Ribautia lewisi, Pereira, Luis Alberto, 2013

Pereira, Luis Alberto, 2013, Ribautia lewisi sp. nov., a new centipede from Argentina with unusual tentorial process (Chilopoda: Geophilomorpha, Geophilidae), Zootaxa 3630 (2), pp. 225-242 : 226-241

Ribautia lewisi sp. nov.

( Figs. 1–61 )

Diagnosis. A Neotropical species of Ribautia characterized by the presence of one cluster of coxal organs in each coxopleuron of the ultimate leg-bearing segment and a claw-like pretarsus in the ultimate legs. Among the Neotropical taxa currently included in the genus, only the present new species, R. combinata Pereira, Uliana & Minelli, 2006 (from Peru), and R. jakulicai Pereira, 2007 (from Argentina) share these two combined features. R. lewisi sp. nov. differs from the two latter by having the following unique traits: female with 45, 47 leg-bearing segments, male with (43?), 45, 47 leg-bearing segments; lateral margins of cephalic plate with a small concavity located anteriorly ( Figs. 11, 12 : a); internal limbs of tentorium bearing an unusual conspicuous tooth-shaped sclerotized process directed inwards; first and second article of telopodites of second maxillae with a very small distoectal process ( Figs. 14 , 15 : b); pore-fields absent on some sternites of mid-body; sternite of female ultimate leg-bearing segment provided with a narrow band of numerous very small setae near the posterior edge ( Fig. 61 ).

Other morphological traits included in Table 1 differentiate R. lewisi sp. nov. from R. combinata and R. jakulicai .

Remarks. For characters differentiating R. lewisi sp. nov. from other Neotropical species of Ribautia , see Discussion below.

Type material examined. ARGENTINA: Entre Ríos Province: Concordia Department: Concordia, 9 December 2007, L. A. Pereira legit: holotype 3, 45 l.-b.s., b.l. 20 mm; paratype A (Ƥ), 45 l. -b.s., b.l. 15 mm; paratype B (Ƥ), 45 l. -b.s., b.l. 16 mm; paratype C (Ƥ), 45 l. -b.s., b.l. 16 mm; paratype D (Ƥ), 45 l. -b.s., b.l. 16 mm; paratype E (Ƥ), 45 l. -b.s., b.l. 16 mm; paratype F (Ƥ), 45 l. -b.s., b.l. 17 mm; paratype G (Ƥ), 45 l. -b.s., b.l. 17.5 mm; paratype H (Ƥ), 45 l. -b.s., b.l. 17.5 mm; paratype I (Ƥ), 47 l. -b.s., b.l. 17 mm; paratype J (Ƥ), 47 l. -b.s., b.l. 19 mm; paratype K (Ƥ), 47 l. -b.s., b.l. 20 mm; paratype L (Ƥ), 47 l. -b.s., b.l. 21 mm; paratype M (Ƥ), 47 l. -b.s., b.l. 26 mm; paratype N (3), 45 l. -b.s., b.l. 17 mm; paratype O (3), 47 l. -b.s., b.l. 16 mm; paratype P (3), 47 l. -b.s., b.l. 17 mm.

Depository of types: MLP.

Other material examined. All specimens from the same locality, date and collector as the type series: 2 ƤƤ juv., 45 l. -b.s., b.l. 12 mm (with 9-10 coxal organs in each cluster), and 13 mm (with 11-12 coxal organs in each cluster); 1 3 subadult, 45 l. -b.s., b.l. 14 mm (with 9 coxal organs in each cluster); 2 3 juv., 45 l. -b.s., b.l. 10 mm (in moulting process), and 12 mm (with 9-10 coxal organs in each cluster); 1 3 juv., 47 l. -b.s., b.l. 11 mm (with 6 coxal organs in each cluster); 4 juv. (sex unknown), 43 l. -b.s., b.l. 4.5 mm (Specimen A) (with 1+1 coxal organs only), 4.5 mm (with 1 + 1 coxal organs only), 10 mm (with 5 coxal organs in each cluster), and 10 mm (with 5–6 coxal organs in each cluster); 1 juv. (sex unknown), 47 l. -b.s., b.l. 4.5 mm (with 1 + 1 coxal organs only). (MLP).

Description. Male holotype. Forty-five leg-bearing segments, body length 19 mm, maximum body width 0.65 mm, length of cephalic plate 0.67 mm, width of forcipular coxosternite 0.56 mm. Colour (of preserved specimen in alcohol) pale yellow, forcipular segment a little darker (pale ochreous).

Antennae. Relatively long, ca. 4.0 times as long as the cephalic plate, distally attenuate, ratio of width of a.a. I/ width of a.a. XIV ca. 1.68: 1. A.a. I nearly as long as wide, remaining a.a. longer than wide. Ventral chaetotaxy: setae on a.a. I–VII of various lengths and relatively few in number; those of a.a. VIII–XIV progressively shorter and more numerous towards the tip of the appendage ( Figs. 1, 2 ). Dorsal chaetotaxy: similar to the ventral side. A.a. XIV with ca. 4–5 claviform sensilla on the external border and ca. 2–3 on the internal border; distal end of this a.a. with ca. 5–6 very small hyaline specialized sensilla apparently not split apically. Ventral and dorsal surface of a.a. II, V, IX and XIII with very small specialized sensilla. On the ventral side these sensilla are restricted to an internal latero-apical area and are represented by two different types: a and b. Type a sensilla are very thin and not split apically ( Fig. 5 : a); type b sensilla ( Fig. 5 : b) are very similar to those on the apex of a.a. XIV. Specialized sensilla on dorsal side are restricted to an external latero-apical area and are represented by similar type a and b sensilla of ventral side ( Fig. 9 : a, b). Number and distribution of specialized sensilla on ventral and dorsal sides of a.a. II, V, IX and XIII, as in Table 2 .

Cephalic plate. Distinctly longer than wide (length/width ratio ca. 1.64: 1). Lateral margins convergent towards the posterior region, showing anteriorly a small concavity ( Figs. 11, 12 : a). Anterior margin slightly concave on the middle; posterior margin straight. Shape and chaetotaxy as in Figure 11 .

Clypeus. With four setae located on the clypeal area; 1 + 1 anterior-lateral setae, posterior to the latter; and two setae in the middle ( Fig. 12 ). Clypeal area with surface very densely areolated ( Fig. 13 ).

Labrum. Mid-piece well developed, with ca. 7 sharp pointed teeth. Side pieces with ca. 9 + 10 filaments of different size. (Compare with Figure 54 , illustrating the labrum of the female paratype M).

Tentorium. Internal limb bearing a conspicuous tooth-shaped sclerotized process directed inwards. (Compare with Figures 54–56 , illustrating the tentoria of female paratype M).

Mandible. Pectinate lamella with ca. 22 hyaline teeth. (Compare with Figure 57 , illustrating a mandible of female paratype M).

First maxillae. Coxosternite without lappets, telopodites with very small lappets. (Compare with Figure 58 illustrating left side of first maxillae of female paratype M). Coxosternite devoid of setae; coxal projections subtriangular, round tipped and provided with 6 + 5 setae ( Fig. 14 ). Article II of telopodites with 3 + 4 large setae on ventral side, and 2 + 2 small sensilla on the external edge ( Fig. 14 ).

Second maxillae. Coxites medially joined through a narrow, hyaline and non-areolate membranous isthmus and provided with 6 + 7 setae near the internal margin and 2 + 2 small sensilla near the external margin ( Fig. 14 ). Process of antero-internal corners of coxosternite well developed with shape and relative size as in Figures 14 , 15 : a. Telopodites with setae of uniform thickness; first and second article with a very small distoectal process ( Figs. 14 , 15 : b); apical claw of telopodite well developed, tip curved inward ( Figs. 14 , 16 ). Chaetotaxy of coxosternites and telopodites as in Figures 14–16 .

Forcipular segment. When closed, the telopodites project slightly beyond the anterior margin of the head. Forcipular tergite trapeziform; chaetotaxy represented by an irregular transverse row of ca. 7 setae of different lengths near the posterior margin and a few smaller setae dispersed on the remaining surface ( Fig. 11 ). Coxosternite with incomplete chitin-lines ( Fig. 17 ); middle part of anterior border bearing 1 + 1 small unpigmented denticles, each provided with an apical seta, aspect and relative size as in Figures 17, 18 . Telopodites: medial edge of trochanteropraefemur apically with a conspicuous unpigmented round-tipped tooth; proximally near the vestigial suture between trochanter and praefemur with a rudimentary unpigmented round-pointed projection ( Figs. 17–19 ). Femur and tibia without denticles. Tarsungulum basally with a well-developed and pigmented subtriangular denticle ( Figs. 17, 19 , 20 ); medial ventral edge of tarsungulum slightly serrate ( Figs. 17, 19 , 20 ). Relative size of poison glands as in Figures 17, 19 , calyx of poison gland subtriangular ( Fig. 21 ). Chaetotaxy of coxosternite and telopodites as in Figures 11 , 17 .

Sternites of leg-bearing segments 1 to penultimate. With a shallow median longitudinal sulcus along all the body length, areolation of its surface as in Figures 25 , 27–30 ). Pore-fields present on sternites 2–22, 26, 30, and 36–44 (penultimate); totally absent on sternites 1, 23–25, 27–29 and 31–35. Sternites 2–12 with undivided porefields, subcircular in shape ( Figs. 22–25 , 33–39 ); sternites 13 ( Fig. 26 ), 14–16, 19–21, 37 ( Fig. 27 ), 38, and 40–44 ( Figs. 28–32 ) with pore-fields subdivided in two subsymmetrical areas; sternites 17, 18, 22, 26 with pores on the left side only; sternites 30, 36, 39 with pores on the right side only. Shape of pore-fields changes along the trunk as in Figures 22–39 . Number of pores as follows: sternite 2 (23); 3 (32); 4 (38); 5 (44); 6 (44); 7 (45); 8 (45); 9 (44); 10 (38); 11 (38); 12 (29); 13 (7 + 8); 14 (3 + 2); 15 (1 + 2); 16 (1 + 1); 17 (0 + 2); 18 (0 + 1); 19 (1 + 3); 20 (2 + 4); 21 (1 + 2); 22 (0 + 1); 26 (0 + 1); 30 (3 + 0); 36 (2 + 0); 37 (1 + 1); 38 (1 + 1); 39 (1 + 0); 40 (3 + 3); 41 (7 + 7); 42 (7 + 8); 43 (6 + 6); 44 (7 + 5).

Legs (pair 1 to penultimate). First pair shorter than the second (ratio ca. 0.85: 1). Legs with setae of uniform thickness, chaetotaxy similar throughout the entire body length. Distribution, number, and relative size of setae as in Figures 40-45 . Claws with two thin and pale accessory spines ventrobasally, one anterior and one posterior, of similar size ( Fig. 46 : a, b).

Ultimate leg-bearing segment. Intercalary pleurites absent at both sides of the ultimate pretergite ( Fig. 47 ); ultimate presternite divided along the sagittal plane ( Fig. 48 ). Length/width ratio of tergite, ca. 0.80: 1; length/ width ratio of sternite, ca. 0.74: 1. Shape and chaetotaxy of tergite and sternite as in Figures 47 , 48 . Coxopleura very slightly protruding at their distal-internal ventral ends, setae small and numerous on the distal-internal ventral area, the remaining coxopleural surface with few larger setae ( Figs. 47 , 48 ). Each coxopleuron with all coxal organs grouped in a cluster opening in the membrane between coxopleuron and sternite, partially or totally covered by the latter ( Figs. 48–50 ). Each cluster with ca. 18 organs arranged as in Figures 49, 50 . Ultimate legs inflated, composed of seven articles. Ratio of length of telopodites of ultimate legs/length of sternite ca. 3.52: 1. Shape and chaetotaxy of ultimate legs as in Figures 47 , 48 . Ultimate pretarsus unguiform, relatively smaller than those of the preceding legs, bearing a single internal spine ventrobasally.

Postpedal segments. Posterior margin of intermediate tergite convex ( Fig. 47 ), posterior margin of intermediate sternite concave ( Fig. 48 ). Posterior margin of first genital sternite very slightly concave at level of gonopods and in the middle ( Fig. 48 ). Gonopods biarticulate, basal article with 5 setae, apical article with 6 setae ( Figs. 51, 52 ); penis dorsally with 4 + 4 apical setae ( Fig. 53 ). Anal organs absent.

Female (paratype K). Forty-seven leg-bearing segments, body length 20 mm, maximum body width 0.68 mm.

Antennae. With similar chaetoaxy than in the male and proportionally shorter (ca. 3.0 times as long as the cephalic plate).

Remaining features similar to those in the male except for the shape and pilosity of the ultimate leg-bearing segment and postpedal segments.

Ultimate leg-bearing segment. Tergite and sternite trapezoidal, length/width ratio of tergite, ca. 0.77: 1; length/ width ratio of sternite, ca. 0.72: 1. Shape and chaetotaxy of tergite and sternite as in Figures 60, 61 . Coxopleura very slightly protruding at their distal-internal ventral ends, setae small and numerous on the distal-internal ventral area, the remaining coxopleural surface with few larger setae ( Figs. 60, 61 ). Each cluster of coxal organs with ca. 21 organs ( Fig. 61 ). Articles of ultimate legs not inflated, much thinner than those of the male ( Figs. 60, 61 ). Ultimate legs proportionally a little longer than those of the male, with ratio of length of telopodites/length of sternite ca. 4.0: 1. Shape and chaetotaxy of ultimate legs as in Figures 60, 61 .

Postpedal segments. Intermediate tergite with posterior margin strongly convex, ( Fig. 60 ), intermediate sternite seemingly covered by the sternite of the ultimate leg-bearing segment ( Fig. 61 ), posterior border of the first genital sternite slightly convex ( Fig. 61 ). Gonopods uniarticulate, very poorly developed, vestigial ( Fig. 61 : a).

Remarks. The adult condition of all type specimens is indicated by mature spermatozoa in the tubula seminifera of the males and spermatozoa in the spermathecae of the females.

In the preceding description, the labrum, mandible, and dorsal side of first maxillae were illustrated on the basis of the female paratype M, because those of the male holotype were not positioned in such a way on the microscope slides to allow the corresponding illustrations to be made properly.

Aspect of the unique 1 + 1 coxal organs present in a tiny juvenile specimen with sex unknown (Specimen A), as in Figure 59 .

All specimens examined without anal organs.

Etymology. This species is respectfully dedicated to Dr. John G.E. Lewis (Taunton, Somerset, United Kingdom) as a personal recognition for all the generous help and expert advice that he has provided me during many years of research on Chilopoda Geophilomorpha .

Ecology. The specimens were collected in the soil (to a depth of about 10–40 cm) in a gallery forest environment adjacent to the west bank of the Uruguay River. (Floristic composition of this vegetation, extension along the water course, and significance on the geographical distribution of diverse groups of vertebrates are described in Arzamendia & Giraudo 2009, Costa 2003, Nores et al. 2005).

Type locality. ARGENTINA: Entre Ríos Province: Concordia Department: Concordia.

Known range. Only known from the type locality.

Figures

FIGURES 1 – 10. Ribautia lewisi sp. nov. (male holotype; ARGENTINA: Entre Ríos Province: Concordia Department): (1) Left a. a. I – VI, ventral. (2) Left a. a. VII – XIV, ventral (claviform sensilla not drawn). (3). Left a. a. II, ventral (b: b type sensilla). (4) Left a. a. V, ventral (b: b type sensilla). (5) Left a. a. IX, ventral (a, b: a, b type sensilla). (6) Left a. a. XIII, ventral (a, b: a, b type sensilla). (7) Left a. a. II, dorsal (a: a type sensilla). (8) Left a. a. V, dorsal (a, b: a, b type sensilla). (9) Left a. a. IX, dorsal (a, b: a, b type sensilla). (10) Left a. a. XIII, dorsal (a, b: a, b type sensilla). Scale bars: 0.1 mm (3 – 10); 0.3 mm (1, 2).

FIGURES 11 – 14. Ribautia lewisi sp. nov. (male holotype; ARGENTINA: Entre Ríos Province: Concordia Department): (11) Dorsal view of anterior region of the body, showing cephalic plate, bases of antennae, forcipular segment, and anterior portion of leg-bearing segment 1 (a: concavity on lateral margins of cephalic plate). (12) Clypeus and bases of antennae (a: concavity on lateral margins of cephalic plate). (13) Clypeal area. (14) First and second maxillae, ventral (a: process of antero-internal corners of coxosternite; b: distoectal process of telopodites). Scale bars: 0.05 mm (13); 0.2 mm (12, 14); 0.3 mm (11).

FIGURES 15 – 19. Ribautia lewisi sp. nov. (male holotype; ARGENTINA: Entre Ríos Province: Concordia Department): (15) Detail of first article of telopodite and antero-internal corner of coxosternite, right side of second maxillae, ventral (a: process of coxosternite, b: distoectal process of telopodite). (16) Claw of right telopodite of second maxillae, ventral. (17) Forcipular segment, ventral. (18) Middle part of anterior border of forcipular coxosternite showing unpigmented denticles, ventral. (19) Detail of poison gland (a), calyx (b), and duct (c) of venom apparatus in right forcipular telopodite, ventral. Scale bars: 0.05 mm (15, 16, 18); 0.2 mm (19); 0.3 mm (17).

FIGURES 20 – 26. Ribautia lewisi sp. nov. (male holotype; ARGENTINA: Entre Ríos Province: Concordia Department): (20) Detail of right forcipular tarsungulum, showing medial ventral edge slightly serrate. (21) Detail of calyx of poison gland in right forcipular telopodite, ventral. (22) Sternite 2. (23) Sternite 6. (24) Sternite 11. (25) Sternite 12 (a: areolation on median longitudinal sulcus). (26) Sternite 13. Scale bars: 0.03 mm (21); 0.1 mm (20); 0.2 mm (22 – 26).

FIGURES 27 – 39. Ribautia lewisi sp. nov. (male holotype; ARGENTINA: Entre Ríos Province: Concordia Department): (27) Sternite 37 (a: areolation on median longitudinal sulcus). (28) Sternite 40. (29) Sternite 41. (30) Sternite 42. (31) Sternite 43. (32) Sternite 44. (33) Pore-field on sternite 3. (34) Pore-field on sternite 4. (35) Pore-field on sternite 5. (36). Pore-field on sternite 7. (37) Pore-field on sternite 8. (38) Pore-field on sternite 9. (39) Pore-field on sternite 10. Scale bars: 0.1 mm (33 – 39); 0.2 mm (27 – 32).

FIGURES 40 – 47. Ribautia lewisi sp. nov. (male holotype; ARGENTINA: Entre Ríos Province: Concordia Department): (40) Left leg (pair 1), ventral. (41) Left leg (pair 2), ventral. (42) Left leg (pair 5), ventral. (43) Left leg (pair 12), ventral. (44) Left leg (pair 27), ventral. (45) Left leg (pair 44), ventral. (46) Claw of the left leg (pair 26), anterior-ventral view (a: anterior spine, b: posterior spine). (47) Ultimate leg-bearing segment and postpedal segments, dorsal. Scale bars: 0.05 mm (46); 0.3 mm (40 – 45, 47).

FIGURES 48 – 50. Ribautia lewisi sp. nov. (male holotype; ARGENTINA: Entre Ríos Province: Concordia Department): (48) Ultimate leg-bearing segment and postpedal segments, ventral. (49) Left cluster of coxal organs, dorsal. (50) Left cluster of coxal organs, ventral. Scale bars: 0.2 mm (49, 50); 0.3 mm (48).

FIGURES 51 – 56. (51 – 53). Ribautia lewisi sp. nov. (male holotype; ARGENTINA: Entre Ríos Province: Concordia Department): (51) Right gonopod, ventral. (52) Left gonopod, ventral. (53) Penis, dorsal. (54 – 56). Ribautia lewisi sp. nov. (female paratype (M); ARGENTINA: Entre Ríos Province: Concordia Department): (54) Labrum (a: sclerotized process on internal limb of tentorium). (55) Detail of sclerotized process (a) on internal right limb of tentorium. (56) Detail of sclerotized process (a) on internal left limb of tentorium. Scale bars: 0.03 mm (55, 56); 0.05 mm (51 – 53); 0.1 mm (54).

FIGURES 57 – 59. (57 – 58). Ribautia lewisi sp. nov. (female paratype (M); ARGENTINA: Entre Ríos Province: Concordia Department): (57) Left mandible. (58) Right side of first maxillae, dorsal. (59) Ribautia lewisi sp. nov. (juvenile (sex unknown) (Specimen A); ARGENTINA: Entre Ríos Province: Concordia Department): Contour of ultimate leg-bearing segment showing 1 + 1 coxal organs, ventral. Scale bars: 0.05 mm (57); 0.1 mm (58, 59).

FIGURES 60 – 61. Ribautia lewisi sp. nov. (female paratype (K); ARGENTINA: Entre Ríos Province: Concordia Department): (60) Ultimate leg-bearing segment and postpedal segments, dorsal. (61) Ultimate leg-bearing segment and postpedal segments, ventral (a: vestigial gonopods). Scale bar: 0.3 mm.

Tables

TABLE 2. Number of type a and b sensilla on antennal articles II, V, IX and XIII in the male holotype of Ribautia lewisi sp. nov.

	Ventral		Dorsal		Figs.
	a	b	a	b
II	-	1	1	-	3, 7
V	-	1	1	1	4, 8
IX	1	1	1	2	5, 9
XIII	1	1	1	5	6, 10