Keratosminthurus tapigu Zeppelini & Brito & Zampaulo & Lima 2020, gen. nov.

Keratosminthurus tapigu gen. nov. sp. nov. Zeppelini, Brito & Lima

Figs. 1–3, 5–19, Table 1

Type material. holotype adult male on slide, Brazil, Pará, Canaã dos Carajás, Serra Sul S 11D (6°23’12.5”S; 50°21’25.0”W), 25.I.2014, leg. B. Nogueira. Holotype deposited at CRFS #5541.

Paratype adult female, Pará, Canaã dos Carajás, Serra Sul S 11D (6°23’12.6”S; 50°21’25.0”W), 30.X.2013, leg. K. Mise. Paratype deposited at CRFS #5503.

Paratype adult male on slide, Brazil, Pará, Canaã dos Carajás, Serra Sul S 11D (6°23’12.6”S; 50°21’25.0”W), 25.I.2014, leg. K. Mise. Paratype (CRFS #5448) deposited at CC /UFRN.

Paratype adult male on slide, Brazil, Pará, Canaã dos Carajás, Serra Sul S 11D (6°23’12.6”S; 50°21’25.0”W), 18.I.2014, leg. K. Mise. Paratype (CRFS #5545) deposited at MUZUSP.

Description. Holotype body length 1,184µm, head 513 µm. Color, brownish yellow body, whitish legs, antennae light purple, eyes in a patch of dark pigment (Fig. 5C left).

Antennae: holotype antennal segments length (µm) I, II, III, IV = 103; 158; 252; 985. Ant I with four normal anterior chaetae, one chaeta and one mic in apical part on posterior side (Fig. 6). Ant II presents nine apical (2 mic), five medial and five basal chaetae (Fig. 7). AOIII of females with two sensilla in separate pits, Ai, Ap and Ae large, Ape and Api short and bristle-like, Aai minute, rod-like and tapering towards apex, other chaetae as normal (Fig. 1 C–D). AOIII of males with two sensilla in separate pits, Ae and Ap thick and curved into a shape of a horn or hook (Fig. 1 A–B and 8), Ai normal, Api and Ape very short and bristle-like, Aai tiny tapering towards apex. Ant IV subdivided into 20 subsegments with 22 whorls, formula is 1 + 18 + 1 = (AI–II) + (M1,17 + BA) + (BM1 + BB), M1 to M17 each with eight chaetae and one or two sensilla, BA with six chaetae, Ant. IV subapical organ present (Fig. 9).

Head: eyes 8 + 8 in blue patch of pigments, two interocular chaetae in each eye patch (Fig. 3), one pair of interocular organ composed of a vesicle adjacent to eye patch connected to a linear crenulated opening is present in adult males. Posterior cephalic spines absent, postero-dorsal chaetotaxy A, B, C, D, E as 5,3,3,5,6; postantennal area with 3+3 smooth (degranulated) circular spots; interantennal region with two α, two β and two γ chaetae and a pair of circular smooth spots; frontal head chaetotaxy a–g, 12,12,10,11,11,14,8 respectively; two elongated narrow smooth areas present at proximal sides of clypeus, and a pair of cuticular spines at distal part in adult males (Fig. 2). Labral chaetotaxy formula a, m, p, pl present 4,2,4,4 chaetae respectively (Fig. 10). Labial ventral groove with 2+2 surrounding chaetae, four anterior labial chaetae; four labial basomedial chaetae (Fig. 11). Labial palp with five proximal chaetae, formula: H, h1, h2; A (2); B, b1, b2, b3, b4, a1; C (3); D, d1, d2; E, e1, e2, l.p. (Fig. 11).

Leg I: coxa, trochanter and femur with two, five (2 sensilla) and 16 (3 sensilla) chaetae respectively. Tibiotarsus as in Fig. 12, whorl I with nine chaetae, Ja thick and slightly curved, region F presents three primary FP chaetae (e, ae, pe), five secondary chaetae FS (e↑, a, ai, pi and pe↓). Pretarsus with one chaetae per side. Unguis inner tooth present, tunica absent. Unguiculus with subapical filament exceeding unguis tip, corner tooth absent or reduced (Fig. 12).

Leg II: coxa, trochanter and femur with two, five (1 sensillum) and 22 (6 sensilla) chaetae respectively. Tibiotarsus as in Fig. 13, whorl I with nine chaetae, Ja thick and straight, region F with three primary FP chaetae (e, ae, pe), five secondary chaetae FS (e↑, a, ai, pi and pe↓). Pretarsus with one chaetae per side. Unguis with a very small inner tooth, tunica absent. Unguiculus with subapical filament exceeding unguis tip, corner tooth well developed (Fig. 13).

Leg III: coxa, trochanter and femur with four, five and 20 (4 sensilla) chaetae respectively, trochanteral spine present. Tibiotarsus as in Fig. 14, whorl I with nine chaetae, Ja thick and straight, region F with three primary FP chaetae (e, ae, pe), five secondary chaetae FS (e↑, a, ai, pi and pe↓). Pretarsus with one chaetae per side. Unguis with a reduced inner tooth, tunica absent. Unguiculus with subapical filament subequal or slightly longer than unguis, corner tooth well developed (Fig. 14).

Ventral tube presents 1 + 1 apical anterior chaetae. Ramus of the tenaculum tridentate, corpus presents two apical chaetae.

Furca: holotype manubrium, dens, mucro length (µm) 165, 393, 162. Dens with 13 anterior chaetae, chaetotaxy I (ae, a, ai): II (ae, a): III (ae, a): IV (ae, a): V (ae, a): VI (a): B (a), formula 3:2:2:2:2:1:1. Posterior dental chaetotaxy (Fig. 15) Ie, I–VIIpe, I–VIIIp, I–VIIpi, I–IIi, Bpe, Bp, Bpi. Mucro with both lamellae smooth, asymmetric tip; mucronal chaeta absent (Fig. 16).

Great abdomen: all chaetae short, smooth and acuminated. Mesothorax with one a and three m chaetae, metathorax with four m and three p chaetae. Trichobothrial complex: ABC form an obtuse angle opening backwards and AB subequal to BC (AB = 140µm, BC = 133µm, AC = 270µm). Abd. I six m and one p; Abd. II chaetae a1 present, b1 equidistant and aligned with BC; chaetae c1 and c2 below trichobothrium C. Central dorsal complex presents three chaetae arranged in triangular pattern and two microchaetae. Posterior lateral complex with 5 + 6 chaetae and posterior dorsal complex presents dI = 7, dII = 9 and dIII = 7. Furca base complex presents 12 and a Neosminthuroid chaeta in male and female. Ventral complex presents two chaetae (Fig. 17). Areas marked in Fig. 17 present a smoother cuticular ornamentation.

Small abdomen of female: Abd. V with three chaetae and trichobothrium D in a papilla at row a, one superior and three inferior chaetae in row p. Abd. VI axial chaetae ams1, ms1 and ps1 present, as1 absent; chaetae as2 and ai6 absent, ams2 and ams3 present; mps1–3 bigger than other chaetae but not spinelike; subanal appendage mi5 large, thick curved and acuminated, reaching upper valve (Fig. 18).

Small abdomen of male: Abd. V with three chaetae and trichobothrium D in a papilla at row a, two superior and three inferior chaetae in row p. Abd. VI axial chaetae as1 and ams1 absent, ms1 and ps1 present; chaetae as2 and ai6 absent, ams2 and ams3 present; mps1–3 normal; male genital papilla with 4 rows (pre genital, a, m, p) with 2, 8, 4, 4 chaetae respectively (Fig. 19).

Etymology. Tapigü is the word for horn in Kuikúru Karib, the ancient language of the indigenous people Kuikúru from “Alto Xingú” region in central Brazil.

Distribution and habitat. Good’s Biogeographic zone 26, extending eastward to zone 27 in the Northeastern region of Brazil (Good 1974, Culik & Zeppelini 2003). The climate according to Köppen’s system is Af: Equatorial rainforest, fully humid (Köppen 1936, Shear 1966, Kottek et al. 2006).

Most records of the new species are from Carajás, a speleological unit at the southeast of the Pará State, in iron caves located at the plateau of the mountain ranges Serra Norte, Serra Sul and Bocaina, and at the geomorphologic unit of São Felix do Xingu range (Fig. 4: N1, S11D, SB and SFX respectivelly) (Valentim & Olivito 2011). This region has about 1000 caves in the official records of natural cavities (CECAV 2019), most of them located in altitude between 350–700m (Fig. 5A left). Iron caves, in general, has its genesis associated to predominantly erosive processes, and happens at the contact zone of the Banded Iron Formation (BIF) and the secondary superficial shields, named “canga”. Most caves in this formation are small, compared to those in limestone rocks, usually not exceeding 50m long in linear development (Fig. 5B). They are generally superficial, without a true aphotic zone, and present important amounts of litter close to the entrances. Even though, there are some few typical caves with hundreds of linear development. The region where the caves are inserted is protected by the association of the conservation unit called Floresta Nacional de Carajás (FLONA Carajás) and other conservation units in the Amazon Forest in southeast of Pará State. At the other hand, the natural areas in the region of São Felix do Xingú are extremely impacted and threatened by agriculture, livestock and illegal gold panning, leading to extensive deforestation, river siltation and contamination (Fig. 4C).

Remarks. this is the first species described for the new genus and presents all the diagnostic features related to the sexual dimorphism as typical for it. Such features differentiate this species and genus from all other known Sminthuridae. The main similarities and differences with the closest related genera are those discussed in the remarks of the description of the new genus. The comparison of the two new species is presented ahead in the text.