Eukoenenia ibitipoca, Souza & Ferreira, 2019

Souza, Maysa Fernanda Villela Rezende & Ferreira, Rodrigo Lopes, 2019, Eukoenenia ibitipoca: the first troglobitic Palpigradi (Arachnida) from a quartzitic cave, Zootaxa 4656 (3), pp. 431-444 : 432-437

Eukoenenia ibitipoca sp. nov.

( Figs. 1–32 , Tables 1–2 )

urn:lsid:zoobank.org:act:29D51787-AB2E-402F-B54D-A3EC8F2146F2

Material examined. Holotype, ♂ (ISLA 13178) ; paratypes, ♂ ( ISLA 13177) and ♀ (ISLA 13176): Brazil, Minas Gerais, Lima Duarte , Gruta das Casas (21°42’39.30”S, 43°53’40.99”W), 16/IX/2013, leg. R. L. Ferreira.

Diagnosis. Frontal organ with two reticulated branches with rounded tips; 5–6 blades pointed–lanceolate and finely reticulated in lateral organs; 5 setae on deutotritosternum; 8 pairs of setae on propeltidium; 3 pairs of setae on metapeltidium; cheliceral fingers with 9 teeth each; coxae II–IV with 4, 4, 2 thick setae, respectively; 6 setae (grt, gla, r, esp and 2 esd) on basitarsus of leg IV; opisthosomal tergites II–VI with 2 pairs of setae t between 1 setae s on each side; opisthosomal sternites IV–VI with 2 pairs of a setae flanked by 1 seta s on each side; first lobe of male genitalia with 13 pairs of setae (2 st + 9 + 2 fusules on each half), second and third lobes with 4 pairs of setae each; first lobe of female genitalia with 10 pairs of setae; flagellum with 14 segments; apical region of the last flagellar segment with a single seta.

Description. Body length without flagellum 1170–1400 μm.

Prosoma. Frontal organ formed by two reticulated branches with rounded tips (43 long) ( Fig. 1 ). Lateral organ with 6 (5 in the holotype) pointed–lanceolate blades (34 long), and finely reticulated ( Fig. 7 ). Propeltidium with 8+8 setae ( Fig. 4 ). Setae t 1, t 2 and t 3 of metapeltidium 92–95, 100 and 95–100 long, respectively ( Fig. 6 ). Deuto–tritoster-num with 5 setae in U–shaped arrangement ( Fig. 5 ). Labrum with 5+5 short setae ( Fig. 3 ). Basal segment of chelicera 235–245 long (dorsal length), with 6 proximal setae (p 4 and p 6 thickened and densely barbed) ( Fig. 2 ), and 3 distal setae: d 3 (112–115 long) longer than d 1 (65–70 long) and d 2 (72 long); d 3 smooth near base and barbed in its distal half, d 1 and d 2 robust, truncated and with tiny projections in the apex; and one apical seta ( Fig. 3 ). Hand of chelicera with 7 setae: 4 dorsal setae, 2 setae in its outer portion (1 close to articulation of movable finger and 1 on a tubercle close to the teeth of the fixed finger) and 1 seta inserted in its inner portion. Fingers with 9 teeth each ( Fig. 3 ).

Coxal chaetotaxy. Pedipalp coxa with 19 setae ( Fig. 8 ); coxa I with 15 setae (including two tiny microsetae) ( Fig. 9 ); coxa II with 4 thick and 10 ordinary setae (including two macrosetae) ( Fig. 10 ); coxa III with 4 thick and 9 ordinary setae (including one macroseta and one adjacent microseta) ( Fig. 11 ) and coxa IV with 2 thick and 8 ordinary setae ( Fig. 12 ).

Pedipalp. tc with 9 setae (two of them considerably smaller than the others); fe with 8 setae; ti with 9 setae; bta1 with 2 m and one normal seta; bta2 with 1 normal seta and 5 m; ta1 with 2 m; ta2 with 5 m and one normal seta ( Fig. 13 ); ta3 with 1 long fs, 1 cs with a basal spine, 2 r, 7 m (the basal denticle of the most apical one is extended to a conspicuous spine) and 13 normal setae ( Fig. 14 ).

Leg I. tc with 13 normal setae (two of them considerably smaller than the others); fe with 9 normal setae; pa with 9 normal setae and 1 tb ( Fig. 15 ); ti with 9 normal setae; bta1 with 1 normal seta, 1 m, 2 tb and 1 fs (with the inner branch shorter than the outer branch); bta2 with 3 m, 1 normal seta, 2 tb and 1 long fs; bta3 with 1 r, 1 grt and 1 small seta ( Fig. 16 ); bta4 with 4 m, 1 normal seta, 1 tb and 1 long fs; ta1 with 5 normal setae (two of them considerably smaller than the others); ta2 with 5 m, 1 tb and 1 long fs ( Fig. 17 ); ta3 with 5 fs (with subequal branches) arranged as fs 1 / fs 2 / fs 3+4 / fs 5, rs (rs / fs 1 = 2.6–2.8), 2 r, 1 cs, 10 m and 8 normal setae ( Fig. 18 ).

IVbta. 6.7–7.2 times longer than wide and with 6 setae (grt, gla, r, esp and 2 esd). Seta r inserted in the distal half of the segment (dr/ IVbta = 0.6); esp, gla and grt inserted in proximal half: grt and gla are inserted in the same level (grt slightly proximal to gla in the right side of female), both distal to esp ( Fig. 22 ).

Opisthosoma. Tergites II–VI with 3+3 dorsal setae, two pairs of t setae (t 1, t 2) between a pair of slender setae (s) ( Fig. 19 ). Sternite III with 2+2 setae. Sternites IV–VI each with 2+2 thickened setae (a 1, a 2) between a pair of slender setae (s) (inserted caudal to the thick setae) ( Fig. 23 ); a pair of pores present between a 1 setae on sternites IV–VI ( Fig. 20 ). Setae a in the opisthosomal sternites of female (62–67 long) and males (57–62 long) with similar shape, becoming gradually thinner from the base to the apex ( Figs 20–21 ). Segments VII–X with 8 setae each, segment XI with 6 setae. The 2 dorsal and 2 ventral setae on the intermediate ring of the flagellum with similar length ( Fig. 23 ).

Male genitalia. 13+13 setae: 2+2 anterior setae (st 1, st 2) close to first lobe, 11+11 setae in the first lobe (including 2+2 fusules). Fusules close to each other, with a dilated conical base, a setiform end and internal canals ( Fig. 24 ). Each half of second lobe subtriangular, with a simple and sharp apex. Each half of third lobe also subtriangular, with a sharp apex and a slightly bifurcate tip; presenting at least seven orifices. The second and the third lobes bear 4+4 setae each ( Fig. 25 ).

Female genitalia. First lobe with 10+10 setae in 5 transverse rows: 2+2 sternal setae (st 1, st 2) followed by 3+3, 1+1, 1+1 and 3+3 distal setae (a 1 = 23 μm, a 2 = 29 μm, a 3 = 32 μm) ( Fig. 26 ). Second lobe with 3+3 setae (x = 32 μm, y = 35 μm, z = 30 μm) and with cuticular spines ( Fig. 27 ). Medial pair of small orifices in the inner portion of the first lobe present. There are also at least five pores on the right side and seven pores on the left side, but it is not possible to determine their distribution on the two lobes correctly.

Flagellum (complete in the holotype and in the female paratype; only the first nine segments remain in male paratype). About as long as the body (1352–1437), formed by 14 segments. Segments 1, 2, 3, 5, 7 and 9 with an apical crown of spikes. The setae in segments I–XI are inserted in distal half, in the segment XII they are inserted at the half of the segment, and in the segment XIII they are inserted in proximal half. Last segment shorter than others, with 7 setae inserted in middle of the segment and one terminal seta ( Figs 28–31 ). The number of setae and the length of each flagellar segment are available in Table 1 .

Measurements of body parts (in μm) and ratios are available in Table 2 . Habitus shown in Fig. 32 .

Etymology. The species is named after the “Parque Estadual de Ibitipoca”, a conservation unit (a state park) created to protect the region in which the Gruta das Casas cave—the type locality of the species—is located. The word “ibitipoca” means “noisy montain” in tupi–guarani language, in allusion to the frequent thunderstorms in the region during the rainy season. The name is to be treated as a noun in apposition.

Habitat. Ibitipoca State Park protects an area of 1488 hectares inserted at the Atlantic rain forest biome, in which the dominant vegetation is grassland on the top of hills and rainforest in the valleys ( Dias et al. 2002) ( Fig. 34 ). There are several caves within the limits of this reserve, but specimens of E. ibitipoca were only found in Gruta das Casas ( Fig. 33 ). The cave extends for around 300 meters and has two adjacent entrances that receive organic input from seasonal floods. However, due to the sandy floor, most of the organic debris is filtered in the conduit close to the entrances and does not reach the innermost parts of the cave. Perennial autogenic drainage arises in one inner conduit and flows into part of the cave chambers, but it has little organic debris. Hence, the cave is extremely oligotrophic. The only visible food resources comprise old bat guano piles and remains of termite nests. The palpigrades were only observed walking on the water surface in small puddles formed by infiltrating water in one conduit in the inner portion of the cave ( Fig. 35 ). It is interesting to note that most palpigrades found in Brazilian caves are observed under rocks (mainly non–troglobitic species) or walking on speleothems (troglobitic species), but the behavior of walking on the water surface is not common in this region. In Europe, for instance, it is common to observe cave palpigrades on the water surface ( Orghidan et al. 1982; Condé 1996; Christian 2014). One of the authors ( RLF) observed palpigrades freely walking on the water surface in Slovenia ( E. austriaca ) and in Bosnia–Herzegovina ( E. remyi ). However, these alleged differences in behavior or microhabitat preference are still speculative, deserv- ing further studies. Finally, although the park is adapted to receive hundreds of tourists each day, and the caves are among the main tourist attractions, Gruta das Casas is closed to tourists. Hence, this cave only receives occasionally few speleologists for scientific research, thus being quite preserved.

Figures

FIGURE 35. Ground floor of Gruta das Casas, showing the occurence points of the three individuals of Eukoenenia ibitipoca sp. nov. (indicated by arrows) found during the sampling.

FIGURES 1–3. Eukoenenia ibitipoca sp. nov. 1, frontal organ, holotype (scale bar 10 μm); 2, proximal setae (p 1– p 6) on basal segment of chelicera, paratype male (scale bar 20 μm); 3, labrum and chelicerae with distal setae (d 1 –d 3) on basal segment, paratype female (scale bar 50 μm).

FIGURES 4–7. Eukoenenia ibitipoca sp. nov., paratype male. 4, propeltidial chaetotaxy (scale bar 150 μm); 5, deuto–tritoster- nal setae (scale bar 20 μm); 6, metapeltidial setae (scale bar 50 μm); 7, blades on left lateral organ (scale bar 20 μm).

FIGURES 8–12. Eukoenenia ibitipoca sp. nov. 8, coxa of right pedipalp, paratype male; 9, coxa of left leg I, paratype male; 10, coxa of right leg II, holotype; 11, coxa of right leg III, holotype; 12, coxa of right leg IV, paratype male. The thickened setae on coxae II, III and IV are indicated by the solid black arrows; unfilled arrows indicate distal part of each coxa. Scale bars 50 μm.

FIGURES 13–14. Eukoenenia ibitipoca sp. nov. 13, trochanter—tarsus 2 of left pedipalp, paratype male (scale bar 200 μm); 14, tarsus 3 of right pedipalp, holotype (scale bar 60 μm).

FIGURES 15–18. Eukoenenia ibitipoca sp. nov. 15, trochanter—patella of left leg I, paratype male (scale bar 200 μm); 16, tibia—basitarsus 3 of left leg I, paratype male (scale bar 200 μm); 17, basitarsus 4—tarsus 2 of left leg I, paratype male (scale bar 100 μm); 18, tarsus 3 of right leg I, holotype (scale bar 100 μm).

FIGURES 19–21. Eukoenenia ibitipoca sp. nov. 19, chaetotaxy of opisthosomal tergites IV and V, paratype female (scale bar 60 μm); 20, chaetotaxy of opisthosomal sternite VI, paratype female; two pores between a 1 setae are indicated by arrows (scale bar 20 μm); 21, chaetotaxy of opisthosomal sternite V, paratype male (scale bar 20 μm).

FIGURES 22–27. Eukoenenia ibitipoca sp. nov. 22, left basitarsus IV, holotype (scale bar 100 μm); 23, opisthosoma, ventral view, paratype male (scale bar 300 μm); 24, first male genital lobe, right half, holotype (scale bar 60 μm); 25, second and third male genital lobes, right half, holotype (scale bar 60 μm); 26, first genital lobe of female (scale bar 60 μm); 27, second genital lobe of female (scale bar 40 μm).

FIGURES 28–31. Eukoenenia ibitipoca sp. nov., female flagellum. 28, segments I–IV; 29, segments IV–VIII; 30, segments VIII–XII; 31, segments XI–XIV. Scale bars 100 μm.

FIGURES 32–34. Eukoenenia ibitipoca sp. nov. 32, live specimen walking on a black tray just before collection; 33, inner part of Gruta das Casas, type locality of the new species; 34, landscape in Ibitipoca State Park region, where the Gruta das Casas is located.