Chaoborus pseudoflavicans, Bang & Shin, 2023

Bang, Woo Jun & Shin, Seunggwan, 2023, A new species of the Chaoborus flavicans complex (Diptera, Chaoboridae) in South Korea, Zootaxa 5360 (1), pp. 57-81 : 59-63

Chaoborus pseudoflavicans sp. nov.

Chaoborus crystallinus (nec De Geer): Komyo 1954: 12.

Chaoborus cf. flavicans (nec Meigen): Dupuis et al. 2008: 240.

Chaoborus flavicans (nec Meigen): An et al. 2012: 39.

Chaoborus sp. (unidentified): Zhang et al. 2019: 747.

Chaoborus JPN sp. (unidentified): Salmela et al. 2021b: 181.

Differential diagnosis.

Adult male. See Samela et al. (2021b) to see the illustrations of C. flavicans species complex. This species can be distinguished from C. posio by its yellowish coloration (dark-almost in C. posio ), and from C. flavicans and C. albipes by the following combination of characters: Tergal bands absent (present in C. flavicans and C. albipes ). Paramere unicolorous, constricted and medially bent, apical claw stout and curved (bicolorous, constricted and medially bent, apical claw narrow and slightly curved in C. flavicans and nearly unicolorous, slightly bent or straight, apical claw stout and curved in C. albipes ).

Pupa. This species may be hardly distinguished due to intraspecific variation in respiratory organ morphology according to its aquatic habitats (pond and lake). Respiratory organs subapically constricted (absent in C. posio ). Length of respiratory horn mostly> 1000 μm and slender form (mostly <1000 μm in C. albipes and C. posio , medially wide in C. posio ).

IV instar larva. Mandibular lateral teeth conspicuous, first lateral tooth about as long as mandibular tooth III (short or inconspicuous in C. flavicans ), number of lateral teeth almost <4 (almost> 5 in C. albipes and C. posio ), number of mandibular fan bristles usually 10 (number> 20 in C. albipes and C. posio ).

Type materials. Holotype. Male (SNUE), 01.II.2023, Haenam-gun , Jeollanam-do, South Korea, 34°28'06.30"N, 126°31'02.31"E, Woo Jun Bang and Jeungjun Lee. Paratypes. 20 adult males and 20 adult females, 100 larvae and 100 pupae ( SNUE); 6 adult males, 6 adult females, and 10 larvae and 10 pupae are deposited at the Regional museum of Lapland, Rovaniemi, Finland ( LMM). all materials from same collection data as holotype. 10 adult males and 10 adult females, pinned. 10 adult males and 10 adult females in 70 % EtOH. All larval and pupal specimens preserved in 70 % EtOH. Three male hypopygia on slides.

Description

Adult male. Head. Dark brown with pale setae; Antennae 14-segmented, bearing whorl pale setae; antennal flagellomeres circular form, basal segments dark brown, but distal segments pale; apical flagellomere dark brown, length of penultimate flagellomere 295 (268–320), apical flagellomere 224 (183–262), penultimate/apical 1.32 (1.03– 1.74, n=7); maxillary palpi 5-segmented, all segments greyish brown with dark brown setae. Length of palpomeres 1–4 (n=5): 1st 76 (69–80), 2nd 110 (99–120), 3rd 249 (204–289), 4th 231 (192–256) ( Fig. 2a–b ). Thorax. Scutum with trident light brown stripes and some black specks scattered, ground color brown with pale setae; scutellum and mediotergite brown, most pleuron colors composed pale to brown areas: antepronotum, postpronotum, anepimeron, anepisternum, metanepsiternum and katepisternum brown (antepronotum slightly darkened than postpronotum), halteres pale, a number of thorax setae (n=12): antepronotum 26 (22–29), postpronotum 5 (3–6), proepisternum 5 (4–6), katepisternum 7 (4–9), anepisternum 11 (8–12) and anepimeron 5 (5–9) ( Fig. 2a ). Leg. Mostly pale, but fourth-fifth tarsomeres slightly darkened than first to third tarsomeres; foreleg, lengths of femur, tibia and five tarsomeres (n=12): femur 2069 (1992–2226), tibia 2259 (2123–2357), tarsomeres: 1st 931 (861–992), 2nd 567 (510–628), 3rd 483 (440–544), 4th 321 (273–385), 5th 218 (161–248); midleg, lengths of femur, tibia and five tarsomeres (n=12): femur 1714 (1648–1775), tibia 1716 (1649–1815), tarsomeres: 1st 735 (701–792), 2nd 443 (415–471), 3rd 355 (334–390), 4th 269 (251–298), 5th 235 (220–242); hindleg, lengths of femur, tibia and five tarsomeres (n=12): femur 2189 (1970–2400), tibia 2170 (1806–2373), tarsomeres: 1st 1250 (1197–1291), 2nd 730 (686–756), 3rd 494 (472–524), 4th 308 (295–330), 5th 260 (235–288) ( Fig. 2a ). Wing. mostly light brown with yellowish scales around the margin, length 4238 (4102–4334), width 881 (867–906), length/width 4.8 (4.9–4.5), fork of R 2+3 517 (395–654), fork of M 1+2 461 (400–490), R 3 1288 (1120–1385), M 1 1136 (1059–1184) (n=10) ( Fig. 2b ). Abdomen. Ground color light brown with black lateral specks but not connected, tergal bands absent, fifth to distal tergal segments slightly darkened ( Fig. 2b ). Hypopygium. Gonocoxite light brown, length 538 (512–547), width 186 (167–206), length/width 2.9 (2.5–3.3, n=7); gonostylus mostly dark brown, length 485 (449–518), width 36 (32–39), length/width 16.19–11.51 (n=7) ( Fig. 3a ); paramere unicolorous, brown, medially bent and constricted, apical claw stout and curved, length 149 (133–160, n=5) ( Fig. 3b–c ).

Adult female. Most are similar with male. Head. Length of penultimate flagellomere 95 (84–115), apical flagellomere 104 (94–134). penultimate/apical 0.92 (0.63–1.30, n=4); maxillary palpi 5-segmented, dark brown, length of palpomeres 1–4 (n=6): 1st 55 (51–63), 2nd 65 (58–69), 3rd 174 (149–209), 4th 149 (131–167). Thorax. Number of setae on thorax (n=8): antepronotum 20 (17–22), postpronotum 5 (5–6), proepisternum 4 (3–5), katepisternum 5 (3–6), anepisternum 11 (10–13), anepimerum 11 (6–11). Leg. Foreleg, lengths of femur, tibia and five tarsomeres (n=6): femur 1591 (1543–1663), tibia 1846 (1776–1902), tarsomeres: 1st 800 (736–874), 2nd 484 (437–511), 3rd 385 (337–423), 4th 255 (227–282), 5th 180 (162–209); midleg, lengths of femur, tibia and five tarsomeres (n=4): femur 1506 (1442–1596), tibia 1456 (1420–1495), tarsomeres: 1st 631 (600–652), 2nd 354 (322– 394), 3rd 286 (281–296), 4th 199 (182–213), 5th 168 (153–180); hindleg, lengths of femur, tibia and five tarsomeres (n=5): femur 1814 (1725–1861), tibia 1836 (1773–1916), tarsomeres: 1st 1098 (1030–1166), 2nd 609 (562–644), 3rd 400 (349–445), 4th 236 (212–263), 5th 175 (161–194). Wing. length 3441 (3383–3517), width 945 (879–991), length/width 3.6 (3.4–4.0), fork of R 2+3 358 (290–406), fork of M 1+2 303 (273–320), R 3 1207 (934–1296), M 1 1105 (832–1254) (n=6).

Pupa ( Fig. 4b ). Mib rib of terminal process incomplete, not reaching the distal margin of paddles, and curved apically; outer rib of terminal process curved shape and smooth with no spines; mid rib and lateral rib almost pale, but mid rib slightly darkened than lateral rib; respiratory organ, slender form, subapically constricted, length 1141 (1016–1187), width 225 (205–309), length/width 4.6 (3.3–5.9, n=10) ( Fig. 4e )

IV instar larvae ( Fig. 4a ). Length of antennae 476 (401–530, n=19); labral blade transparent and serrated, length 229 (201–279), width 48 (31–58), length/width 4.8 (3.5–9.0, n=14) ( Fig. 4d ); a number of mandibular fan bristles 10.8 (10–13, n=19); mandibular teeth, mandibular tooth 1,2 and 4 darkened apically, mandibular tooth 3 dark; lateral teeth conspicuous, first lateral tooth about as long as mandibular tooth 3 (subordinate tooth), average number of lateral teeth 3.4 (3–4, n=21) ( Fig. 4c ); a number of anal fan setae 23 (21–26, n=15).

Etymology. The name of this species reflects its taxonomic history, as it was often identified as C. flavicans and remained undescribed for a prolonged period within the C. flavicans species complex.

DNA barcodes & neighbor-joining tree. Partial COI sequences from larvae to adults were obtained. Based on the pairwise distance histogram, the intraspecific variation within the species complex ranged up to 4.9% (with a mode of 1.3%), while the minimum interspecific variation was 11.1% (with a mode of 15.4%). These results suggest that the genetic distances in the C. flavicans species complex are sufficient to delimitate and identify species ( Fig. 5 ). In addition, it showed that the collected chaoborids are identical to Chaoborus JPN sp. sequenced in Zhang et al. (2019), and supported by the NJ tree, which clustered these sequences into a single group (> 99% support), similar to the COI-based tree of Salmela et al. (2021b). In the tree, C. pseudoflavicans sp. nov. formed a single cluster ( Fig. 6 ). All results confirmed that C. pseudoflavicans sp. nov. is a new distinct species that has not yet been identified.

Distribution. Korea (new record) and Japan.

Remarks. The new species has been mentioned in some taxonomic works (e.g. Komyo 1954, Salmela et al. 2021b), and included in the molecular phylogeny of Zhang et al. (2019). While it was previously believed that this taxon was endemic to Japan ( Salmela et al. 2021b), the morphological and molecular analyses showed that this species also occurs in the Korean Peninsula. In conclusion, the paramere of C. pseudoflavicans sp. nov. was practically identical to that of C. albipes , except for slightly greater curvature in the median position of the paramere. Additionally, the presence or absence of the tergal band in adults, the differences in mandibular teeth of larvae, and the DNA barcode confirmed it is a distinct species in the species complex.

Bionomics. The immature specimens of this new species were collected from a small, lightly iced, fishless pond (10 × 10 m) in February and March 2023. The water was eutrophic, and colored light brown with Typha spp. , and fallen leaves. Chironomid larvae and Notonecta spp. were also collected with the chaoborid larvae.

Figures

FIGURE 2. Chaoborus pseudoflavicans sp. nov., adult male habitus in the (a) lateral and (b) dorsal views (scale bar 1.0 mm).

FIGURE 3. Chaoborus pseudoflavicans sp. nov., hypopygium, (a) dorsal view (scale bar 200 μm), (b) parameres viewed in different positions (scale bar 50 μm). gst = gonostylus, pm = paramere, gx = gonocoxite, ac = apical claw.

FIGURE 4. Chaoborus pseudoflavicans sp. nov., immature stages, (a) larva, habitus in lateral view (scale bar 1.0 mm), (b) pupa, habitus in lateral view (scale bar 1.0 mm), (c) larval mandibles (scale bar 50 μm), (d) larval blades (scale bar 50 μm), (e) respiratory organ (scale bar 500 μm). lb = larval blade, ant = antenna, md = mandible, ans = anal fan setae, ro = respiratory organ, tp = terminal process, Lt = lateral teeth, I–IV = mandibular teeth, III being the subordinate tooth.

FIGURE 5. The distribution of pairwise genetic distances based on the pairwise distance model using the DNA barcoding regions (COI) of four species in the complex. The intraspecific variation is in black, and the interspecific variation in light blue.

FIGURE 6. A neighbor-joining tree of the Chaoboridae species based on the pairwise distance model using the mitochondrial DNA barcoding region (COI). In all, 552 COI sequences (C. pseudoflavicans sp. nov., eight specimens sequenced in this study) were used to construct the NJ tree using MEGA 11. The red asterisk indicates that the collected Chaoborids clustered with Chaoborus JPN sp. (MK281356) with> 99% support, and black asterisks indicate the species of the C. flavicans species complex. The light blue shading indicates the recorded species of Chaoboridae in South Korea. Three species of Culicidae are used as outgroups. Triangles represent collapsed clades to save space. F = female, M = male, P = pupa, L = larva.