Neelus murinus Folsom, 1896 sensu Massoud & Vannier (1967)

Schneider, Clément, 2017, Morphological review of the order Neelipleona (Collembola) through the redescription of the type species of Acanthoneelidus, Neelides and Neelus, Zootaxa 4308 (1), pp. 1-94 : 75-90

Neelus murinus Folsom, 1896 sensu Massoud & Vannier (1967)

Figs 1 b, 3C, 4C, 5, 10, 37–49.

Material examined. Original material. One slide labeled “ Neelus murinus, Jardin Botanique, Toulouse ” was found in the collection of the MNHN. It is probably part of the material observed by Massoud & Vannier (1967), collected by Cassagnau. The slide has a female in bad condition.

Other material. 7 ♀ on slides ( MNHN-EA 040210 –216 ), 3 spm mounted for SEM ( MNHN-EA 041011 ), France, Dordogne , Rouffignac-de-Sigoulès, Fontanguillère Cave, 10.viii.2012, captured with brush on a pond of water, C. Schneider leg., [ MNHN].

1 ♀ on slide ( MNHN-EA 040218 ), France, Dordogne , Hautefort, subterranean river of La Reille, 12.viii.2012, extracted with Berlese-Tullgren funnel from moist dead wood, C. Schneider leg., [ MNHN].

1 juvenile on slide ( MNHN-EA 040217 ), France, Île-de-France, Paris, Muséum National d’Histoire Naturelle, Îlot Buffon-Poliveau , 48°50'29"N 2°21'32"E, 04.v.2013, extracted with Berlese-Tullgren funnel from soil and litter of dry leaves and dead wood, C. Schneider leg., [ MNHN].

2 ♀ on slides ( MNHN-EA 040219, 220 ), 6 spm mounted for SEM ( MNHN-EA 041008 ), France, Île-de-France, Paris, Muséum National d’Histoire Naturelle, Îlot Buffon-Poliveau , 48°50'29"N 2°21'32"E, 18.iv.2011, extracted with Berlese-Tullgren funnel from soil and litter of dry leaves and dead wood, C. Schneider leg., [ MNHN].

Diagnosis. Whitish with patches of brown-orange. 1.1 mm length. Postero-dorsal area of the head with setulae. Labrum: chaetae a1 with an external, basal tooth, a2 smooth. Posterior pair of post-labial chaetae smooth. Ant. IV with ten S-chaetae S, a and sa tubular with rounded apex. Abdomen with numerous microspines (tertiary rods). Manubrium with 3 + 3 posterior chaetae—1 + 1 proximal and 2 + 2 distal. dp with 2 + 2 chaetae. Mucro tip slightly bilobate.

Description. Adult ( Figs 1 b, 3C, 4C, 5, 10A, 37–46).

Size. Length from labrum to anus of the biggest specimens ~ 1100 µm.

Pigmentation. In alcohol whitish with large patches of brown-orange.

Body shape and segmentation. Habitus as in Figs 37 A, B. Orthognathous. Head rather flattened in the frontal plane, ratio height: length ~ 0.56 ( Fig. 37 A, B). Antennae directed laterally with a slight curve toward the anterior direction, slender, with four distinct antennomeres ( Figs 37 A, B, F, 38A). Total length of antenna ~ 147 µm; max width (Ant. III) ~ 25.5 µm; ratio width: length ~ 0.16; ratio length of Ant. I: Ant. II: Ant. III: Ant. IV ~ 0.15: 0.70: 0.80: 1. Each side of head with a postero-lateral process that forms a posterior concavity and a posterolateral corner ( Figs 37 A, B, C, 38A, B); precoxal areas of Th. I well-developed, forming an antero-lateral convex lobe ( Figs 37 A, B, C, 38B). The posterior concavities of the head match the convex shape of the precoxal areas of Th. I ( Figs 37 A, B, C, 38B). Point of insertion of head on Th. I aligned with antero-posterior axis of the head. Th. I diameter reduced, without difference of level between head–Th. I but with steep curve between Th. I–II ( Fig. 37 A, B, C). Th. I in one part, neck missing ( Fig. 37 D, E). Th. I widest in posterior part, slightly inferior to head posterior width ( Fig. 38 A). Th. I with: (i) a posterior transversal fold reaching laterally the limit of Th. I–Th. II; (ii) an anterior transversal bulge forming when head standing up straight, this bulge delimited posteriorly by an indistinct dorsal fold and anteriorly by the connection of Th. I with the head ( Fig. 37 C, D, E). Connection of Th. I with the head as a shallow fold. Terga from Th. II to Abd. V fused ( Fig. 37 A, B). On each side a dorso-lateral fold is present at the Th. II–Th. III putative limit, this fold subdividing dorsally in two slighter folds before shading off, and shading off laterally without reaching the leg insertion ( Fig. 37 A, B). Specimens prepared for SEM display deep dorso-median depressions: one roughly matches Th. II putative area; another could match Th. III putative area; also two pairs of shallow depressions are observed on the anterior part of the abdomen ( Fig. 37 B). In the posterior part of the abdomen, there is a transversal protuberance—devoid of chaetae—preceding the fold that delimit anteriorly Abd. VI ( Fig. 37 A, B). Posterior granule T of the dorso-median line missing. Precoxal area of Th. II with weak anterior lobe covering partially the sensory field, not reaching subcoxa 1 ( Fig. 37 A, B, C), precoxal area of Th. III with anterior process bearing a ventral lobe reaching the level of subcoxa 1 ( Fig. 37 A, B). Each coxa long and bended. On leg I length of coxa> tibiotarsus> femur ~ trochanter. On legs II and III length of coxa> tibiotarsus ~ femur ~ trochanter ( Fig. 43 A–G). Abd. VI sternum clearly separated posteriorly from Abd. VI tergum by anal aperture; separated anteriorly from Abd. V sternum by a steep curve; fused laterally with the great abdomen and displaying the same covering of dermastra than the tergum. Abd. V sternum with genital plate cryptic, enclosed deeply between Abd. IV and Abd. VI. Abd. IV sternum enlarged, creating a large ventro-posterior side bearing the furca ( Fig. 37 A, B). Abd. I–III sterna reduced with tenaculum being stuck to ventral tube ( Fig. 46 A). Manubrium/ dens articular processes: manubrium with weak process bearing hardened peg with convex tip that connects to concave tip of strong, projecting process of dens ( Fig. 45 F, G). Manubrium strong. Dens with a proximal part (dp) wider than the distal part (dd) ( Fig. 45 A, E). No suture or articular process between dp and dd but dens flexible at this point (fixed specimens often exhibit a flexion of the dens between dp and dd with subsequent folds in the integument, Fig. 45 A, E). Ratio length of manubrium: dp: dd: mucro ~ 0.73: 0.53: 1: 0.84.

a1 a2

Granulation. Primary granulation made of ordinary hexagonal pattern (six primary granules connected with bridges). Four morphological variations of primary granules pattern observed: (i) ordinary; (ii) thickening of all the granules of the hexagon—width increased but not height, bridges shortened and visible surface of the base of the integument reduced—occurs on the labrum around m- and p-row of chaetae, on the apical part of the maxilla outer lobe palp, on the labial palp and on the apical sac of the ventral tube; (iii) with distortion of the granules—primary triangular shape being stretched—occurs on the posterior side of the dens ( Fig. 45 B); (iv) with heterogeneity of size between the six granules of a same hexagon—the largest granules brighter than the others in SEM and the smallest granules being shady in SEM and organized as a succession of circular depressions (dark spots, Fig. 38 D, E). Commonest dermastra with 6–8 edges ( Fig. 38 D) but up to 18 edges can be observed. Dermastra covering head dorsally and laterally (with an anteriorly limit between cl.a- and cl.m-rows of chaetae, Fig. 3 C), trunk terga, partially Abd. VI sternum ( Fig. 45 H), subcoxae 1 and scarcely, posterior side of subcoxae 2 II and III.

Integumentary channels. Integumentary channels present on head, Th. I and Th. II–III ( Figs 4 C, 10A, 37C, D, 38A–C, E, 41C, 42A). On each side of head, channels as a tree rooted on linea ventralis, splitting in two ventral branches directed posteriorly and rejoining each other in the posterior corner of the head, one of which extending on Th. I where it splits in eight terminal branches ( Figs 4 C, 10A, 37C, D, 38A–C, 41C). Bed of head—Th. I channels devoid of granules, edges as bulges of integument in the basal part (from linea ventralis to the first split), further becoming thin rims of squeezed primary granules up to displaying a smooth aspect ( Fig. 38 A–C). On each side of Th. II and III, channel as a single branch rooted on linea ventralis and growing laterally between leg II and leg III. Bed of Th. II–Th. III channel covered of primary granules, edges as bulges of integument ( Fig. 38 E).

Chaetae. Ten morphological variations of chaetae on head and trunk: (i) ordinary chaetae; (ii) setulae, peculiarly small and thin chaetae weakly contrasted in light microscopy mostly found on the vertex of the head and dorsally on trunk (6, 7 µm, Fig. 1 b); (iii) flexible chaetae, peculiarly thin and flexible mesochaetae (16, 17 µm, Fig.

42G); (iv) s-chaetae, short and swollen chaetae (s1–s3) found on trunk ( Fig. 42 B–D); (v) τ-chaetae, long and flexible chaetae shaped as trichobothria with basal ring implanted in a small depression of the integument and weakly contrasted in light microscopy, found on trunk (>50 µm, Figs 39 C, 42H); (vi) wax rod secretory crypts associated to a sensory field, (vii) free wax rod secretory crypts; (viii) tertiary wax secretory rods, short, conical chaetae with round apex and basal ring weakly sunk in the integument, found on Th. III and abdominal terga (3–5 µm, Fig. 42 E), (ix) inner swollen chaetae of sensory fields ( Fig. 42 F, I) and (x) neosminthuroid chaetae ( Fig. 42 J).

Wax secretory rods and sensory fields. Six pairs of sensory fields (sf1–6) on head and trunk, each field associated with a wax rod secretory crypt ( Figs 3 C, 10A, 37A–B, 41B, C, 42A). On head: sf1 preantennal with a long and flexible inner chaeta ( Figs 39 A, 41B); sf2 postantennal with a long and flexible inner chaeta ( Figs 39 B, 41C). On trunk: sf3 dorsally on Th. II with three large candlelight-shaped inner chaetae ( Figs 37 C, 42A, F); sf 4 in precoxal area of Th. II and sf 5 in precoxal area of Th. III each with two candlelight-shaped inner chaetae ( Figs 39 C, D, 42A, I); sf6 on dorsal, posterior part of the abdomen with a candlelight-shaped inner chaeta ( Figs 39 E, 42A). Eight pairs of free wax rod secretory crypts including seven in Th. III tergum area (wrc1–7) and one in abdominal terga area (wrc8; Figs 10 A, 42A).

Mouth parts. Left mandibula with about four apical teeth ( Fig. 40 E), right mandibula with about 5 teeth and a process between apex and molar plate ( Fig. 39 B). Molar plate with round anterior process ( Fig. 39 A, B). Maxilla with six lamellae.

Labium. Basomedian field with four chaetae and basolateral field with two ventral chaetae (microchaeta + mesochaeta) and a dorsal macrochaeta on tubercle ( Fig. 41 A). Basomedian field separated from basolateral field by a shallow furrow. Palp with six strong papillate chaetae (H, A, B, C, D, E, Fig. 40 E, F). H, B and D each with two guard hairs, E with one guard hair ( Fig. 40 E, F). Papilla B reaching the same level as hypostomal papilla H ( Fig. 40 E, F). Papillate chaeta H shorter than the guard hairs with a swollen, rounded apex ( Fig. 40 E, F). A small organite is perceptible at the base of papilla A ( Fig. 40 E, F).

Maxillary outer lobe and oral fold. Maxillary palp with a macrochaeta (20 µm) in the sub-basal papilla, a strong and straight macrochaetae (26 µm) in the apical papilla ( Fig. 40 G, H). Apical papilla with a hair in subapical, ventro-median position. Sublobal plate with two minute hairs ( Fig. 40 H). Oral fold with two macrochaetae ( Fig. 41 A, B).

Labrum. Labrum anterior part with a large dorsal projection that bears the a- and m-rows of chaetae and bring them in anterior position in regard to the labral ridge ( Figs 2 F, 40I, J). Thus labral ridge in ventral position, roughly at the same level as p-row of chaetae on antero-posterior axis. Labral ridge sclerotized, without hairs. p-row with five ordinary mesochaetae, m-row in dorsal, sub-apical position with five strong, smooth chaetae, a-row in ventral, sub-apical position with 2 + 2 strong chaetae ( Fig. 40 I, J). a1 with an external, basal tooth, a2 smooth ( Fig. 40 I, J). a-row separated from m-row by an integumentary crest ( Fig. 40 I, J).

Head chaetotaxy. Postero-dorsal area with 12 + 12 setulae ( Figs 3 C, 41C). Postero-lateral area with 3 + 3 setulae ( Figs 3 C, 41C). Antero-dorsal area with 1 + 1 setulae, 8 + 8 macrochaetae and two unpaired chaetae ( Figs 3 C, 41B, C). Antero-lateral area with 7 + 7 macrochaetae ( Figs 3 C, 41A, B). Ventral area with 3 + 3 post-labial macrochaetae (30 µm, Figs 4 C, 41A).

Antenna chaetotaxy. Fig. 40 K, L. Ant. I with three chaetae on dorsal side. Ant. II with six chaetae in two whorls—a chaeta in basal whorl, five chaetae in apical whorl. Ant. III with: 14 mesochaetae in four rough whorls—distribution from base to apex: 1, 3, 3 and 7 chaetae; five apical S-chaetae (S1–S5)– S1 and S4 long and tubular, S2 and S3 short and tubular, S5 short and flam-shaped. Ant. IV with: 19 mesochaetae, whorls unclear; 12 S-chaetae with round apex including 10 long (S), one shorter than S with curved apex (Sx, 6 µm) and one thicker than S (Sy); two sensory rods with round apex in apical (a) and sub-apical position (sa); a sub-apical organite Or with two apical filaments, in basal position in regard to sa, and apical position in regard to S-chaeta Sx. On Ant. III, S1–3 ornamented with longitudinal whorls of striation, S4 not observed. On Ant. IV, S and Sy ornamented with external denticulation, Sx smooth or only faint denticulation.

Th. II–Abd. V terga chaetotaxy. Th. II–Abd. V terga with a total of 26 + 26 chaetae, including 4 + 4 flexible chaetae, 2 + 2 ordinary chaetae and 20 + 20 setulae; 12 + 12 τ-chaetae all in the thoracic or anterior abdominal area; 4 + 4 s-chaetae (s1, s2, s3, s3’); 8 + 8 wrc and around 92 + 92 tertiary rods ( Figs 10 A, 42A). Dorso-lateral areas of Th. II with 8 + 8 setulae, 2 + 2 flexible chaetae (a3, p4) on the edge of sf3 and 2 + 2 τ-chaetae ( Figs 10 A, 42A, G); Precoxal areas of Th. II with 2 + 2 chaetae (including 1 + 1 flexible chaetae a9), 1 + 1 τ-chaetae, and 1 + 1 flamshaped s-chaetae s1 ( Figs 10 A, 39C, 42A, B). Dorso-lateral area of Th. III–anterior abdomen with 7 + 7 setulae, 8 + 8 τ-chaetae, 7 + 7 wrc, wrc3 being much thicker than the other, 24 + 24 tertiary rods and 2 + 2 s-chaetae (s3, s3’; Figs 10 A, 42A, D). Precoxal areas of Th. III with 2 + 2 mesochaetae (including 1 + 1 flexible chaetae a9) and 1 + 1 τ-chaetae ( Figs 10 A, 39D, 42A). Posterior area of the abdomen (until Abd. V included) with 5 + 5 setulae, 1 + 1 wrc, about 68 + 68 tertiary rods and 1 + 1 s-chaetae (s2; Figs 10 A, 42A, C). s1 flam-shaped, s2, s3, s3’ T-shaped with rounded tips ( Figs 39 E, 42A–D).

Legs chaetotaxy. On leg I: subcoxa 1, subcoxa 2 and coxa each with a chaeta ( Fig. 43 A); trochanter with four chaetae (2 proximal, 2 distal, Fig. 43 B); femur with 10 chaetae of various size and strength ( Fig. 43 C); tibiotarsus with 16 strong chaetae in roughly five whorls distributed from the most proximal to the most distal approximately as 3, 3, 3, 2, 5. On leg II: subcoxa 1, subcoxa 2 each with a chaeta, proximal ( Fig. 43 D); coxa with a proximal chaeta ( Fig. 43 D); trochanter with three chaetae (1 proximal, 2 median, Fig. 43 D); femur with 10 chaetae of various size and strength ( Fig. 43 D, E); tibiotarsus with 18 strong chaetae in roughly five whorls distributed from the most proximal to the most distal as 3, 3, 5, 2, 5 ( Fig. 43 D, E). On leg III: subcoxa 1 with three chaetae ( Fig. 43 F); subcoxa 2 with a chaeta ( Fig. 43 F); coxa with two proximal chaetae); trochanter with four chaetae (1 proximal microchaeta, 1 median mesochaeta, 2 distal microchaetae, Fig. 43 F); femur with 10 chaetae of various size and strength ( Fig. 43 G); tibiotarsus with 17 chaetae in roughly five whorls distributed from the most proximal to the most distal approximately as 3, 3, 4, 2, 5 ( Fig. 43 G). The strong chaetae on femur and tibiotarsus are ornamented with longitudinal striations and external faint teeth ( Fig. 44 A, D). See Tables 9, 10, 11 for a summary.

Claws. ( Fig. 44 A–E). Each pretarsus bearing two microchaetae with round apex, one on anterior side and one on posterior side. Unguis: lamellae L, la and lp each with a strong smooth edge, la and lp clearly separated, lamella Bp well developed. Unguiculus: basal tubercle reduced to a very small integumentary process, unguiculal lamella with an anterior crest Ca and a posterior crest Cp. Claw I the slenderest, claw III the bulkiest.

Abd. VI. ( Fig. 45 H). Anal valves without neat integumentary differentiation from the tergum and sternum, albeit devoid of dermastra and roughly delimited with folds. Chaetotaxy of anterior part of the tergum as follows: 2 + 2 anterior macrochaetae (a1, a2), 1 + 1 median macrochaetae (a3) and 1 + 1 median microchaetae (µ.av), 1 + 1 posterior macrochaetae (m1) (greater than the other). Dorsal anal valve with an unpaired mesochaeta (av). Ventral anal valves each with 2 + 2 microchaetae (µ.av) and 1 + 1 mesochaetae (av). Anterior region of the sternum with 6 + 6 macrochaetae (1 + 1 greater than the others) and 1 + 1 mesochaetae, dermastra limited to an inner area.

Genital plate. Female with 4 + 4 mesochaetae, 1 + 1 microchaetae ( Fig. 45 H). Male unknown.

Abd. IV sternum. Axial area with 1 + 1 macrochaetae and 3 + 3 mesochaetae, lateral areas with 1 + 1 mesochaetae and 1 + 1 neosminthuroid chaetae (ns; Figs 42 J, 45H). Neosminthuroid chaetae short, the basal half ornamented with longitudinal striation and faint spicules, the apical half ornamented with spicules ( Fig. 42 J).

Abdominal appendages. Manubrium with 3 + 3 posterior chaetae (1 + 1 proximal, 2 + 2 distal, Fig. 45 E). Dens proximal part with two posterior chaetae, axial one longer than lateral one; distal part with a basal, posteroexternal spine (E3), two median spines (postero-external E2 and postero-internal J2), five apical spines (three anterior AE1, A1, AJ1, one postero-external E1 and one postero-internal J1) and one posterior apical chaeta (P1; Fig. 45 A–E). E2, E3 and J2 with a basal ring; E1, J1, AE1, AJ1 and A1 without basal ring ( Fig. 45 A–E). Mucro with a slight constriction at 3/5 from the base, with thin lamellae and around 18 teeth on each posterior lamellae, mucro tip slightly bilobate ( Fig. 45 A, D, E). Tenaculum with two medians lobes without chaeta, 3 + 3 apical teeth, basal tubercles as two small, hardened bumps on each side ( Fig. 46 A, B). Ventral tube with a posterior lobe and 2 + 2 apical mesochaetae ( Fig. 46 C, D).

Juvenile ( Figs 3 C, 4C, 5, 10B, 47–49).

Size. Length from labrum to anus of the specimen ~ 280 µm.

Pigmentation. Whitish (in ethanol).

Body shape and segmentation. Habitus as in Fig. 47 . Orthognathous, head rounded, ratio height: length ~ 0.8. Total length of antenna ~ 70 µm; max width (Ant. III) ~ 18 µm; ratio width: length ~ 0.26; ratio length of Ant. I: Ant. II: Ant. III: Ant. IV ~ 0.2: 0.80: 1: 0.80. Precoxal areas not so prominent. Abd. IV sternum not so enlarged. Ratio length of head: length of thorax: length of abdomen ~ 1.75: 1.75: 1. Length of manubrium: dp: dd: mucro ~ 0.75: 0.45: 1: 0.88. A pair of dorsal internal organ is clearly visible in postero-dorsal position of sf3 ( Fig. 48 B). A dark mark is visible dorsally on the abdomen, in axial position between s3, origin unclear (integument or internal, Fig. 48 B).

Granulation. Dermastra present.

100Μm

A – C

50Μm

Integumentary channels. Not precisely observed, present on head, Th. I, Th. II–Th. III as the adult but apparently less developed ( Fig. 48 A, B).

Chaetae. Nine morphological variations on head and trunk: (i) ordinary chaetae; (ii) s-chaetae, short and swollen chaetae (s1–s3) found on trunk; (iii) τ-chaetae (bases position reported, chaetae not directly observed); (iv) wax rod secretory rod crypts associated to sensory fields, (v) free wax rod secretory crypts (wrc); (vi) tertiary wax secretory rods as strong spines on abdomen ( Fig. 48 B), (vii) tertiary wax secretory rods as very small conical microchaetae on thorax ( Fig. 48 B), (viii) inner swollen chaetae of sensory fields and (ix) neosminthuroid chaetae.

Wax secretory rods and sensory fields. Wax rod secretory crypts in sensory fields stronger than wrc, each sensory field reported in the adult present ( Figs 10 B, 48A, B). Inner chaeta of sf1 absent, inner chaeta of sf2 similar in shape than the flexible chaetae of Th. II, sf5 with only one inner chaeta ( Figs 10 B, 48A, B).

Labium, maxilla outer lobe, oral fold, labrum. Not precisely studied, all chaetae observed in the adult apparently present.

Head chaetotaxy. Postero-dorsal area with 10 pairs of microchaetae ( Figs 3 C, 48A); postero-lateral area with two pairs of microchaetae ( Figs 3 C, 48A); antero-dorsal area dorsally with eight pairs of mesochaetae and an unpaired mesochaeta (a0 absent; Figs 3 C, 48A), antero-lateral area with five pairs of mesochaetae ( Figs 3 C, 48A). Ventral area with 3 + 3 post-labial mesochaetae ( Fig. 4 C).

Antenna chaetotaxy. ( Fig. 49 A, B) Ant. I–III as the adult: Ant. I with 3 chaetae, Ant. II with six chaetae including five in apical verticil, Ant. III with 14 chaetae, seven in apical verticil and five S-chaetae S1–S5. Ant. IV with: 19 ordinary chaetae; nine S-chaetae including seven thin and long (S, three missing in regard to adult), a short and thin (Sx) and a long and thick (Sy); two apical and sub-apical sensory rods (a, sa) and a short organite Or.

Th. II–Abd. V terga chaetotaxy. Th. II–Abd. V terga a total of 16 + 16 chaetae, 12 + 12 τ-chaetae all in the thoracic region, 4 + 4 s-chaetae (s1, s2, s3, s3’), 4 + 4 sensory fields, 5 + 5 wrc, 7 + 7 tertiary wax rods as microspines (thoracic region) and 10 + 10 tertiary wax rod as strong spines (abdominal area; Figs 10 B, 48B). Dorso-lateral area of Th. II with: 5 + 5 chaetae; 2 + 2 τ-chaetae, one in postero-dorsal position to sf3, the other in postero-ventral position to sf3 ( Figs 10 B, 48B). Precoxal areas of Th. II with 1 + 1 curved, tubular s-chaetae (s1), 1 + 1 chaetae and 1 + 1 τ-chaetae ( Figs 10 B, 48B). Dorso-lateral area of Th. III–anterior abdomen with 4 + 4 chaetae, 8 + 8 τ-chaetae, 4 + 4 wrc, 2 + 2 s-chaetae (s3, s3’), 6 + 6 tertiary rods ( Figs 10 B, 48B). Precoxal areas of Th. III with 1 + 1 chaetae and 1 + 1 τ-chaetae ( Figs 10 B, 48B). Posterior area of the abdomen (until Abd. V included) with 5 + 5 chaetae, 1 + 1 wrc, 10 + 10 strong tertiary rods and 1 + 1 s-chaetae (s2; Figs 10 B, 48B). Also with at least 1 + 1 small tertiary rods (probably 2 + 2, the second pair unclear on available specimen ( Figs 10 B, 48B). The base of a very transparent element of unknown morphology is also present (as a tertiary rod in the adult, Figs 10 B, 48B). s1 tubular with rounded apex, shape of s2, s3 and s3’ not observed.

Legs chaetotaxy. Not analyzed

Claws morphology. Similar to the adult.

Abd. VI. Tergum with 3 + 3 mesochaetae, 2 + 2 microchaetae (including µ.av) and an unpaired microchaeta (av; Figs 10 B, 48B). Sternum with 6 + 6 chaetae ( Figs 10 B, 48B).

Abd. IV sternum. With 2 + 2 microchaetae, 2 + 2 mesochaetae and 1 + 1 neosminthuroid chaetae ( Fig. 48 B).

Abdominal appendages. Manubrium with 3 + 3 posterior chaetae ( Fig. 48 B). Dens proximal part with a posterior chaeta; postero-external spine (E3) absent ( Fig. 49 C). Tenaculum with 3 + 3 apical teeth. Ventral tube with 2 + 2 apical mesochaetae.

Discussion. According to Bonet (1947), Neelus murinus has either 4 + 4 posterior chaetae on the manubrium—2 + 2 proximal and 2 + 2 proximal, or 3 + 3 posterior chaetae—2 + 2 proximal and 1 + 1 distal (= subspecies Neelus murinus bolivari ). This character was not described by Folsom (1896) and Christiansen & Bellinger (1981). The specimens from Poland described by Stach (1957), from Scandinavia described by Fjellberg (2007) and from France described by Massoud & Vannier (1967) and in the present work have 3 + 3 chaetae—1 + 1 proximal and 2 + 2 distal on the manubrium. At intraspecific level, the number of chaetae on the manubrium is invariable among all the species of Neelipleona I could study. It is possible that Neelus murinus sensu Massoud & Vannier (1967) , Neelus murinus sensu Bonet (1947) and Neelus murinus bolivari are three different species. Christiansen (2009) stated that the illustrations of Scandinavian specimens from Fjellberg (2007) do not match the nearctic specimens but did not give more explanations. The respective habitus illustrated by Fjellberg (2007) and Bonet (1947) are indeed different but I don’t think that is significant. Bias due to preparation and also different drawing styles can explain the differences. The description of Fjellberg (2007) based on clear characters matches with my observations on French specimens. Bonet (1947) indicates that the dens is subdivided in Neelus murinus , while Fjellberg (2007) and I observed no subdivision on European specimens. I believe that it is a misinterpretation from Bonet (1947). Redescription from topotype is necessary to complete the species revision.

Neelus murinus sensu Massoud & Vannier (1967) is closely related to Neelus koseli with a very similar trunk chaetotaxy. Neelus klisurensis is clearly different from those two species with the absence of the numerous tertiary rods on the abdomen and the presence of lanceolate and cylindro-conical macrochaetae on the thorax.

Figures

FIGURE 1. Chaetae on posterior part of head, shape and size. (A) Chaetae on the same scale, (B) chaetae with length normalized; setulae: (a) Neelides folsomi, (b) Neelus murinus; mesochaetae: (c) Neelides folsomi, (d) Megalothorax rapoporti, (e, f) Megalothorax granulosus, (g) Megalothorax svalbardensis, (h) Megalothorax perspicillum, (i) Megalothorax willemi, (j) Megalothorax nigropunctatus; macrochaetae: (k) lanceolate, Megalothorax potapovi, (l) cylindro-conical, Acanthoneelidus pratensis, (m, n) ordinary and gladiuform, Megalothorax massoudi.

FIGURE 2. External morphology of the mouth region. From labrum to labium (A) Neelides folsomi (simplified), (B) Megalothorax perspicillum and (C) Sphaeridia pumilis. Labium (D) Parisotoma sp. ventral side. Labrum (E) without anterior process, (F) with anterior process. Legend: blf = basolateral field of labium; blf tub. = tubercle of the basolateral field; bmf = basomedian field of labium; mol = maxilla outer lobe; of = oral fold; * indicates in Sphaeridia pumilis the chaeta putatively homologous with the chaeta on tubercle of basolateral field in Neelipleona.

FIGURE 3. Diagram of the dorsal chaetotaxy of the head. (A) Neelides folsomi; (B) Acanthoneelidus pratensis; (C) Neelus murinus; (D) Megalothorax nigropunctatus; (E) Megalothorax perspicillum; (F) Megalothorax granulosus, integumentary channels not represented. In gray, chaetae absent in juvenile.

FIGURE 4. Diagram of the ventral chaetotaxy of the head. (A) Neelides folsomi; (B) Acanthoneelidus pratensis; (C) Neelus murinus; (D) Megalothorax nigropunctatus; (E) Megalothorax minimus; (F) Megalothorax granulosus.

FIGURE 10. Diagram of the chaetotaxy of the trunk. Neelus murinus, (A) adult, (B) juvenile. arrow indicates the basal ring of an undetermined chaeta in the juvenile, tertiary rod in the adult, ‘? ’ indicates a pair of tertiary wax rods unclear on the specimen, the alternate hypothesis of homology of wrc is indicated in parenthesis.

FIGURE 37. Neelus murinus. (A, B) Whole body, lateral view; (C) focus on Th. I, lateral view, (D) dorsal view; (E) organization of Th. I with pattern of folds in gray, integumentary channels in white; (F) antennae shape in frontal view, oscillations observed in live animals symbolized in gray. Legend: 1 = latero-posterior process of the head; 2 = anterior lobe of precoxal area I; 3 = anterior lobe of precoxal area II; 4 = anterior lobe of precoxal area III with ventral process; 5 = furrow between Th. II / Th. III; 6 = posterior bump of the abdomen. Scale bars = 100 µm.

FIGURE 38. Neelus murinus. (A) Whole body, ventral view; (B) head, postero-ventro-lateral view, (C) Th. I, ventral view; (D) integument on thoracic terga with dermastra; (E) integument on thoracic terga near insertion of legs II and III, with integumentary channel, dermastra and large wrc 3. Scale bars (A, B) = 100 µm, (C) = 20 µm, (D, E) = 100 µm.

FIGURE 39. Neelus murinus. Sensory fields (A) sf 1 on forehead, (B) sf 2 on headback, (C) sf 4 on precoxal area of Th. II, (D) sf 5 on precoxal area of Th. III, arrow indicates the second inner chaeta, (E) sf 6 on posterior part of abdomen, (F) posterior part of abdomen with high density of dermastra, (G) linea ventralis and ventral thoracic organs. Scale bars = 10 µm.

FIGURE 40. Neelus murinus. (A) Left mandibula; (B) right mandibula; (C) maxilla, (D) maxilla, other side; labial palp, (E) focus on ventral chaetae, (F) focus on apical chaetae; maxilla outer lobe, (G) palp, external side, (H) palp and sublobal plate, internal side; labrum anterior process (I) posterior side, (J) anterior side and labral ridge; antenna (K) ventral side, (L) dorsal side.

FIGURE 41. Neelus murinus. Chaetotaxy of the head, (A) anterior part, ventro-lateral side, (B) dorsal side, (C) posterior part, dorsal side. Legend: blf = basolateral field of labium; bmf = basomedian field of labium; of = oral fold; Sc 1. I = subcoxa 1 I; sf 1, 2 = sensory fields 1, 2 with inner chaetae.

FIGURE 42. Neelus murinus. Chaetotaxy of the trunk terga and Abd. IV, VI sterna (A) lateral side; focus on: (B) s-chaeta s 1, (C) s-chaeta s 2, (D) s-chaeta s 3 ’, (E) smallest and greatest tertiary rods, (F) inner chaeta of sf 3, (G) flexible chaeta, (H) τchaeta, (I) inner chaeta of sf 5, (J) neosminthuroid chaeta. Legend: s - = swollen chaetae; ns = neosminthuroid chaeta; τ = τchaeta basal ring; wrc = free wax rod secretory crypt. The arrow indicates the large wrc on thorax.

FIGURE 43. Neelus murinus. Chaetotaxy of the legs. Leg I (A) from subcoxa 1 to coxa, (B) trochanter, (C) from femur to tibiotarsus; leg II (D) from subcoxa 1 to claw with precoxal area and sf 4, (E) femur and tibiotarsus; leg III (F) from subcoxa 1 to trochanter with precoxal area and sf 5, (G) femur and tibiotarsus.

FIGURE 44. Neelus murinus. Claws. Claw I (A) anterior side, (a) transversal section of the main lamella, (b) transversal section of the unguiculal lamella, (B) posterior side; claw II (C), posterior side; claw III (D) anterior side, (E) posterior side. Legend of unguis: Bp = internal lamella; L = main lamella; la and lp = externo-basal lamellae respectively anterior and posterior. Legend of unguiculus: Ca = anterior crest; Cp = posterior crest; l. ung. = unguiculal lamella. Scale bars (A, D) = 20 µm.

FIGURE 45. Neelus murinus. Furca, (A) general view, (B) spine E 2 and deformed granules; (C), spines AE 1 and E 1; (D) mucro; (E) chaetotaxy, posterior side; articular process manubrium / dens, (F) anterior view, (G) lateral view. (H) Abd. VI, genital plate and Abd. IV ventro-posterior chaetae. Scale bars (A) = 100 µm, (B, C, D) = 10 µm.

FIGURE 46. Neelus murinus. (A, B) Tenaculum; Ventral tube (C) anterior side, (D) lateral side. Scale bars (A) = 10 µm, (C) = 20 µm.

FIGURE 47. Neelus murinus, juvenile. Whole body in lateral view.

FIGURE 48. Neelus murinus, juvenile. Chaetotaxy of (A) the head, dorsal side, and subcoxa 1 I, (B) the terga of the trunk, Abd. IV and VI sterna and manubrium. Only the basal rings of the s-chaetae s 2, s 3 and s 3 ’ and of the τ-chaetae are represented, arrow indicates the basal ring of an undetermined chaeta, ‘? ’ indicate a pair of tertiary wax rods unclear on the specimen.

FIGURE 49. Neelus murinus, juvenile. Antenna (A) ventral side, (B) Ant. IV dorsal side; (C) dens and mucro, posterior side;