Megalothorax tatrensis, Papáč, Vladimír & Kováč, Ľubomír, 2013

Papáč, Vladimír & Kováč, Ľubomír, 2013, Four new troglobiotic species of the genus Megalothorax Willem, 1900 (Collembola: Neelipleona) from the Carpathian Mountains (Slovakia, Romania), Zootaxa 3737 (5), pp. 545-575 : 546-551

Megalothorax tatrensis sp. nov.

Figs 1–16

Megalothorax n. sp. Mock et al. (2003)

Megalothorax sp. 1 Papáč & Kováč (2012)

Diagnosis. Mucronal lamellae smooth ( minimus -group). Connection of integumentary channels with linea ventralis ventrally on head circular. Sensory fields 3–6 with flame-shaped sensilla. Unpaired chaeta a0 between basis of antennae present; posterior part of head with ordinary chaetae. Basomedian field of labium with 3+3 chaetae. Mesochaeta p4 on Th. III far posteriorly to wax rod crypt 2, a6/a5 on Th. III as macrochaetae. Spherical sensillum s3 on abdomen absent. Macrochaeta on subcoxae 1 (leg I) present. Manubrium with 4+4 dorsal chaetae (2+2 proximal, 2+2 distal). Retinaculum with 3+3 teeth.

Type material. Holotype: female on slide (No. 14–11), Slovakia, Low Tatras, Jaskyňa Mŕtvych Netopierov (Dead Bats Cave), Biela chodba Corridor, aphotic zone, 300 m from cave entrance, surface of water pool, 8.ix.2011, leg. Z. Višňovská. Paratypes: 1 ex. on slide— subadult female, (No. 14–11), same data as in holotype. Type material (holotype and 1 paratype) saved in collection of MNHN, Paris.

Other material. Slovakia, Horehronské podolie Mts., Bystrianska Cave, 2 ex.—females on slides (No. A–02– 85), aphotic zone, 30 m from the cave tour exit, pitfall trap, 7.v.–22.x.2002, leg. Ľ. Kováč.

Low Tatras, Demänovská Jaskyňa Mieru (Demänovská Cave of Peace), 1 ex.— juvenile on slide (No. 272– 11), 5 m from the cave entrance, aphotic zone, water surface of iron container, 12.v.2011, leg. Ľ. Kováč and P. Ľuptáčik. Hipman´s Cave system, Jaskyňa Starý Hrad (Starý Hrad Cave) 1 ex.—female on slide (No. 95–08), cca 500 m from cave entrance, surface of water pool, 22.x.2008, leg. V. Papáč.

Description. Body length 0.38–0.55 mm, habitus typical of the genus. Body colour whitish with black and brownish pigment scattered in patches over the head, thorax, abdomen and subcoxae. Cuticle finely granulated, integumentary channels observed on ventral side of head and dorsally on fore and back parts of head, connection of channels with l. v. ventrally on head circular.

Head. Head length and width as 170 and 155 µm, respectively. Dorsal chaetae smooth and pointed, thickened chaetae absent ( Fig. 1 ); unpaired chaeta a0 between the basis of antennae as mesochaeta (8 µm). Frontal part with ordinary chaetae (10 µm) and 1+1 lateral macrochaetae (14 µm), median row as ordinary chaetae (10 µm), posterior part with lateral chaetae longer (14 µm) than axial (12 µm). 1+1 lateral chaetae between labial palp and basis of antenna. Clypeo-labral formula: a0, 2, 4, 5, 4 / 5, 5, 4 ( Fig. 2 ). Pattern of labral chaetae ( Fig. 2 ): a-row 2R1 + 2R2, m-row m + 2r1 + 2r2 and p-row with five ordinary chaetae. Anterior chaetae R1 and R2 thick, curved, R2 (up to 14 µm) longer than R1 (up to 9 µm); R1 with external edge roughly serrate in the middle; R2 with external edge finely serrate. Medial chaetae (m-row) thick, smooth and equal (10 µm), medial chaeta m moved anteriorly. Posterior chaetae (p-row) smooth, equal (10 µm, Fig. 2 ). Integumentary channels present dorsally on fore and back parts of head ( Fig. 58 ). Basomedian field of labium with 3+3 chaetae ( Fig. 6 ), medial ones slightly longer (15 µm) than axial and lateral (13 µm). Basolateral field with 1 ordinary chaeta, oral fold with 2 chaetae. Ventral side of head with 3+3 smooth postmedian chaetae ( Fig. 6 ); 2+2 anterior chaetae unequal: lateral ones longer, curved (19 µm), axial shorter, straight (15 µm); 1+1 posterior chaetae straight (15 µm). Labial palp typical for the genus, as in Fig. 6 . Mandible normal, with 5–7 apical teeth ( Fig. 3 ). Maxillary outer lobe with 1 enlarged terminal chaeta (16 µm), 1 basal chaeta and 1 sublobal hair ( Fig. 5 ). Maxilla with 1 lamella extending beyond fringed lamellae ( Fig. 4 ).

Thorax and abdomen ( Fig. 7 ). Dorsal side of thorax and abdomen covered with micro-, meso- and macrochaetae (6, 10 and 14–18 µm, respectively) and 8+8 wax rods (wrc1–8) as tiny, straight chaetae (2 µm) placed in small cuticle depressions. Th. II with 8+8 medial chaetae around thoracal sensory fields and 4+4 lateral chaetae around sensory fields at leg II base; 1+1 lateral sensillum s1. Th. III medially with 7+7 chaetae and 4+4 wrc, laterally at leg III base with 3+3 chaetae and 2+2 wrc around sensory field; chaeta p4 more posteriorly to wrc2, chaeta a6 stouter and longer than a5. Abd. I–V with 18+18 dorsal chaetae of unequal length, 2+2 wrc and 1+1 globular sensillum s2, chaetae β4 and ε1 absent. Abd. VI with 9 dorsal chaetae ( Fig. 10 ). Anal field with 3 anal valves, each with 1 chaeta. Abd. VI sternum with 9+9 chaetae of which 4+4 situated in front of genital plate. Female genital plate furnished with 2+2 chaetae ( Fig. 10 ). Manubrium base (Abd. IV sternum) with 2+2 chaetae and laterally with 2+2 broad neosminthuroid chaetae with ciliated tip (9 µm; Fig. 10 ).

Appendages. Antennal segments III and IV not separated ( Fig. 11 ). Length of antennae up to 95 µm, ratio antenna/head = 0.54; lengths of antennal segments I, II, III–IV as 17, 20, 58 µm, respectively. Ant. I segment furnished with 1 short chaeta (8 µm). Ant. II segment with 1 longer (10 µm) and 3 shorter (8 µm) chaetae arranged in whorl. Ant. III with 6 ordinary chaetae, 5 of them in distal position arranged in whorl. Ant. III organ consists of 2 small ovoid sensilla with striate rim (9 µm) and 2 long, transparent sensilla Sg—in external and dorsal position (16 µm each). Ant. IV with 7 ordinary chaetae arranged mostly on internal side, dorso-external side with 10 long, thin and curved macrosensilla S finely blunt at tip (20 µm); ventrally with 1 long and thick sensillum Sy (15 µm), 1 short and thick sensillum Sx (5 µm) and 1 ordinary chaeta x (9 µm); dorsally with cup-like subapical organite Or (3 µm); subapically with 6 ordinary chaetae (6–8 µm) and apically with 2 rod-like chaetae a and sa (10 µm). Complete chaetotaxy of antenna provided in Table 3. Chaetae numbers of legs I–III ( Figs. 13–15 , 7 ), number of long chaetae in parenthesis: scx I: 1(1), 1(1), 2 (2); scx II: 0, 1 (1), 1 (1); coxae: 1, 1 (1), 1 (1); trochantera: 2, 3, 4; femora: 6(1), 8(1), 8(1) and tibiotarsi: 12, 12, 10. Thin meso- or microchaetae in following numbers on leg I: coxa with 1, trochanter with 2, femur with 3; on leg II: femur with 4; on leg III: trochanter with 1, femur with 1. For complete chaetotaxy of legs see Table 4. Unguis narrow and elongated, both unguis and unguiculus unequally long in leg I, II and III: unguis 25, 22 and 21 µm, respectively, unguiculus 13, 11 and 11 µm, respectively. Length ratio unguis I (inner margin) / Ti. I width (25 / 16 µm) = 1.56. Unguis furnished with 2 lateral teeth la, lp and long inner tooth Bp. Unguiculus untoothed without apical filament, reaching almost 1/2 of unguis; tip of basal tubercle slightly projecting over the broad basal lamellae ( Fig. 10 ). Tubus ventralis with 2+2 distal chaetae, posterior lobe absent ( Fig. 14 ). Retinaculum with 3+3 teeth, chaeta on corpus absent ( Fig. 15 ). Furca well developed ( Fig. 12 ), length of manubrium, dens (proximal, distal part) and mucro: 55, 30, 43 and 37 µm, respectively. Manubrium dorsally with 4+4 chaetae, proximal and distal part both with 2+2 chaetae (8 µm). Proximal part of dens (dp) with 1+1 dorsal chaetae (10 µm). Distal part of dens (dd) dorsally with 1 medial, smooth chaeta (8 µm) and 4 broad spines (5 µm): 2 external and 2 internal; ventrally with 3 apical spines in transversal row (one spine 4 µm; Fig. 12 ). Dental spines as leave-shaped integumental structures lacking basal circle. Mucro with smooth dorsal lamellae, in distal quarter gradually constricted, pointed at the apex; length of mucro: 37 µm, width in the middle part: 5 µm.

Sensory fields ( Figs 1 , 7 ). 6+6 s.f. placed in crater-like depressions, each with secretory rod (8 µm), i.e. blunt, straight chaeta with basally inserted in cuticle in upper margin of field. S.f. have following arrangement: (a) anterior and posterior field on head (s.f. 1 and 2, 20 x 15 µm; internal spine in posterior field present (4 µm); (b) thoracal field (s.f. 3, 30 x 25 µm; Fig. 7 a) with 3 internal flame-shaped spines (1 greater curved —4–5 µm, 2 smaller—3 µm) and 6 external chaetae (2 macrochaetae—14–18 µm, 3 mesochaetae—10 µm, 1 microchaeta—6 µm); (c) abdominal field (s.f. 6, 30 x 25 µm; Fig. 7 d) with 1 internal curved, flame-shaped spine (3 µm), 5 external chaetae (14–18 µm), 1 spherical sensillum s2 (4 µm) and wax rod wrc8; (d) field at base of leg II (s.f. 4, 20 x 15 µm; Fig. 7 b) 2 internal flame-shaped spines (3 µm), 4 external chaetae (14–18 µm) and microsensillum s1 (5 µm) above the field; (e) field at base of leg III (s.f. 5, 20 x 15 µm; Fig. 7 c) 2 internal flame-shaped spines (3 µm), 3 external chaetae (18 µm) and wax rods wrc 5,6 on its posterior margin.

Only females known.

Etymology. The new species is named after the Low Tatras Mts., the main area of its distribution.

Ecology and distribution. Specimens of M. tatrensis sp. nov. were sampled from several meters up to cca 500 m from the cave entrances mostly on surface of the water pool. The new species was also collected by pitfall traps indicating its wider range of cave microhabitats occupied. It was discovered in four caves of central Slovakia located in two adjacent karst areas: (1) Low Tatras Mts. (Dead Bats Cave, Hipman´s Cave system and Demänovská Cave of Peace) and (2) Horehronské Podolie Mts. (Bystrianska Cave). The air temperature in internal part of the caves moves around 6 °C. Discovery of the new species confirms the presence of obligate cave-dwelling fauna in territory of the Western Carpathians, the Low Tatras Mts. being locally covered by mountain glaciers during Pleistocene glacial periods. Interesting is its co-occurence with M. carpaticus sp. nov. and M. hipmani sp. nov. (described below) in the Demänovská Cave of Peace. M. tatrensis most likely represents species with endemic distribution restricted to the karst of the Low Tatras Mts. and neighbouring limestone foothills.

Discussion. M. tatrensis sp. nov. belongs to „ minimus -group“ by smooth edges of mucro and modified internal chaetae of sensory fields in form of flame-shaped spine. It is very similar to M. minimus and M. carpaticus sp. nov. by presence of chaeta x on Ant. IV. M. minimus has T-shaped internal sensilla in s.f. 3–6 and Abd. I–V terga with 20+20 chaetae that clearly distinguishes it from other species of the minimus -group. The new species differs from others of the genus by presence of ordinary dorsal chaetae on posterior side of head (thickened meso- and macrochaetae in M. minimus and M. carpaticus sp. nov.). Moreover, in M. tatrensis sp. nov. chaeta on scx I as macrochaeta, whereas in M. minimus as mesochaeta and in M. carpaticus sp. nov. as micro- or mesochaeta. M. tatrensis sp. nov. differs from the two species by 10 chaetae on Ti. III (11 chaetae in M. minimus and M. carpaticus sp. nov.). Moreover, in M. tatrensis sp. nov. ratio unguis I length / Ti. I width is higher than M. carpaticus sp. nov. (1.56 vs. 1.4). For other differential characters see Tables 3–5.

Figures

FIGURES 1 – 6. Megalothorax tatrensis sp. nov.: 1, head, dorsal side; 2, anterior part of head with labrum, chaetae of anterior row enlarged; 3, mandible; 4, head of maxilla; 5, maxillary outer lobe, o. f. — oral fold, b. s. — basal chaeta, sl. h. — sublobal hair, t. h. — terminal hair; 6, ventral side of head with labium and connection of integumentary channels with linea ventralis, b. f. l. — basolateral field of labium.

FIGURES 7 – 10. Megalothorax tatrensis sp. nov.: 7, chaetotaxy and arrangement of sensory fields on thorax and abdomen, a—thoracal sensory field (enlarged), b—sensory field at leg II base (enlarged), c—sensory field at leg III base (enlarged), d—abdominal sensory field (enlarged); 8, tubus ventralis; 9, retinaculum; 10, Abd. V – VI with anal and female genital field, Abd. VI te—tergum, Abd. VI st—sternum, gp—genital plate, ns—neosminthuroid chaetae, avanal valve chaetae.

FIGURES 11 – 12. Megalothorax tatrensis sp. nov.: 11, right antenna, dorsal view (sensillum of Ant. III organ and apical organite enlarged); 12, furca, posterior view.

FIGURES 13 – 16. Megalothorax tatrensis sp. nov.: 13, leg I; 14, leg II; 15, leg III; 16, unguis and unguiculus of leg I.

FIGURES 58 – 61. Integumentary channels on head: 58, Megalothorax tatrensis sp. nov. — dorsally; 59, Megalothorax carpaticus sp. nov. — dorsally, a—ventrolateral view of head with integumentary channels; 60, Megalothorax hipmani sp. nov. — on headback; 61, Megalothorax draco sp. nov. — dorsally and laterally on headback.