Adisianus pinheadi

Description. Body (head + trunk) length of the type series ranging between 0.57 mm and 1.40 mm, holotype with 1.02 mm, male average size = 0.62 mm, female average size = 1.12 mm, entire type series average size = 0.98 mm. Antennae and legs striped with dark purple pigments, head and lateral body weakly violet with purple spots, large abdomen dorsally with an anterior longitudinal stripe, posteriorly with a large dark spot, furca and ventral tube pale (Fig. 3). Head (Figs 3 – 5). Antennae shorter than the body length, with 0.53 mm in holotype. Antennae segments ratio I: II: III: IV of the holotype as 1: 1.78: 3.19: 5.02 mm (Figs 3, 4 A – C). Ant I with 6 – 7 chaetae, one of them rough, blunt and spine-like (Fig. 4 A). Ant II with 17 – 18 chaetae plus one apical bothriotrichum-like sensillum, one apical chaeta rough, blunt and spine-like (Fig. 4 A). Ant III with 38 – 40 chaetae, one basal chaeta on its 1 / 3 rough, blunt and spine-like, Aai short in both sexes, thicker in males, apical organ typical, with two sense rods inside independent invaginations (Fig. 4 B). Ant IV with six subsegments: subsegment I (basal one) with 35 chaetae plus two ventrobasal sensilla; subsegments II – IV with 10 chaetae each, two shorter than the others; subsegment V weakly separated from VI, with 11 chaetae, two shorter than the others; subsegment VI with about 37 chaetae plus two apical curved and one subapical mushroom-like sensilla, apical bulb present (Fig. 4 C). Eyes 8 + 8, lens D remarkably smaller than the others, with two interocular chaetae, one of them rough and blunt (Fig. 4 D). Frontal area lines A – E with 3 (+ 1) / 2 / 1 / 2 – 3 / 2 – 3 chaetae respectively, line A with two, line C with one, line E with 2 – 3 rough blunt spine-like chaetae, respectively. Oval organs in the interantennal area not seen, apparently missing. Interantennal area lines α and γ with 2 and 2 chaetae respectively, the external α as a rough blunt spine-like chaeta. Clypeal area a – f lines with 8 / 7 (+ 1) / 7 (+ 0 – 1) / 5 / 4 (+ 1) / 5 dorsal and ventral chaetae combined, respectively, plus three extra chaetae with unclear homologies between a and pl lines (Figs 4 D, 5 A). Prelabral and labral chaetae formula as: 6 pl / 5 p, 5 m, 4 a, labral p 2 and m 1 longer than the others, labral a 2 on papillae, labral intrusions present (Figs 4 D, 5 B). Ventral head with nine basolabial and five post-labial chaetae on lines a – c, respectively; labial basomedian field with four, basolateral field with five chaetae, respectively; post-labial region with 2 – 3 oval organs (Fig. 5 A). Maxillary outer lobe apical chaeta slightly smaller than the basal chaeta, none barbed (without basal tooth), sublobal plate with one chaeta-like appendage (Fig. 5 C). Mandibles ordinary, not elongated, left mandible with four, right mandible with 5 – 6 incisive apical teeth, respectively (Fig. 5 D). Maxilla capitulum spherical (globular), not elongated, as detailed in Fig. 5 E. Labial palp with five proximal chaetae, formula of guard chaetae of each papilla as: H (2), A (0), B (5), C (0), D (4), E (3) + a blunt lateral process not reaching the papilla E base (Fig. 5 F). Trunk (Figs 3, 6 – 7). Trunk length of holotype 0.86 mm. Large abdomen: elongate, thorax continuous with abdomen, without any visible segmentation or constrictions (Figs 3 A, 6). Female with about 35 rough spine-like chaetae. Th II lines a / m with 1 / 2 chaetae, respectively; Th III lines a / m / p with 1 / 5 / 3 chaetae, respectively, p line only with rough blunt spine-like chaetae; Abd I lines a / m / p with 4 / 3 / 1 chaetae, respectively, with 2 / 2 rough blunt spine-like chaetae in lines m / p respectively; Abd II lines a / m / p with 5 / 7 / 5 – 6 chaetae, respectively, lines a / m / p with bothriotricha A / B / C, respectively, lines a / m / p with 2 / 4 / 2 rough blunt spine-like chaetae, respectively; Abd III – IV dorso-posterior longitudinal lines dI- 1 / dII- 1 / dIII- 1 / dIV- 1 / dV- 1 with 7 / 6 / 5 / 5 / 6 chaetae, respectively, with two unpaired chaetae in line dI- 1, with 4 / 3 / 2 / 2 / 1 rough spine-like chaetae in lines dI- 1 / dII- 1 / dIII- 1 / dIV- 1 / dV- 1, respectively, most as blunt chaetae and one acuminate in line dI- 1. Two lines under bothriotrichum C with 4 / 5 chaetae, one of them as a bothriotrichum-like sensillum (S chaeta) (Fig. 6 A). Male with 26 – 29 rough spine-like chaetae. Th II lines a / m with 1 / 2 chaetae, respectively; Th III lines a / m / p with 1 / 5 / 3 chaetae, respectively, with 2 / 2 rough blunt spine-like chaetae in lines m / p respectively; Abd I lines a / m / p with 2 / 1 / 1 chaetae, respectively, one rough blunt spine-like chaeta in line m; Abd II lines a / m / p with 4 – 5 / 6 / 5 – 6 chaetae, respectively, lines a / m / p with bothriotricha A / B / C, respectively, lines a / m / p with 1 – 2 / 3 / 2 – 3 rough blunt spine-like chaetae, respectively; Abd III – IV dorso-posterior longitudinal lines dI- 1 / dII- 1 / dIII- 1 / dIV- 1 / dV- 1 with 7 / 6 / 4 / 3 / 6 chaetae, respectively, with two unpaired chaetae in line dI- 1, with 4 / 2 / 1 / 1 / 2 rough spine-like chaetae in lines dI- 1 / dII- 1 / dIII- 1 / dIV- 1 / dV- 1, respectively, most as blunt chaetae and one acuminate in line dI- 1. Two lines under bothriotrichum C with 5 / 6 chaetae, one of them as a bothriotrichum-like sensillum (S chaeta) (Fig. 6 B). Parafurcal area with 12 chaetae in three lines on both sexes, plus a rough neosminthuroid chaeta. Small abdomen (Fig. 7). Including Abd V – VI in both sexes. Female: Abd V with bothriotricha D and E present, D longer than E, plus five surrounding chaetae, two of them rough acuminate and one rough blunt spine-like chaetae. Abd VI dorsal anal valve with as 1 – 4, ams 2 – 3, ms 1 – 4, mps 1 – 2 and ps 1 – 2 chaetae, plus an extra chaeta without clear homology (?) between lines as and ams, as 1, ms 1 and ps 1 unpaired, as 1 – 3 and? as rough acuminate spine-like chaetae, ams 3 as an oval organ. Ventral anal valves each with aai 1 – 3, ai 1 – 5, ami 1, mi 1 – 6, mpi 1 – 2 and pi 1 – 3 chaetae, ai 1 as a rough acuminate spine-like chaeta, ami 1 as an oval organ, mi 5 as a long slightly blunt and smooth subanal appendage, curved toward the anus (Fig. 7 A). Female genital plate with 5 – 6 chaetae in the ventral region of the opening (Fig. 7 A). Male: Abd V bothriotricha D and E present, D longer than E, plus five surrounding chaetae, three of them as rough acuminated spine-like chaetae. Abd VI dorsal anal valve with as 2 – 3, ams 2, ms 1 – 4, and ps 1 – 2 chaetae, ms 1 and ps 1 unpaired, as 2 – 3, ams 2 and ms 3 as rough blunt spine-like chaetae, ms 2 as a smooth blunt spine-like chaeta, oval organ (ams 3) absent. Ventral anal valves each with aai 1, ai 1 – 4, ami 1, mi 1 – 5, mpi 1 and pi 1 – 3 chaetae, mi 2 as a rough blunt spine-like chaeta, ami 1 as an oval organ (Fig. 7 B). Male genital plate with 6 – 7 genital chaetae (Fig. 7 B). Legs (Figs 8, 9 A – C). Legs length of holotype as: leg I 0.29 mm, leg II 0.37 mm, leg III 0.38 mm (Fig. 8). Leg I: epicoxa, subcoxa and coxa with 1 / 0 / 1 chaetae respectively; trochanter with four chaetae, one short and spiniform, plus two oval organs; femur with 15 chaetae and one oval organ; tibiotarsus with 53 chaetae, about 14 of them as rough chaetae on the ventral side, plus one oval organ, distal whorl with nine chaetae, five as regular chaetae, Ja chaeta thick with a ciliate edge and three slightly capitate tenent hairs (Fig. 8 A). Leg II: epicoxa, subcoxa and coxa with 1 / 1 / 2 (+ 1) chaetae respectively, coxa with a small spiny sensillum in a large alveolus, plus an oval organ; trochanter with six chaetae, one smaller than the others, plus two oval organs; femur with 16 chaetae, one short and curved, another one short and straight, plus one oval organ; tibiotarsus with 51 chaetae, about 12 of them as rough chaetae on the ventral side, plus one oval organ, distal whorl with nine chaetae, six as regular chaetae and three slightly capitate tenent hairs (Fig. 8 B). Leg III: epicoxa, subcoxa and coxa with 1 / 1 / 3 (+ 1) chaetae respectively, coxa with a small spiny sensillum in a large alveolus, plus an oval organ; trochanter with six chaetae, one of them reduced, plus two oval organs; femur with 14 chaetae, one of them reduced, plus one oval organ; tibiotarsus with 54 chaetae, about 13 of them as rough chaetae on the ventral side, plus an oval organ, distal whorl with nine chaetae, seven as regular chaetae and two slightly capitate tenent hairs (Fig. 8 C). Empodial complexes I – III similar to each other, with a single anterior pretarsal chaeta on each; ungues without tunica or cavity, with a single apical tooth, lateral and dorsal teeth absent; unguiculi I – III reduced, without teeth or serrations, with a short apical filament (Figs 9 A – C). Abdominal appendages (Figs 9 D – G). Ventral tube corpus without chaetae, each lateral flap with a single short smooth chaeta; sacs long and warty. Each tenaculum ramus with three teeth; corpus with three chaetae in total. Size of furcal structures of holotype as: manubrium 0.16 mm, dens 0.28 mm and mucro 0.10 mm; ratio manubrium: dens: mucro = 1: 1.68: 0.60. Manubrium with 7 + 7 chaetae, the four lateral ones enlarged (Fig. 9 D). Dens dorsally (posterior side) with 23 chaetae (Fig. 9 E), ventrally (anterior side) with 5 – 6 chaetae, with the following formula from apex to the proximal region: 4,0 – 1 ... 1, subapical chaeta with two types of morphology (Fig. 9 F). Mucro flattened and spatulate, with smooth edges, mucronal chaeta absent (Fig. 9 G).

Figs 3 – 9, Table 1

Diagnosis of the species. Lateral body weakly pigmented. Ant I – III, dorsal head and large abdomen with rough blunt spine-like chaetae. Ant I – III each with one, frontal head with 7 – 8 rough blunt chaetae, of which 3 – 4 in lines C and E, line B lacking such structures; frontal head with one unpaired regular chaeta on A line. Male with 6 – 7 genital chaetae. Tenaculum with 3, manubrium with 7 chaetae, respectively. Dens with 23 dorsal chaetae, formula of ventral chaetotaxy from apex to base as: 4,0 – 1 ... 1.

Remarks. The new species is similar to A. fuscus and A. maculatus in the presence of rough blunt spine-like chaetae on head, antennae and abdomen, and manubrium with more than 20 chaetae. It is likely more closely related to A. fuscus as they share: Ant I and III with one rough blunt chaeta each (Ant III with two, Ant I without such structures in A. maculatus), frontal head B line lacking rough blunt chaetae (1 + 1 in A. maculatus), and male with 6 + 6 or 7 + 7 genital chaetae (4 + 4 in A. maculatus). The main features able to separate Adisianus pinheadi sp. nov. and A. fuscus are the color pattern, the presence of an unpaired chaeta on frontal head of the new species (absent in A. fuscus), manubrium with 7 + 7 chaetae (8 + 8 in A. fuscus), and tenaculum with three apical chaetae (two in A. fuscus). More details and comparisons between Adisianus species are listed in Table 1.

Distribution and habitat. Adisianus pinheadi sp. nov. specimens were sampled in an ecological transition area between the Cerrado and Caatinga biomes, at “ Floresta Nacional de Palmares ” (Palmares National Forest), located in the rural area of Altos municipality, Piauí State. The total size of the area is around 168 ha and the maximum temperatures range from 36 ° to 38 ° C. The vertical structure of the vegetation is well diversified, comprising five distinct strata: herbaceous / creeping, sub-shrub, shrub, tree, and canopy. The Palmares National Forest protects a portion of the “ Cocais Forest ”, with species that are ecologically and culturally representative of the Caatinga and Cerrado, and serves as a valuable testimony to these ecosystems (Brasil 2022). This is the first record of the genus in Brazil outside the Northern region, where Adisianus fuscus and A. maculatus were described from the Amazon Forest biome (Bretfeld 2002).

Etymology. The new species is named after the male character “ Pinhead ” from the cult horror film “ Hellraiser ” (1987, written and directed by Clive Barker). The name references the abundant spine-like chaetae on the dorsal surface of the head (see Fig. 4 D), which bear a resemblance to Pinhead’s distinctive appearance in the movie. A somewhat similar morphology is also observed in A. fuscus and A. maculatus.

Type material. Holotype female in slide. Brazil, Piauí State, Altos municipality, Palmares National Forest (5 º 02 ’ 55.1 ” S; 42 º 35 ’ 44.1 ” W), Northern Caatinga-Cerrado transitional region, 06 / IV / 2022, Mesquita, C. P., Souza, S. S. coll (CC / UFRN). Paratypes: 4 females, 2 males and 3 juveniles in slides, same data of holotype (CC / UFRN).