Megalothorax draco, 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 : 562-565

Megalothorax draco sp. nov.

Figs 45–57

Megalothorax sp. 4 Papáč & Kováč (2012)

Diagnosis. Mucronal lamellae serrate ( incertus -group). Connection of integumentary channels with linea ventralis on head crossed. Unpaired chaeta a0 between the basis of antennae present; thickened macrochaetae on posterior part of head present. Basomedian field of labium with 4+4 chaetae. Sensory fields 2–6 with globular sensilla. Mesochaeta p4 on Th. III next to wax rod crypt 2, a6/a5 on Th. III as microchaeta/ macrochaeta. Spherical sensillum s3 on abdomen present. Macrochaeta on subcoxae I (leg I) present. Unguis clearly elongated. Manubrium with 4+4 dorsal chaetae (3+3 proximal, 1+1 distal). Retinaculum with 4+4 teeth.

Type material. Holotype: female on slide (No. 90–09), Romania, Bihor Mts., Drăcoaia Cave, Channel Passage, aphotic zone, 200 m from entrance, surface of water pool, 10.x. 2009, leg. V. Papáč. Paratypes: 6 ex. on slides— 5 females, 1 male (No. 90–09), same data as in holotype. Type material (holotype and 3 paratypes) saved in collection of MNHN, Paris. Other paratypes saved in collection of PJSU, Košice, Slovakia.

Description. Body length 0.45–0.55 mm, males smaller than females (up to 450 µm), habitus typical of the genus. Body colour whitish. Cuticle finely granulated, integumentary channels observed on ventral side of head and dorsally on posterior parts of head, connection of channels with l. v. ventrally on head crossed.

Head. Head length and width as 150 and 140 µm, respectively. Dorsal chaetae smooth and pointed ( Fig. 45 ); unpaired chaeta a0 between the basis of antennae present. Frontal part with ordinary chaetae (8–10 µm), medial part with mesochaetae (12 µm) and posterior part behind antennae with ordinary mesochaetae (12 µm), macrochaetae (14 µm) and thickened macrochaetae (16–18 µm). 1+1 lateral chaetae between labial palp and basis of antenna. Clypeo-labral formula: a0, 2, 4, 5, 4 / 5, 5, 4 ( Fig. 45 ). Pattern of labral chaetae: a-row with 2R1+2R2, m-row with m+2r1+2r2 and p-row with 5 ordinary chaetae. Anterior chaetae R1 and R2 thick, curved, R2 (13 µm) longer than R1 (9 µm); R1 with external edge serrate with 2 striking spines; R2 with external edge very finely serrate. Medial (m-row) and posterior chaetae (p-row) equal (8 µm) and smooth. Integumentary channels present dorsally and laterally on headback ( Fig. 61 ). Basomedian field of labium with 4+4 chaetae, medial chaetae slightly longer (12 µm) than others (10 µm), 1 smaller chaeta laterally near basolateral field ( Fig. 49 ). Basolateral field with 1 ordinary chaeta, oral fold with 2 chaetae. Ventral side of head with 3+3 smooth postmedian chaetae ( Fig. 49 ); 2+2 anterior as equal, curved macrochaetae (16 µm); posterior 1+1 as slightly curved macrochaetae (16 µm). Mandible normal with 5 apical teeth ( Fig. 48 ). Maxillary outer lobe with enlarged terminal chaeta, 1 basal chaeta and 1 sublobal hair ( Fig. 47 ). Maxilla with 1 lamella extending beyond fringed lamellae ( Fig. 46 ).

Thorax and abdomen ( Fig. 50 ). Dorsal side of thorax and abdomen sparsely with micro-, meso- and macrochaetae (5, 10 and over 20 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 rods wrc, laterally at leg III base with 3+3 chaetae and 2+2 wrc around sensory field; mesochaeta p4 next to wrc2; chaeta a5 stout and long, a6 as microchaeta. Abd. I–V terga with 19+19 chaetae, 2+2 wrc and 2+2 globular sensilla s2 and s3, chaeta β2 missing ( Figs. 50 g, h). Abd. VI with 9 dorsal chaetae ( Fig. 50 f). Anal field with 3 anal valves, each with 1 chaeta. Abd. VI with 9+9 ventral chaetae (2+2 axial shorter). Female genital plate furnished with 2+2 chaetae ( Fig. 50 f), male plate with 14–18 chaetae arranged around genital opening ( Fig. 51 ). Manubrium base (Abd. IV sternum) with 3+3 chaetae, laterally with 2+2 broad neosminthuroid chaetae with ciliated tip (9 µm; Fig. 50 f).

Appendages. Antennal segments III and IV not separated ( Fig. 52 ). Length of antennae up to 80 µm, ratio antenna/head = 0.50; lengths of antennal segments I, II, III-IV as 11, 14 and 50 µm, respectively. Ant. I furnished with 1 short chaeta (8 µm). Ant. II with 4 chaetae arranged in whorl, 1 of them slightly longer (10 µm) than others (8 µm). Ant. III with 9 ordinary chaetae. Ant. III organ consists of 2 ovoid sensilla with striate rim (10 µm), 2 long guard sensilla Sg, external and dorsal (15 µm each). Ant. IV with 6 ordinary chaetae arranged mostly on internal side, external side with 10 thin, curved macrosensilla S finely blunt at the tip (14–18 µm); ventrally with 1 long and thick sensillum Sy (13 µm), 1 thick and basally swollen short sensillum Sx (6 µm) with curved tip and 1 ordinary chaeta x; dorsally with globular subapical organite Or (4 µm); subapically with 5 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. 54–56 , 50 ), longer chaetae in parenthesis: scx I: 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), 7(2), 7(3) and tibiotarsi: 12, 12, 10. Thin meso- or microchaetae with following numbers on leg I: coxa with 1, femur with 2; on leg II: trochanter with 1; 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 27, 25 and 21 µm, respectively, unguiculus 9, 8 and 11 µm, respectively. Length ratio unguis I (inner margin) / Ti. I width (27/13 µm) = 2.0 8. Unguis furnished with 2 lateral teeth la, lp and 1 inner tooth Bp slightly projecting proximal part of unguis ( Fig. 57 ). Unguiculus untoothed, apical filament absent, basal lamellae broader, protruding basal tubercle absent. Unguiculus of leg III longer and stouter than in fore legs. Tubus ventralis with 2+2 distal chaetae, posterior lobe absent ( Fig. 50 d). Retinaculum with 4+4 teeth, chaeta on corpus absent ( Fig. 50 e). Furca well developed ( Fig. 53 ), length of manubrium, dens (proximal, distal part) and mucro: 55, 28, 52 and 36 µm, respectively. Manubrium dorsally with 4+4 chaetae of which 3+3 proximal (axial 12 µm, lateral 8 µm) and 1+1 distal (8 µm). Dens in proximal part (dp) with 1+1 dorsal macrochaetae (14 µm). Distal part of dens (dd) dorsally with 1 medial, smooth chaeta (7 µm) and 4 broad spines with apical filament (4–6 µm): 2 external and 2 internal; ventrally with 3 tight apical spines (5 µm). Spines as leave-shaped integumental structures lacking basal circle. Mucro broad (width in the middle part up to 12 µm, length 36 µm) paddle-like, with dorsal lamellae serrated (8–9 teeth) and rounded tip ( Fig. 53 a).

Sensory fields ( Fig. 45 , 50 ). 6+6 s.f. placed in small depressions each with secretory rod (8 µm), i.e. blunt, straight chaeta with basal part inserted in the cuticle in upper margin of the field. S.f. have following arrangement: (a) anterior and posterior field on head (s.f. 1 and 2, anterior 15 x 8 µm, posterior 20 x 13 µm; Fig. 45 ), posterior field with 1 internal globular sensillum (3 µm); (b) thoracal field (s.f. 3, 25 x 15 µm; Fig. 50 c) with 1 internal globular sensillum and 6 external chaetae (2 lateral as macrochaetae); (c) abdominal field (s.f. 6, 25 x 15 µm; Fig. 50 g) with 1 internal globular sensillum, 5 marginal chaetae (1 mesochaeta, others macrochaetae), spherical sensillum s2 and wax rod wrc8; (d) field at base of leg II (s.f. 4, 20 x 15 µm; Fig. 50 b) with 1 internal globular sensillum, 4 external chaetae (2 mesochaetae, 2 macrochaetae) and sensillum s1 (5 µm) placed above the field; (e) field at base of leg III (s.f. 5, 20 x 15 µm; Fig. 50 a) with 1 internal globular sensillum, 3 external chaetae (1 mesochaeta, 2 macrochaetae) and wax rods wrc 5,6 on its posterior margin.

Both sexes known. Except genital plates no other sexually dimorphic characters observed.

Etymology. The new species is named after the type locality—Drǎcoaia Cave in the Sighistel Valley, Bihor Mts, western Romania.

Distribution. At present M. draco sp. nov. is known only from type locality—Drǎcoaia Cave, Bihor Mts., Romania.

Discussion. M. draco sp. nov. belongs to „ incertus -group“ by both mucronal lamellae serrate and modified internal chaeta of sensory fields in form of globular sensillum. It differs from M. massoudi and M. hipmani sp. nov., other two troglomorphic species of the group, by thickened axial macrochaetae on posterior side of head (ordinary axial mesochaetae in M. massoudi ), length of chaeta a5 and a6 on Th. III (macrochaetae vs. meso- and microchaeta), shape of apical organite Or on Ant. IV (globular vs. cup-like), shape of mucro (paddle-like vs. elongated) and by presence of sensillum s3 on abdomen (present in M. hipmani sp. nov. and M. draco sp. nov., absent in M. massoudi ). For other differential characters see Discussion in M. hipmani sp. nov. and Tables 3–5.

Figures

FIGURES 45 – 49. Megalothorax draco sp. nov.: 45, head, dorsal side; chaetae of anterior row enlarged; 46, head of maxilla, different views; 47, maxillary outer lobe; 48, mandible; 49, ventral side of head with labium and connection of integumentary channels with linea ventralis.

FIGURES 50 – 51. Megalothorax draco sp. nov.: 50, chaetotaxy and arrangement of sensory fields on thorax and abdomen, a—sensory field at leg III base (enlarged), b—sensory field at leg II base with sensillum s 1 (enlarged), cthoracal sensory field (enlarged), d—tubus ventralis, e—retinaculum, f—Abd. V – VI with anal valve, female genital plate and neosminthuroid chaetae (enlarged), g—abdominal sensory field (enlarged), h—sensillum s 3 enlarged, av—anal valve, gp—genital plate, ns—neosminthuroid chaetae; 51, male genital plate.

FIGURES 52 – 53. Megalothorax draco sp. nov.: 52, right antenna, dorsal view (sensillum of Ant. III organ and apical organite enlarged); 53, furca, posterior view, a—lateral view of mucro.

FIGURES 54 – 57. Megalothorax draco sp. nov.: 54, leg I; 55, leg II; 56, leg III; 57, 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.