Megalothorax roseus Panina & Potapov, 2022

Panina, Kseniya, Babenko, Anatoly & Potapov, Mikhail, 2022, Two new « nosed » species of the genus Megalothorax (Collembola: Neelidae) from Russia, Zootaxa 5188 (4), pp. 383-395 : 385-388

Megalothorax roseus Panina & Potapov , sp. nov.

Figs 2–17 , Table 1‒2

Type material. Holotype, Russia (European part), Kanin Peninsula, outskirts of Shoina settlement [67 ° 53 ’ N, 44 ° 09 ’ E], birch forest with rich herbs, 24.07.2017, leg. A. Babenko. 4 paratypes, in the same location. The holotype and 4 paratypes deposited in the collection of the Department of Zoology & Ecology, Moscow State Pedagogical University.

Other material. Russia (Asian part), Kemerovo region, Biyskaya Griva, Turachak-Tashtagol road [52 ° 52 ′ N, 87 ° 61 ′ E], pass, coniferous forest ( Abies ), 09.10.2020 ; Kemerovo region, Tashtagolsky district, Tashtagol-Kuzedeevo road [52 ° 97 ′ N, 87 ° 73 ′ E], Abies forest on slope, 08.10.2020 ; Kemerovo region, Novokuznetskiy district, Kuzedeevo settlement [53 ° 74 ′ N, 88 ° 09 ′ E], old pine forest along Kondoma river , 09.10.2020; Kemerovoregion, Kuznetsky Alatau ridge, near Raspadskaya mine [53 ° 74 ′ N, 88 ° 09 ′ E], mixed forest on slope ( Fig. 36 ), 09.10.2020. All leg. M. Potapov and N. Kuznetsova. ; Nenets Autonomous Okrug, Bolvanskaya Guba, left bank of the Yachay River [68 ° 05 ′ N, 54 ° 47 ′ E], willow grove (a strip of willow bushes between the meadow and the swamp), 18– 24.07.2015, leg. O. Makarova & M. Bizin. All kept in MSPU . Two specimens from type locality kept in SMNG .

Description. General aspect. Habitus and segmentation typical of the genus. Body length up to 0.35 mm. Specimens whitish in alcohol. Body chaetotaxy sparse including chaetae, s-chaetae, trichobothria, neosminthuroid chaetae, wax-rods and inner sensilla within sensory fields 2–6. Chaetae ordinary on body, without any remarkable development.

Integument. Secondary granulation made of the usual dorsal rough granules. Integumentary channels extending laterally and dorsally in anterior and posterior parts of head. Anterior canal branching. Channels connection with linea ventralis circular on the head (observation basing on one specimen). Detailed topology of channels not studied.

Sensory fields and wax rods ( Figs 5 , 7 , 9 ). Sensory field sf 1 with one wrc-chaeta (wrc) and without inner sensilla (s). Sf 2 with one s and one wrc, Sf 3 with three s and one wrc, Sf 4 and sf 5 with two s and one wrc. Sf 6 with one s and two wrc. All inner sensilla of sf 3–6 globular ( Figs 7 , 9 ). Inner sensilla of sf 2 broad flame-shaped. A total of 14 + 14 wrc (2 + 2 on head, 12 + 12 on body), including free 7+7 wrc not associated with sensory fields, notated as wrc 1–wrc 7.

Mouthparts. Labrum as typical for the genus ( Fig. 3 ). Chaetae a1 and a2 not forked, with one or two teeth. Labium with 4 + 4 proximal chaetae ( Fig. 4 ). Basomedian field with 3+3 chaetae. Basolateral field with 1 + 0 chaetae (one tubercle and no ventral chaeta). Labial palp ( Fig. 4 ), as common for the genus (A, B, C, D, E, b1, b2, d1, d 2, 2e, H, h1, h2). Oral fold and maxillary outer lobe as typical for the genus, without sublobal hair. Maxillary head without strong modification.

Head chaetotaxy. Forehead chaetotaxy as on Figs 2, 5, 6 . Clypeal-labral formula: a0, 2, 2, 5, 4/ 5, 5, 4 ( Fig. 2 ). Chaetae a0 present. Head with four (rarely two) papillae grouped together forming a wart, the papillae devoid of secondary granules ( Figs 2, 5, 6 ). Dorsal posterior area with 18 lanceolate chaetae ( Fig. 5 ). Ventral side with three pairs of postlabial chaetae ( Fig.4 ). Trend for posterior chaetae to be longer and stronger than anterior chaetae.

Antennal chaetotaxy ( Fig. 8 ). Ant. I and II with one and four chaetae, respectively.Ant. III with 8–9 chaetae and two long S-chaetae (S1 and S4). Striations of Ant III sensory organ short sensilla (S2 and S3) distinguishable in light microscopy. Ant. IV with seven chaetae (including X-chaeta) and ten S-chaetae. Sensory organ with Sx, Sy, Or, a, Sa. Organite (Or) of Ant IV short, seems apically flared. Diagram of the chaetotaxy of the antenna nearly as for M. processus sp. nov. ( Fig. 26 ). Summary on antennal chaetotaxy provided in Table 1 .

Body chaetotaxy. Th. II with 12 + 12 chaetae, 1 + 1 tubular and curved s1-sensilla ( Figs 7 , 9 ). Th. III with 11 + 11 chaetae, 6 + 6 free wax-rods (wrc1–6). Chaetae p4 not close to wrc2 ( Fig. 7 ). Chaeta a5 slightly shorter than chaeta a6. Abd I–V terga with 17 + 17 ordinary chaetae, 1 + 1 free wax-rods, 1 + 1 globular sensillum s2. Globular sensillum s3 absent ( Figs 7 , 9 ). Chaetae of body subequal, slightly thickened.

Legs chaetotaxy. Typical of the genus ( Table 2 ), consisting of ordinary chaetae of variable size ( Figs 13–15 ).

Claws. Claw III bulkier than claw I and II. Claws subequal in unguis length (with a trend as unguis I>unguis II> unguis III). Unguis basal and posterior auxiliary lamellae (la, lp and Bp) well developed ( Figs 16–17 ). Unguiculus 0.5-0.6 as long as unguis.

IV sternum and furca. Abd. IV sternum with 2 + 2 neosminthuroid chaetae and at least 2+2 chaetae (not 1+1, the observations are uncertain). Manubrium with 2 + 2 posterior chaetae and 1 + 1 pegs with convex tip articulated with a corresponding concavity of the dens ( Figs 10, 12 ). Proximal subsegment of dens with a posterior chaeta ( Figs 10, 12 ); distal subsegment posteriorly with two basal spines and one chaeta at the middle. Anterior side of dens with five apical spines, spines without elongated apex ( Fig. 11 ). Mucro tri-edged, posteriorly gutter-like and with anterior crest ( Figs 10–12 ). Mucro narrowing in the distal 2/5. Edges are entirely smooth with one notch. Chaetotaxy of Abd. V and VI not studied, looks generally as for the genus.

Tenaculum and ventral tube. Tenaculum with 3 + 3 hook-like teeth (as in M. processus sp. nov., Fig. 35 ). Ventral tube bulky with two apical pairs of chaetae.

Males not found.

Name derivation. The name reflects the similarity of the wart on the forehead with a rose (flower).

Discussion. Megalothorax roseus sp. nov. can be attributed to neither minimus - nor incertus -group in understanding of Schneider & D’Haese (2013). The new species shows all characters of the former group, except for globular sensilla inside the trunk sensory fields which are the characteristic of the incertus -group. The unique character of M. roseus sp. nov. is the four papilla wart which was unknown among congeners so far. M. potapovi and M. sanctistephani also have a process on forehead though its shape is completely different. Both species also differ in the form of inner sensilla (flame-shaped vs. globular in M. roseus ) and the number of chaetae on the forehead and body (more complete in M. potapovi , and regretfully unknown for body of M. sanctistephani ).

From the widespread M. willemi and M. minimus , M. roseus sp. nov. clearly differs notably by the shape of the inner sensilla (globular vs. flame shapes).

Among species not fully described the new species can be compared with M. interruptus Hüther, 1967 ( Sudan) , which is also close to M. laevis Schneider, Zon & d’Haese, 2018 . Apart from the wart, M. roseus sp. nov. differs from M. interruptus by the absence (vs. presence in M. interruptus ) of the second pair of dorsal globular sensillum s3.

The shape of the sensilla of sensory fields depends on location in new species: from flamed-shape in sf 2 on head to globular on body. The same pattern is observed in M. laevis .

See also the Discussion part to M. processus sp. nov.

Distribution and ecology. Megalothorax roseus sp. nov., previously recorded from the East-European tundra as Megalothorax sp.3 ( Babenko et al. 2017), seems to be widespread in the Central Palaearctic being found from northern (Kanin Peninsula) to relatively southern (Altai Mts) areas. It mostly occurs in different types of forest floor.

Figures

FIGURES 2–6. Megalothorax roseus sp. nov.:2—forehead, front view; 3—chaetae of labrum, front view; 4—labrum, labium, postlabial area, and maxillary palp; 5—head, dorsal view; 6—forehead, lateral view. Ant. —antenna, ia—inter-antennal position, a0—unpaired chaetae on forehead, sf—sensory field, pr.l.—pre-labral, pr.a.—pre-antennal, cl.a.—clypeal anterior, cl.m.—clypeal median, cl.p.—clypeal posterior, f.p.—frontal posterior, f.m.—frontal median, f.a.—frontal anterior, pa.p.p— postantennal posterior, pa.a.—postantennal anterior, mol—maxillary outer lobe, sh—possible location of sublobal hair, A–E: labial papillae, b,d,e—accessory papillae, H, h1, h2—hypostomal chaetae, f.p.w.—four papilla wart.

FIGURES 7–8. Megalothorax roseus sp. nov.: 7—body chaetotaxy, dorsal view; 8—antenna, dorsal and ventral views. sf— sensory field, s1, s2—swollen sensilla on body, wrc—wax-rods (this is the same free wax rod generating crypt as in Schneider et al. 2013), S—S-chaetae, thickened chaetae on Ant. III–IV; Sy, Sa, Sx, a, Or—sensory organ.

FIGURES 9–12. Megalothorax roseus sp. nov.: 9—body chaetotaxy, lateral view; 10–12—furca, lateral (10), anterior (11), and posterior (12) view; 12—furca, posterior view. Abbreviations as in Fig. 7.

FIGURES 13–17. Megalothorax roseus sp. nov.: 13–15—legs I (13), II (14), and III (15), lateral view; 16—claw III, anterior view; 17—unguiculus I, posterior view.

FIGURES 36–37. Altai habitats for M. roseus sp. nov. (36, Kuznetsky Alatau ridge) and M. processus sp. nov. (37, entrance to Chuyskaya basin).

FIGURES 24–26. Megalothorax processus sp. nov. and M. roseus sp. nov.: 24–25—antenna, dorsal (24) and ventral (25) views; 26—diagram of the chaetotaxy of the antenna for M. roseus and M. processus. Abbreviations as in Fig. 8.

FIGURES 31–35. Megalothorax processus sp. nov.: 31—body chaetotaxy, lateral view; 32—claw III, lateral view; 33— unguiculus I, posterior view; 34—claw I, anterior view; 35—rami of tenaculum (variation). Abbreviations as in Figs 9–12.