Downsiomyia rajaveli, Natarajan & Gopalakrishnan & Kumar & Kumar, 2022

Natarajan, R., Gopalakrishnan, S., Kumar, Pradeep & Kumar, Ashwani, 2022, A new species of the genus Downsiomyia Vargas (Diptera: Culicidae) from Himachal Pradesh, India, Zootaxa 5205 (6), pp. 575-584 : 576-583

Downsiomyia rajaveli , n. sp.

( Figs 1 , 2 )

Diagnosis. Downsiomyia rajaveli is a distinctive species, with the adult female readily recognizable by having the apical 0.5 of the scutum with silvery-white scales divided by a longitudinal dark band; white scales on the scutellum; absence of pale scales on the prescutellar area; and in the larva by having seta 1-C slender without pigment and bifurcate or trifurcate apically; comb with more than 20 scales, each fringed at the apex; seta 1-S with 3 branches and about as long as the siphon at the point of attachment.

Female ( Fig. 1A–F ). Medium-sized mosquito. Head: Dorsal surface of vertex black, a line of narrow silvery scales to eye margins, this line rather widened dorsomedially, a few dark upright forked scales on occiput; antenna, clypeus, maxillary palpus and proboscis black; palpus short, only about 1/7 length of proboscis. Thorax: Scutal integument dark, about anterior half of scutum white-scaled, this area broadly divided anteriorly by a median longitudinal area of dark scales (1 specimen with a few silvery scales on anterior margin in middle) ( Fig. 1A ), lateral margin of pale scaling continued posteriorly along lateral scutal angle to posterior limit of paratergite; no acrostichal and dorsocentral setae; prescutellar area with dark scales, no pale scales on margin of prescutellar bare space; scutellum with white scales, more on midlobe, a few on lateral lobes; antepronotum with broad silvery scales; postpronotum with a few flat dark scales posteriorly just before setae; integument of pleura almost black ( Fig. 1B ) with a patch of flat silvery scales covering upper and lower mesokatepisternum, upper proepisternal area, lower prealar area and mesepimeron; 3–5 upper proepisternal setae. Legs: Forefemur with narrow area of pale scales ventrobasally; midfemur dark, posteriorly pale ventrally on basal half, tapering to ventral margin just beyond midlength; hindfemur with approximately basal two-thirds white, apical third dark-scaled; tibia and tarsi of all legs dark-scaled. Abdomen: Tergum I with a broad lateral patch of silvery-white scales, terga II–VII with prominent silvery-white basolateral patches, dorsal aspects dark except basolateral patches visible in dorsal view, a complete narrow basal white band present on VIII. Genitalia ( Fig. 1C ): Width of tergum VIII greater than length, covered with minute spicules, moderately pigmented, broad proximally, broadly rounded distally with a number of long stout and a few fine setae. Width of sternum VIII about equal to length, minute spicules present, posterior margin with slight median emargination, numerous short, curved setae on posterior margin. Tergum IX moderately long, pigmented, U- shaped with 3 moderately long, slender setae apically on each lobe ( Fig. 1D ). Insula (partially damaged), lip-like, depressed medially with 1–3 long, slender setae ( Fig. 1F ). One large and 2 medium spermathecal capsules ( Fig. 1E ).

Male. Unknown.

Pupa ( Fig. 2A,B ). A single pupal exuviae was used for the description. Cephalothorax ( Fig. 2A ): Trumpet length 0.6 mm. Seta 1-CT single, stronger and longer than setae 2,3-CT; setae 2,3-CT double; seta 4-CT triple; seta 5-CT as long as seta 7-CT, double; seta 6-CT single; seta 7-CT single, branched beyond midlength; seta 8-CT double or triple; seta 9-CT double. Metanotum: Seta 10-CT as long as seta 12-CT, 4-branched; seta 12-CT triple. Abdomen ( Fig. 2B ): Length 3 mm; seta 1-II with 4 branches, seta 1-III,IV double, seta 1-V–VII single; seta 3-II about half length of following segment, seta 3-V equally distant from setae 1,5-V; seta 5-I single or double, 5-IV,V single, long, 1.5 length of following tergum, 5-VI,VII single, shorter than following tergum; seta 9-VII with 2 strong aciculate branches; seta 4-VIII single; seta 9-VIII with 6 strong aciculate branches. Paddle: Length 0.72 mm, index 1.08; seta 1-Pa single.

Larva, fourth-instar ( Fig. 2C–E ). A single somewhat damaged larval exuviae was used for this description. Head ( Fig. 2C ): Length 0.88 mm. Dorsomentum with 10 lateral teeth.Antenna length 0.44 mm, slightly swollen just before insertion of seta 1-A, tapered distally, with slender sparse spicules, basal spicules elongate; seta 1-A inserted just before midlength, with 13–16 weak aciculate branches. Seta 1-C elongate, slender; seta 4-C well developed with 16,18 branches, slightly shorter than setae 5,6-C; seta 5-C with 18,19 branches; seta 6-C with 14,15 branches; seta 7-C with 15,18 branches; setae 4,6,7-C arranged more or less in straight line; seta 5-C inserted between setae 4,6-C; seta 8-C with 6 branches; seta 9-C with 5 branches; seta 10-C with 5 branches; seta 11-C with 24,27 branches; seta 12-C with 7 branches; seta 13-C double; seta 14-C with 4 branches; seta 15-C with 3 branches; setae 14,15-C and basal maxillary seta 1-Mx double with rather stiff tapered branches. Thorax: Integument not speculate (smooth), no stellate setae. Abdomen: Integument same as thorax, some setae slightly stellate; seta 6-I–VI double. Segment VIII: Comb ( Fig. 2E ) with 23,26 short, evenly fringed scales. Siphon ( Fig. 2D ): Length 0.84 mm, dark brown, pale apically, without spicules, acus weakly developed; pecten on basal 0.4, with 13,16 spines, 3,4 small spines distally, each spine with strong distinct denticles near middle of ventral margin and a few fine denticles proximally; seta 1-S with 3 branches, about as long as width of siphon at point of attachment. Segment X: Saddle incomplete, with long, stout spicules dorsolaterally on posterior margin; seta 1-X double, slightly longer than saddle; seta 2-X with 4 branches; ventral brush (seta 4-X) with 5 pairs of setae, each with 3,4 branches.

Type material. HOLOTYPE: Female (A36802) with associated larval (Le14111) and pupal (Pe14111) exuviae mounted on same microscope slide and dissected genitalia (G36802) mounted on a separate slide . PARATYPES: Two females (A36790, A36813) with dissected genitalia (G36790, G36813) on microscope slides. The specimens are deposited in the National Mosquito Museum , Indian Council of Medical Research ( ICMR)- Vector Control Research Centre , Indira Nagar , Puducherry, India. They bear the following collection data: INDIA: Himachal Pradesh, Kangra District, way to Triund (32° 14′ 473″ N; 76° 18′ 532″ E; 1907 m a.s.l), collected on 21.07.201 8, as larvae from tree holes, collected by N. Krishnaraj.

Etymology. Downsiomyia rajaveli is named in honour of DrA.R.Rajavel(deceased),former taxonomist,Scientist ‘E’, at the ICMR-Vector Control Research Centre, Puducherry, India. He is recognised for his uncompromised, tremendous contribution to the study on mosquito diversity in different ecological zones in India and the founder of the Culicid Biodiversity Cell and National Mosquito Museum of the ICMR-Vector Control Research Centre. He very much inspired and mentored colleagues and students in the field of mosquito systematics.

Bionomics. Adults of Do. rajaveli emerged from larvae collected from tree holes. Larvae of Ochlerotatus (Finlaya) oreophilus Edwards, 1916 were found with the new species. Nothing is known of the bionomics of the adults.

TABLE 1. (Continued)

Phylogenetic analyses. Two specimens, the holotype and one paratype, were subjected to DNA barcoding and the mitochondrial COI sequences amplified were deposited in GenBank, accession numbers OP271461 and OP271462 . The sequences were subjected to phylogenetic analysis along with COI sequences of six species of Downsiomyia available in GenBank, and the results support the recognition of Do. rajaveli as a distinct clade in the genus ( Fig. 3 ). With reference to Fig. 3 , it is noteworthy that the specimen of Do. nivea from Malaysia (KY81567.1) is not conspecific with the two specimens from India (OM368624.1 and ON506043.1) that are identified as this species. Because Do. nivea was described from the Philippines (Ludlow 1903), it would seem likely that the specimens from one or the other or both countries were misidentified.

Taxonomic discussion. Although only three adult females and the larval and pupal exuviae of a single female were available, these seem to be sufficient, even in the absence of adult males and male genitalia, to recognize them as belonging to a new species. Based on characters of the adult females, female genitalia and larval exuviae, Do. rajaveli is a member of the Albonivea Group of the genus. The characters are as follows. In the adult female, integument of scutum with large snow-white patches in front, separated medially by a longitudinal dark stripe; acrostichal and dorsocentral setae absent; tarsi entirely dark-scaled. In the female genitalia, the characteristic Ushaped tergum IX with 3 setae apically on each lobe; insula lip-like with 1–3 setae in lateral patches. In the larva, seta 1-A with many branches; setae 4–7-C well developed with many branches; spermatheca with 1 large and 2 small capsules.

The female of Do. rajaveli resembles the females of seven species of Downsiomyia by having the lateral white-scale areas of the scutum completely divided by a dark median longitudinal stripe. These species include Do. axitiosa ( Kulasekera, Knight & Harbach, 1990) from East Malaysia, Do. dorseyi ( Knight, 1946) from Australasia, Do. ganapathi ( Colless, 1958) from Malaysia, Do. lactea ( Knight, 1946) from the Philippines, Do. mohani from India, Do. nipponica ( La Casse & Yamaguti, 1948) from the Ryukyu Archipelago of Japan and Do. nishikawai ( Tanaka, Mizusawa & Saugstad, 1979) also from the Ryukyu Archipelago. The combination of characters that distinguish the female of Do. rajaveli and the other species are given in Table 1 .

Larvae of members of Downsiomyia can be divided into two groups based on the number of seta 4-X (ventral brush), i.e. (1) four pairs and (2) five or more pairs. Downsiomyia rajaveli has the ventral brush with five pairs of setae, similar to Do. axitiosa , Do. dorseyi , Do. ganapathi , Do. leonis ( Colless, 1958) from Singapore and Do. litorea ( Colless, 1958) also from Singapore. The comb scales of Do. rajaveli , rounded apically and fringed at sides and apex, are quite similar to the comb scales of Do. axitiosa and Do. litorea . The comb scales of these three species are quite different from the comb scales of the other species, which have a long apical spine and mostly with fringe at base, except Do. dorseyi , Do. ganapathi and Do. leonis , which have short, apically pointed comb scales that are fringed at the sides. The important characters of these six species are compared in Table 2 .

Along with Do. rajaveli , six other species in the genus Downsiomyia are known to occur in India, including Do. albolateralis , Do. albonivea , Do. mohani , Do. nivea , Do. niveoides and Do. novonivea . The females of these species, except Do. mohani , differ from rajaveli by the absence of divided silvery-white scale-patches at the front of the scutum. The larva of Do. rajaveli seems to be unique among all these species with regard to the comb scales, which are evenly fringed with a rounded apex, as opposed to being spine-like in the other species. As noted above, the COI sequences of Do. nivea from Kerala, India are distinct from those of Do. nivea from Sarawak, Malaysia ( KY817567 ) ( Fig. 3 ). Downsiomyia nivea in India, reported by (Tewari & Hiriyan 1995), is not conspecific with the type specimens of Do. nivea from the Philippine Islands ( Reinert & Harbach 2006), which needs to be studied to determine its taxonomic status.

Figures

FIGURE 1. Downsiomyia rajaveli sp. nov. Adult female: A, Dorsal aspect of head and thorax; B, lateral aspect of thorax; C, female genitalia; D, tergum IX; E, spermatheca; F, insula. Ce, cercus; I, insula; PGL, postgenital lobe; SCa, spermathecal capsule; IX-Te, tergum IX.

FIGURE 2. Downsiomyia rajaveli sp. nov. Pupal exuviae: A, Cephalothorax; B, abdominal segments. Fourth-instar larval exuviae: C, Head; D, siphon; E, comb scales. Cs, comb scale; CT, cephalothorax; H, head; S, siphon.

FIGURE 3. Phylogenetic tree of mitochondrial COI sequences for species of Downsiomyia. The GenBank accession number and the country of origin are included for each specimen included in the analysis.