Discothyrea kalypso 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 : 51-55

Discothyrea kalypso Hita Garcia & Lieberman sp. n.

( Figs. 2B , 4K , 6K , 7K , 8K , 9K , 10K , 11K , 12K , 14K , 39 ,

40 ; Supp Video S11 [online only])

Type Material

HOLOTYPE, pinned worker, TANZANIA, Pwani, Mafia, Mafia Island, Mlola Forest , −7.89576, 39.82842, 20 m, primary forest, leaf litter, 9.–13.III.2008 (P. Hawkes, Y. Mlacha & F. Ninga) ( SAMC: CASENT0235468 ).

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 (CASENT0235468) 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 11).

Diagnosis

The following character combination distinguishes D. kalypso from the remainder of the complex: eyes absent; frontal lamella disciform in profile, without conspicuous, round basal fenestra; mesosoma low, gracile (LMI 42; DMI2 81), not dorsally convex in profile; propodeum denticulate, denticles short and somewhat blunt; mesotibia without distinct ventral spur; abdominal sternite 3 rectangular in profile, ventral margin straight; erect pilosity absent from mesosoma and abdominal terga.

Worker Measurements and Indices (n = 1)

EL 0.00; HL 0.45; HW 0.35; SL 0.23; PH 0.19; PW 0.28; DML

0.30; PrH 0.22; WL 0.45; HFL 0.24; PeL 0.05; PeW 0.16; PeH 0.15; LT3 0.28; LT4 0.26; OI 0; CI 78; SI 51; LMI 42; DMI 62; DMI2 81; ASI 86; HFI 53; DPeI 320; LPeI 300.

Worker Description

Head somewhat elongate (CI 78), posterior head margin straight to weakly concave; posterodorsal corners of head rounded; in frontal view, sides of head gently convex; anterolateral corners of gena relatively well-defined; eyes absent; frontal lamella low and disciform in profile, without distinct apex, with conspicuous, elliptical basal fenestra; medial clypeus very narrow, anteromedially projecting, slightly emarginate apically, lateral clypeus broadly curving between antennal sockets and anterolateral corners of head, bearing very short curved setae. Antenna with relatively shorter scape (SI 54), scape moderately incrassate, gently bent; pedicel campaniform, slightly longer than broad; true antennomere count nine; apparent antennomere count nine; flagellomeres basad apical club highly compressed, taken together only about as long as apical club. Ventral head with narrow, horizontal postoccipital ridge with very short, roughly triangular anteromedian prolongation; median region of hypostoma rounded, arms narrowed, somewhat spatulate apicolaterally; palpal formula not examined. Mandible edentate except for well-defined, triangular prebasal denticle; basal angle squared; ectal face of mandible with carina running from baswal angle to apex, confluent with margin distal to prebasal denticle.

Mesosoma gracile, sloping posteroventrally, pronotum slightly higher than propodeum; in dorsal view mesosoma conspicuously slender and elongate (DMI 54; DMI2 81), pronotum not significantly wider than propodeum; pronotal humeri slightly rounded; posterior propodeal margin concave; posterodorsal corners of propodeum denticulate, denticles distinct but very short, laterally flattened, slightly diverging posterolaterally; declivitous face of propodeum distinctly concave in profile and oblique posterior view; propodeal spiracle small and very inconspicuous, directed posterodorsally; propodeal lobes well-developed, lobate.

Legs short (HFI 53) and rather slender; mesotibia without distinct ventral spur.

Petiolar node strongly attenuated dorsally, about 3.0 times higher than long (LPeI 300); in profile anterior face of node sloping posterodorsally, apex peaked, posterior face sloping posteroventrally; in dorsal view, petiole rectangular, about 3.2 times wider than long (DPeI 320), sides slightly convex; in anterior view, petiolar outline pentagonal, edges well-defined, angles somewhat rounded; in oblique anterior view, anterior face flat; subpetiolar process broad, lobate, apex rounded.

Abdominal segment 3 with tergite elongate-campaniform, anteriorly prolonged slightly over petiole, widest posteriorly; sternite subquadrate, in profile anterior and ventral faces flat, posterior face sloping slightly posterodorsally; prora well-defined, laterally with two triangular projections, medially straight; AS 3 with large median ridge extending anteriorly to prora; AT3 weakly longer than AT4 (ASI 86); AT4 slightly prolate hemidemispherical; AS 4 with anterior overlapping about median one-third of AS 3, anterior margin straight in ventral view; successive abdominal segments short, telescopic, often concealed.

Sculpture on head, mesosoma, and abdominal segment 3 foveolate-reticulate, foveolae becoming smaller on front of head Model 11. 3D surface model of D. kalypso sp. n. holotype (CASENT0235468). An interactive version of this model is available in the HTML version of this article online and at https://sketchfab.com/3d-models/2ae729d691ae4faa96b e3ce6e27b19c3.

and more dilute on lateral mesosoma; mandible with fine piligerous punctulae with fairly shiny interspaces; AT4 coriarious-punctulate, somewhat shinier than AT3.

Setation on head very dilute, short appressed pubescence, appearing glabrous at lower magnification; scape with velvety appressed pubescence; mesosoma and AT3 with short, dilute appressed pubescence almost entirely restricted to dorsal surfaces; AT4 with slightly longer but still inconspicuous appressed pubescence; successive abdominal segments with relatively short, mostly decumbent or subdecumbent setae, a few longer and more erect setae present on posterior segmental margins; legs with velvety appressed pubescence, similar to that on scape; ectal face of mandible with relatively long but fine appressed to decumbent setae; masticatory margin with row of straight, stout setae.

Color uniformly dull but clear yellowish.

Etymology

Kalypso was a nymph in Greek mythology who lived on a secluded island, best known from Homer’s epos ‘The Odyssey’. The species is named in reference to the isolated type locality on Mafia Island, Tanzania. The specific epithet is given as an appositive noun.

Distribution and Biology

At present known only from the type locality, the Mlola Forest on Mafia Island, Tanzania ( Fig. 4K ). It was collected from leaf litter in a primary coastal forest habitat at an elevation of 20 m.

Comments

The only other species known from Mafia Island is D. mixta but both belong to different species complexes and cannot be confused with each other. Furthermore, D. kalypso is moderately similar to D. maia , from which it can be distinguished most readily by the proportions of the mesosoma and development of the propodeal denticles and declivity, and the characters of the third abdominal sternite, which has a more strongly developed median ridge and a characteristically shaped prora. Additional differences are shorter appendages and overall smaller size, and the evenly rounded profile of the frontal lamella which has (indistinct) faces in the D. maia . Although both species are known only from the holotype, the ranges are entirely disjunct and widely separated. Discothyrea kalypso is also quite similar in general habitus to D. michelae , being rather slender and gracile, but lacks the characteristic petiolar shape and standing pilosity of the latter.

Variation

Since D. kalypso is only known from the holotype, there is no information about intraspecific variation.

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. 39. Stacked digital color images of D. kalypso sp. n. holotype (CASENT0235468—from https://www.antweb.org, photographerWill Ericson). (A) body in profile, (B) body in dorsal view, (C) head in full-face view.

Fig. 40. Still images from shaded surface display volume renderings of D. kalypso sp. n. holotype (CASENT0235468) 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.