Isognathotermes phallicaecalis 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 : 99-103

Isognathotermes phallicaecalis Josens & Deligne sp. nov.

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Figs 26–31, 33, 51–52, distribution map: Fig. 53; Table 10

Diagnosis

Soldiers and workers of Isognathotermes phallicaecalis sp. nov. and I. phalloides sp. nov. share the same kind of phalloid cecum, extended forward in a finger-like process that can be swollen distally or capped or crowned ( Figs 52, 56), which distinguishes them from all other species of Isognathotermes ; they have morphologically similar soldiers, with a slight difference in the curvature of the mandibles ( Fig. 22); however, they come from different ecosystems: continental evergreen forest in the case of I. phallicaecalis , forest galleries in the case of I. phalloides .

The worker of I. phallicaecalis sp. nov. has a finitimus EVA and is among the small workers in the genus Isognathotermes . Its head is, on average, somewhat wider than that of I. phalloides sp. nov. ( Fig. 30).

The soldier’s EVA can generally be recognized as belonging to the finitimus pattern; on average it has longer mandibles than I. phalloides sp. nov.: SMlL = 2.17 –2.53 mm (vs 1.99–2.36 mm in I. phalloides ).

The imago is unknown.

This species is also defined by its ecology and chorology: to date it has been found only in forested environments of the northern Congo Republic and Cameroon ( Fig. 53).

Etymology

The epithet phallicaecalis from the Greek φαλλός ( phallos, phallus) and the Latin caecalis (of the caecum) refers to the caecum phalloid morphology in workers and soldiers.

Material examined

Twelve samples from three locations.

Holotype

CONGO REPUBLIC • soldier; Loundoungou ; 2°22.827′ N, 17°4.226′ E; 4 Dec. 2017; Y. Roisin leg.; study code: DJ 0529; GenBank nos MN646722 ( COI) MN685925 ( COII) MN685986 ( 28S) PQ679196 (mitogenome); BE RMCA INS.Iso.059288.

Paratypes

CONGO REPUBLIC • soldier, worker; same data as for holotype; BE RMCA INS.Iso.059936 .

Other material examined

CAMEROON • soldier; Dja Rock ; 3°20.73′ N, 12°42.84′ E; 30 Mar. 2015; J. Šobotnik leg.; study code: DJ B320; BE RMCA INS. Iso. 059287 .

CONGO REPUBLIC • soldier, worker; Mokabi ; 3°8.796′ N, 16°57.869′ E; 8 Dec. 2017; Y. Roisin leg.; study code: DJ 0527; GenBank no PQ679190 (mitogenome); BE RMCA INS.Iso.059290 • soldier, worker; Mokabi ; 3°8.795′ N, 16°57.826′ E; 8 Dec. 2017; Y. Roisin leg.; study code: DJ 0528; BE RMCA INS.Iso.059289 • soldier, worker; Loundoungou ; 2°22.929′ N, 17°4.301′ E; Dec. 2018; S. Lenz leg.; study code: DJ 0759; GenBank no PV564652 (mitogenome); BE RMCA INS.Iso.059296 • soldier, worker; Loundoungou ; 2°22.93′ N, 17°4.301′ E; Dec. 2018; S. Lenz leg.; study code: DJ 0760; GenBank no PV564657 (mitogenome); BE RMCA INS.Iso.059291 • soldier, worker; Loundoungou ; 2°22.93′ N, 17°4.301′ E; Dec. 2018; S. Lenz leg.; study code: DJ 0761; GenBank no PQ679202 (mitogenome); BE RMCA INS.Iso.059297 • soldier, worker; Loundoungou ; 2°22.93′ N, 17°4.301′ E; Dec. 2018; S. Lenz leg.; study code: DJ 0762; BE RMCA INS.Iso.059292 • soldier, worker; Loundoungou ; 2°22.93′ N, 17°4.301′ E; Dec. 2018; S. Lenz leg.; study code: DJ 0763; BE RMCA INS.Iso.059295 • soldier, worker; Loundoungou ; 2°22.93′ N, 17°4.301′ E; Dec. 2018; S. Lenz leg.; study code: DJ 0764; BE RMCA INS. Iso.059293 • soldier, worker; Loundoungou ; 2°22.93′ N, 17°4.301′ E; Dec. 2018; S. Lenz leg.; study code: DJ 0765; BE RMCA INS.Iso.059298 • soldier, worker; Loundoungou ; 2°22.93′ N, 17°4.301′ E; Dec. 2018; S. Lenz leg.; study code: DJ 0766; GenBank no PV564655 (mitogenome); BE RMCA INS. Iso.059294 .

Historical review

This species is described here; the imago is still unknown. It was recently discovered by three of us (JŠ, YR & SL) in Cameroon and Northern Congo.

Description

Imago

The imago is unknown.

Soldier

COLOUR. Head capsule tending towards faded palette (Cf4–Cf5); there is a gradient from a darker frons to a paler back. Antennae and labrum concolorous with or somewhat paler than frons. Mandibles dark (C7–C8) with an abrupt clearing on their bases (C5–C6) which is concolorous with frons. Thorax and legs generally paler (C3–C4) than head capsule. Abdomen grey to red-brown owing to digestive bolus, sometimes with a yellowish tinge on tergites.

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 always with 3–6 large setae on each lobe. Thorax: pro- and mesonotum with a small number of setae mainly located on margins. Legs: fore coxa bear 1–3 spines on carina and none (rarely one) on ventral side; trochanter with 2–8 spines; fore, mid, and hind tibia bearing 3, 2, 2 apical spurs and 0, 2, 0 subapical spurs respectively and a row of 8–15 spines along their shaft. Abdomen: tergites with some large setae, mainly on their posterior margins. Sternites with long setae, erect or slightly directed forward, often coloured, and smaller setae directed backwards.

STRUCTURE (measurements in Table 10; Figs 51–52). Size: the soldiers of I. phallicaecalis sp. nov. are medium sized among of the genus Isognathotermes ( Fig. 28). Head capsule: always clearly sclerotised, appreciably longer than wide. Dorsal view: lateral sides mostly subparallel with a clear narrowing near posterior fourth ( Fig. 51), from antennal sockets sides converge more or less clearly towards bases of mandibles; posterior side regularly rounded or with a short straight middle part; upper profile concave. Angle between extended mandibles and frons a little obtuse; frons without any or with a week anterior hump. Gulamentum in ventral view always constricted in its posterior half, with sides of anterior part forming an acute widening or a kind of ear on each side. Antennae: of 14.5–15 articles. Labrum: always deeply bifurcate and wider than long, with lyre-shaped sides; lobes angular, with fine, translucent tips; anterior margin concave. Mandibles: sabre-like with a middle-sized curvature in the genus Isognathotermes ; inner edges generally smooth with one distinct but very small marginal tooth, near molar tooth on each mandible; mandibles clearly shorter than head; entire surface of both mandibles smooth and glossy. Right mandible slightly more curved than left. Thorax: pronotum sellate, as wide as 59–64% of head width, with generally entire anterior and posterior margins. Fore coxa flanged ventrally resulting in a more or less sharp carina. Gut: enteric valve seating on left side, best seen in ventral view, situated in second half of abdomen. Caecum always rather well developed, best seen in ventral view, near centre of abdomen, as a typical finger-like process, extended forward and generally swollen distally or seeming to be capped ( Figs 52, 56). Arrangement of enteric valve cushions showing trilateral symmetry, the odd cushions being 20–25% longer than the even cushions, with a pilosity becoming very dense distally showing the place where a hump would be expected (in comparison with the worker’s EVA).

Worker

COLOUR. Head capsule pale (C2–C3). Antennae: proximal articles pale (C2), distal articles two levels darker (C4). Thorax, nota, and legs pale (C1–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 3–6 spines on carina and 1–2 on ventral side; fore trochanter with 5–7 spines; fore, mid, and hind tibia bearing 3, 2, 2 apical spurs and 0, 2, 0 subapical spurs respectively and a row of 6–15 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 10; Figs 51–52). Size: the workers of I. phallicaecalis sp. nov. are, on average, medium sized among the genus Isognathotermes ( Fig. 30). Head capsule: weakly sclerotised (except mandibles). Antennae of 14.5 (rarely 14) articles. Labrum: cupola shaped. Left mandible: apical tooth well developed with a sharp tip when fresh; marginal teeth three in number, first marginal tooth well developed but with a blunt tip even when fresh, second marginal tooth faint (visible as an undulated edge and disappearing in worn mandibles), third marginal tooth with a blunt tip; premolar tooth with its proximal end not hidden under molar prominence; 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 tooth well developed with a sharp tip when fresh; second marginal tooth 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 66–71% 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 second half of abdomen. Arrangement of enteric valve cushions of the finitimus pattern ( Fig. 5) with triradial symmetry: the odd PCs, in their downstream part, bear a higher density of rather short bristles on a globular bulge, the latter sometimes weakly developed; supporting bristles are numerous: 18–33 on each side of the odd PCs ( Fig. 51); secondary cushions are wide at the upstream end, narrowing noticeably downstream with a homogeneous spine scattering. Caecum always well developed, best seen in ventral view, near centre of abdomen, as a finger-like process, extended forward and often swollen distally or seeming to be capped ( Figs 52, 56).

Chorology-ecology

To date, this species is only known from two sites in the northern Congo Republic and one in Cameroon (in the northwestern Congolian lowland forest ecoregion: Fig. 53).

Molecular data

This species was previously published under the label “pha2” (DJ 0529), established as sister to I. planifrons ( Hellemans et al. 2021) . Six mitogenomes of I. phallicaecalis sp. nov. are published alongside this work (GenBank accessions: see Supp. file 3 and ‘Material examined’). The mitogenomes exhibit less than 1.21% dissimilarity with each other (Supp. file 4); and a dissimilarity of up to 2.26% with I. phalloides sp. nov. – the other samples exhibiting phalloid caeca – which justifies the creation of two different (new) species. Of note, I. phallicaecalis sp. nov. is paraphyletic with respect to I. similifinitimus sp. nov. ( Fig. 33), to which mitogenomes are less than 1.50% dissimilar. Even though these two species were found non-monophyletic, the clear morphological and anatomical differences (e.g., caecum) support their recognition as distinct species. Our use of (maternally inherited) mitogenomes only may have limited our ability to resolve their evolutionary relationships. Thus, we posit that their respective paraphylies may either stem from incomplete lineage sorting, or mitogenome introgression following hybridization. Future analyses leveraging nuclear loci will be crucial to shed further light on their relationships.