A new genus and species of mandibulate nasute termite (Isoptera, Termitidae, Syntermitinae) from Brazil

Abstract Acangaobitermes krishnai gen. et sp. n., is described here, based on soldiers and workers collected in Brazil. Some characteristics suggest a close kinship with Noirotitermes Cancello & Myles, and both genera share the following traits absent in all other Syntermitinae: the microsculpturing on the soldier head capsule surface with internal granulations; the piercing mandibles with a single very reduced marginal tooth and the worker very similar in both genera. The most conspicuous differences between Acangaobitermes and Noirotitermes are the shape of the soldier head, the frontal tube and pronotum. The shape of the soldier head in Noirotitermes is unusual, with a very broad and short frontal tube, four conspicuous protuberances like sharp corners at the rear, while in the new genus the posterior contour of the head is devoid of these protuberances. The frontal tube of Acangaobitermes is elongate and conical, while in Noirotitermes it is short and very broad. The pronotum of Acangaobitermes is saddle-shaped as is usual in other Syntermitinae, while it is aberrant in Noirotitermes.

In the past, the mandibulate nasutes were considered an ancestral group of Nasutitermitinae but recent studies highlighted an evolutionary history independent of true nasutes (Noirot 2001, Ohkuma et al. 2004, Inward et al. 2007). Engel and Krishna (2004) proposed Syntermitinae as a subfamily of Termitidae including four of the thirteen genera of mandibulate nasutes, and they affirm that the other mandibulate genera of Nasutitermitinae "may eventually be included" in the subfamily.
In this work we describe a new monotypic termite genus that seems to be closely related to Noirotitermes. Both genera share traits absent in all other Syntermitinae: the microsculpturing on the soldier head capsule surface with internal granulations; the piercing mandibles upturned, with a single reduced marginal tooth; and the worker almost identical in both genera.

Materials and methods
The studied samples, including the holotype and paratypes, are in the Museum of Zoology of the University of São Paulo, São Paulo, Brazil (MZUSP). All comparisons with other syntermitine genera where based on data from taxonomic reviews or original descriptions [Armitermes (Rocha 2011), Cahuallitermes (Constantino 1994), Labiotermes (Constantino et al., 2006), Macuxitermes Bandeira 1992, Constantino 1997), Noirotitermes (Cancello and Myles 2000), Paracurvitermes (Constantino and Carvalho 2011) and Syntermes (Constantino 1995)] and examination of material in the MZUSP collection, that has specimens of all type species of syntermitine genera.
Terms used for pilosity are comparative: bristles are long erect setae with wellmarked bases; hairs are shorter than bristles, less rigid and with inconspicuous bases; microscopic hairs are very short and visible only under at least 50 × magnification (not illustrated in the figures). Gut terminology follows Noirot (2001).
The morphometric characters used here and their correspondence with Roonwal's system (Roonwal 1970) are indicated in parentheses as follows: length of head capsule, LH (9); width of head capsule, WH (18); length of frontal tube, LFT (28); length of left hind tibia, LT (85). All measurements were taken with a micrometric reticle.
Line drawings were made with a camera lucida, soldier photographs were obtained with a digital camera coupled to a stereomicroscope Leica M205C, and images of different depth of focus were further processed and merged with software. Worker mandibles were dissected and prepared for scanning electron microscopy. The worker enteric valve was mounted on Entellan (Merck) and photographed under an optic microscope. Scales are indicted in each illustration.
Etymology. From Tupi, indigenous South American language, acangaobi meaning funneled head and the Latin termes meaning termite, in reference to soldier head capsule shape in profile. The name is masculine.
Description. Imago. Unknown. Soldier. Monomorphic. Head capsule sub-quadrangular with almost parallel lateral margins and two very discrete saliencies on the latero-posterior corners (Fig. 7, arrows). Surface of head capsule covered with numerous minute and closely set points of about equal diameter, forming a conspicuous and characteristic microsculpture (Figs 7-8). Frontal tube conical and upturned, in profile, apex with a relatively wide aperture surrounded by a white membrane. Antennae with 14 articles. Piercing slender mandibles; blade strongly curved inwards and upturned; a very small tooth at the base of the blade and a molar plate/prominence fully developed with no ridges. Clypeus very reduced. Labrum with a rounded and flat hyaline tip. Posmentum subrectangular with antero-lateral margins slightly concave. Coxae with a keel shape projection, pointing outwards and situated at distal antero-lateral margins (Fig. 2, arrow). Tibial spurs 2:2:2.
Worker digestive tube. Crop asymmetrical, without any constriction separating it from gizzard. Cuticular armature of gizzard with 24 visible folds, six of first order, six of second and 12 of third; ratio between columnar and pulvillar belt approximately equal to one; pulvilli without armature or ornamentation. Mesenteron tubular. Short mixed seg-ment present. Mesenteric tongue on the external side of the mesenteric arch, slightly strangled proximally. Two pairs of Malpighian tubules attached at the mesenteron-proctodeum junction, one internal side to the mesenteric arch and the other external. First proctodeal segment (P1), diagonal to body axis, more enlarged than mesenteron with about same size of proximal portion of paunch (P3a); distal end of P1 narrowed, forming a short neck prior to the attachment to P3. Enteric valve (P2) at the left side of the body. P3 slightly constricted between P3a and P3b. Dorsal torsion well-developed. P3 joined to colon (P4) on left side, isthmus short and parallel to body length. P4a dilated, U-Turn and P4b tubular.

Comparisons with other genera of Syntermitinae
Soldiers of Syntermes, Cornitermes, Labiotermes, and Procornitermes have a short frontal tube, not exceeding the labrum; a well-developed hyaline tip to the labrum; straighter cutting mandibles, with well-developed marginal teeth; and a larger body size. Soldiers of Cahuallitermes have straighter cutting mandibles, with well-developed marginal teeth; a well-developed hyaline tip to the labrum; and a larger body size. Soldiers of Embiratermes and Ibitermes have a larger body size, straighter and large mandibles, with well-developed marginal teeth in Embiratermes or totally absent in Ibitermes. Soldiers of Cyrilliotermes and Curvitermes have aberrant mandibles, with a molar plate, molar prominence and marginal teeth very similar to their corresponding worker mandibles; apical tooth fish-hooked in Curvitermes, reduced in Cyrilliotermes; and the frontal tube cylindrical and elongate in Cyrilliotermes (see more details of these two genera, including the dissected soldier mandibles, in Mathews 1997, page 226). Paracurvitermes has a broader head capsule with well developed conical and shorter frontal tube than Acangaobiermes; the mandibles are much longer, less curved with triangular teeth, very different from the new genus. The soldiers of Rynchotermes have strongly curved mandibles; a very long frontal tube; procoxae with a spine-like lateral projection; and a much larger body size. Soldiers of Armitermes have the pronotum, mesonotum, and metanotum with serrate lateral margins; mandibles with well-developed marginal teeth; and a larger body size (see Rocha, 2011, for a redescription and new illustrations of the genus). Lastly, the genus Macuxitermes has dimorphic soldiers, with an aberrant head shape; pronotum, mesonotum and metanotum with serrate lateral margins; and mandibles with well-developed marginal teeth.
Despite differences in the shape of the soldier head, Acangaobitermes shares many exclusive traits with Noirotitermes. The worker of Acangaobitermes is very similar to that of Noirotitermes, with same mandibular pattern, body size and shape (elongate), labrum and digestive tract, including the enteric valve armature. The worker differences between both genera are: the inner margin of apical teeth in left and right mandibles are much more concave in Noirotitermes than in the new genus; the M3 in left mandible and M2 in right mandible both are larger in Acangaobitermes than in Noirotitermes; and the insertion of the enteric valve is in the body axis, while in Noirotitermes it is perpendicular to the body axis.
The soldiers of both species have the same microsculpturing on the head capsule surface and the internal granulations (Fig. 8), that are otherwise absent in all other species of Syntermitinae. The piercing, upturned mandibles, with a single marginal tooth reduced are nearly identical in both genera, while in all other Syntermitinae the marginal teeth are well-developed (or completely absent in Ibitermes). The two occipital saliencies are present in both genera and in Macuxitermes, but are much more discrete in Acangaobitermes (Fig. 7, arrows).
The most conspicuous differences between the new genus and Noirotitermes are the shapes of the soldier head and pronotum. The pronotum is aberrant in Noirotitermes and saddle-shaped in Acangaobitermes, as is usual for other Syntermitinae. The shape of the soldier head in Noirotitermes is unusual, with a very broad frontal tube and two protuberances like sharp corners at the rear, while in the new genus the frontal tube is elongate and conical, similar to Armitermes, and the posterior rear part of the head is devoid of conspicuous projections. Diagnosis. As for the genus (vide supra). Etymology. Named in honor of Dr Kumar Krishna, for his important contributions to termite taxonomy.

Acangaobitermes krishnai
Description. Imago. Unknown. Soldier. Shape of head, frontal tube, labrum, mandibles, pronotum under generic description. Antennae with 14 articles, 2nd half size of 1st, 3rd half of 2nd, 4th half of 3rd, 5th twice the size of 4th, subsequent articles sub-equal and similar to third. Scattered bristles, short hairs and microscopic hairs on top and lateral sides of head capsule, few bristles at rear portion. Frontal tube with microscopic hairs along its length and hairs around aperture of frontal tube. Pronotum with bristles on margins, plus two pairs of bristles at middle of anterior lobe. Mesonotum and metanotum with a row of bristles on posterior margins. Abdominal tergites and sternites with short hairs over Worker. External morphology under generic description. Head capsule with scattered bristles, antennae with some short hairs and sparse bristles, pronotum with bristles on margins and over surface of anterior lobe, mesonotum and metanotum with bristles on posterior margins. Abdominal tergites and sternites with short hairs over surfaces and bristles on posterior margins.
Digestive tube (Figs 4a-4e, 6). Coiling gut pattern and gizzard armature under generic description. P2 armature (Fig. 6) with three longitudinal equidistant cushions covered with strong and erect spines oriented perpendicular to gut contents flow,  among the cushions minor spines settled at different orientations. P3 internally ornamented with long cuticular filaments (as described in Noirot 2001).
Biology. All the samples were collected in the soil or in nests of Cornitermes cumulans (Kollar) and Armitermes euamignathus Silvestri, in areas of openformation. The specimens from state of Goiás are collected in a Cerrado formation. From the state of Rondônia in a border line between primary forest and pasture. From Minas Gerais state in a "Campo rupestre", a characteristic altitudinal field, with granitic outcrops and composed by xeric vegetation.

Discussion
Relationships among the mandibulate nasute genera are not yet clear, despite considerable evidence that they are a monophyletic group (e.g., Inward et al., 2007). Rocha (2011) conducted a taxonomic revision and a phylogenetic analysis of the genus Armitermes, including all type species of the genera of Syntermitinae. This analysis supports the hypothesis that Macuxitermes, Acangaobitermes, and Noirotitermes form a monophyletic group and that the last two are most closely related, with the occipital saliencies and the type of folds and their arrangement on the enteric valve as synapomorphies for the three genera.