Discothyrea penthos 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 : 62-65

Discothyrea penthos Hita Garcia & Lieberman sp. n.

( Figs. 4O , 6O , 7O , 8O , 9O , 10O , 11O , 12O , 14O , 48 , 49 ; Supp. Video S15 [online only])

Type Material

HOLOTYPE, pinned worker, IVORY COAST, Monogaga , [4.81833, −6.49028], ca. 20 m, collection code ANTC42121, 24.X.1980 (V. Mahnert & J.L. Perret) ( BMNH: CASENT0790105 ) . PARATYPES, seven pinned workers with same data as holotype ( BMNH: CASENT0790107 ; CASC: CASENT0247383 ; MCZC: MCZ- ENT00593560; MHNG: CASENT0247381 , CASENT0247382 , CASENT0790106 ; SAMC: CASENT0247379 ) .

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 (CASENT0790105) 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 15).

Nontype Material

IVORY COAST: Abidjan, Adiopodoume Forest Biological Reserve , [5.335, −4.131], ca. 30 m, 4.III.1977 (I. Löbl) ; Abidjan, Banco Forest, Model 15. 3D surface model of D. penthos sp.n. holotype (CASENT0790105). An interactive version of this model is available in the HTML version of this article online and at https://sketchfab.com/3d-models/77dcda4c218d4a7fbbe a30c6bb2832c5 .

[5.38694, −4.05275], ca. 20 m, I.1963 (W.L. Brown); Tai Forest, [5.75, −7.12], ca. 250 m, 12.VIII.1975 (T. Diomande); Tai Forest, [5.75, −7.12], ca. 250 m, 17.X.1980 (V. Mahnert & J.L. Perret).

Diagnosis

The following character combination distinguishes D. penthos from the remainder of the complex: masticatory margin of mandible edentate; anterior clypeal margin usually asetose or with only short, inconspicuous setae; anterolateral corner of gena sharply demarcated but not dentate; in dorsal view mesosoma conspicuously thick, robust and stocky (DMI 62–65; DMI2 94–95); mesotibiae without apicoventral spur; propodeum dentate, teeth relatively large and subtended by narrow lamellulae; abdominal sternite 3 produced as squared to trapezoidal lobe, with distinct anterior, ventral, and posterior surfaces in profile; AT4 only weakly longer than AT3 (ASI 105–112); erect pilosity absent on all dorsal surfaces.

Worker Measurements and Indices (n = 10)

EL 0.01–0.02; HL 0.53–058; HW 0.46–0.49; SL 0.30–0.31; PH 0.29–0.33; DML 0.34–0.39; PW 0.33–0.37; PrH 0.34–0.38; WL 0.52–0.59; HFL 0.32–0.38; PeL 0.06–0.08; PeW 0.20–0.26; PeH 0.21–0.23; LT3 0.33–0.38; LT4 0.36–0.40; OI 2–4; CI 84–87; SI 52–57; LMI 53–56; DMI 62–65; DMI2 94–99; ASI 105–112; HFI 61–68; DPeI 329–429; LPeI 300–386.

Worker Description

Head broad (CI 84–87); posterior head margin straight, posterodorsal corners of head broadly rounded. In frontal view sides of head subparallel to slightly convex; head appearing subquadrate posterad antennal sockets; eyes very small (OI 2–4) but distinct and round, situated about a third of the way between anterolateral corner of gena and posterior head margin; eyes just visible in frontal view; anterolateral corner of gena sharply demarcated, approximately right-angled, sometimes slightly projecting laterally; frontal lamella roughly rhomboid in profile, with three distinct edges: anterior edge shortest, sloping posterodorsally; dorsal edge longest, sloping dorsally; lamella thinner and more translucent basally but without distinct fenestra; medial clypeus convex, lateral clypeus curving fairly strongly between antennal sockets and anterolateral corners of head, bearing numerous short curved setae. Antenna with moderately long scape (SI 52–57), scape moderately incrassate, gently bent; pedicel subglobose, broader than long; true antennomere count eleven; apparent antennomere count nine to twelve; flagellomeres basad apical club highly compressed, taken together only about as long as apical club. Ventral head with well-developed, sinuate preoccipital ridge with short, triangular anteromedian carina; medial region of hypostoma rounded, arms wide, spatulate apicolaterally; palpal formula not examined. Mandible with a small subapical angle; basal angle rounded to angulate; ectal face with weak carina extending from subapical angle to basal angle, leaving narrow, curved, depressed region.

Mesosoma in dorsal view conspicuously thick, robust and stocky (DMI 62–65; DMI2 94–95); evenly convex, pronotum only slightly higher than propodeum; in dorsal view, mesosoma narrowed posteriorly, pronotum distinctly wider than propodeum, inclusive of laterally divergent propodeal dentae; pronotal humeri somewhat narrowly rounded; posterior propodeal margin strongly concave; posterodorsal corners of propodeum dentate, dentae large, triangular, laterally flattened, mostly opaque, subtended by narrow but darkly pigmented lamellulae outlining propodeal concavity, hence propodeum laterally marginate; declivitous face of propodeum strongly concave in profile and oblique posterior view; propodeal spiracle large, directed posterodorsally; spiracle conspicuous due to polished, unsculptured area posterodorsad spiracle, extending to base of propodeal tooth, strongly contrasting with surrounding foveolate sculpture; propodeal lobes well-developed, flangelike.

Legs moderately long (HFI 61–68) and slender; mesotibia without apicoventral spur or seta; mesobasitarsus relatively short, about as long as tarsomeres II–IV taken together.

Petiolar node strongly attenuated dorsally, but appearing thick in profile since attenuation strongest medially; node about 3.0 to 3.8 times higher than long (LPeI 300–383); in profile, anterior face of node convex, apex blunt to rounded, curving evenly into convex posterior face, hence posterior face indistinct; in dorsal view, petiole roughly trapezoidal, sides divergent posteriorly, anterior face concave, about 3.3 to 4.3 times broader than long (DPeI 329–429); in anterior view, petiolar outline roughly pentagonal, edges poorly defined, angles strongly rounded; in oblique anterodorsal view, anterior face concave; subpetiolar process broadly falcate, curved, apex rounded.

Abdominal segment 3 with tergite broadly campaniform, widest just anterad end of segment; sternite somewhat squared in profile; AS 3 with wide median ridge extending anteriorly to prora, broadening to lobe posteriorly; prora well-defined, concave in ventral view; constriction between abdominal segments 3 and 4 distinct; AT4 weakly longer than AT3, about 1.1 times longer (ASI 105–112); AT4 bulbous, hemidemispherical; AS 4 with well-developed, wide anterior lip, overlapping most of the width of AS 3, anterior border weakly convex in ventral view; successive abdominal segments short, telescopic, often concealed.

Sculpture similarly foveolate on head, dorsal mesosoma, declivitous face of propodeum, petiole, abdominal segment 3 and AT4; foveolae becoming smaller on front of head; becoming foveolatereticulate on lateral mesosoma; area posterodorsad propodeal spiracle smooth and unsculptured; mandible with numerous, fine piligerous punctulae.

Setation very dilute and inconspicuous, consisting entirely of appressed pubescence, slightly longer on abdominal terga; body appearing glabrous at lower magnification; metapleural gland bulla with distinctly longer but fine, yellowish guard setae; scape and legs with short, somewhat sparse velvety appressed pubescence; ectal face of mandible with relatively long, curved, appressed setae; masticatory margin with row of short, straight seate.

Color more or less uniformly bright luteous-orange to yellowish.

Etymology

In Greek mythology, ‘Penthos’ was the spirit of grief, lamentation, and mourning. The specific epithet recognizes the highly threatened and rapidly diminishing rainforest habitat from which this species and most other Afrotropical Discothyrea originate. The specific epithet is given as an appositive noun.

Distribution and Biology

Discothyrea penthos is only known from four rainforest localities in Ivory Coast where it seems to live in leaf litter ( Fig. 4O ). This is the only species apparently endemic to the Guinean rainforests of West Africa.

Comments

This is another distinctive species distinguishable on the basis of the almost subquadrate head, conspicuous propodeal teeth, and the distinctive shape of abdominal sternite 3. The latter character is only found in two other species: D. hawkesi and D. kalypso . These two are easily separated since they are generally smaller, have shorter limbs, and are also more elongated and less robust than D. penthos . Furthermore, D. penthos is strongly sculptured throughout most of the body but displays a distinctly smooth and shiny area around the propodeal spiracle. The only species of the complex found in sympatry with D. penthos is D. venus , but both cannot be confused. Among a series of other differences, D. venus possesses a much larger AT 4 in relation to AT3 (ASI 158–183), has much more reduced sculpture, and lacks the conspicuous shape of abdominal sternite 3.

Variation

Despite being known from several localities in Ivory Coast, intraspecific variation appears to be negligible in this species.

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. 48. Stacked digital color images of D. penthos sp. n. paratype (CASENT0247383—from https://www.antweb.org, photographerWill Ericson). (A) body in profile, (B) body in dorsal view, (C) head in full-face view.

Fig. 49. Still images from shaded surface display volume renderings of D. penthos sp. n. holotype (CASENT0790105) 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.