Discothyrea aisnetu 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 : 29-31

Discothyrea aisnetu Hita Garcia & Lieberman sp. n.

( Figs. 4C , 6C , 7C , 8C , 9C , 10C , 11C , 12C , 14C , 23 , 24 ; Supp Video S3 [online only])

Type Material

HOLOTYPE, pinned worker, TANZANIA, Kilimanjaro Region, Mwanga, Kindoroko Forest Reserve , −3.7452, 37.64267, 1739 m, primary forest, leaf litter, Winkler, collection code CEPF-TZ-5.2, 5.–8.IX.2005 (P. Hawkes, J. Makwati & R. Mtana) ( SAMC: CASENT0235475 ) . PARATYPES, one worker with same data as holotype ( BMNH: CASENT0250399 ); and one worker with same data as holotype except collection code CEPF-TZ-5.4 and hand collected ( CASC: CASENT0250394 ) .

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 (CASENT0235475) 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 3).

Diagnosis

The following character combination separates D. aisnetu from the other species of the complex: mesosomal profile high-rounded and extremely convex; relatively large species (HW 0.57–0.61; WL 0.80– 0.90); in dorsal view mesosoma relatively thin and slender (DMI 53–58; DMI2 85–88); mesotibia without apicoventral spur; AT3 around 1.1 to 1.2 times longer than AT4 (ASI 85–90).

Worker Measurements and Indices (n = 3)

EL 0.03; HL 0.68–0.70; HW 0.57–0.61; SL 0.43–0.45; PH 0.40–0.43; PW 0.46–0.48; DML 0.52–0.57; PrH 0.49–0.53; WL 0.80–0.90; HFL 0.55–0.58; PeL 0.15–0.17; PeW 0.33–0.37; PeH 0.30–0.31; LT3 0.50–0.56; LT4 0.45–0.50; OI 4; CI 84–87; SI 63–67; LMI 44–51; DMI 53–58; DMI2 85–88; ASI 85–90; HFI 64–69; DPeI 218–220; LPeI 184–200.

Worker Description

Head slightly longer than broad (CI 84–87), posterior head margin nearly straight; posterodorsal corners of head rounded; sides of head slightly constricted laterally between eyes and anterolateral corner of gena, this region appearing concave in frontal view; eyes present, small (OI 4), round, comprising several ommatidia, situated around one-third of way between corner of gena and posterior head margin; eyes just visible in frontal view; frontal lamella triangular in profile, apex rounded; lamella more or less evenly translucent across its disc, without fenestra; medial clypeus broad, gently convex, lateral clypeus curving gently between antennal sockets and anterolateral corners of head, bearing short, dense, curved setae. Antenna with long scape (SI 63–67), scape somewhat expanded apically, gently bent; pedicel campaniform, longer than broad; true antennomere count nine; apparent antennomere count nine to eleven, flagellomeres basad apical club relatively long, taken together longer than apical club; club relatively narrow. Ventral head with postoccipital ridge well-defined, with very short anteromedian carina; hypostoma very wide overall, median region bluntly triangular, arms only slightly narrowed, similar in width across their entire length; palpal formula not examined. Mandible edentate; basal angle rounded; ectal face with low carina originating near basal angle and becoming confluent with masticatory margin at apical one-fourth, leaving narrow, arcuate, depressed medial region on masticatory margin.

Mesosoma in profile robust, high-rounded and extremely convex; in dorsal view mesosoma relatively thin and slender (DMI 53–58; DMI2 85–88) and distinctly narrowed posteriorly, pronotum significantly wider than propodeum; pronotal humeri broadly rounded; posterior propodeal margin indistinct or appearing straight; in profile, propodeum without distinct juncture between dorsal and declivitous faces, lacking angles or denticles, not marginate; propodeal declivity sloping, at most barely concave in oblique posterior view; propodeal spiracle distinct, aperture round, directed posteriorly; propodeal lobes well-developed, flange-like.

Legs moderately long to long and narrow (HFI 64–69); mesotibia without apicoventral spur, with small but distinct seta inserted in apical pit; mesobasitarsus very elongate, almost as long as remaining tarsomeres taken together.

Petiole node quite thick, about 1.8 to 2.0 times higher than long (LPeI 184–200), rounded-cuneate in profile; in profile anterior Model 3. 3D surface model of D. aisnetu sp. n. holotype (CASENT0235475). An interactive version of this model is available in the HTML version of this article online and at https://sketchfab.com/3d-models/1bf459295c6941d6b11 51aa006e3382a.

face of node sloping posterodorsally, gently curved, apex rounded, hence without distinct posterior face; in dorsal view, node roundedrectangular to nearly elliptical, around 2.2 times broader than long (DPeI 218–220), sides convex; in anterior view, petiolar outline broadly disciform, without distinct angles, dorsally rounded; in ventral view, sides distinctly curved, outline campaniform; subpetiolar process elongate-triangular, weakly spiniform to digitate, anteriorly projecting, apex approximately rounded; petiolar spiracles very large, round in ventral view.

Abdominal segment 3 campaniform, widest posteriorly, sternite rounded and distinctly bulging in profile; AS 3 with weak medial carina; prora present as a fine carina, weakly concave in ventral view; AT3 around 1.1 to 1.2 times longer than AT4 (ASI 85–90); AT4 gently recurved hemidemispherical; AS 4 with anterior lip short and narrow, scarcely overlapping AS 3, anterior margin straight in ventral view; successive abdominal segments short, telescopic, often concealed.

Sculpture on head evenly punctate-reticulate, sculpture equally developed over head except medial clypeus distinctly smoother; mandibles fairly smooth but with fine piligerous punctulae; mesosoma similarly punctate-reticulate on dorsum and sides, punctae sometimes arranged in concentric lines just anterad pronotomesepisternal junction; declivitious face of propodeum finely reticulate to confused-rugulose; petiole and abdominal segment 3 (tergite and sternite) similarly punctate-reticulate, punctures on AT3 piligerous; abdominal tergite 4 distinctively shinier and less coarsely sculptured than AT3 with fine piligerous punctulae and posteriorly with a few scattered, shallow punctae.

Setation on head and scape fairly short, dense, appressed and white pubescence; ectal face of mandible with fairly long, thin, curved, spaced setae; masticatory margin with row of straight, stout setae; mesosoma with well-developed appressed pubescence, more abundant on dorsum and lateral pronotum than remainder of mesosoma, shortest and most diffuse on sides of propodeum; petiole heavily setose, setae appressed to decumbent, quite long and thick, especially on dorsum of node; setae obscuring petiolar sculpture; ventral margin of petiolar sternite with row of straight, erect hairs; abdominal segment 3 with fairly long, mostly appressed setae, similar on tergite and sternite; AT4 more heavily setose; dorsum most strongly pubescent, becoming more diffuse ventrolaterad; successive abdominal segments with long, flexuous, curved pilosity; legs with appressed, fine pubescence, on tibiae and tarsi generally longer than on femora.

Color luteous-orange to deep iron-red, appendages yellow.

Etymology

The specific epithet is the Latin interjection ‘Aisne tu?’ meaning roughly ‘Could it be?’ (lit. ‘Do you say?’), recalling the authors’ reactions upon first viewing this aberrant species.

Distribution and Biology

At present the species is known only from the type locality, the Kindoroko Forest Reserve in Tanzania ( Fig. 4C ), which is a montane rainforest located at an altitude of 1739 m. Discothyrea aisnetu was sampled from leaf litter.

Comments

This highly characteristic species displays a unique mesosomal shape not seen in the remainder of the African Discothyrea fauna. Within the traegaordhi -complex it is a rather large species with long limbs, comparatively distinct flagellomeres and relatively narrow apical club. This is a character set shared only with D. poweri . However, it remains unclear if these two species are closely related since apart from the differently shaped mesosomal outline, D. aisnetu also lacks the mesotibial spur present in D. poweri , which is an important diagnostic character.

Variation

Discothyrea aisnetu varies slightly in color and in the pattern of punctae on the lateral pronotum just anterad the pronotomesepisternal juncture: they are more or less arranged in concentric broken lines.

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. 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. 23. Stacked digital color images of D. aisnetu sp. n. holotype (CASENT0235475 - from https://www.antweb.org, photographerWill Ericson). (A) body in profile, (B) body in dorsal view, (C) head in full-face view.

Fig. 24. Still images from shaded surface display volume renderings of D. aisnetu sp. n. holotype (CASENT0235475) 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.