Allokoenenia stygia, Souza & Ferreira, 2022

Souza, Maysa Fernanda Villela Rezende & Ferreira, Rodrigo Lopes, 2022, Two extraordinary troglobitic species of Allokoenenia (Eukoeneniidae: Palpigradi) from Brazil: first records of this initially monotypic genus more than a century after its description, European Journal of Taxonomy 789, pp. 11-48 : 27-37

Allokoenenia stygia sp. nov.

urn:lsid:zoobank.org:act:C37DF62D-1144-4E02-9076-4BF344AEB140

Figs 10–19

Diagnosis

Frontal organ formed by 2 reticulated and lanceolate branches; 3 blades finely reticulated in the lateral organs; 5 setae on deutotritosternum; 7 pairs of short setae on propeltidium; 3 pairs of setae with similar lengths on metapeltidium; cheliceral fingers with 9 teeth each; 2 thickened dorsal setae proximally inserted in the cheliceral hand; coxae II–IV with 3, 3, 0 thick setae, respectively; 6 setae (grt, r, gla, esp and 2 esd) on basitarsus of leg IV; opisthosomal tergites II–VI with 2 pairs of robust setae (one pair of setae t between one setae s on each side); opisthosomal sternites IV–VI with 2 pairs of a setae flanked by 1 s seta on each side; opisthosomal segment XI with 2 pairs of ventral setae arranged in 2 rows; first lobe of female genitalia with 11 pairs of setae.

Etymology

The species epithet is derived from Styx, a Titan goddess and also one of the five rivers that form the boundary between Earth and the Underworld according to Greek mythology. From the Latin ‘stygius’ derived from the Ancient Greek ‘Στυγιος’ (‘Stúgios’, ‘relating to Styx’), from ‘Στυγξ’ (‘Stúx’, ‘Styx, chief river of underworld’). The name is a noun in apposition.

Material examined

Holotype

BRAZIL • ♀; Pará, Canaã dos Carajás, SB _0114 cave; 6°21′10.22″ S, 49°58′38.20″ W; 326 m a.s.l.; 10–31 Jan. 2013; F.F. Pellegatti et al. leg.; MZSP 54247 .

Paratype

BRAZIL • 1 ♀; Pará, Canaã dos Carajás, SB _0112 cave; 6°21′12.66″ S, 49°58′38.20″ W; 331 m a.s.l.; 10–31 Jan. 2013; F.F. Pellegatti et al. leg.; MZSP 54249 .

Description

Adult female

MEASUREMENTS AND RATIOS. See Table 2.

BODY LENGTH. Without flagellum: 1030‒1295 μm.

PROSOMA. Frontal organ formed by 2 reticulated and lanceolate branches (40 long) ( Fig. 10A). Lateral organ with 3 blades pointed-lanceolate (24‒27 long) and finely reticulated ( Fig. 10B). Propeltidium with 7 +7 short setae ( Fig. 10D). Setae t 1, t 2 and t 3 of metapeltidium 72‒75, 67‒80 and 80‒82 long, respectively ( Fig. 10C). Deuto-tritosternum with 5 setae in U-shaped arrangement ( Fig. 11A). Labrum with 5+ 5 short setae. Basal segment of chelicera 280‒310 long (dorsal length), with 6 proximal setae (p 4 and p 6 thickened and densely barbed; remaining setae sparsely barbed, with p5 more conspicuous than usual) ( Fig. 11B), and 3 distal setae: d 3 (142) longer than d 1 (55‒60) and d 2 (62); d 3 smooth near base and barbed in distal half, d 1 and d 2 thin, flexible and with tiny projections at apex ( Fig. 10E); and 1 apical seta. Hand of chelicera with 7 setae: 4 dorsal setae (2 inserted close to base of article and considerably thicker than others) ( Fig. 11D), 2 setae in outer portion (1 close to articulation of movable finger and 1 on tubercle close to teeth of fixed finger) and 1 seta inserted in inner portion. Fingers with 9 teeth each.

COXAL CHAETOTAXY. Pedipalp coxa with 18 setae ( Fig. 12A); coxa I with 11 ordinary setae and 2 microsetae ( Fig. 12B); coxa II with 3 thick setae, 2 macrosetae, and 8 ordinary setae ( Fig. 12C); coxa III with 3 thick setae, 1 macroseta, and 8 ordinary setae (including 1 small seta adjacent to macroseta) ( Fig. 12D) and coxa IV with 8 ordinary setae (thick seta absent) ( Fig. 12E).

PEDIPALP. tc with 8 (9 in paratype) setae (2 considerably smaller than others); fe with 8 setae; ti with 8 setae; bta1 with 2 m and 1 normal seta; bta2 with 2 normal setae and 4 m; ta1 with 2 m; ta2 with 6 m ( Fig. 13); ta3 with 1 long fs, 1 cs with conspicuous spine, 2 r, 8 m (1 with basal denticle and conspicuous spine) and 12 normal setae ( Fig. 16A).

LEG I. tc with 11 normal setae (2 considerably smaller than others); fe with 9 normal setae; pa with 9 normal setae and 1 tb ( Fig. 14A); ti with 9 normal setae; bta1 with 2 normal setae, 2 tb and 1 fs (with subequal branches); bta2 with 2 m, 2 normal setae, 2 tb and 1 fs (with subequal branches) ( Fig. 14B); bta3 with 1 r, 1 grt and 1 short normal seta; bta4 with 5 m, 1 tb and 1 long fs; ta1 with 5 normal setae (2 considerably smaller than others); ta2 with 5 m, 1 tb and 1 long fs ( Fig. 15A); ta3 with 5 fs (with subequal branches) arranged as fs 1 / fs 2 + 3 / fs 4+5, rs (rs / fs 1 = 2.4), 2 r, 1 cs with conspicuous spine, 9 m and 9 normal setae ( Fig. 15B).

LEG II. tc with 3 normal setae; fe with 5 normal setae; pa and ti with 1 thick seta and 4 normal setae each; bta with 6 normal setae; ta with 1 r, 1 m and 9 normal setae.

LEG III. tc with 2 normal setae; fe, pa, and ti with 1 thick seta and 4 normal setae each; bta with 6 normal setae; ta with 1 r, 1 m and 9 normal setae.

LEG IV. tc with 3 normal setae; fe with 1 m and 2 normal setae; pa and ti with 1 thick and 4 normal setae each; bta with grt, r, gla, esp, and 2 esd; ta1 with 4 normal setae; ta2 with 8 normal setae.

IVBTA. 7 × longer than wide and with 6 setae (grt, r, gla, esp and 2 esd). Seta r inserted around middle of article (dr / IVbta =0.55); gla inserted close to r and grt inserted in proximal half ( Fig. 16B).

OPISTHOSOMA. Tergites II–VI with 2+2 dorsal robust setae, one pair of t setae (t 1 = 37‒50 μm) between pair of s setae (s =25‒35 μm) ( Fig. 11E). Sternite III with 2+ 2 setae. Sternites IV–VI each with 2 +2 thickened setae (a 1 =50‒62 μm, a 2 = 55‒65 μm) between pair of slender setae (s =45‒52 μm) (inserted caudal to thick setae); pair of pores present between a 1 setae on sternites IV‒VI ( Fig. 11F). In paratype, presence of inconspicuous paired cavities in intersegmental furrows between sternites III–IV, IV–V, and V–VI, 1 at each side of opisthosoma; these cavities not observed in holotype. Segments VII–X with 8 setae each (4 dorsal and 4 ventral). Segment XI elongated (1.08‒1.14 × as long as wide), with dorsal row of 2+ 2 long setae (inner pair =122 μm; outer pair=112 μm) inserted around half and two pairs of ventral setae, one inserted in proximal half (62 μm) and other around half (77–82 μm). Intermediate ring of flagellum lost or absent in both specimens ( Figs 11C, 17).

FEMALE GENITALIA. First lobe with 11 +11 setae in 5 transverse rows: 2 +2 sternal setae (st 1, st 2) followed by 3+3, 1+1, 1 +1 and 4+ 4 distal setae (a 1 =20 μm; a 2 =25 μm; a 3 = 30 μm; a 4 =37 μm); interior surface of first lobe with group of 3 orifices on either side and medial pair of small orifices ( Fig. 18A). Second lobe with 3+ 3 setae (x = 10–11 μm; y = 35–37 μm; z = 25–34 μm), and with cuticular spines; presence of group of 4 orifices on each half ( Fig. 18B).

FLAGELLUM. Not preserved.

Male and immatures

Unkown.

Distribution

Known only from SB_0114 and SB_0112 caves (municipality of Canaã dos Carajás, Pará State, Brazil).

Remarks

Allokoenenia stygia sp. nov. fits the diagnosis of Allokoenenia by the relative width of the last opisthosomal segments. The flagellum was lost during the collection and therefore its morphology remains unknown. As with A. afra , A. canhembora sp. nov., and Allokoenenia sp. , the ventral setae on the last opisthosomal segment of this new species is arranged in two rows.

Allokoenenia stygia sp. nov. differs from A. afra by the shape of frontal organ ( Figs 1C, 10A), and by the number of blades on lateral organs (3 vs 1) and deutotritosternal setae (5 vs 1) ( Silvestri 1913). Considering the new congeneric species herein described, A. stygia sp. nov. differs from both by presenting the two most proximal setae on cheliceral hand thickened, the cs seta of leg I with a conspicuous spine, trochanter of leg I with 11 setae (vs 12 setae), coxa I with 13 setae (vs 15), coxa IV without thick seta (vs one seta), a single pair of t setae on opisthosomal tergites II–VI (vs two pairs), 6 setae on bta IV (vs 5 setae) and 3 blades on lateral organs (vs 4 in Allokoenenia sp. and 5 in A. canhembora sp. nov.). Additionally, the new species can be distinguished from A. canhembora sp. nov. by having 2 pairs of thickened setae (a) on opisthosomal sternites IV–VI (vs 3 pairs) and 11 pairs of setae on the first lobe of female genitalia (vs 10 pairs).

Habitat and threats

Individuals of Allokoenenia stygia sp. nov. ( Fig. 19E) were found in two adjacent iron ore caves (about 90 m bee-line from each other) located in a ferruginous plateau known as Serra da Bocaina ( Fig. 19D), inserted in the domain of Amazon Forest ( Fig. 19A), Northern Brazil. Other caves in this region were sampled, but no specimens of this species were found at other localities. These two caves, named SB_0114 ( Figs 19B–C) and SB_0112, have horizontal projections of 89 and 16.1 m, respectively, and are formed by a single spongiform gallery ( Fig. 19G). In 2017, a National Park was created (Parque Nacional dos Campos Ferruginosos) incorporating the Serra da Bocaina region. This conservation unit has 790.9 km 2 and protects two important iron ore formations within the Carajás geological province: the Serra da Bocaina and the Serra do Tarzan. However, although the top and the slopes of those plateaus are preserved, most of the area (especially in the surroundings of the Serra da Bocaina) is very altered by human activities (especially pastures) ( Fig. 19D, F). Fortunately, the area where the SB_0112 and SB_0114 caves are located is preserved. At the same time, despite the recently created conservation unit, frequent criminal fires hit the region, often advancing over the forest. Such fires usually come from conflicts between the local farmers and landless people, and such impacts may represent a threat for the species, especially when considering its very restricted distribution.