Eukoenenia lundi, Souza & Ferreira, 2020

Souza, Maysa Fernanda Villela Rezende & Ferreira, Rodrigo Lopes, 2020, Three new cave-dwelling Eukoenenia (Palpigradi: Eukoeneniidae) from limestone caves in Northern Minas Gerais state, Brazil, Zootaxa 4808 (2), pp. 251-283 : 264-272

Eukoenenia lundi sp. nov.

( Figs. 10–17 , Tables 1, 3, 4)

urn:lsid:zoobank.org:act:0F62D4B6-15CC-4632-A667-4989E413CD62

Material examined. Holotype: ♀ (ISLA 50399): Brazil, Minas Gerais, Luislândia, Lapa Sem Fim Cave (695 m. a.s.l., 16° 8’54.87”S, 44°37’40.09”W), 17.iv.2014, leg. R. L. Ferreira . Paratype: ♂ ( ISLA 50400), same data of holotype, except 12.iv.2017 .

Diagnosis. Five finely reticulated blades in lateral organs; 5 setae on deutotritosternum; 10 pairs of setae on propeltidium; 3 pairs of setae on metapeltidium; cheliceral fingers with 9 teeth each; coxae II–IV with 3, 3,1 thick setae; 5 setae (grt, r, esp and 2 esd) on basitarsus of leg IV; opisthosomal tergites II–VI with two pairs of setae t between one seta s on each side; opisthosomal sternites IV–VI with two pairs of a setae flanked by one s seta on each side; first lobe of male genitalia with 13 pairs of setae (2st + 9 + 2 fusules on each half), second and third lobes with 5 and 4 pairs of setae, respectively; first lobe of female genitalia with 11 pairs of setae; apical region of the last flagellar article with a single seta.

Description.

Body length without flagellum: 815 – 1210 μm.

Prosoma. Frontal organ (30 – 35 μm) formed by two reticulated branches with rounded tips ( Fig. 11A ). Lateral organ with five blades (30 – 32 μm) pointed-lanceolate and finely reticulated ( Fig. 10A ). Propeltidium with 10 + 10 setae ( Fig. 11A ). Setae t 1, t 2 and t 3 of metapeltidium 55 – 57, 87 – 90 and 62 – 70 μm long, respectively ( Fig. 11B ). Labrum with 5 + 5 short setae. Deuto-tritosternum with 5 setae in U-shaped arrangement ( Fig. 10B ). Basal segment of chelicera (dorsal length: 177 – 182 μm) with 6 proximal setae (p 4 and p 6 thickened and densely barbed; p 1 slightly thinner and barbed) ( Fig. 10C ), 3 distal setae: d 3 (75 – 87 μm long) longer than d 1 (35 – 40 μm long) and d 2 (37 μm long); d 3 smooth near base, with tiny projections in the distal half (more densely arranged on the apex); d 1 and d 2 thin and with tiny projections in the apex ( Fig. 10D ); and 1 apical seta. 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.

Coxal chaetotaxy. Pedipalp coxa with 18 setae ( Fig. 11C ); coxa I with 15 setae (including two tiny microsetae) ( Fig. 11D ); coxa II with 3 thick and 10 ordinary setae (including two macrosetae) ( Fig. 11E ); coxa III with 3 thick and 9 ordinary setae (including one macroseta and one adjacent microseta) ( Fig. 11F ) and coxa IV with 1 thick and 8 ordinary setae ( Fig. 11G ).

Palp. tc with 9 setae, two of which are considerably smaller than the others ( Fig. 12A ); fe with 8 setae; ti with 9 setae ( Fig. 12B ); bta1 with 2 m and 1 normal seta; bta2 with 2 normal setae and 4 m; ta1 with 2 m ( Fig. 12C ); ta2 with 6 m; ta3 with 1 fs (branches with similar lengths), 1 cs with a basal spine, 2 r, 13 m and 7 normal setae ( Fig. 12D ).

Leg I. tc with 13 normal setae, two of which are considerably smaller than the others ( Fig. 13A ); fe with 9 normal setae; pa with 9 normal setae and 1 tb ( Fig. 13B ); ti with 9 normal setae; bta1 with 2 m, 2 tb and 1 fs (with the inner branch shorter than the outer branch); bta2 with 3 m, 1 normal seta and 2 tb ( Fig. 13C ); bta3 with 1 r, 1 grt and 1 microseta; bta4 with 5 m, 1 tb and 1 long fs; ta1 with 5 normal setae; ta2 with 5 m, 1 tb and 1 long fs ( Fig. 13D ); ta3 with 5 fs (with equal branches) arranged as fs 1 / fs 2 / fs 3 / fs 4+5, rs (rs / fs 1 =3.2 – 5.3), 2 r, 1 cs, 13 m and 5 normal setae ( Fig. 14A ).

IVbta. 5.7 – 5.8 times longer than wide and with 5 setae (grt, r, esp and 2 esd). Seta r inserted in the distal half of the segment (dr / IVbta = 0.58 – 0.6); esp and grt inserted in proximal half ( Fig. 14B ).

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. 15A ). Sternite III with 2 + 2 setae. Sternites IV–VI each with 2 + 2 thickened setae with similar shape and length on both specimens (female: a 1 50 μm, a 2 52–55 μm; male: a 1 47–52 μm, a 2 52–55) between a pair of slender setae inserted caudal to the a setae; it was not possible to observe pores between a 1 setae on sternites IV–VI ( Figs 15B – C ). Segments VII–XI with 8 setae each. The 2 dorsal and 2 ventral setae on the intermediate ring of the flagellum with similar length.

Female genitalia. First lobe with 11 + 11 setae in 5 transverse rows: 2 + 2 sternal setae (st 1, st 2) followed by 2 + 2, 1 + 1, 2 + 2 and 4 + 4 distal setae (a 1 = 15, a 2 = 17 μm, a 3 = 25 μm, a 4 = 32 μm); presence of a group of 3 orifices on either side on the interior surface of the first lobe and a medial pair of smaller orifices ( Fig. 14C ). Second lobe with 3 + 3 setae (x = y = 32 μm, z = 27 μm); presence of cuticular spines and a group of 4 orifices on each half ( Fig. 14D ).

Male genitalia. 13 + 13 setae: 2 + 2 anterior (st 1, st 2) setae close to first lobe and 11 + 11 setae in the first lobe (including 2+2 fusules). Fusules with a dilated conical base, a setiform end and internal canals; f 2 slightly larger than f 1 ( Fig. 14E ). Each half of second and third lobes subtriangular and with 5 and 4 (w, x, y and z) setae, respectively ( Fig. 14F ). The apexes of both lobes are not readable.

Flagellum. (complete in the paratype and missing the first three articles in the holotype). About as long as the body (1003 μm), formed by 14 articles. Articles I, II, III, V, VII and IX with an apical crown of spikes. The setae on articles I–XII are inserted in the distal half, on article XIII in the proximal half. Last article shorter than the others, with 7 setae in its proximal half and one terminal seta ( Fig. 16 ). The number of setae and the length of each flagellar article are shown in Table 1 .

Measurements and ratios are given in Table 4.

Etymology. The species is named after the Danish naturalist Peter Wilhelm Lund, who worked in several caves of the Minas Gerais state during the 19 th century, made great paleontological discoveries and is considered the founder of speleology as a science in Brazil. Furthermore, we also intend to honor the caving group named “Espeleo Grupo Peter Lund” for their important contributions to the knowlegde of caves lacated in the northern Minas Gerais state, as well as the support given to us during our collections in the area.

Remarks. The presence of 5 setae (absence of one esp and of the gla setae) on basitarsus IV promptly distinguishes Eukoenenia lundi sp. nov. from most Eukoenenia species described to date, since this character state is shared only with the troglobitic species E. virgemdalapa Souza & Ferreira, 2012 from Brazil and E. brignolii Condé, 1979 from Italy. The number of teeth on cheliceral fingers (8 vs. 9), of blades on lateral organs (3 vs. 5), of slender setae (s) on opistosomal sternites IV – VI (2 pairs vs. 1 pair) and of setae on second lobe of male genitalia (4 vs. 5) are enough to distinguish E. brignolii from the new species ( Condé 1979). On the other hand, E. lundi sp. nov. has many other characteristics in common with E. virgemdalapa , like the coxal formula and the chaetotaxy of propeltidium and opisthosoma, which indicates that they may be closely related species ( Souza & Ferreira 2012 b). Apart from differences in the values of measurements and ratios (e.g. L: 815 – 1210 v s. 1670; B: 240 – 265 vs. 340; btaIV: 117 – 125 vs. 174; btaIV/a: 5.68 – 5.85 vs. 7.7), these two species differ in the number of blades in the lateral organs (5 vs. 7 – 8) and in the shape of the frontal organ (branches with rounded tips vs. branches distally expanded). The chaetotaxy of the genital lobes cannot be compared, because the single female of E. virgemdalapa (the male is unknown) presents an asymmetric setation (10 + 11) on the first lobe ( Souza & Ferreira 2012 b). Additional morphological comparisons with other Brazilian Eukoenenia are shown in Table 3.

Individuals of E. florenciae ( Rucker, 1903) were also collected in the same cave in which E. lundi sp. nov. occurs (see “habitat and threats” section for more detailed information). Despite the syntopy, they share few morphological features (e.g. absence of gla seta on bta IV, presence of five setae on deutotritosternum and 10 pairs of setae on propeltidium), being easily differentiated by a great number of traits: numbers of blades in the lateral organs (3 vs. 5), cheliceral teeth (8 vs. 9), metapeltidial setae (2 pairs vs. 3 pairs), esp setae on bta IV (2 vs. 1), setae on opithosomal sternites IV–VI (2 s + 4 a on each half vs. 1 s + 2 a), coxal formula (4, 4, 2 vs. 3 3, 1), setation of first genital lobe of female (10 pairs vs. 11 pairs) and shape of frontal organ (branches with pointed tips vs. rounded tips) ( Rucker 1903; Christian & Christophoryová 2013). Eukoenenia florenciae was probably introduced in this area by human activity, as already reported by Souza & Ferreira (2012 a, 2016) for other Brazilian caves.

Considering features recently introduced into taxonomy (e.g. the complete chaetotaxy of pedipalp and leg I), the presence of 18 setae on the pedipalp coxa seems to be unusual, shared only with E. draco (Peyerimhoff, 1906) ( Mayoral & Barranco 2013) . Most Eukoenenia species described or revisited lately have 19 setae on this article: E. florenciae , E. spelaea , E. bonadonai Condé, 1979 , E. strinatii Condé, 1977 , E. roscia , E. lanai Christian et al., 2014 , E. valenciana , E. indalica Mayoral & Barranco, 2017 , E. amatei Mayoral & Barranco, 2017 , E. navi , E. eywa , E. neytiri , E. ibitipoca Souza & Ferreira, 2019 and E. igrejinha Souza & Ferreira, 2019 ( Christian & Christophoryová 2013; Christian et al. 2014; Barranco & Mayoral 2014; Mayoral & Barranco 2017 a, 2017 b; Souza & Ferreira 2018, 2019 a, 2019 b).

The mean values of the morphometric ratios used to infer the degree of adaptation of palpigrades to the cave habitat (IVbta/ti = 0.92; B/IVbta = 2.09) suggest a moderate degree of troglomorphism. The lateral organs formed by 5 blades is shared with the troglobitic species E. maros Condé, 1992 , E. pyrenaica ( Hansen, 1926) , E. naxos , E. bouilloni Condé, 1980 , E. sendrai Barranco & Mayoral, 2014 , E. navi , E. neytiri , E eywa , E. jequitinhonha Souza & Ferreira, 2016 and E. cavatica Souza & Ferreira, 2016 ( Hansen 1926; Condé 1980, 1989, 1992; Barranco & Mayoral 2014; Souza & Ferreira 2016, 2018).

Habitat and threats. Lapa Sem Fim cave (LSF) is the only known habitat of E. lundi sp. nov. Although five other caves near the type locality were sampled, no additional specimens were found, suggesting that the species might be endemic to that cave. With around 15 km of mapped passages, LSF is the largest known cave in Minas Gerais state. The hypogenic cave presents an intricate labyrinthine system of conduits accessible through two entrances ( Figs 17A – B ), each one leading into a conduit with an intermittent watercourse. Nevertheless, most of the cave conduits are extremely dry, since they are located above the drainage level ( Fig. 17C ). The few moist chambers in the upper level (usually full of speleothems) receive humidity coming from percolating water. Specimens of E. lundi sp. nov. were only observed in moist areas inside the cave ( Fig. 17D ), no one was detected close to the entrances or in the drainage conduit. In these areas several palpigrades were found, but all belonged to E. florenciae , a parthenogenetic edaphic species introduced to Brazil, occurring in several above-ground habitats and caves in the states of Minas Gerais (municipalities of Candeias, Lavras, Pains, Doresópolis, Arcos, Bambuí, Iguatama, Piumhi, Prudente de Moraes, Pedro Leopoldo, Matozinhos, Córrego Fundo, Lagoa da Prata, Lagoa Santa, Sete Lagoas, Curvelo, Cordisburgo, Medina, Paracatu, Vazante, Cabeceira Grande, Arinos, Unaí, Lassance, Montes Claros, Itacarambi, Januária, Caraí, Jequitinhonha, Coração de Jesus, Buenópolis, Brasília de Minas, Capelinha, Felício dos Santos and Luislândia), Bahia (municipalities of São Desidério and Santa Maria da Vitória) and Tocantins (municipality of Dianópolis).

Figures

FIGURE 10. Eukoenenia lundi sp. nov., female holotype. A, blades on lateral organ; B, deutotritosternal setae; C, proximal setae (p1–p6) on basal segment of chelicera; D, distal setae (d1–d3) on basal segment of chelicera. Scale bars 20 μm.

FIGURE 11. Eukoenenia lundi sp. nov., female holotype. A, propeltidial chaetotaxy; B, metapeltidial setae; C, coxa of left pedipalp; D, coxa of left leg I; E, coxa of right leg II; F, coxa of right leg III; G, coxa of right leg IV. The thickened setae on coxae II, III and IV are indicated by arrows. Scale bars: 100 μm (Fig. A), 40 μm (Fig. B) and 60 μm (Figs. C–G).

FIGURE 12. Eukoenenia lundi sp. nov., pedipalp, female holotype. A, trochanter, left side; B, femur and tibia, left side; C, basitarsus 1–tarsus 1, right side; D, tarsi 2 and 3, right side. Scale bars 80 μm.

FIGURE 13. Eukoenenia lundi sp. nov., leg I, left side, female holotype.A, trochanter; B, femur and patella; C, tibia-basitarsus 2; D, basitarsus 3–tarsus 2. Scale bars 80 μm.

FIGURE 14. Eukoenenia lundi sp. nov. A, leg I, tarsus 3, left side, holotype (scale bar 80 μm); B, leg IV, basitarsus, right side, holotype (scale bar 60 μm); C, first lobe, female genitalia (scale bar 40 μm); D, second lobe, female genitalia (scale bar 40 μm); E, first lobe, male genitalia, left half (the sternal setae inserted close to the lobe are not shown) (scale bar 30 μm); F, second and third lobes, male genitalia, left half (scale bar 30 μm). Dotted circles and ellipses in Figs. C and D represent cuticular orifices; empty circles in Figs. E and F represent insertions of detached setae.

FIGURE 15. Eukoenenia lundi sp. nov. A, chaetotaxy of opisthosomal tergite III, male paratype; B, chaetotaxy of opisthosomal sternite V, male paratype; C, chaetotaxy of opisthosomal sternite IV, female holotype. Scale bars 20 μm.

FIGURE 16. Eukoenenia lundi sp. nov., flagellar articles, male paratype. A, articles I–VII; B, articles VII–XI; C, articles XI–XIV. Scale bars 100 μm.

FIGURE 17. Eukoenenia lundi sp. nov. A, Lapa Sem Fim cave, type locality of the new species, plan view; blue arrows point cave entrances (larger arrow indicates the main entrance); collecting site highlighted in red; B, main entrance of Lapa Sem Fim; C, inner portion of Lapa Sem Fim, close to the collecting site; D, live specimen in Lapa Sem Fim. Photos: Lucas M. Rabelo (D) and Rodrigo L. Ferreira.