellum distinctly contrasting, blackish to brownish. Wing pale brown. Anal segment brown to dark brown with contrasting dark brown to pale gonostylus.

Head. (Fig. 1A ). Eyes bare, hairs absent on inner lateral margin; frontal tubercle spherical and well developed; coronal suture reduced, coronal setae absent; temporals 6, uniserial, including 4 inner and 2 outer verticals. Antenna 13-segmented, 790 µm long; last flagellomere (Fig. 1C-D , apical part) 265 µm long, strongly clubbed and bilobed apically, bearing numerous characteristic curved sensilla chaetica; antennal groove begins on segment 3 and reaches the last flagellomere; AR 0.9. Palp 5-segmented, segments 1-2 fused; length (in µm) of segments: 30, 45, 70, 65, 125; palpomere 3 (Fig. 1F ) with 2 sensilla clavata, sensilla coeloconica absent. Clypeus (Fig. 1H ) inverted safety helmet shaped, with 5 setae in 3 rows.

Thorax. Lobes of antepronotum (Fig. 1J ) not gaping and thinner dorsally; acrostichals 2, starting about 150 µm from tip of antepronotum; dorsocentrals 7-8, uniserial; prealars 4; humeral pit absent, notopleural suture (Fig. 1L ) with parapsidal fork bent forwards; scutellum with 6 uniserial setae, inserted medially (3 on each side of the midline); preepisternum bare.

Wing. Brachiolum with 1 seta. Number and distribution of setae on veins: R, 5; R1+2, 0; R2+3, 1; remaining veins bare; squama with 4-5 setae in 1 row.

Legs. Femora of PI and PII subequal, tarsomere ta5 of PI-PIII of same size (100 µm long). Tibial spurs present on PI-PIII; length (in µm) of spurs: 50 (PI), 60 (PII), 25 (PIII); pseudospurs absent. Sensilla chaetica present on tibiae and tarsomeres ta1-ta5 of PI-PII, only present on tarsomeres ta1-ta5 of PIII. Length (µm) and proportions of legs as in Table 1 .

Abdomen. Tergites II-VI (Fig. 2A ) with a novel chaetotaxy: two longitudinal rows of setae, 3 to 6 setae on each side of the midline, fewer on tergites V and VI. Hypopygium as in Fig. 2C (dorsal) and G (ventral, with tergite IX, anal point and gonostylus ommited). Tergite IX about 50 µm long and 100 µm maximum width, broadly semi-circular, postero-median and caudal areas with 15 setae (5 located medially, 10 mostly located close to base of anal point); a distinct hump present medio-dorsally, clearly visible in lateral view (Fig. 2D ). Anal point (Fig. 2C, D ) 25 µm long, 30 µm wide at base, triangular, short and sharply pointed apically, distal part markedly curved upwards (when viewed laterally as in Fig. 2D ), basal margin broadly semi-circular. Laterosternite IX with 8 setae (4 on each side). Sternapodeme and phallapodeme as in Fig. 2G , transverse sternapodeme bowed anteriorly; phallapodeme unusual, comma-like. Virga (Fig. 2C, I ) well developed and branched apically. Gonocoxite 160 µm long, 80-90 µm wide at base; widest at base and rounded apically; dorsal distal half parallel-sided; ventrally broadly expanded (Fig. 2G ), the lobe occupying about 75% of the total length of the gonocoxite, with several stout setae placed in 2 arched rows. Superior volsella swollen. Inferior volsella (Fig. 2C, H ) broadly subtriangular at base, inwardly projecting and narrowing into a spherical transparent apex; anterior margin concave, with sclerotization; posterior margin convex, with 3-4 stout setae in 1 row. Gonostylus 55 µm long, 35 µm maximum width, atypically shaped for the genus as shown in Fig. 2C, E, F , globular or bean-like (depending on the angle of view); dorsally (Fig. 2C ) with 3-4 stout setae located on distal and lateral parts, anteriorly with distinct sclerotization; ventrally (Fig. 2F ) with conspicuous sclerotization anteriorly, with stout setae in a circular row; crista dorsalis absent; megaseta (Fig. 2C, E ) 10-12 µm long, tongs-like and well-developed, inserted dorsally halfway from the apex, only visible in dorsal view. HV (total body length divided by length of gonostylus 10 times) = 4.27; HR (length of gonocoxite divided by length of gonostylus) = 2.91.

Female, pupa and larva: unknown.

Differential diagnosis.

According to Ashe and O’Connor (2012), currently there are six valid Synorthocladius species reported from the Palaearctic Region: S. asamasecundus Sasa & Hirabayashi, 1991, S. ginzanpequea (Sasa & Suzuki, 2001), S. mongolwexeus (Sasa & Suzuki, 1997); S. semivirens ; S. tamaparvulus Sasa, 1981 and S. tusimoijekeus (Sasa & Suzuki, 1999).

The new species is a Synorthocladius based on characters provided in the generic descriptions of Cranston et al (1989) and Liu and Wang (2005): small species (wing length 1.85 mm); antenna with 13 flagellomeres, with groove beginning on flagellomere 3, apical flagellomere with characteristic curved sensilla chaetica, antennal ratio less than 1 (0.9); eyes bare, temporal setae few (6), uniserial; antepronotal lobes fused medially, acrostichals few (2), dorsocentrals and scutellars uniserial; wing membrane without setae, squama with sparse setal fringe (4/5); anal point short and without setae; inferior volsella bilobed. However, S. federicoi sp. nov. is very different from previously described species in the following respects:

Frontal tubercles broadly globular (Fig. 1A); indistinct in S. semivirens (Fig. 11B), absent in S. tamaparvulus (Sasa 1981, fig. 11B);

Inner temporals of 4 setae in 1 row (Fig. 1A); with a single seta in S. semivirens (Fig. 1B);

Last flagellomere of antenna distinctly bilobed apically (Fig. 1C, D); rounded and simply clubbed in S. semivirens (Fig. 1E) and S. tamaparvulus (Sasa 1981, fig. 11C);

Lobes of antepronotum not gaping (Fig. 1J); gaping in S. semivirens (Fig. 1K);

Notopleural suture with parapsidal branch arched (Fig. 1L); sinuate in S. semivirens (Fig. 1M);

Unusual pattern of setae on tergites II-VI (Fig. 2A); more generally distributed in S. semivirens (Fig. 2B) and S. tamaparvulus (Sasa 1981, fig. 11F);

Tergite IX with a distinct hump (Fig. 2D); linearly elongate in S. semivirens (Fig. 2J);

Basal part of anal point semi-circular and slightly bent downwards (Fig. 2C, dorsal; Fig. 2D, lateral); sub-circular and strongly projecting downwards in S. semivirens (Fig. 2K, dorsal; Fig. 2J, lateral);

Virga branched (Fig. 2C, I); absent in S. semivirens and S. tamaparvulus;

Inferior volsella broadly subtriangular basally, narrowing towards apex and ending in a unique (for the genus) spherical lobe; elongate finger-like to nose-like in both S. semivirens (Fig. 2L, M) and S. tamaparvulus (Sasa 1981, figs 12A, E);

Gonostylus unusual in shape (globular or bean-like as in Fig. 2C, E, F); elongate and more or less parallel-sided in S. semivirens and S. tamaparvulus, as illustrated by Cranston et al. (1989, fig. 9.83E), Liu and Wang (2005, figs 4, 8), Langton and Pinder (2007, fig. 192D) and Sasa (1981, fig. 12A, E).

Figures

Figure 1. Male imago of Synorthocladius spp. Head (dorsal, left side) with vertex, coronal area and temporals of A S. federicoi sp. nov. B S. semivirens. Antenna, apex of last flagellomere of C, D S. federicoi sp. nov. E S. semivirens. Palpomere 3 of F S. federicoi sp. nov. G S. semivirens. Clypeus of H S. federicoi sp. nov. I S. semivirens. Lobes of antepronotum and acrostichals of J S. federicoi sp. nov. K S. semivirens. Humeral area of L S. federicoi sp. nov. M S. semivirens. The arrows indicate some distinguishing characters.

Figure 2. Male imago of Synorthocladius spp. Chaetotaxy of tergites II-VI of A S. federicoi sp. nov. B S. semivirens. S. federicoi sp. nov. C hypopygium in dorsal view D tergite IX and anal point in lateral view E megaseta, dorsal F gonostylus, other aspect in ventral view G hypopygium, ventral H inferior volsella I virga. S. semivirens J tergite IX and anal point in lateral view K anal point, dorsal L, M inferior volsella, two aspects. The arrows indicate some distinguishing characters.