Thinophilus maritimus Mukherjee & Pramanik, 2023

Mukherjee, Koustav, Pramanik, Debdeep, Naskar, Atanu & Banerjee, Dhriti, 2023, A new species of Thinophilus Wahlberg (Diptera: Dolichopodidae: Hydrophorinae) from coastal India with re-description of Thinophilus tesselatus Becker (Diptera: Dolichopodidae: Hydrophorinae), Zootaxa 5375 (4), pp. 478-494 : 481-482

publication ID	https://doi.org/ 10.11646/zootaxa.5375.4.2
publication LSID	lsid:zoobank.org:pub:A9122AD8-C47A-4FE3-8A94-0E53611D253A
DOI	https://doi.org/10.5281/zenodo.10248487
persistent identifier	https://treatment.plazi.org/id/9F16D575-FFB9-1309-FF6B-FDC4FE11FEF1
treatment provided by	Plazi
scientific name	Thinophilus maritimus Mukherjee & Pramanik
status	sp. nov.

Treatment

Thinophilus maritimus Mukherjee & Pramanik sp. nov.

( Figs 1–12 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 View FIGURE 9 View FIGURE 10 View FIGURE 11 View FIGURE 12 )

Type material. HOLOTYPE: 1♂, ZSI 26033 /H6, INDIA: West Bengal: Sagar Island, Bay of Bengal , 21°37′55.45″N, 88°4′47.16″E, alt 0 m, sweep netting, 18 Feb. 2021.coll. K. Mukherjee. GoogleMaps PARATYPES: 4 ♂, 2 ♀, barcoded ZSI 26034 /H 6 ♂, ZSI 26035 /H 6 ♀, Bakkhali , Bay of Bengal, 21°33′24.19″ N, 88°16′15.40″ E, alt 0 m, sweep netting, 7 Aug. 2021, coll. K. Mukherjee & D. Pramanik. GoogleMaps

Diagnosis. A large species, mostly dark metallic green with whitish greyish tomentum. Scape, pedicel and postpedicel mostly brown; bulbous postpedicel; arista white except for brown base. 9–10 dorsocentral bristle decreasing in length anteriorly. All coxae metallic green with whitish tomentum; hind coxa lacks lateral setae. All tarsomeres orange-yellow with dark brown bands at the tip of each; terminal tarsomere mostly dark. Mid basitarsus with a protuberance. Hind femur twice as long as fore and mid femora; hind tibia moderately swollen with modified basitarsus which appears as a bifurcated process at the apical end of hind tibia.

Description. Male ( Figs 1–2 View FIGURE 1 View FIGURE 2 ). Body length 6.0– 6.8 mm, wing length 4.5–5.2 mm. Head ( Fig. 3 View FIGURE 3 ): Eyes dichoptic, red with dense white pubescence, widely separated at ocellar region; postcranium dark metallic green, white pollinose; vertex slightly sunken, metallic green, whitish tomentum. Metallic green frons with violet reflections and whitish tomentum denser than on vertex; 2 proclinate ocellar setae present; 6 black upper postocular setae present along with dense white hairs on postgena; pair of inner vertical setae present; subtriangular clypeus with white tomentum; white triangular palpus with white hairs ( Fig. 3A, B View FIGURE 3 ). Antennal scape brown along basal three-fourths, distally yellowish, apex curved inside; pedicel brown with white tomentum bearing small white hairs at base; postpedicel bulbous, brown with white tomentum, longer than wide; arista dorsal, bare, white, base swollen and dark brown ( Fig. 3C View FIGURE 3 ); postpedicel equal in length to scape; length ratio of scape to pedicel to postpedicel to arista, 0.24/0.06/0.18/0.37. Thorax ( Fig. 4 View FIGURE 4 ): Metallic green with purple reflections, whitish tomentum throughout; dark green pleura with denser whitish tomentum than scutum; acrostichals absent; 9–10 dorsocentral bristles, decreasing in length anteriorly; 1 humeral; 1 posthumeral; 1 notopleural; 2 supra-alars; postalar absent; anterior spiracle white; scutellum concolorous with thorax, 2 strong longer marginals and 2 shorter hair-like laterals. Wing ( Fig. 5 View FIGURE 5 ): Grey, simple, narrow; M 1 moderately sinuous after dm-m crossvein; R 4+5 and M 1 converge at apical area but do not meet each other; ratio of costal section between R 2+3 and R 4+5 to costal section between R 4+5 and M 1 6:4; ratio of crossvein dm-m to distal part of M 4 6:5; lower calypter dirty yellow with white cilia, pilose; halter light yellow. Legs ( Fig. 6 View FIGURE 6 ): All coxae metallic green with whitish tomentum; fore and mid coxae with single black bristle, hind coxa lacks lateral setae; fore, mid and hind femora concolorous with coxae. Fore and hind tibiae concolorous with coxae and femora, mid tibia orange yellow. All tarsomeres orange yellow with dark brown bands at tip of each tarsomere, terminal tarsomere of all legs completely darkish brown. Foreleg ( Fig. 6A View FIGURE 6 ): Fore femur basally black and yellow apically, without MSSC, posterolaterally bearing row of black bristles from base to apex, apical 4 bristles larger; ventrally with scattered bristly hairs of various lengths. Fore tibia light brown except for yellowish basal one-third, bearing yellowish hairs all over with black apical bristle both dorsally and ventrally. All tarsomeres yellowish with blackish apex; basitarsus equal to combined length of remaining segments, bearing row of long yellowish bristles along entire length (MSSC); row of setae dorsally and rows of setae ventrally; claws symmetrical; length of femur, tibia and tarsomeres (in mm): 1.17/0.88/0.88/0.23/0.21/0.22/0.21. Midleg ( Fig. 6A View FIGURE 6 ): Mid femur concolorous with fore femur, with two ventral rows of black small bristles, 3–4 larger bristles at base and 2–4 bristles at apex. Mid tibia yellow, ventrally bearing row of yellowish hairs along entire length, forming very long hairs at apex. Mid basitarsus with protuberance at apical third bearing row of black spines anteriorly and posteriorly; other tarsomeres with black and yellow hairs; claws same as on foreleg; length of femur, tibia and tarsomeres (in mm): 1.46/1.40/1.04/0.23/0.2 0/0.17/0.27. Hindleg ( Fig. 6B View FIGURE 6 ): Hind femur twice length of fore and mid femora, curved in middle, without MSSC, bare of bristles. Hind tibia metallic darkish green with white tomentum, moderately swollen with apical process; basitarsus shaped as stout curved process with bifurcation at apex, foot-shaped terminally with long yellowish hairs on outer branch on basal third; other branch bare (MSSC). Tarsomere 2 yellow with row of long yellow hairs ventrally; other 3 tarsomeres together equal in length to tarsomere 2; claws same as on foreleg; length of femur, tibia and tarsomeres (in mm): 2.71/1.54/0.69/0.73/0.26/0.27/0.31. Abdomen ( Fig. 7 View FIGURE 7 ): First and second segments dorsally dark green with silvery and black pubescence, remaining segments darker with whitish pubescence; ventrally dull yellowish with white pubescence. Male genitalia ( Figs 8–9 View FIGURE 8 View FIGURE 9 ): Dark brown pair of surstylus with furcated and pincershaped tips; cerci not fused, pale whitish brown with small pale white hairs throughout and larger hairs along edges; phallus strap-shaped, strongly curved, not coiled. Female ( Fig. 10 View FIGURE 10 ): Body length 6.6–6.7 mm Wing length 5.1–5.2 mm. Similar to male except lacking secondary sexual characters, otherwise as follows: All coxae and trochanters black with yellowish-white tomentum; fore femur black, with yellowish apex; mid femur black on basal half, remaining yellowish; hind femur more than 1.5 times longer than preceding femora, distinctly curved, black except yellowish apex; all femora covered with yellowish and black pubescence; all tibia yellow except black infuscation at apex of hind tibia, with hind tibia slightly longer than other tibiae; all tibia covered with black and pale yellow pubescence; all tarsomeres yellow with black apex, with apical 2 tarsomeres blacker; 6 acanthophorite setae present on each hemitergite 9+10; female genitalia as in figure ( Fig. 11 View FIGURE 11 ).

Etymology. From the Latin ‘ maritimus ’ (of the sea), as the specimens were collected along the coast of the Bay of Bengal.

Behaviour. The specimens were seen in clusters or groups in areas where the sands were moist and along the edges of seawater ( Fig. 12 View FIGURE 12 ). They were not seen on dry sands. During the survey, the females were relatively easier to catch than males, mostly because as soon as the males were approached closer than approximately 1.5–2 m, they mostly jumped on the sea waves, kept floating on the waves, perfectly balancing themselves even on larger waves, and returned back to the shore only when the said distance was maintained again. Females were not seen showing this behaviour. Therefore, we hypothesize that the modified hind limbs of males might have a role in the floating behaviour.

Barcoding. DNA barcoding of one male (Accession no: ON255696) and female paratype (Accession no: ON255707) of our species was obtained, and both specimens displayed 100% similarity, confirming that the sexes are correctly associated. The closest and most similar sequence for both the specimens are identified as “ Dolichopodidae sp” sharing only 87% similarity in BOLD. In the constructed phylogenetic tree ( Fig. 13 View FIGURE 13 ), Thinophilus maritimus sp. nov. clusters within the genus Thinophilus where the other three genera, Scellus Loew , Hydrophorus Fallén and Thambemyia Oldroyd show definite distinction from our specimen. In spite of the clustering of our specimen with that of the genus Thinophilus , their distinction with sequences of available Thinophilus species in BOLD is also evident, thereby confirming our specimen as a new species.

Distribution. West Bengal, India.

Remarks. Thinophilus maritimus sp. nov. was collected from the sandy delta beaches of Sagar Island and Bakkhali along the coast of the Bay of Bengal of South 24 Parganas district of West Bengal, India. According to the key to New World genera ( Bickel 2009), the species belongs to the subfamily Hydrophorinae and ends at couplet 55 with the genus Thinophilus , but it completely lacks lateral setae on the hind coxa. However, we assign this species to Thinophilus due to several morphological similarities, and its clustering within the Thinophilus group in the phylogenetic tree. Some other species such as T. parvulus Samoh, Satasook & Grootaert, 2017 ; T. spinatoides Samoh, Satasook et Grootaert, 2017 ; T. subpalpatus Grichanov, 2023 also lack lateral setae on the hind coxa ( Samoh et al. 2017; Grichanov 2023b).