Discothyrea gaia 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 : 43-45

Discothyrea gaia Hita Garcia & Lieberman sp. n.

( Figs. 4H , 6H , 7H , 8H , 9H , 10H , 11H , 12H , 13A , 14H ,

33 , 34 ; Supp Video S8 [online only])

Type Material

HOLOTYPE, pinned worker, ZIMBABWE, Manicaland, Melsetter, Umtali (= Mutare ), −19.8, 32.86667, 1700 m, collection code ANTC42123, II.1969 (R. Mussard) ( BMNH: CASENT0790100 ) . PARATYPES, six pinned workers with same data as holotype ( BMNH: CASENT0790101 ; CASC: CASENT0247040 ; MCZC: MCZ-ENT00593562; MHNG: CASENT0247037 , CASENT0247038 , CASENT0790099 , MHNG-ENTO- 00012649; SAMC: CASENT0790102 ) .

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 (CASENT0790100) 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 8).

Nontype Material

ZIMBABWE, Manicaland, Melsetter, Umtali (= Mutare ), [−18.94, 32.69], ca. 1700 m, II.1969 (R. Mussard) .

Diagnosis

The following character combination distinguishes D. gaia from the remainder of the complex: moderately thick petiole (DPeI 192–255; LPeI 194–264); comparatively shorter legs (HFI 54–58); mesotibia with distinct apicoventral spur; abundant, short and fine appressed pubescence more or less evenly distributed over entire body.

Worker Measurements and Indices (n = 8)

EL 0.04–0.05; HL 0.53–0.61; HW 0.43–0.51; SL 0.29–0.36; PH 0.29–0.35; PW 0.31–0.38; DML 0.43–0.51; PrH 0.33–0.40; WL 0.60–0.74; HFL 0.35–0.41; PeL 0.09–0.12; PeW 0.21–0.25; PeH 0.20–0.27; LT3 0.30–0.41; LT4 0.36–0.47; OI 7–9; CI 79–84; SI 54–60; LMI 46–49; DMI 50–53; DMI2 67–76; ASI 112–125; HFI 54–58; DPeI 192–255; LPeI 194–264.

Worker Description

Head clearly longer than broad (CI 79–84), subrectangular; posterior head margin straight, posterodorsal corners of head rounded. In frontal view, sides of head subparallel; eyes relatively large (OI 7–9), round, usually with several distinct ommatidia, situated almost halfway between anterolateral corner of gena and posterior head margin; eyes just visible in frontal view; frontal lamella in profile quite low, broadly triangular to lobate, apex convex to subacute; lamella slightly translucent, evenly so across its disc, without basal fenestra; medial clypeus gently to distinctly convex, prolonged anteromedially, lateral clypeus curving broadly between antennal sockets and anterolateral corners of head, bearing short curved setae. Antenna with moderately long scape (SI 54–60), scape moderately incrassate, gently bent; pedicel campaniform, longer than broad; true antennomere count eight; apparent antennomere count eight to eleven, flagellomeres basad apical club highly compressed, taken together only slightly longer than apical club. Ventral head with moderately developed postoccipital ridge, without or with very Model 8. 3D surface model of D. gaia sp. n. holotype (CASENT0790100). An interactive version of this model is available in the HTML version of this article online and at https://sketchfab.com/3d-models/9956253ce2a04153b46 3d0efe493b464.

short anteromedian carina; medial region of hypostoma roundedtriangular, arms strongly narrowed, similar in width across their length; palpal formula not examined. Mandible edentate; basal angle round to somewhat truncate confluent with prebasal median irregularly shaped carina running halfway of masticatory margin; ectal face with longitudinal carina confluent with masticatory margin for most of its length, leaving a narrow comma-shaped depressed region including basal angle.

Mesosoma gently sloping posteroventrally, pronotum slightly higher than propodeum; in dorsal view mesosoma conspicuously slender and elongate (DMI 50–53; DMI2 67–76) with concave sides, pronotum wider than propodeum and narrowest point of mesosoma around midpoint; pronotal humeri rounded; posterior propodeal margin straight; posterodorsal corners of propodeum rounded; declivitous face of propodeum very weakly concave in profile and oblique posterior view; propodeal spiracle inconspicuous, directed posterolaterally; propodeal lobes well-developed, lobate.

Legs short (HFI 55–56); mesotibia with apicoventral spur; mesobasitarsus relatively short, about as long as tarsomeres II–IV taken together.

Petiolar node thick, scarcely attenuated dorsally, about 1.9 to 2.6 times higher than broad (LPeI 194–264); in profile anterior face of node subvertical to shallowly sloping posterodorsally, apex thickly rounded to truncate, posterior face shallowly sloping posteroventrally; in dorsal view, petiole rectangular, sides divergent posteriorly, about 1.9 to 2.5 times broader than long (DPeI 192–255); in anterior view, petiolar outline roughly disciform, dorsum broadly rounded, angles not distinct; in oblique anterior view, anterior face flat; in ventral view, roughly trapezoidal, sides divering posteriorly; subpetiolar process variable in shape, lobate to subrectangular, in general fairly short, apex broadly rounded to flat; petiolar spiracles elliptical to reniform in ventral view.

Abdominal segment 3 campaniform, widest point of tergite just anterad end of segment; AS 3 deepest around its midpoint in profile, lacking distinct medial ridge or lobe; AS 3 without carinate prora, but still with anterior face distinctly depressed, anterior margin of ventral face weakly concave in ventral view; AT4 between 1.1 and 1.3 times longer than AT3 (ASI 112–125); AT4 hemidemispherical; AS 4 with moderately well-developed anterior lip, overlapping around the median one-third of AS 3, anterior margin convex in ventral view; successive abdominal segments short, telescopic, often concealed.

Sculpture generally reduced; head, petiole, mesosomal dorsum, abdominal segment 3 shallowly punctulate-reticulate, gena somewhat more coarsely punctate; lateral mesosoma and declivitous face of propodeum becoming weakly rugulose to substrigulate, particularly on lower surfaces; mandible rather roughly sculptured with piligerous punctulae; AT4 somewhat shinier than AT3, mostly smooth but with numerous minute piligerous punctulae.

Setation consisting of abundant but short and fine appressed pubescence more or less evenly distributed over entire body; petiolar node, AT3 and AT4 with variably developed layer of standing pilosity, sometimes predominantly decumbent with a few scattered erect setae, at other times numerous short erect setae present; successive abdominal segments with dense, distinctly longer, standing pilosity; ectal face of mandible with abundant, curved, appressed to decumbent setae; masticatory margin with row of straight setae inserted on mesal face.

Color uniformly dull testaceous orange to matte sandy brown, head sometimes slightly darker.

Etymology

In Greek mythology, Gaia was the primordial goddess of the Earth. The species is named for the habit of Discothyrea nesting cryptically in humus and leaf litter. The specific epithet is given as an appositive noun.

Distribution and Biology

Discothyrea gaia is known only from the type locality in eastern Zimbabwe ( Fig. 4H ). Based on the location of the collecting site, it appears that it was collected in savannah or woodland.

Comments

Discothyrea gaia is an easily recognizable species within the Afrotropical fauna. The presence of a conspicuous apicoventral spur on the mesotibia separates it from most other group members, except D. poweri and D. traegaordhi . The latter two lack any standing pilosity on the dorsal surfaces of the body, which is present in D. gaia . Not considering setation, D. gaia possesses shorter legs (HFI 54–58) and a thinner petiole (DPeI 192–255; LPeI 194–264) compared with D. poweri (DPeI 135–173; LPeI 152–194). The petiole of D. gaia is also generally thinner compared with the one of D. traegaordhi (DPeI 235–289; LPeI 236–313). However, there is some overlap in the morphometric ranges of these species. Furthermore, on the basis of the presence of a distinct mesotibial spur, relatively larger eyes (OI 7–10), and a Southern African distribution, it seems intuitive that D. gaia belongs to a putative clade that also contains D. poweri and D. traegaordhi .

Variation

Varies mainly in the shape of the subpetiolar process, which may be lobate or nearly rectangular. The color is inconsequentially variable from testaceous orange to matte brownish, with variable infuscation of the head.

Figures

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. 13. Diagnostic plate showing still images from surface volume renderings of mesotibiae and mesotarsi with mesotibial apicoventral spur, if present, colorized in green. (A) D. gaia, (B) D. poweri, (C) D. traegaordhi, (D) D. dryad, (E) D. maia, (F) D. wakanda.

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. 33. Stacked digital color images of D. gaia sp. n. paratype (CASENT0247040—from https://www.antweb.org, photographer Michele Esposito).(A) body in profile,(B) body in dorsal view,(C) head in full-face view.

Fig. 34. Still images from shaded surface display volume renderings of D. gaia sp. n. holotype (CASENT0790100) 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.