Chaudhuriomyia, Paul, Nilotpol & Mazumdar, Abhijit, 2015

Paul, Nilotpol & Mazumdar, Abhijit, 2015, Chaudhuriomyia, a new tanypod genus of Macropelopiini (Diptera: Chironomidae: Tanypodinae) from the Eastern Himalaya, Zootaxa 3955 (4), pp. 537-548 : 538-541

Chaudhuriomyia gen. n.

Type-species. Chaudhuriomyia binduensis sp. n. by present designation.

Etymology. The genus is named in honor of Professor Prasanta Kumar Chaudhuri, Dept. of Zoology, The University of Burdwan, West Bengal, India, for his valuable contributions in the study of Chironomidae from Indian subcontinent.

Generic diagnosis. Adult:

Male. Small species; wing length 1.95–1.98 mm.

Head: Eye iridescent; with dorsomedial extension 4–5 ommatidia at minimum wide, temporal multiserial, postocular absent, outer verticals long; palp segments 3 and 4 longer, pedicel pale with long setae; terminal flagellomere offset basally, 2.8–3.5 × as long as broad, AR 1.98–2.23; clypeus roughly triangular.

Thorax: Antepronotum with clear medial gap, scutal tubercle absent, acrostichals biserial, dorsocentrals irregularly placed, prealars and postnotals present.

Wing: With moderate covering of macrotrichia over entire membrane; RM and FR darkened. Anal lobe moderately developed, squama fringed, brachiolum with 2 setae.

Leg: Pale yellow in color, bands in femur and tibia absent, pulvilli reduced, long empodium present in between tarsal claws of mid and hind legs, tibial comb on fore leg absent, surface of spurs plain without any fine short bristle. Mid and hind legs with pointed claw, only fore leg with blunt claw.

Abdomen: Tergites setose with moderate bands.

Hypopygium: Tergite IX with postero-marginal band of setae, maximum 4–5 setae along band width. Anal point arched, gonocoxite cylindrical with strong short dorsomedian setae, volsella absent; gonostylus short and robust, almost 0.40–0.45 × gonocoxite length; phallapodeme short, sternapodeme curved and anteriorly directed.

Female. Similar to male with usual sex differences: Coloration as in male but more brownish; antennae with 14 flagellomeres, AR 0.19–0.23; wing length 2.48–2.54 mm. Claw of fore tibia not blunt. Apex of hind and mid tibia with 4–5 Sch along with 5–6 Sch on each ta1–ta3 of both mid and hind legs.

Genitalia: Notum 3.5 × as long as ramus; well-developed gonapophysis VIII with few long setae, gonapophysis VIII lobe caudomesally attached to rounded labium, vaginal opening more or less ‘Ω’ shaped; segment X covered with moderate setae. Seminal capsules sub-equal, not properly sclerotized, without funnelshaped neck. Postgenital plate compressed and cerci prominent.

Immature:

Pupa. Small to medium in size, up to 5.20 mm long.

Cephalothorax: Both Dc1 and Dc2 equally long, simple, without any granulation; Sa simple. Thoracic horn almost flat, swollen apically and triangular, 0.5–0.6 × as long as broad. External membrane of thoracic horn with few spines, horn sac supported with rod like connection, filling the entire lumen of the horn and connected directly to the Plastron plate; plastron plate indistinct, somewhat plunged in the lumen with a distinct or indistinct aeropyle; thoracic comb and basal lobe absent.

Abdomen and Anal lobe: Tergite I with distinct, elongated and pigmented scar. Tergites II–VII with spiniform D1 setae arising from a sclerotized tubercle; D3 elongated and apically hooked on segments II–VII except VI. Shagreen on segments I–II as single points, other segments with grouped shagreen. Segments VII–VIII with 5 LS setae. Anal lobe large, rounded, 1.8 × as long as broad. Inner border fringed with few setae, outer border fringed along most of its margin, toothed with fine spines distally, ending in a blunt toothed tubercle not divergent distally.

Larva. Medium size larvae, up to 6.22 mm long. Head capsule brown, body yellowish with white bands.

Antenna: About as long as mandible; basal segment about 6 × as long as basal width; style short, no intersegmental band between segments 2 and 3; segment IV fragile and somewhat bristle like, ring organ exactly in middle of distal 1/3 segment. Blade shorter than flagellum I–IV.

Mandible: Evenly curved; apical tooth almost 0.5 × as long as mandible, seta subdentalis 11–13 long, basal tooth apprised; ventrolateral seta 1 simple, seta 2 with two branches, setae 3 branched and short.

Maxilla: Basal segment of palp about 2.60 × as long as wide, ring organ placed middle of maxilla.

Mentum and M appendages : Dorsomentum with 6 teeth; inner most end of dorsomentum lobe bifid, 2 small inner and 3 large outer teeth on each side; one minute, indistinct, outermost tooth attached basally on both sides. Pseudoradula extending to the base of M appendage; granules fine, dense, uniformly distributed forming a stripe shape.

Ligula and Paraligula: ligula with 5 teeth; inner tooth slightly inwardly bent, outer tooth not bent. Paraligula bifid; a small point arising in the base of paraligula.

Pecten hypopharyngis: 18–21 teeth, middle teeth larger. Apically pointed and shield shaped.

Cephalic setation: Ventrally S9 and S10 long simple setae closely placed, SSm branched; S9, S10 and SSm forming a triangle, VP placed postero-lateral respect to S10. Dorsally S7, S8 and DP almost in a straight line, S7 slightly laterally placed. S7 pore large with simple seta.

Body: Anal tubules spindle or conical in shape; procercus 5 × as long as wide with 9 anal setae. Posterior proleg with 13 claws, gradually curved from larger to smallest one, largest claw with 3 inner spines. Body with few fringed swim-setae.

Remarks. The new genus Chaudhuriomyia can be easily separated from all the other Macropelopiini thanks to a unique combination of characters. Male adult: multiserial temporal setae, absence of scutal tubercle and femoral bands, absence of fine bristle of upper surface of tibial spurs, absence of comb in fore tibia, presence of long empodium, blunt claw in fore leg, tergite IX with postero marginal band of setae, gonostylus length less one half of gonocoxite length. Female adult: 4–5 Sch present on apex of hind and mid tibia along with 5–6 Sch on each ta1–ta3 of both mid and hind legs, with a poorly sclerotized seminal capsule without neck. Pupa: indistinct plastron plate with one aeropyle, elongate and pigmented scar, simple Dc1 and Dc2, rounded anal lobe with blunt toothed tubercle. Larva: large pore size in S7 cephalic seta, unequal mental teeth, inner tooth of ligula slight inwardly bent, teeth of pecten hypopharyngis in one row, absence of labral sclerite and long procercus.

Taxonomic position. Tribe Macropelopiini included 11 genera, most of them closely related to each other ( Fittkau & Murray 1986; Murray & Fittkau 1989; Cranston & Epler 2013); only the combination of characters present in all life stages allows to separate them. Diagnosis for a new genus is difficult particularly in a tribe where generic limits are narrow. Chaudhuriomyia gen. n. differs from Alotanypus in absence of inferior volsella in adult male, shape of thoracic horn sac and presence of rounded anal lobe structure in pupa, and shape of ligula in larvae. The proposed genus differs also from Guassutanypus in number and distribution of setae of tergite IX; coloration of thorax and distribution of prealars, scutellars and postnotal of adult; respiratory atrium and anal lobe structure in pupa, and dorsomental teeth and cephalic setal pattern of larvae. The proposed genus separates from Brundiniella and Radotanypus in absence of inferior volsella of male, presence of rounded anal lobe and number of LS setae in pupa, whereas larvae differ in base structure of smallest claw of parapod and apical end of pecten hypopharyngis. The male imagine of the new taxon differs from Psectrotanypus in size of gonostylus which is about 0.75 × gonocoxite length. Derotanypus and Psectrotanypus larvae have a ligula with 4 teeth and numerous slender projections of paraligula instead of ligula with 5 teeth and a paraligula with 2. Derotanypus and Psectrotanypus are easily separable from the new genus in the pupal stage in shagreen pattern, thoracic horn and anal lobe. Fittkauimyia easily differs from Chaudhuriomyia in the uniserial arrangement of temporal setae in adult, presence of numerous pores of thoracic horn and lateral fringe of setae in segments II–VII in pupa, and complete arc of dorsomentum in M appendage in larva. Recently included genus Wuelkerella from Neotropical ( Añón Suárez & Sublette 2012) can be separated from Chaudhuriomyia in many male adult characters like lateral bundles of seta in tergite IX, heel of gonostylus, thoracic chaetotaxy, thoracic horn and anal lobe in pupa. Remaining three genera of the tribe Macropelopiini Apsectrotanypus , Bilyjomyia and Macropelopia show very close and similar characters with Chaudhuriomyia . A comparative account of some important characters of aforementioned genus along with newly proposed one are summarized in table 1 for adult, pupa and larva.

Apsectrotanypus Bilyjomyia Macropelopia Chaudhuriomyia Eye Iridescent Iridescent Not iridescent Glittering and Iridescent

Last segment of antenna Not offset basally, 2 × as long as Offset basally, 3–4.9 × as Offset basally or conical, Offset basally, 2.8–3.5 × as long as

broad long as broad (Niitsuma pers. 1.5–4 × as long as broad broad comm.)

Scutal tubercle Absent Present but small Present Absent

Band or mark on femur and Faint band or mark present Band or mark present Band or mark present Band or mark absent

tibia

Tibial spur Cover with fine small bristle Cover with fine small bristle Cover with fine small Bare, smooth bristle

Fore leg claw Pointed Pointed Pointed Blunt, somewhat Spatula like

Number and position of seta on Many, medially placed Few, placed on postero- Few to many, irregularly Placed as postero-marginal band

tergite IX marginal area placed

Aeropyle Absent Present, 2–3 in number Absent Large, 1 in number

Dc1 and Dc2 Unequal, granulated Unequal, granulated Unequal, granulated Equal, not granulated

D1 seta of tergites II–VII Arising from tubercle Arising from large tubercle Arising from markedly Arising from markedly large

large tubercle sclerotized tubercle

Shagreen pattern on tergites Solitary Serial rows of 2–5 in grouped Solitary to serial rows or Tergites I–II solitary, rest in

in grouped grouped

Anal lobe Not rounded, convex outwardly, Conical, spine only on inner Conical or convex Rounded, spinules and setae both

fringe setae on inner margin margin outwardly, spine only on present on inner margin inner margin

Labral sclerite Absent Present Absent Absent

Inter segmental band between Present, broad Present, moderately broad Present, apparently small Absent

antennal segment 2 and 3

Inner tooth of ligula Outwardly bent Not bent, straight Not bent, straight Slight inwardly bent

Pecten hypopharyngis Apical teeth large, small points Medial and mesal teeth large, Teeth biserial, medial Teeth only in single row, medial present small points arranged in teeth large, small points teeth larger, no small points biserial present

Small claws of parapod Not broad base, apically Broad base, apically deeply Not broad base, apically Not broad base, apically not depressed depressed not depressed and weekly depressed and strongly curved curved

Although larva, pupa and adult male of Chaudhuriomyia conform to diagnoses of the tribe Macropelopiini , each stage differs significantly in generic identity.

In the key to larvae of Tanypodinae in Cranston & Epler (2013), the genus may be coupled with 14, and the new proposed genera now placed as a 14a, we could not proceed further in key, because due to defused character. Genus would not couple with Alotanypus , Brundiniella, Radotanypus or Apsectrotanypus , rather if we ignore ring organ placed middle in maxilla then it would couple with 13 along with Macropelopia . The pupa may be coupled with 8 to Apsectrotanypus in Fittkau & Murray (1986) but differs in presence of aeropyle, non-granulated Dc1, pattern of shagreen and shape of anal lobe, and now it may be placed as 8a beside Apsectrotanypus . Legs not infuscate or banded and reduced pulvilli do not match with Apsectrotanypus or Radotanypus, see couplet 16 in Murray & Fittkau key (1989) to adult males; to sum up, adult male may be coupled with 16 and this genera now may place as 16a beside Apsectrotanypus .

Distribution. An unassociated pupal exuviae collected by M.W. Heyn and N.W. Charles Jr. in Alajuela Province of Costa Rica can now being placed under this new genus. Due to unavailability of associated life stages in that time, it was recorded as ‘nr. Macropelopia sp.’ (Watson Jr. & Heyn 1992, pp. 257–262). The pupal exuviae showed great similarity with pupa of new genus in respiratory horn, tergal setal pattern and anal lobe structure. These striking similarities allow to assign this pupa to new genus Chaudhuriomyia (Watson pers. comm.). So the pupa reported as Chaudhuriomyia sp.1., supports the evidence that it is present in two different zoogeographic region of the world. Its presence in the Oriental region and Neotropical region suggests fairly dispersal or vicariance; at present the distribution pattern of Chaudhudiomyia appears sparse and widely apart.