Discothyrea venus Hita Garcia & Lieberman, 2019

Hita-Garcia, Francisco, Lieberman, Ziv, Audisio, Tracy L., Liu, Cong & Economo, Evan P., 2019, Revision of the Highly Specialized Ant Genus Discothyrea (Hymenoptera: Formicidae) in the Afrotropics with X-Ray Microtomography and 3 D Cybertaxonomy, Insect Systematics and Diversity 5, pp. 1-84 : 75-78

Discothyrea venus Hita Garcia & Lieberman sp. n.

( Figs. 2C , 4S , 6S , 7S , 8S , 9S , 10S , 11S , 12S , 14S , 56 ,

57 ; Supp. Video S19 [online only])

Type Material

HOLOTYPES, pinned worker, IVORY COAST, Abidjan, Banco National Park , [5.38694, −4.05275], ca. 20 m, primary forest, dead trunk, collection code ANTC42125, 3.II.1977 (I. Löbl) ( BMNH: CASENT0790116 ) . PARATYPES, six workers with same data as holotype ( BMNH: CASENT0790115 ; CASC: CASENT0247017 ; HLMD: HLMD-Hym-2397; MCZC: MCZ-ENT00593559; MHNG: CASENT0247013 ; SAMC: CASENT0247016 ) .

Cybertype. Volumetric raw data (in DICOM format), 3D rotation video, still images of surface volume rendering, and 3D surface (in PLY format) of the physical holotype (CASENT0790116) in addition to stacked digital color images illustrating head in full-face view, profile and dorsal views of the body. The data are deposited at Dryad (Hita Garcia et al. 2019, http://doi.org/10.5061/ dryad.3qm4183) and can be freely accessed as virtual representation of the type. In addition to the cybertype data at Dryad, we also provide a freely accessible 3D surface model of the holotype at Sketchfab (Model 19).

Nontype Material

ANGOLA: R. Kahingo, [−7.39, 20.51], ca. 650 m, gallery forest, 20.VI.1964 ( Mwaoke ); R. Mussungue, mouth, Route Turisme, [−7.3697, 20.813], ca. 630 m, gallery forest, 8.XI.1963 (L. Carvalho) ;

CAMEROON: Ebolowa, [2.92, 11.13], 640 m, 22.VIII.1940 (A.I. Good); Nkoemvon , [2.7517, 11.0814], ca. 630 m, 5.I.1980 (D. Jackson) ; GHANA: Aiyaola Forest Reserve, Kade, [6.1510, −0.945], ca. 210 m, primary forest, 6.X.1992 (R. Belshaw); Ashanti, Ofinso, [6.93, −1.65], ca. 230 m, cocoa plantation, 2.XI.1992 (R. Belshaw); Atewa Forest Reserve , nr. Kibi, [6.1747, −0.5861], ca. 400 m, 26.II.1992 (R. Belshaw); Eastern, Bunso, nr. Tafo, [6.28761, −0.46948], ca. 240 m, primary forest, 6.XI.1992 (R. Belshaw) ;

IVORY COAST: Abidjan, Banco National Park , [5.38694, −4.05275], ca. 20 m, primary forest, 3.II.1977 (I. Löbl); Adiopodoume, [5.335, −4.131], ca. 30 m, 31.X.1980 (V. Mahnert & J.L. Perret) ; Abidjan, Banco Forest, collection code A50, [5.39, −4.05], 79 m, 11.I.1963 (W.L. Brown); Agboville, Yapo Forest , near Yapo-Gare , [5.77105, −4.12376], ca. 80 m, 21.–23.III.1977 (I. Löbl); Man, ravine at foot of Mt. Tonkoui , [7.4014, −7.5791], ca. 640 m, 9.III.1977 (I. Löbl); Nzi Noua, N. of Ndouci, [6.03283, −4.84893], ca. 60 m, degraded forest, 13.I.1977 (W.L. & D.E. Brown) ; UGANDA: Kibale National Park, Kanyawara Biological Station , 0.56437, 30.36059, 1510 m, rainforest, 6.–16.VIII.2012 (G. Fischer) .

Diagnosis

The following character combination distinguishes D. venus from the remainder of the complex: masticatory margin of mandible edentate; anterolateral corner of gena not denticulate/dentate; propodeum laterally and dorsally strongly concave posteriorly; metatibae without apicoventral spur; lower portion of declivitous face of propodeum transversely substrigulate; AT4 extremely enlarged, bulbous, and much longer than AT3 (ASI 158–183).

Worker Measurements and Indices (n = 12)

EL 0.00–0.01; HL 0.41–0.48; HW 0.33–0.40; SL 0.20–0.26; PH 0.20–0.25; PW 0.26–0.32; DML 0.24–0.30; PrH 0.25–0.29; WL 0.39–0.47; HFL 0.25–0.33; PeL 0.05–0.07; PeW 0.15–0.19; PeH 0.14–0.18; LT3 0.19–0.24; LT4 0.33–0.39; OI 0–3; CI 80–84; SI 48–55; LMI 51–55; DMI 62–69; DMI2 95–107; ASI 158–183; HFI 63–74; DPeI 250–321; LPeI 233–300.

Worker Description

Head longer than broad (CI 80–84), posterior head margin slightly convex overall, with very weak impression medially; posterodorsal corners of head quite broadly rounded; in frontal view, sides of head convex; eyes absent or extremely minute (OI 0–3), a tiny pigmented spot situated about a third of the way between anterolateral corner of gena and posterior head margin, not visible in frontal view; frontal lamella lobate in profile, apex blunt to rounded; lamella with well-defined translucent basal fenestra; medial clypeus broad, convex, sides of medial clypeus subparallel laterad antennal sockets, lateral clypeus curving fairly strongly between antennal sockets and anteroalteral corners of head, entire clypeal margin bearing very short curved setae. Antenna with usually shorter scape (SI 48–55), scape moderately incrassate, gently bent; pedicel subglobose, width and length subequal or slightly broader than long; apparent antennomere count seven to eleven (usually seven to eight) but often not discernable and extremely difficult to count, flagellomeres basad apical club highly compressed, taken together only about as long as apical club. Ventral head with weakly sinuate preoccipital ridge with short but distinct anteromedial carina; median region of hypostoma rounded-triangular, arms distinctly narrowed, slightly spatulate apicolaterally; palpal formula not examined. Mandible edentate or with slight preapical swelling, without prebasal denticle; basal angle denticulate; ectal face with carina extending from base of basal denticle, becoming confluent with masticatory margin preapically, leaving narrow, comma-shaped depressed region.

Mesosoma gently convex in profile, pronotum slightly higher than propodeum; in dorsal view, mesosoma conspicuously thick, robust and stocky (DMI 59–66; DMI2 95–102), strongly narrowed posteriorly, pronotum much wider than propodeum; pronotal humeri rounded; posterior propodeal margin distinctly concave; posterodorsal corners of propodeum strongly angulate but lacking differentiated denticles; declivitous face of propodeum strongly concave in profile and oblique posterior view; propodeal spiracle directed posterolaterally, often relatively conspicuous due to small patch of shiny, polished sculpture offsetting spiracular opening from remainder of propodeum; propodeal lobes short, truncate.

Legs relatively long (HFI 63–74) and slender; mesotibia without apicoventral spur; mesobasitarsus relatively short, subequal in length to tarsomeres II–IV taken together.

Petiolar node moderately attenauted dorsally, about 2.3 to 3.0 times as high as long (LPeI 233–300); in profile, anterior face of node convex, apex peaked, posterior face sloping posteroventrally; in dorsal view, petiole subrectangular, sides diverging posteriorly, about 2.5 to 3.2 times as broad as long (DPeI 250–321); in anterior view, petiolar outline roughly pentagonal, edges poorly defined and angles rounded; in oblique anterior view, anterior face flat; subpetiolar process short, dentate, apex acute.

Abdominal segment 3 short, broadly campaniform, widest point just anterad end of segment; sternite more or less evenly convex in profile; AS 3 without median ridge or lobe; prora finely carinulate, concave in ventral view; AT4 around 1.6 to 1.8 times as long as AT3 (ASI 158–183), AT4 bulbous, swollen hemidemispherical, or more elongate, shaped as quarter of prolate ellipsoid; AS 4 with broad, well-developed anterior lip, overlapping most of the width of AS 3, anterior margin concave in ventral view; successive abdominal segments short, telescopic, often concealed, projecting strongly anteriorly due to size and shape of AT4.

Sculpture in general shallow and somewhat indistinct; head, dorsal mesosoma, and petiole similarly and evenly punctatereticulate, punctae often more pronounced on head than mesosoma; mandible fairly smooth except for small piligerous punctae; lateral mesosoma with punctae particularly indistinct, interspaces of punctae variably coalescent, forming weak rugulae; declivitous face of propodeum transversely substrigulate over around the ventral half; abdominal segment 3 weakly punctulate; AT4 with even finer piligerous punctulae.

Setation generally very fine and dilute, similar over all tagma and consisting entirely of short, appressed white pubescence; pubescence slightly longer on abdominal segment 3 and AT4, slightly reduced on lateral mesosoma; ectal face of mandible with moderately long, curved, appressed to decumbent setae; masticatory margin with row of short straight setae; scape and legs with similarly short, velvety pubescence; abdominal segments 5 to 7 with standing setae, quite Model 20. 3D surface model of D.wakanda sp.n. holotype (CASENT0790326). An interactive version of this model is available in the HTML version of this article online and at https://sketchfab.com/3d-models/862743aa29d24113957 b4c3ca277d82a.

long relative to setation on remainder of body (but rather short relative to that of segments 5 to 7 on most other Afrotropical species).

Color testaceous-orange, sometimes lightly infuscated on dorsal surfaces.

Etymology

Venus was the Roman goddess of love, beauty, and prosperity. Among her local epithets was Venus Kallipygos, ‘she of the beautiful buttocks’; the species is named in reference to the hypertrophied fourth abdominal tergite. The specific epithet is given as an appositive noun.

Distribution and Biology

This species is patchily but widely distributed throughout Equatorial Africa ( Fig. 4S ). Currently, it is known from many localities in Ivory Coast and Ghana, some in Cameroon and Angola, and one in Western Uganda. With the exception of Kibale Forest in Uganda, which is situated at an elevation of around 1500 m, all other known localities are lowland rainforests ranging from 30 m to 650 m elevation. The highly disjunct distribution is likely due to a sampling bias, and we think it is highly probable that D. venus will also be found in more or even all countries of the Congo Basin.

Comments

Discothyrea venus is a highly conspicuous species within the Afrotropical fauna. The character combination given in the diagnosis above discriminates it clearly from the remainder of the genus. To the best of our knowledge, the dramatically enlarged fourth abdominal tergite in particular (ASI 156–194) is not approximated by any other congener.

Variation

Considering the relatively broad distribution in West and Central Africa, it is surprising to see only very little variation. The eyes are entirely absent in some individuals, while in others they are present but minute, more like an indistinct pigmented spot. The length of the abdominal terga is somewhat variable but the fourth tergite is always significantly larger than the third. The development of sculpturation, particularly on the lateral mesosoma, is somewhat variable between individuals, with some possessing more pronounced punctae, but overall is similarly shallow and indistinct.

Figures

Fig. 2. Still images generated from surface display volume renderings of petiole and gaster showing different proportions of abdominal segments III (in orange) and IV (in blue). (A) D. mixta, (B) D. kalypso, (C) D. venus.

Fig. 4. Maps showing the known distribution ranges of Afrotropical Discothyrea species.

Fig. 6. Diagnostic plate showing still images from surface volume renderings of the head in full-face view (the remainder of the body virtually removed). All Afrotropical species are shown, species names are embedded in each particular image for better comparison and orientation.Specimen codes are given inTable 1.

Fig. 7. Diagnostic plate showing still images from surface volume renderings of the head in profile (the remainder of the body virtually removed).All Afrotropical species are shown, species names are embedded in each particular image for better comparison and orientation. Specimen codes are given inTable 1.

Fig. 8. Diagnostic plate showing still images from surface volume renderings of the right mandible in dorsal view (the remainder of the body virtually removed).All Afrotropical species are shown,species names are embedded in each particular image for better comparison and orientation.Specimen codes are given inTable 1.

Fig. 9. Diagnostic plate showing still images from surface volume renderings of the mesosoma in profile (the remainder of the body virtually removed). All Afrotropical species are shown, species names are embedded in each particular image for better comparison and orientation.Specimen codes are given inTable 1.

Fig. 10. Diagnostic plate showing still images from surface volume renderings of the body in dorsal view with focus on mesosoma.All Afrotropical species are shown, species names are embedded in each particular image for better comparison and orientation. Specimen codes are given inTable 1.

Fig. 11. Diagnostic plate showing still images from surface volume renderings of the posterior propodeum in posterior view (the remainder of the body virtually removed). All Afrotropical species are shown, species names are embedded in each particular image for better comparison and orientation. Specimen codes are given inTable 1.

Fig. 12. Diagnostic plate showing still images from surface volume renderings of the petiole and gaster in profile (the remainder of the body virtually removed).All Afrotropical species are shown, species names are embedded in each particular image for better comparison and orientation.Specimen codes are given inTable 1.

Fig. 14. Diagnostic plate showing differences in body pilosity. (A) D. mixta (CASENT0235473),(B) D. oculata (CASENT0235467),(C) D. aisnetu (CASENT0235475), (D) D.athene (CASENT0235476),(E) D.chimera (CASENT0235471),(F) D.damato (CASENT0247362),(G) D.dryad (CASENT0247371),(H) D.gaia (CASENT0247040), (I) D. gryphon (CASENT0247367), (J) D. hawkesi (CASENT0235470), (K) D. kalypso (CASENT0235468), (L) D. maia (CASENT0790541), (M) D. michelae (CASENT0235469), (N) D. patrizii (CASENT0235472), (O) D. penthos (CASENT0247383), (P) D. poweri (SAM-ENT-0011509), (Q) D. schulzei (CASENT0247370), (R) D. traegaordhi (CASENT0790122), (S) D. venus (CASENT0247017), (T) D. wakanda (CASENT0790326).With the exception of F, L, R,T, all other images are from https://www.antweb.org—photographers Michele Esposito and Will Ericson.

Fig. 56. Stacked digital color images of D. venus sp. n. paratype (CASENT0247017—from https://www.antweb.org, photographer Michele Esposito).(A) body in profile,(B) body in dorsal view,(C) head in full-face view.

Fig. 57. Still images from shaded surface display volume renderings of D. venus sp. n. holotype (CASENT0790116) showing virtually segmented body parts. (A) Body in dorsal view, (B) body in profile, (C) head in full-face view, (D) head in dorsal view, (E) head in anterodorsal view, (F) head in anterior view, (G) head in profile, (H) head in ventral view, (I) posterior propodeum in posterior view, (J) petiole in profile, (K) petiole and gaster in profile, (L) petiole in dorsal view, (M) petiole in anterior view, (N) petiole oblique anterior view, (O) gaster in dorsal view, (P) petiole in ventral view, (Q) abdominal sternite 3 in ventral view, (R) mesotibia and mesotarsus in anterior view.