Pectiniunguis gaigei ( Chamberlin, 1921 )

Pereira, Luis Alberto, 2010, Redescription Of Pectiniunguis Gaigei (Chamberlin, 1921) From Guyana, With New Distributional Data And Complementary Descriptive Notes On Similar Neotropical Species (Chilopoda: Geophilomorpha: Schendylidae), Papéis Avulsos de Zoologia 50 (20), pp. 297-321 : 298-313

Pectiniunguis gaigei ( Chamberlin, 1921)

( Figs. 1-50 )

Adenoschendyla gaigei Chamberlin, 1921:18-20 .

Pectiniunguis gaigei : Chamberlin, 1923:394; Attems, 1929:81-82; Crabill, 1959:326; Pereira & Coscarón 1975 (1976):72; Pereira et al., 1994:174; Pereira et al., 1995:338; Pereira et al., 1997:85; Pereira et al., 1999:177; Pereira et al., 2000:3, 54; Foddai et al., 2000:128, 179; Pereira et al., 2001:143, 144, 146.

Diagnosis: A Neotropical species of Pectiniunguis without pore-field on the first sternum; all pore-fields undivided; pore-fields in an uninterrupted series along all the body length; parunguis of walking legs thin and pale; last leg praetarsus as a small tubercle with numerous spines. Among the Neotropical species of the genus, all these combined traits are also present in P. geayi , P. ducalis , and P. roigi , from which P. gaigei is differentiated by the following unique traits (characters for P. geayi , P. ducalis , and P. roigi are given in parentheses): a.a. XIV with claviform sensilla on the external margin only (on the external and internal margins); ratio length of telopodite of last legs/ length of last sternum of male last leg-bearing segment, ca. 7.2: 1 (ca. 5.6 to 6.5: 1); ratio width of trochanter/width of praefemur of male last legs 1: 1.05 (1: 1.20).

Morphological traits in Table 1 differentiate P. gaigei from P. geayi , P. ducalis , and P. roigi .

Type material examined: Paratype female MCZ TC-161 , 55 leg-bearing segments, body length 35 mm (Reference Adenoschendyla gaigei Chamberlin ), from GUYANA: Dunoon : “first mourie”, 27 August 1914, F.M. Gaige leg. (Mandibles in a permanent slide, but rest of the body in alcohol) . Paratypes MCZ TC-162 (here individualized as A, B and C): paratype male (A), 53 leg-bearing segments, body length 29 mm; paratype female (B), 55 leg-bearing segments, body length 26 mm; paratype male (C), 57 leg-bearing segments, body length 28 mm. (Reference Adenoschendyla gaigei Chamberlin ), from GUYANA: Dunoon , Sand-hill forest, 27 August 1914, F.M. Gaige leg. (Paratype A with head and mouth parts in a permanent slide, but trunk in alcohol. Paratypes B and C in alcohol). Antennal articles II-XIV missing from both antennae of paratype C .

Remark: The holotype M.C.Z., 2182 (sex not specified), mentioned by Chamberlin in the original description, was not received for revision.

Female (paratype MCZ, TC- 161): Fifty-five leg-bearing segments, body length 35 mm, maximum body width 1 mm, length of cephalic shield 1.05 mm, width of forcipular coxosternum 1.36 mm. Ground color (of preserved specimen in alcohol) orange yellow, (forcipular segment and leg-bearing segments I to VIII dark orange).

Antennae: ca. 3.3 times as long as the cephalic plate, distally slightly attenuate; all articles, except the first, longer than wide. Setae on a.a. I to IV-V of various lengths, few in number, those of remaining articles progressively shorter and more numerous towards the tip of the appendage ( Figs. 1, 2 ). Terminal a.a. with ca. 29 claviform sensilla on the external border and absent on the internal border ( Fig. 3 ). Distal end of this a.a. with ca. 8 very small specialized sensilla apparently not split apically ( Fig. 3 ). Right antenna: dorsal and ventral surface of a.a. II, V, IX and XIII ( Figs. 4, 5 ) 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. 4a ); type b sensilla ( Fig. 4b ) are very similar to those on the apex of the terminal a.a. Specialized sensilla on dorsal side represented by three different types: a and b, similar to a and b of ventral side ( Fig. 5a, b ); and type c sensilla much bigger, not divided apically and darker (brownish-ochreous) in color ( Fig. 5c ). Number and distribution of specialized sensilla on right a.a. II, V, IX and XIII, as in Table 2.

Left antenna, abnormal (with 15 a.a.); number and distribution of specialized sensilla as in Table 3.

Cephalic plate: longer than wide (ratio ca. 1.2: 1), shape and chaetotaxy as in Fig. 6 .

Clypeus: with 1+1 postantennal setae, 4+5 medial setae and 1+1 praelabral setae ( Fig. 7 ). Anterior middle part bearing a subcircular area with surface densely reticulated ( Fig. 8 ).

Labrum: with 39 teeth, those of central arc dark and round tipped, the lateral ones less sclerotized, each with a relatively long and very sharp medial extension ( Fig. 9 ).

Mandible: dentate lamella subdivided into three-four distinct blocks; left mandible ( Fig. 10 ) with 3,3,3 teeth and right mandible ( Fig. 11 ) with 3,3,2,1 teeth. Pectinate lamella with ca. 23 hyaline teeth.

First maxillae: with lappets on both coxosternum and telopodites ( Fig. 13 ). Coxosternum with 1+1 large setae and 3+3 small setae, median projections of coxosternum subtriangular, well developed and provided with 3+3 setae. Article II of telopodite with 6+7 ventral setae and ca. 9+8 dorsal sensilla ( Figs. 12 , 13 ).

Second maxillae ( Figs. 12 , 14-17 ): with 15+14 setae on the coxosternum, arranged as in Figs. 12 , 14 . Apical claw of telopodites well developed, bipectinate, ventral edge with ca. 23 teeth ( Fig. 17 ), dorsal edge with ca. 30 teeth.

Forcipular segment: when closed, the telopodites do not extend beyond the anterior margin of the head; tergum with an irregular transverse median row of ca. 9 large setae and a few additional smaller setae scattered on the remaining surface. Telopodites: trochanteropraefemur with ratio greatest length/greatest width equal to ca. 1.30: 1 ( Fig. 18 ), bearing a small, not sclerotized, and pale pigmented tooth on apical medial edge ( Figs. 18, 19 ). All remaining articles lack teeth. Calyx of poison gland cylindrical ( Fig. 19 ). Chaetotaxy of coxosternum and telopodites as in Fig. 18 .

Walking legs: with similar chaetotaxy along entire body length; distribution, number, and relative size of setae as in Fig. 20 . Claws with three thin and pale ventrobasal parunguis, one anterior and two posterior of similar size ( Fig. 21 ).

Sterna: pore-fields present in an uninterrupted series, from the second to the antepenultimate sternum. All pore-fields undivided. Form of fields changing along the trunk as in Figs. 22-29 . Number of pores on selected sterna: sternum II (99); VII (132); VIII (142); XXIV (69); XXVI (40); XXXII (44); XLVIII (63); LIII (130).

Last leg-bearing segment: with pleurites at the sides of praetergum. Praesternum not divided along the sagittal plane; shape and chaetotaxy of sternum and tergum as in Figs. 30 , 36 . Coxopleura slightly protruding at their distal internal ventral ends, setae small and numerous on distal internal ventral area, remaining surface with few bigger setae. Two compound (“heterogeneous”) coxal organs in each coxopleuron ( Fig. 32 ); internal cuticular structure of each outer lobe with ca. two-four individualized areas of mucous layer joined to a common channel ( Figs. 33 ; 34, 35b ). Coxal organs open on the membrane between coxopleuron and sternum, covered by the latter ( Fig. 32 ). Last legs with seven podomeres, shape and chaetotaxy as in Figs. 30 , 36 . Praetarsus as a very small tubercle with ca. 6 small apical spines ( Fig. 31 ).

Terminal segments: intermediate tergum with posterior margin convex ( Fig. 36 ), intermediate sternum with posterior margin slightly concave ( Fig. 30 ); first genital sternum with posterior margin concave. Gonopods uniarticulate ( Fig. 30 ).

Male (paratype MCZ, TC- 162 (A)): Fifty-three leg-bearing segments, body length 29 mm, maximum body width 0.9 mm. All features similar to those in the female except for the shape and chaetotaxy of the last leg-bearing segment and terminal segments.

Last leg-bearing segment: form and chaetotaxy of tergum and sternum as in Figs. 44, 45 . Coxopleura very slightly protruding at their distal-internal ventral ends, setae numerous on distal-internal ventral area, remaining surface with few setae. Podomeres of terminal legs with shape and chaetotaxy as in Figs. 44, 45 . (Praefemur, femur and tibia proportionally narrower than those in the female).

Terminal segments: intermediate tergum with posterior margin convex ( Fig. 44 ); first genital sternum with posterior margin medially convex, laterally concave ( Fig. 45 ). Gonopods biarticulate, basal article with ca. 12 setae and distal with ca. 10 setae ( Figs. 45, 48 ); penis with 2+2 dorsal apical setae ( Fig. 49 ).

Variation: One of the two males herein revised, has 53 leg-bearing segments and the remaining has 57 (probably males with 55 leg-bearing segments also occur in nature); the two revised females have 55 leg-bearing segments (but possibly, other numbers exist for this sex).

Clypeus with 0+1 or 1+1 praelabral setae. (The original description only mentions two praelabral setae).

Female paratype MCZ, TC- 161 with posterior coxal organs having ca. 5-6 outer lobes on ventral side and ca. 4-6 on dorsal side; anterior coxal organs relatively smaller, with ca. 4-5 lobes on ventral side (number of dorsal lobes not stated). (For details on fine structure and function of coxal organs, see Rosenberg & Seifert (1977); Lewis (1981); and Rosenberg (1982, 1983)).

The maximum body length given for this species is 45 mm (sex not specified).

Remarks: Chamberlin mentions the following material in his original description: “ British Guiana, Dunoon: Labba Creek sand hills, July 27; clay jungle by first landing on Labba Creek, August 12; sand-hill forest, August 14, 17, 18, 22, 24, 27, September 4; east trail along river September 2, 1914; F.M. Gaige. Many specimens collected under leaves and logs, in rotten wood and damp earth, etc. Type, M.C.Z., 2182”. The author states: “Pairs of legs in the male, fifty-three; in the female, fifty-five”. But it is striking that among the “many specimens” he mentions only those numbers were represented (in fact, one of the male paratypes here revised, has 57).

The original description of Chamberlin does not refer to a specimen in particular. It only includes 4 figures (head and forcipular segment in dorsal view; forcipular segment in ventral view; labrum; and coxosternum of second maxillae), and lacks information on the specialized sensilla of antennal articles; relative size of pore fields; details of structure of coxal organs; form of last leg praetarsus; etc.

About sexual dimorphism, the author only mentions “Anal legs alike in stoutness and pilosity in the two sexes” (but this was in error, because the praefemur, femur and tibia of the male last legs are proportionally narrower than those in the female). On the other hand, no morphological details are given for the terminal segments of any sex.

The female paratype MCZ TC-162 (B) and male paratype MCZ TC-162 (C) were collected during an incomplete moulting cycle (on temporary microscopic slides, the new cuticle can be observed by transparence underlying the external exuviae – which is not damaged and nor yet detached) .

The exuviae of the female paratype MCZTC-162 (B) shows an abnormal (claw-like) praetarsus on the left last leg ( Figs. 38, 39 ), being remarkable in that this praetarsus appears tubercle-like (normal condition) in the corresponding underlying new exoskeleton.

The left antenna of the male paratype MCZ TC-162 (A) is abnormal, having 15 articles (distribution of specialized sensilla as in Table 4) .

Right antenna of same specimen with 14 articles (distribution of specialized sensilla as in Table 5).

In all specimens examined, the claviform sensilla are absent on the internal side of the a.a. XIV. This trait is also confirmed on the two specimens in the moulting process cited above (in which these sensilla are absent on the exuviae as well as on the underlying new cuticle).

Ecology: The specimens of Pectiniunguis gaigei were collected in jungle environments under leaves and logs, in rotten and damp earth.

Type locality: ‘ British Guiana, Dunoon: Labba Creek sand hills’.

Known range: GUYANA: Dunoon, Labba Creek; Sand hills.

Figures

FIGURES 1‑5: Pectiniunguis gaigei (Chamberlin, 1921), (female paratype MCZ TC-161; GUYANA:Dunoon), (Reference Adenoschendyla gaigei): (1) Right a.a. I-VI, ventral; (2) Right a.a. VII-XIV, ventral; (3) Distal portion of right a.a. XIV, ventral (a: claviform sensilla, b: apical specialized sensilla); (4) Right a.a. XIII, ventral (a, b: a, b type sensilla); (5) Right a.a. XIII, dorsal (a, b, c: a, b, c type sensilla). Scale bars: 0.4 mm (1, 2); 0.05 mm (3); 0.1 mm (4, 5).

FIGURES 6‑12: Pectiniunguis gaigei (Chamberlin,1921),(female paratype MCZ TC-161; GUYANA:Dunoon), (Reference Adenoschendyla gaigei): (6) Cephalic shield and basis of antennae; (7) head capsule and basis of antennae, ventral; (8) clypeal area; (9) labrum; (10) dentate lamella of left mandible; (11) dentate lamella of right mandible; (12) first and second maxillae, ventral. Scale bars: 0.5 mm (6, 7); 0.1 mm (8); 0.3 mm (9, 12); 0.05 mm (10, 11).

FIGURES 13‑21: Pectiniunguis gaigei (Chamberlin, 1921), (female paratype MCZ TC-161; GUYANA: Dunoon), (Reference Adenoschendyla gaigei): (13) Left first maxilla, dorsal; (14) Detail of coxosternum and pleurites of right second maxilla, ventral; (15) Detail of coxosternum and pleurites of left second maxilla, dorsal; (16) Telopodite of left second maxilla, dorsal; (17) Claw of telopodite of right second maxilla, ventral; (18) Forcipular segment, ventral; (19) Detail of conduct and calyx of poison gland, in left forcipular telopodite, dorsal; (20) Right leg I, ventral; (21) Claw of right leg I, ventral. Scale bars: 0.2 mm (13); 0.3 mm (14, 15, 19, 20); 0.15 mm (16); 0.1 mm (17); 0.4 mm (18); 0.03 mm (21).

FIGURES 22‑29: Pectiniunguis gaigei (Chamberlin, 1921), (female paratype MCZ TC-161; GUYANA: Dunoon), (Reference Adenoschendyla gaigei): (22) Sternum II; (23) Sternum VII; (24) Pore field on sternum VIII; (25) Pore field on sternum XXIV; (26) Pore field on sternum XXVI; (27) Pore field on sternum XXXII; (28) Pore field on sternum XLVIII; (29) Pore field on sternum LIII. Scale bars: 0.4 mm (22, 23); 0.1 mm (24-29).

FIGURES 30‑33: Pectiniunguis gaigei (Chamberlin, 1921), (female paratype MCZ TC-161; GUYANA: Dunoon), (Reference Adenoschendyla gaigei): (30) Last leg-bearing segment and terminal segments, ventral; (31) Detail of distal end of last podomere of right last leg, ventral; (32) Right coxal organs, ventral; (33) Right anterior coxal organ, ventral. Scale bars: 0.3 mm (30, 32); 0.1 mm (33); 0.01 mm (31).

FIGURES 34‑36: Pectiniunguis gaigei (Chamberlin, 1921), (female paratype MCZ TC-161; GUYANA: Dunoon), (Reference Adenoschendyla gaigei): (34) Detail of internal cuticular structure of two lobes on right anterior coxal organ, ventral (a: common channels; b: individualized areas of mucous layer; (external contour of lobes not delineated)); (35) Detail of internal cuticular structure of a lobe on right anterior coxal organ, ventral (a: common channel; b: individualized areas of mucous layer; c: contour of lobe); (36) Last leg-bearing segment and terminal segments, dorsal. Scale bars: 0.05 mm (34, 35); 0.4 mm (36).

FIGURES 37‑43: (37-39): Pectiniunguis gaigei (Chamberlin, 1921), (female paratype MCZ TC-162 (B), GUYANA: Dunoon: Sandhill forest), (Reference Adenoschendyla gaigei): (37) Detail of anterior margin of forcipular coxosternum and basal internal edge of trochanteropraefemur; (38) Apical article of left last leg with abnormal (claw-like) praetarsus, ventral; (39) Detail of abnormal praetarsus of left last leg, ventral. (40-43): Pectiniunguis gaigei (Chamberlin, 1921), (male paratype MCZ TC-162 (A), GUYANA: Dunoon, Sand-hill forest), (Reference Adenoschendyla gaigei): (40) Right a.a. I-VI, dorsal; (41) Right a.a. VII-XIV, dorsal; (42) Detail of right a.a. XIV, ventral (a: claviform sensilla, b: apical specialized sensilla, c: internal chitinous thickening); (43) Detail of anterior margin of forcipular coxosternum and basal internal edge of trochanteropraefemur. Scale bars: 0.2 mm (37, 38, 43); 0.04 mm (39); 0.5 mm (40, 41); 0.1 mm (42).

FIGURES 44‑50: (44-49): Pectiniunguis gaigei (Chamberlin, 1921), (male paratype MCZ TC-162 (A), GUYANA: Dunoon, Sand-hill forest), (Reference Adenoschendyla gaigei): (44) Last leg-bearing segment and terminal segments, dorsal; (45) Last leg-bearing segment and terminal segments, ventral; (46) Detail of distal end of last podomere of left last leg, ventral; (47) Detail of distal end of last podomere of right last leg, ventral; (48) Left gonopod, ventral; (49) Penis, dorsal. (50): Pectiniunguis gaigei (Chamberlin, 1921), (male paratype MCZ TC-162 (C), GUYANA: Dunoon: Sand-hill forest), (specimen collected during an incomplete moulting cycle), (Reference Adenoschendyla gaigei): Right anterior coxal organ and anterior half of right posterior coxal organ, ventral (a: exuvial remnants). Scale bars: 0.3 mm (44, 45); 0.1 mm (49, 50); 0.05 mm (46, 47, 48).