Isognathotermes acristatus Josens & Deligne, 2025

Josens, Guy, Deligne, Jean, Harry, Myriam, Roy, Virginie, Akama, Pierre D., Coulibaly, Tenon, Dosso, Kanvaly, Goergen, Georg, Hasson, Michel, Kasangij, Patrick Kasangij A, Kifukieto, Carmel, Ru, Bruno Le, Loko, Laura Estelle Yêyinou, Ndiaye, Abdoulaye Baila, Roisin, Yves, Sion, Noémie, Šobotnik, Jan, Stiblik, Petr, Kuenda, Soki Kue Di, Traoré, Saran, Viage, Manuela, Wango, Solange Patricia, Kaymak, Esra, Bourguignon, Thomas & Hellemans, Simon, 2025, An integrative revision of the genus Isognathotermes (Termitidae: Cubitermitinae) with description of seven new species and four new subspecies, European Journal of Taxonomy 1024, pp. 1-197 : 39-43

Isognathotermes acristatus Josens & Deligne sp. nov.

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Figs 26–34, distribution map: Fig. 47; Table 2

Diagnosis

This species is rather atypical in the genus Isognathotermes ; the worker is small sized and characterised by its odd PCs without crests but furnished with strong setae at the place where crests would be expected ( Fig. 34); it could therefore be confused with a species of Ternicubitermes ( bilobatodes EVA). The PCs carry a low number (5–10) of supporting bristles; it could therefore also be confused with a species of Cubitermes (sensu Hellemans et al. 2021) . However, it has carinated fore coxae bearing 3–4 strong spines (the workers of Ternicubitermes and Cubitermes have unarmed conical coxae). It is also characterised by a high PC elongation index: WVPOdd-Elg = 9.79–13.6.

The soldier is small sized in the genus Isognathotermes and can be recognised by its very weakly curved mandibles (even less curved than those of I. rectimalatus sp. nov.): SMlc = 0.11–0.16 mm.

The imago is medium sized in the genus Isognathotermes and can hardly be distinguished from I. severus or I. ugandensis ugandensis . It has larger ocelli than I. ugandensis (IOc D = 0.20–0.22 mm).

To date, this species is only known from Angola.

Etymology

The epithet acristatus , from Greek α (without) and Latin cristatus (crested) refers to the quasi absence of crests on the odd PCs of the enteric valve, even in the worker caste.

Material examined

Four samples from two locations.

Holotype

ANGOLA • soldier; Mussende ; 10°33.17′ S, 15°39.492′ E; 25 Oct. 2021; M. Hasson leg.; study code: DJ 0811; GenBank no PQ679177 (mitogenome); BE RMCA INS. Iso. 059148.

Paratypes

ANGOLA • soldier, worker, ♂ (alate), ♀ (queen); same data as for holotype; BE RMCA INS.Iso.059149 .

Other material examined

ANGOLA • soldier, worker; Cangandala N.P.; 9°49.33′ S, 16°40′ E; 1 Mar. 2019; M. Viage leg.; study code: DJ 0865; GenBank no PQ679228 (mitogenome); BE RMCA INS.Iso.059145 • soldier, worker; Cangandala N.P.; 9°49.33′ S, 16°40′ E; 1 Mar. 2019; M. Viage leg.; study code: DJ 0866; GenBank no PQ679192 (mitogenome); BE RMCA INS.Iso.059147 • soldier, worker; Cangandala N.P.; 9°49.33′ S, 16°40′ E; 1 Mar. 2019; M. Viage leg.; study code: DJ 0868; BE RMCA INS.Iso.059146 .

Historical review

Specimens of this species were recently collected by two of us (MV & MiH) in Angola; the imago, the soldier, and the worker are described here.

Description

Imago

COLOUR. Head capsule: well sclerotised and dark (C6); fontanelle slightly (one level) paler. Postclypeus concolorous with head capsule. Antennae C4–C5. Thorax: pronotum concolorous with head capsule; meso- and metanotum C4 slightly paler than head. Legs tibia C5 slightly paler than femur C4. Abdomen: tergites C5. Sternites appreciably paler in middle (C3) with both sides darker (C5) posterior sternites darker (C4–C5) than anterior.

SETATION. Head capsule, with some prominent setae set amongst a high density of short, fine setae forming a dense mat. Labrum and postclypeus with some prominent setae mixed with shorter ones. Antennae with some prominent setae, some more numerous smaller setae and, mainly distally on most articles, a bunch of very fine, bent setae (visible only at high magnification, 50 × or more). Thorax: pronotum with prominent setae mainly on margins and shorter ones in middle; meso- and metanotum with some fine, pale setae, arranged in a medio-longitudinal strip, visible at 80 ×, with some large setae on posterior lobe. Legs very pilose, furnished (among numerous fine setae) with 9–10 stronger setae on the carina of fore coxa and 3–4 on the ventral side of fore coxa and 8–9 on trochanter; tibia pilose, fore, mid, and hind tibia furnished with 15–30 spines and bearing 3, 2, 2 apical spurs and 0, 2, 0 subapical spurs respectively. Abdomen: tergites with many large and small setae. Sternites with long setae, erect or directed slightly forward, and many long and smaller setae directed backwards.

STRUCTURE (measurements in Table 2, Fig. 34). Size: the imagines of I. acristatus sp. nov. are medium sized in the genus Isognathotermes ( Fig. 26). Head capsule: compound eyes shortly oval; ocelli rather large (IOcD> 0.20 mm) oval, removed from eyes by a distance equal to 0.8–0.9 ocellus small diameter; fontanelle generally a tiny round or elongate marking. Antennae: 16 articles, shortened to 13 by amputation in queen. Labrum: cupola shaped, wider than long. Left mandible with apical tooth small sized in the genus ( Fig. 27) and more prominent than first marginal; marginal teeth three in number but second one only suggested by an undulation of edge between first and third marginal teeth; only the apical tooth is acute in unworn specimen; premolar tooth unobstructed and clearly visible in dorsal view; molar tooth bearing a rounded molar prominence dorsally and ending posteriorly in a tiny acute apophysis. Right mandible with apical tooth always more prominent than first marginal; marginal teeth two in number; second marginal tooth with a blunt tip even when fresh; molar tooth bearing a ventral rounded flange and ending posteriorly in a kind of heel. Thorax: pronotum appreciably wider than long and narrower than head width (including the eyes), straight to very weakly sellate with anterior lobe short and very slightly elevated. Fore coxa flanged ventrally resulting in a sharp carina. Gut not studied.

Soldier

COLOUR. Head capsule C4–C6. Antennae and labrum concolorous or somewhat paler than head capsule. Mandibles dark (C6–C8) with an abrupt clearing on their bases (two levels) which is generally the same colour as frons. Thorax and legs paler than head capsule (C2–C4). Abdomen grey to red-brown owing to digestive bolus.

SETATION. Head capsule with few scattered setae; on frons a dense bunch of setae surrounds and overhangs fontanelle. Antennae with some prominent setae, more numerous smaller setae and at distal extremity of distal articles, a bunch of fine, bent setae (visible only at high magnification, 50 × or more). Labrum with 4–5 large setae on each lobe. Thorax: pro- and mesonotum with a small number of setae mainly located on margins. Legs: fore coxa with at least one fine seta and 2–6 spines or strong setae on carina and not any spine on ventral side; trochanter generally with some strong lined-up setae; fore, mid, and hind tibia bearing 3, 2, 2 apical spurs and 0, 2, 0 subapical spurs respectively (the latter sometimes weakly developed) and a row of 6–15 spines along their shaft. Abdomen: tergites with some large setae, mainly or only on their posterior margins. Sternites with long setae, erect or slightly directed forward, often coloured, and smaller setae directed backwards.

STRUCTURE (measurements in Table 2, Fig. 34). Size: the soldiers of I. acristatus sp. nov. is among the small soldiers in the genus Isognathotermes ( Fig. 28). Head capsule: always clearly sclerotised; appreciably longer than wide. Dorsal view: lateral sides mostly subparallel with a very slight narrowing near posterior third or fourth; from antennal sockets sides converge towards bases of mandibles; posterior side regularly convex. Slightly to strongly concave upper profile; angle between extended mandibles and frons obtuse; frons with a small bump that overhangs the fontanelle. Gulamentum in ventral view constricted in its posterior half, with sides of anterior part smoothly rounded to extended into a kind of angular ears. Antennae: of 14–15 articles. Labrum: deeply bifurcate and wider than long, with almost straight sides; rounded lobes without translucent tips; anterior margin concave. Mandibles: sabre-like; inner edges smooth with one distinct but small marginal tooth, near molar tooth on each mandible; mandibles clearly shorter than head; entire surface of both mandibles smooth and glossy. Mandibles very slightly curved, among the least curved in the genus. Right mandible slightly more curved than left. Thorax: pronotum sellate, as wide as 52 to 56% of head width, with straight anterior and posterior margins. Fore coxa flanged ventrally resulting in a sharp carina. Gut: enteric valve seating on left side, best seen in ventral view, situated in second half of abdomen. Caecum rather small, best seen in ventral view, near centre of abdomen, three- to four-lobed. Arrangement of enteric valve cushions showing trilateral symmetry, the odd cushions narrow and longer than the even ones (as in the muneris EVA).

Worker

COLOUR. Head capsule pale (C2–C3). Antennae: proximal articles pale (C2), distal articles two levels darker (C4). Thorax, nota, and legs pale (C2–C3). Abdomen grey to red-brown owing to digestive bolus.

SETATION. Head capsule and postclypeus with few, erect, scattered setae. Labrum with few, robust scattered setae. Antennae with some prominent setae, some more numerous smaller setae and at distal extremity of distal articles, a bunch of fine, bent setae (visible only at high magnification, 50 × or more). Thorax: nota with some scattered setae. Legs: fore coxa carinated, bearing one fine seta and furnished with 3–4 spines on carina and 1–3 on ventral side; fore trochanter with 6 lined up spines; fore, mid, and hind tibia bearing 3, 2, 2 apical spurs and 0, 2, 0 subapical spurs respectively and a row of 7–15 spines. Abdomen: tergites with scattered setae. Sternites with long setae, erect or slightly directed forward, often coloured, and smaller setae directed backwards.

STRUCTURE (measurements in Table 2, Fig. 34). Size: the workers of I. acristatus sp. nov. are medium sized in the genus Isognathotermes .( Fig. 30). Head capsule: weakly sclerotised (except mandibles). Antennae: 14–14.5 articles. Labrum: cupola shaped. Left mandible: apical tooth well developed but shorter than in most other species; marginal teeth three in number, first marginal well developed but with a blunt tip even when fresh, second marginal faint (visible as an undulated edge and disappearing in worn mandibles), third marginal with a blunt tip; premolar tooth unobstructed and clearly visible in dorsal view; molar tooth bearing a rounded molar prominence dorsally and ending posteriorly in a tiny acute apophysis. Right mandible: apical tooth well developed with a sharp tip when fresh; marginal teeth two in number; first marginal well developed with a sharp tip when fresh; second marginal smaller and with a blunt tip even when fresh; molar tooth bearing a ventral rounded flange and ending posteriorly in a kind of heel. Thorax: pronotum sellate, as wide as about 63% of head width. Fore coxa flanged ventrally resulting in a sharp carina. Gut: enteric valve seating on left side, best seen in ventral view, situated in posterior half of abdomen. Arrangement of enteric valve cushions of the muneris pattern with triradial symmetry: the odd PCs, in their downstream part, are narrow and bear strong, bent setae; supporting bristles are few: 5–10 on each side of the odd PCs; secondary cushions are wide at the upstream end, narrowing noticeably downstream with a homogeneous spine scattering. Caecum rather small, visible in ventral view, near centre of abdomen, shortly lobed (3–4 small lobes).

Chorology-ecology

This species is only known from Angola, its geographic distribution ( Fig. 47) is linked with the Angolan Miombo woodland ecoregion.

Molecular data

Mitogenomes of I. acristatus sp. nov. (three samples) exhibit less than 1% dissimilarity with each other (Supp. file 4: GenBank accessions: see supplementary Supp. file 3 and ‘Material examined’), and much more with other species. The species acristatus is found sister–group to all other Isognathotermes species ( Fig. 33); its atypical EVA -very simple and comparable to the EVA of Cubitermes or Ternicubitermes - may represent the ancestral state of this genus’ EVA.