Megalothorax dobsinensis, Papáč & Raschmanová & Kováč, 2019

Papáč, Vladimír, Raschmanová, Natália & Kováč, Ľubomír, 2019, New species of the genus Megalothorax Willem, 1900 (Collembola: Neelipleona) from a superficial subterranean habitat at Dobšinská Ice Cave, Slovakia, Zootaxa 4648 (1), pp. 165-177 : 167-174

Megalothorax dobsinensis sp. n.

Figs 2–18

Material examined. Holotype: female on slide (350–16), Slovakia, Slovak Paradise ; cold section of scree slope at entrance of Dobšinská Ice Cave; 48.8680°N, 20.3041°E; alt= 969 m; 4.x.2016; extraction of soil; N. Raschmanová and Ľ. Kováč leg. Para- types: male and 7 females on slides (350–16), same data as the holotype. Type material (holotype and 3 paratypes) saved in the Apterygota collection of MNHN, Paris. Other paratypes saved in collection of SCA, Rimavská Sobota, Slovakia.

Other material. Slovakia: Slovak Paradise ; cold section of scree slope at entrance of Dobšinská Ice Cave: 2 females and male on slides, 10.v.2017 (43–17), 5 juveniles and male on slides (44–17), 3 females on slides (46–17), 2 females and male on slides (47–17); 13 females, 2 males, 3 juveniles on slides and 4 individuals in alcohol, 4.x.2016, (352–16). All specimens collected by N. Raschmanová and Ľ. Kováč.

Slovakia: Veľká Fatra Mts. , Harmanecká Cave, 48.8139°N, 19.0401°E; alt= 821 m; 3 males and 8 females (30–14), 30 m from entrance, Izbica Hall; direct collection on surface of water pool; 18.ix. 2014; V. Papáč leg.

Diagnosis. White, with few dots of black pigments scattered on dorsal part of head, thorax, abdomen and subcoxae. Presence of integumentary triangle instead of chaeta X on Ant. IV. Labium: basomedian fields with 3+3 chaetae, basolateral fields with 1+1 chaetae. Integumentary channels branched on posterior part of head, present also on anterior part, connection of channels with l. v. circular . Some chaetae enlarged and thickened, of which 7+7 dorsal, posterior on head and 3+3 on Th. II tergum. Inner chaeta of sf2 slender with pointed apex, other inner chaetae of sf3–6 T- and candlelight-shaped. Dorsal s-chaetae s2 globular, absence of dorsal s-chaetae s3. Abd. I to V terga with 19+19 ordinary chaetae. Each claw of ordinary morphology, subequal. Tenaculum with 3+3 teeth. Abd. IV sternum with 2+2 chaetae. Mucronal lamellae smooth, thin.

Description. General aspect. Habitus and segmentation typical of the genus. Length from labrum to anus: ~550 μm. Body chaetotaxy sparse including ordinary chaetae, s-chaetae, τ-chaetae as trichobothria (hardly visible), neosminthuroid chaetae, wax rod secretory elements and special swollen chaetae within sf2–6. Length of chaetae ranging from microchaetae [inferior to 6 μm] to mesochaetae [6–15μm] and macrochaetae [superior to 15 μm]. Shape of chaetae ranging from simple to thickened.

Integument. Integumentary channels branched laterally and dorsally in posterior and anterior part of head ( Figs 2 , 16 ). Cephalic channels connection with l. v. circular ( Figs 5 , 17 ).

Sensory fields and wax rods. A total of 14+14 wax rod secretory crypts (2+2 on head, 12+12 on body), including the ones inserted in each of 6+6 sensory fields ( Figs 2 , 6, 15, 16, 18). sf1 without inner chaeta ( Fig. 1 ). sf2 with one slender inner chaeta with pointed apex ( Fig. 2 ). sf3 with three inner chaetae, bigger one is more T-shaped. sf4 and 5 each with two inner chaetae, bigger one is more T-shaped. sf6 with one inner T-shaped chaeta (Fig. 6, 15, 18).

Mouth parts. Labrum with mesochaetae in a - and m -row ( Fig. 2 ), a1, 2 with one small external tooth and with slightly serrate outward tip; m0 almost on the same level as m1. Oral fold with 2+2 mesochaetae. Maxillary outer lobe: palp with sub-apical mesochaeta and apical papillate macrochaeta, edge of apical papilla with integumentary lobes ( Figs 2, 3 ); sublobal plate with two mesochaetae (6 μm). Basomedian fields of labium with 3+3 mesochaetae ( Fig. 5 ), basolateral fields with 1+1 mesochaetae on tubercle. Labial palp chaetal equipment typical of the genus, guard hairs strong in regard of papillate chaetae. Maxillae typical of the genus. Both mandibulae with five apical teeth and well-developed molar plate ( Fig. 4 ), right mandibula with simple tooth between apex and molar plate. Ridge of the labrum with two pikes.

Head chaetotaxy. 7+7 thickened posterior macrochaetae distinctly longer and stronger than anterior chaetae (16 μm, Fig. 2 ). Dorsal anterior area with 10 pairs of chaetae (9+9 mesochaetae, 1+1 macrochaetae) and two axial mesochaetae. Lateral anterior area with 1+1 mesochaetae. Dorsal posterior area with 12 pairs of chaetae (7+7 thickened macrochaetae, 2+2 thickened mesochaetae and 3+3 ordinary mesochaetae ( Figs 2 , 16 ). Ventral side with three pairs of post-labial mesochaetae ( Figs 5 , 17 ).

Antennal chaetotaxy. Illustrated in Fig. 10 and summarized in Table 2 . Ant. I with one mesochaeta.Ant. II with four chaetae: thickened mesochaetae (10 μm) and 3 ordinary mesochaetae (6 μm). Ant. III with 9 ordinary meso- chaetae, 2 long S-chaetae (S1, S4, more than 20 μm) and 2 short S-chaetae (S2, S3, 8–10 μm). S2 and S3 protruding from shallow cupule but partially covered by strong integumentary lobe. S2, S3 ornamentation feebly visible. S 4 in apical position to S1, on the same level as S2, S3. Ant. IV with 12 S-chaetae (10 S, Sy and Sx), 6 micro- and mesochaetae (without chaeta X) a small organite Or, 2 apical and subapical rods (a, sa). S-chaetae S with blunt apex, chaeta X missing, integumentary triangle lobe placed immediately above chaeta Sx.

Thoracic terga chaetotaxy. Th. II with 12+12 chaetae of different length, 1+1 s-chaetae s1 tubular (5 μm) and 3+3 τ-chaetae (Figs 6, 18). Chaetae including 5+5 macrochaetae (same length of a2, a4, a7, a8, a9,) and 7 + 7 mesochaetae. Th. III with 10+10 chaetae, 6+6 free wax-rod generating crypts (wrc1–6) and 5+5 τ-chaetae (Figs 6, 18). Chaetae including 4+4 macrochaetae (a6, a7, a8, a9), 6+6 mesochaetae (stouter a1, a5, p2, p3, p4 and slender a3). Chaeta p4 moved posteriorly from wrc2. Chaeta a6 stronger than a5 (Fig. 6). Pattern of folds on Th I. is similar to M. minimus (sensu Schneider, 2017).

Legs chaetotaxy. Legs with ordinary chaetae of variable size as in Figs 6, 12–14 and summarized in Table 3 . Subcoxa 1 I with a mesochaeta, coxa I with a microchaeta. Subcoxa 1, 2 II with a mesochaeta, coxa II with a macrochaeta. Subcoxa 1, 2 III and coxa III with respectively 2, 1, 1 macrochaetae. Anterior and posterior microchaetae present on each pretarsus.

Foot complex. Each claw with ordinary morphology ( Figs 12–14 ), subequal in unguis length and subtly in the proportion of unguiculus. Unguis basal and posterior auxiliary lamellae (la, lp and Bp) well developed, Bp more protrude only on claw II and III. Each unguiculus with a well developed lobe not or feebly protruding. Ratio unguis length vs tibiotarsus length on leg I–III respectively as 0.54, 0.60, 0.58.

Abd. I–V terga chaetotaxy. With a total of 19 + 19 chaetae, 1+1 τ-chaetae, 2+2 free wax-rod generating crypts (wrc7, 8), 1+1 globular s-chaetae s2 (Fig. 6, 15). Chaetae including 13+13 mesochaetae (the longest α1, α2, β2, β3, δ4, η1 reaching 14 μm) and 6+6 macrochaetae (α3, ε2, ε3, ζ2, η2, η3, 17 μm). Chaeta α3 close to wrc7, both clearly anterior to β3. Chaetae β4 missing.

Abd. VI and genital chaetotaxy. Abd. VI with 9 dorsal mesochaetae, axial unpair a0 shorter than lateral a- and m-row chaetae (12–13 μm) (Fig. 9); each anal valve with mesochaeta av; with 9+9 ventral mesochaetae, in male were not observed additional ventral cylindrical swollen chaetae sm. Genital plate: female with 2+2 microchaetae; male with 10+10 mesochaetae arranged in circle.

Other sterna. Abd. IV sternum with 2+2 neosminthuroid chaetae and 2+2 posterior mesochaetae (Fig. 9). Manubrium with 2+2 posterior mesochaetae ( Fig. 10 ). Proximal subsegment of dens with one posterior mesochaeta; distal subsegment posteriorly with two basal spines, one median mesochaeta and two apical spines, anteriorly with three apical spines, posterior spines with slightly elongated apex. Mucro with a narrowing in the apical 2/5, lamellae edges smooth. Tenaculum with 3+3 hook-like teeth (Fig. 7). Ventral tube with two apical pairs of mesochaetae (Fig. 8).

Etymology. The new species is named after the type locality, Dobšinská Ice Cave situated in Central Europe,Western Carpathians.

Affinities. M. dobsinensis sp. n. belongs to the minimus species group ( Schneider & D’Haese 2013; Papáč & Kováč 2013). Within this group, it shares the absence of chaeta X on Ant. IV and branched integumentary structure on forehead with M. sanctistephani Christian, 1998 and M. tuberculatus . But it differs from both species by the presence of T-shaped inner chaetae in sensory fields (vs. candlelight-shaped), abdominal chaetotaxy ( M. dobsinensis sp. n. has 19+19 chaetae with missing β4 vs. 20+20 chaetae in M. tuberculatus and M. sanctistephani ) and various number of ordinary chaetae on Ant. III ( M. sanctistephani with 6 chaetae, M. tuberculatus 8 chaetae and M. dobsinensis sp. n. 9 chaetae) and Ant. IV ( M. sanctistephani with 5 chaetae, M. tuberculatus 4 chaetae and M. dobsinensis sp. n. 6 chaetae). Moreover, M. sanctistephani lacks integumentary triangle lobe and chaeta X on Ant. IV, and chaeta a0 on head is replaced by an oval depression.

Recently described M. hipmani Papáč & Kováč, 2013 belongs to incertus group of species and therefore is easily distinguished from the new species (serrate vs. smooth mucro and globular vs. T-shaped inner chaetae in sf). The thickened macrochaetae on hind margin of head clearly separate M. dobsinensis sp. n. from M. tatrensis Papáč & Kováč, 2013 . M. dobsinensis sp. n. is the most similar to M. carpaticus . The main differences between both species are chaetotaxy of Ant. IV (absence or presence of chaeta X on Ant. IV and different number of ordinary chaetae: 6 in M. dobsinensis sp. n. vs. 8 in M. carpaticus ) and shape of inner sensillae in sf (T- vs. candlelight-shaped).

Ecology and distribution. The new species was discovered at the entrance parts of Dobšinská Ice Cave ( DIC) and Harmanecká Cave (HC) located in central karst regions of the Western Carpathians. Both caves are seasonally open to public, with electric lighting and a guided path. The specimens were found in a typical MSS habitat, i.e. stony debris covered with soil and litter at the cave entrance ( DIC), and also on the surface of water pool inside the cave 30 m from the entrance (HC). The caves are situated at relatively high elevations, 969 m ( DIC) and 821 m a.s.l. (HC).

Other Carpathian Megalothorax congeners were also found in moist soils and litter, and in cave environment. The combination of morphological features of the new species seems to be related to troglophilous mode of life. Regarding this, M. dobsinensis sp. n. has less morphologically specialized claws to cave environment than M. car- paticus, M. tatrensis and M. hipmani , but more than M. minimus and M. willemi . Overall geographic distribution of M. dobsinensis sp. n. remains uknown, the species is probably distributed across the whole Western Carpathians Mts at cold sites associated with superficial subterranean habitats of MSS type.

Figures

FIGURE 1. A, Dobšinská Ice Cave, entrance: collapse doline (Photo: Ľ. Kováč); B, Dobšinská Ice Cave, cold site at the cave entrance: limestone scree covered by soil, leaves and pioneer vegetation, mostly mosses and liverworts (Photo: Ľ. Kováč); C, Harmanecká Cave, entrance morphology (Photo: Ľ. Kováč); D, Harmanecká Cave, Izbica Hall, twilight zone, limestone scree on the bottom partly covered with sediment, algae, cyanobacteria and mosses (Photo: P. Fenďa).

FIGURE 16. Megalothorax dobsinensis sp. n.: 16, diagram of dorsal chaetotaxy of head.

FIGURE 17. Megalothorax dobsinensis sp. n.: 17, diagram of ventral chaetotaxy of head and cuticular channels.

FIGURES 2–5. Megalothorax dobsinensis sp. n.: 2, head, dorsal side; 3, outer lobe of maxilla; 4, left mandibula; 5, ventral side of head with labium and connection of epicuticular channels with linea ventralis.

FIGURES 10–11. Megalothorax dobsinensis sp. n.: 10, antenna, dorsal view (S-chaetae S2, S3 on Ant. III enlarged); 11, furca, posterior view.

FIGURES 12–14. Megalothorax dobsinensis sp. n.: 12, part of the leg I; 13, part of the leg II; 14, part of the leg III.

FIGURE 15. Megalothorax dobsinensis sp. n.: 15, abdominal sensory field with T-shaped inner chaeta.

FIGURE 18. Megalothorax dobsinensis sp. n.: 18, diagram of chaetotaxy of thorax and abdomen.