Pectiniunguis minutus ( Demange, 1968 )

Pereira, Luis Alberto, 2011, A Further Contribution To The Knowledge Of Pectiniunguis Minutus (Demange, 1968), A Little Known Dwarf Schendylid Centipede From Western Equatorial Africa (Chilopoda: Geophilomorpha), Papéis Avulsos de Zoologia 51 (20), pp. 307-323 : 307-323

Pectiniunguis minutus ( Demange, 1968)

( Figs. 1-43 )

Pleuroschendyla minuta Demange, 1968: 283-284 . Pleuroschendyla minuta : Mauriès, 1968: 771. Pectiniunguis minutus : Pereira & Demange, 1991: 95;

Pereira, Minelli & Foddai, 1999: 177.

Diagnosis: A Pectiniunguis species with 35, 37 or 39 leg-bearing segments; body length 12-16 mm; ventral pore-fields present on the anterior region of the body only (absent on first sternite). It can be easily differentiated from all the other species currently assigned to the genus, by the very low number of leg-bearing segments and very small body size. The following traits, are also distinctive features for this species: poison glands unusually large, extending along the entire forcipular telopodite and the anterior half of the forcipular coxosternite ( Fig. 16 : c); a.a. II-XIII all wider than long ( Fig. 1 ); claw of waking legs with two accessory spines only (one anterior and one posterior, Figs. 18, 19 ); pleurites of second maxillae somewhat expanded on the anterior-external area ( Figs. 14 , 37-39 ); a.a. XIV with claviform sensory setae on the external edge only ( Fig. 36 ); coxosternite of first maxillae without setae ( Fig. 14 ); pretarsus of ultimate legs represented by a small tubercle with two diminutive apical spines ( Figs. 28 , 35 , 43 ).

Type material examined: All specimens from Gabon: Bélinga, H. Coiffait leg. (Ref. Pleuroschendyla minuta Demange ); 25 March 1963: allotype female with 37 leg-bearing segments, body length 13 mm; 10 May1963: holotype male with 35 leg-bearing segments, body length 12 mm; paratype male with 35 leg-bearing segments, body length 11.5 mm. ( MNHN Collection Myriapodes et Onycophores: M206) .

Other material examined: Gabon: Bélinga : Station 154 T, route du camp VI. Forêt tropicale, 27 February 1963, H. Coiffait leg. (Ref. Pleuroschendyla minuta Demange ), female with 39 leg-bearing segments, body length 13 mm ( MNHN Collection Myriapodes et Onycophores: M206) .

Remarks: The original description mentions the four specimens cited above, and an additional non type from “Bélinga: Station 129 T, carrière, route du débarcadère, Forêt tropicale” (sex and number of leg-bearing segments not specified), but this latter was not revised in the present study.

Male paratype: Thirty-five leg-bearing segments, body length 11.5 mm, maximum body width 0.50 mm. Width of cephalic plate, ca. 0.41 mm. Width of forcipular coxosternite, ca. 0.40 mm. Ground color (of preserved specimen in alcohol) pale yellowish.

Antennae: ca. 2.4 times as long as the cephalic plate, distally slightly attenuate; a.a. II to XIII all wider than long, a.a. XIV longer than wide ( Fig. 1 ). Setae on a.a. I to VI of different lengths and few in number, those of remaining articles progressively shorter and more numerous towards the tip of the appendage ( Fig. 1 ). Apical a.a. with ca. 15 claviform sensilla on the external border and absent on the internal border (similar to the holotype, Fig. 36 ); distal end of this a.a. with ca. 4 specialized sensilla apparently not split apically, (similar to the holotype, Fig. 36 ). Dorsal and ventral surface of a.a. II, V, IX and XIII ( Figs. 2-7 ) 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 divided apically ( Fig. 5 : a); type b sensilla are similar to those on the apex of the terminal a.a. but with two very small apical branches ( Fig. 5 : b). Specialized sensilla on dorsal side restricted to an external latero-apical area on a.a. II, V and IX ( Figs. 2, 4 , 6 ) and to an internal and external sublateral apical areas on a.a. XIII ( Fig. 7 ), and are represented by three different types: a, similar to a of ventral side ( Fig. 7 : a); b, similar to b of ventral side, with two very small apical branches on a.a. II ( Fig. 2 : b) but apparently not divided apically on a.a. V, IX and XIII ( Figs. 4 , 6-7 : b); and type c sensilla, much bigger than type b, not divided apically and darker (brownish-ochre in colour) ( Figs. 6-7 : c). Distribution of type a, b and c sensilla on a.a. II, V, IX and XIII as in Table 2 .

Cephalic plate: slightly longer than wide (ratio length/ width ca. 1.10: 1), shape and chaetotaxy as in Fig. 8 .

Clypeus: with 1+1 postantennal setae, 2+2 median setae and 1+1 prelabral setae arranged as in Fig. 9 .

Labrum: with 18 small teeth, those of the central arc dark and round tipped, the lateral ones less sclerotized, each with a very sharp medial extension ( Fig. 10 ).

Mandible: dentate lamella subdivided into two distinct blocks, with 5, 3 teeth; pectinate lamella with ca. 12 hyaline teeth ( Figs. 11-12 ).

First maxillae: with lappets on the coxosternite and telopodites, those of coxosternite very poorly developed ( Fig. 13 ). Coxosternite without setae; coxal projections subtriangular, well developed and provided with 1+1 setae ( Fig. 14 ). Article II of telopodite with 2+2 setae on ventral side and 3+3 sensilla on dorsal side ( Figs. 13-14 ).

Second maxillae: with 5+5 setae on the coxosternite arranged as in Fig. 14 . Apical claw of telopodite well developed, bipectinate, ventral edge with ca. 12 teeth, dorsal edge with ca. 15 teeth ( Fig. 15 ). Pleurites somewhat expanded on their anterior external edge ( Fig. 14 ).

Forcipular segment: when closed, the telopodites do not extend beyond the anterior margin of the head. Forcipular tergite with an irregular transverse median row of ca. 12 large setae and a few additional smaller setae scattered on the remaining surface. All articles of the telopodites without teeth. Poison glands unusually large (shape and relative size as in Fig. 16 : c). Calyx of poison gland subcylindrical and very short ( Figs. 16, 17 : b). Pilosity of coxosternite and telopodites as in Figure 16 .

Walking legs: chaetotaxy similar throughout the entire body length. Distribution, number and relative size of setae as in Fig. 18 . Claws with two thin and pale accessory spines ventrobasally, one anterior and one posterior (shape and relative size as in Fig. 19 ).

Sternites of leg-bearing segments 1 to penultimate: pore-fields present from sternite 2 to 20 inclusive (wholly absent on the remaining sternites). All fields undivided, transversally subovoidal, shape and relative size changing along the trunk as in Figs. 20-25 . Number of pores on selected sternites: sternite 2 (18 pores); 4 (37); 9 (48); 14 (46); 19 (16); 20 (9).

Ultimate leg-bearing segment: intercalary pleurites absent at both sides of the ultimate pretergite. Ultimate presternite not divided along the sagittal plane; length/width ratio of the tergite, 0.73: 1; length/ width ratio of the sternite, 0.56: 1. Shape and chaetotaxy of tergite and sternite as in Figs. 26-27 . Coxopleura slightly protruding at their distal-internal ventral ends, setae small and numerous on the distal-internal ventral area, remaining surface with few larger setae. Two compound (‘heterogeneous’) coxal organs in each coxopleuron ( Figs. 26, 27 , 29 ). Coxal organs open on the membrane between coxopleuron and sternite, partially covered by the latter ( Figs. 27 , 29 ), internal cuticular structure as shown in Fig. 29 (a: individualized areas of mucous layer). Ultimate legs inflated, composed of seven articles. Ratio of length of telopodites of ultimate legs/length of sternite ca. 4.03: 1. Shape and chaetotaxy of ultimate legs as in Figs. 26-27 . Ultimate pretarsus represented by a rudimentary sub-terminal tubercle with 2 diminutive spines ( Fig. 28 ).

Postpedal segments: intermediate tergite with posterior margin strongly convex ( Fig. 26 ), intermediate sternite and first genital sternite with posterior margin medially slightly convex, laterally slightly concave ( Fig. 27 ). Gonopods biarticulate, basal article with ca. 10 setae, apical article with ca. 6 setae ( Figs. 27 , 30 ), penis with 1+1 apical setae on dorsal side ( Fig. 31 ).

Female allotype: Thirty-seven leg-bearing segments, body length 13 mm, maximum body width 0.60 mm. All features similar to those in the male except for the shape and chaetotaxy of the ultimate leg-bearing segment and postpedal segments.

Ultimate leg-bearing segment: tergite and sternite trapezoidal, length/width ratio of tergite 0.67: 1; length/ width ratio of sternite 0.63: 1. Shape and chaetotaxy of tergite and sternite as in Figs. 32-33 . Coxopleura slightly protruding at their distal-internal ventral ends; setae distributed on the distal ventral-lateral areas, the remaining surface without setae ( Figs. 32-33 ). Articles of ultimate legs not inflated, much thinner than those of the male ( Figs. 32-33 ). Ultimate legs proportionally much shorter than those of the male, with ratio of length of telopodites/length of sternite ca. 2.11: 1. Shape and chaetotaxy of ultimate legs as in Figs. 32-33 .

Postpedal segments: intermediate tergite with posterior margin strongly convex ( Fig. 32 ), intermediate sternite with posterior margin straight to slightly concave; first genital sternite with posterior margin medially convex, laterally slightly concave ( Fig. 33 ). Gonopods uniarticulate ( Fig. 33 ).

Variation: males with 35, and females with 37 or 39 leg-bearing segments.

The posterior limit of the ventral pore-field series is at the sternite 20 in the male holotype and male paratype (both with 35 leg-bearing segments); sternite 22 in the female allotype (with 37 leg-bearing segments); and sternite 28 in the non-type female (with 39 leg-bearing segments).

Anterior coxal organs with two outer lobes, posterior coxal organs with two-three out- er lobes ( Fig. 29 : b); each lobe internally, with one-three individualized areas of mucous layer ( Figs. 29 : a, 34, 40-42). (For details on fine structure and function of coxal organs, see Rosenberg & Seifert (1977); Lewis (1981); Rosenberg (1982, 1983)).

The body is (according to the original description) “ 12-16 mm ” long. (View comments on this trait, below).

Other features with non-significant variation.

Remarks: The adult condition of the four specimens herein revised is indicated by the tubula seminifera full of mature spermatozoa in the males, and the two spermathecae full of spermatozoa in the females.

The original description by Demange is very short, only includes two figures (labrum, and ultimate leg-bearing segment and postpedal segments in ventral view), and completely lacks information on chaetotaxy of the antennae; kind and number of specialized sensilla on a.a. II, V, IX and XIII; pilosity of clypeus; shape and chaetotaxy of the forcipular segment; relative size of the ventral pore-fields; pilosity of walking legs; details of internal structure of the coxal organs; form of pretarsus of the ultimate legs; shape of the female postpedal segments; etc.

The author states “champs poreux présents du 2e segment au 21-22e segment” (but the posterior limit of the ventral pore-field series varies as detailed above). Of the body length he says “ 12-16 mm ”, but none of the four specimens here revised exceeds 13 mm in length, “ 16 mm “ could refer to the specimen from “ Bélinga. Station 29 T, carrière, route du débarcadère. Forêt tropicale” (not examined in the present contribution, as stated above) .

Type locality: Gabon: Bélinga region.

Known range: Only known from the type locality.

Figures

FIGURES 1‑5: Pectiniunguis minutus (Demange, 1968), (male paratype; Gabon: Bélinga): (1) Left antenna, ventral; (2) Left a.a. II, dorsal (a, b: a, b type sensilla); (3) Left a.a. V, ventral (a, b: a, b type sensilla); (4) Left a.a. V, dorsal (a, b: a, b type sensilla); (5) Left a.a. IX, ventral (a, b: a, b type sensilla). Scale bars: 0.05 mm (2-5); 0.2 mm (1).

FIGURES 6‑12: Pectiniunguis minutus (Demange, 1968), (male paratype; Gabon: Bélinga): (6) Left a.a. IX, dorsal (a, b, c: a, b, c type sensilla); (7) Left a.a. XIII, dorsal (a, b, c: a, b, c type sensilla); (8) Cephalic plate and bases of antennae; (9) Clypeus and bases of antennae; (10) Labrum; (11) Right mandible; (12) Left mandible. Scale bars: 0.05 mm (6-7, 10-12); 0.2 mm (8-9).

FIGURES 13‑19: Pectiniunguis minutus (Demange, 1968), (male paratype; Gabon: Bélinga): (13) Left side of first maxillae, dorsal; (14) First and second maxillae, ventral; (15) Claw of right telopodite of second maxillae, dorsal; (16) Forcipular segment, ventral (a: duct, b: calyx, c: poison gland; (17) Detail of the duct (a) and calyx (b) of poison gland in left forcipular telopodite, ventral; (18) Left waking leg (pair 8), ventral; (19) Claw of left waking leg (pair 8), ventral view. Scale bars: 0.03 mm (15, 19); 0.1 mm (13, 17-18); 0.2 mm (14, 16).

FIGURES 20‑25: Pectiniunguis minutus (Demange, 1968), (male paratype; Gabon: Bélinga): (20) Sternite of leg-bearing segment 2; (21) Sternite of leg-bearing segment 4; (22) Sternite of leg-bearing segment 9; (23) Sternite of leg-bearing segment 14; (24) Sternite of leg-bearing segment 19; (25) Sternite of leg-bearing segment 20. Scale bar: 0.1 mm.

FIGURES 26‑28: Pectiniunguis minutus (Demange, 1968), (male paratype; Gabon: Bélinga): (26) Ultimate leg-bearing segment and postpedal segments, dorsal; (27) Ultimate leg-bearing segment and postpedal segments, ventral; (28) Detail of distal end of apical article of right ultimate leg, ventral (a: pretarsus). Scale bars: 0.02 mm (28); 0.4 mm (26-27).

FIGURES 29‑32: (29-31) Pectiniunguis minutus (Demange, 1968), (male paratype; Gabon: Bélinga): (29) Left coxal organs, ventral (a: individualized areas of mucous layer, b: outer lobe); (30) Left gonopod, ventral; (31) Penis, dorsal. (32) Pectiniunguis minutus (Demange, 1968), (female allotype; Gabon: Bélinga): Ultimate leg-bearing segment and postpedal segments, dorsal. Scale bars: 0.04 mm (30-31); 0.1 mm (29); 0.2 mm (32).

FIGURES 33‑38: (33-35) Pectiniunguis minutus (Demange, 1968), (female allotype; Gabon: Bélinga): (33) Ultimate leg-bearing segment and postpedal segments, ventral; (34) Left coxal organs, ventral (a: individualized areas of mucous layer, b: outer lobe); (35) Detail of distal end of apical article of left ultimate leg, ventral (a: pretarsus). (36-38) Pectiniunguis minutus (Demange, 1968), (male holotype; Gabon: Bélinga): (36) Distal half of right a.a. XIV, ventral view (a: claviform sensilla, b: apical specialized sensilla); (37) Detail of pleurite, coxopodite and base of telopodite of second maxillae, right side, ventral (a: pleurite); (38) Pleurite, coxopodite and base of telopodite of second maxillae, left side, dorsal (a: pleurite). Scale bars: 0.03 mm (35); 0.05 mm (36); 0.1 mm (34, 37-38); 0.2 mm (33).

FIGURES 39‑43: (39) Pectiniunguis minutus (Demange, 1968), (male holotype; Gabon: Bélinga): Detail of pleurite, coxopodite and basis of telopodite of second maxillae, left side, ventral (a: pleurite). (40-43) Pectiniunguis minutus (Demange, 1968), (female non type; Gabon: Bélinga: Station 154 T, route du camp VI. Forêt tropicale): (40) Right coxal organs, ventral (a: individualized areas of mucous layer); (41) Left coxal organs, ventral (a: individualized areas of mucous layer, b: outer lobe); (42) Coxal organs, dorsal (a: individualized areas of mucous layer); (43) Detail of distal end of apical article of right ultimate leg, ventral (a: pretarsus). Scale bars: 0.02 mm (43); 0.1 mm (39-42).