Chaleponcus dabagaensis, Kraus, 1958

Enghoff, Henrik, 2014, A mountain of millipedes I: An endemic species-group of the genus Chaleponcus Attems, 1914, from the Udzungwa Mountains, Tanzania (Diplopoda, Spirostreptida, Odontopygidae), European Journal of Taxonomy 100, pp. 1-75 : 10-17

General description of the Chaleponcus dabagaensis group

This description only applies to males and, as far as non-gonopodal characters are concerned, only includes a selection (cf. above).

Non-gonopodal characters

BODY LENGTH. ca. 2–5 cm. Midbody vertical diameter 1.6–3.5 mm. 38–54 podous rings, no apodous

rings in front of telson. The 21 species may conveniently be divided into four size groups (cf. Figs 2–3 ):

• Large species, diameter 2.8–3.5 mm, 48–54 podous rings: C. basiliscus sp. nov., C. circumvallatus sp. nov., C. ibis sp. nov., C. krai sp. nov.

• Medium-sized species, diameter 1.6–2.4 mm, 41–49 podous rings: C. dabagaensis , C. hamerae sp. nov., C. howelli sp. nov., C. mwabvui sp. nov., C. mwanihanensis sp. nov., C. nectarinia sp. nov., C. netus sp. nov., C. nikolajscharffi sp. nov., C. quasimodo sp. nov., C. scopus sp. nov., C. teres sp. nov., C. termini sp. nov., C. vandenspiegeli sp. nov., C. vilici sp. nov.

• Small species, diameter 1.6–1.8 mm, 38–41 podous rings: C. malleolus sp. nov., C. tintin sp. nov.

• ‘Long, thin species’, diameter 1.5–1.8 mm, 45–49 podous rings: C. gracilior sp. nov.

COLOUR. Bleached in most studied specimens, but a pale middorsal longitudinal band is often discernible.

LIMBUS (examined on the dorsal side of midbody rings). Lobulate to serrate. Lobes often triangular and pointed, but sometimes rounded or spatulate, sometimes very shallow, rarely virtually absent, often longitudinally striolate, sometimes apically denticulate. See Fig. 4.

CLAWS OF WALKING LEGS. With a long (> claw proper) accessory claw. Tip of tarsus usually with a moderate number of strong setae (“normal setation”), but in two species, C. circumvallatus sp. nov. and C. ibis sp. nov., with a dense whorl of stout setae surrounding the claw like a palisade. See Fig. 5.

TELSON. Preanal ring with wrinkled/coriaceous sculpture dorsally. Anal valves with wrinkled/coriaceous sculpture, except along caudal and ventral margins; in almost all species each with a dorsal denticle of variable size, and often also with a smaller ventral denticle; denticles when present well set off from rest of valve rather than just being “sharp corners” (compare Fig. 6 A–C, with fig. 3 in Frederiksen 2013b). Each valve with three setae. Free margin (‘lip’) of anal valves raised in most species and provided with three small extensions (‘ravelins’) on which the setae are borne. These setiferous tubercles not protruding in lateral view. See Fig. 6.

BODY RING 7. Body ring 7 of males modified, with posterior shallow concavities for accommodation of gonopods. The detailed shape of the concavities varies among species, in parallel with variations of gonopod shape, but this has not been studied in detail here.

Gonopods

COXA ( Fig. 7 ). In anterior or posterior view 3–4 × as long as broad. Free margin of proplica straight, shallowly concave or shallowly sinuous from base to proplical lobe (prl) at ca. 2/3 of the length of the proplica. Metaplica basally with an anteriad flange (mf) usually ending in a blunt or triangular process (mfp). Free margin of metaplica variable, but at ca. 2/3 of its length, the metaplica carries a metaplical shelf (ms) on which a metaplical shelf-spine (mss) is inserted. Distal to prl and ms, proplica and metaplica join to form an apical ‘hood’, the cucullus (cu). The cucullus may take many different shapes and together with the metaplical shelf-spine defines the general ‘profile’ of the gonopod coxa which is often species-specific ( Fig. 9 ).

TELOPODITE ( Figs 8 , 10 ). Basomere including torsotope without spines, arculus 90°. First full (360°) turn of torsotope very tight, leaving no space inside the spiral, but last half (180°) turn, a more open spiral, leaving room for a triangular to semicircular torsotope process (tp) on the basal side of the spiral (tp was described for C. dabagaensis by Kraus (1958) as a blunt peg in the position corresponding to that of a femoral spine: “Kein Femoraldorn, auf der Vorderseite jedoch an dessen Stelle ein stumpfer Zapfen”). The torsion of the torsotope begins with an anteriad bend. Posttorsal narrowing unremarkable, not very pronounced.

SOLENOMERE (slm). Solenomore originating on apical side of telopodite, just after posttorsal narrowing, whiplike, taeniate, irregularly curving in specimens prepared for SEM, longitudinally fluted (sometimes indistinctly) and sometimes also with tiny retrorse spines in distal part. A slender proximal spine (ps) often originating from base of solenomere, sometimes accompanied by a small ± lamellar outgrowth and/or a second small spine.

TELOMERE. Telomore highly variable, originating on basal side of telopodite, just after posttorsal narrowing, starting with a proximal lobe (pxl) lying closely against posterior base of slm. Telomere continuing distally to pxl in simple, large main stem (st), anterior margin of st forming shallow lobe (st’) lying closely against proximal part of slm. Distal part of telomere very complicated, consisting of several lamellar parts; two or three lamellae can be distinguished, but these may each have accessory lamellae, carry variously shaped spines and have more or less serrated margins. I have been unable to homologize the various lamellae etc. of the telomere between species; thus, what is called anterior lamella in one species may be homologous with what it called posterior lamella in another. For example, the very characteristic anterior lamella in C. krai sp. nov. is remarkably similar to the posterior lamella in C. nectarinia sp. nov., but whether these two structures are homologous, or whether different parts of the telomere have evolved convergently to serve similar needs, remains unclear.

Included species (alphabetically)

Chaleponcus basiliscus sp. nov., C. circumvallatus sp. nov., C. dabagaensis Kraus, 1958 , C. gracilior sp. nov., C. hamerae sp. nov., C. howelli sp. nov., C. ibis sp. nov., C. krai sp. nov., C. malleolus sp. nov., C. mwabvui sp. nov., C. mwanihanensis sp. nov., C. nectarinia sp. nov., C. netus sp. nov., C.

nikolajscharffi sp. nov., C. quasimodo sp. nov., C. scopus sp. nov., C. teres sp. nov., C. termini sp. nov., C. tintin sp. nov., C. vandenspiegeli sp. nov., C. vilici sp. nov.

The species cannot easily be arranged in subgroups. For practical reasons the descriptions are organised

as follows:

• Species in which the gonopod coxa has an obvious lateral process (exceptionally, C. basiliscus sp. nov., two processes): C. netus sp. nov., C. dabagaensis Kraus, 1958 , C. quasimodo sp. nov., C. malleolus sp. nov., C. scopus sp. nov., C. nikolajscharffi sp. nov., C. mwanihanensis sp. nov., C. basiliscus sp. nov.

• Species without an obvious lateral coxal process in which the metaplical shelf-spine (mss) is long and projects ± mesad: C. krai sp. nov., C. nectarinia sp. nov., C. circumvallatus sp. nov., C. ibis sp. nov., C. vandenspiegeli sp. nov.

• Species without an obvious lateral coxal process in which the metaplical shelf-spine (mss) is not long and projecting ± mesad ( C. vilici sp. nov. has the lateral side of the coxa somewhat angled, which reminds of a small lateral process): C. vilici sp. nov., C. teres sp. nov., C. hamerae sp. nov., C. termini sp. nov., C. gracilior sp. nov., C. mwabvui sp. nov., C. howelli sp. nov., C. tintin sp. nov.

Species in which the gonopod coxa has an obvious lateral process

(exceptionally, C. basiliscus sp. nov., two processes)

Figures

Fig. 2. Body size of males of 13 species of the Chaleponcus dabagaensis group: Number of podous rings and vertical midbody diameter in large, small and ‘long, thin’ species (cf. text), as well as medium sized species in which the gonopod coxa has an obvious lateral process.

Fig. 3. Body size of males of 8 species of the Chaleponcus dabagaensis group: Number of podous rings and vertical midbody diameter in medium-sized species in which the gonopod coxa has no obvious lateral process.

Fig. 4. Limbus types in Chaleponcus species, SEM micrographs, external view, except I: internal view. — A. Lobes pointed, more than twice as long as broad (C. scopus sp. nov.). B. Lobes pointed, slightly less than twice as long as broad (C. howelli sp. nov.). C. Lobes pointed, almost equilateral triangles (C. netus sp. nov.), D. Lobes rounded, slightly longer than broad (C. dabagaensis Kraus, 1958). E. Lobes broadly rounded, slightly shorter than broad (C. hamerae sp. nov.). F. Lobes spatulate (C. gracilior sp. nov.). G. Lobes rounded, broader than long, spinose, ridged (C. krai sp. nov.). H. Lobes ca. 3 times as broad as high, rounded, spinose (C. teres sp. nov.). I. Lobes rounded, much broader than high, smooth (C. malleolus sp. nov.). J. No lobes (C. circumvallatus sp. nov.). Scales: 0.01 mm (A– F, J), 0.001 mm (G–I).

Fig. 5. Chaleponcus spp., tip of tarsus and claw of walking legs. — A. C. mwanihanensis sp. nov. as an example of normal setation. B–C. C. circumvallatus sp. nov. with the claw surrounded by a ’palisade’ of setae. Scales 0.1 mm.

Fig. 6. Telson types in Chaleponcus species. — A. Dorsal and ventral anal valve spines well developed (C. nectarinia sp.nov.).B.Spinesverylong(C.circumvallatussp.nov.).C.Dorsal spinewell developed, ventral spinebarelyindicated(C.mwabvuisp.nov.).D.Nospines(C.teressp.nov.).E.Setiferoustuberclesonravelins (C. nectarinia sp. nov.). F. With setiferous tubercles, not on ravelins (C. mwabvui sp. nov.). Scales 0.1 mm.

Fig. 7. Gonopod coxa terminology, left coxa of Chaleponcus termini sp. nov., mesal(-posterior) view. cu = cucullus, mf = anteriad metaplical flange, mfp = metaplical flange process, ms = metaplical shelf, mss = metaplical shelf-spine, prl = proplical lobe.

Fig. 9. Chaleponcus spp., outline of coxite of left gonopod, posterior view. (The ’transverse’ plane of the gonopod is usually slightly at angles with the exact transverse plane of the millipede, so it may be necessary to tilt the gonopod slightly in order to obtain the view shown on the drawings.) The stippled lines indicate the place where the telopodital basomere emerges from the coxal cavity. Not to scale.

Fig. 8. Gonopod telopodite terminology. — A. Left telopodite of Chaleponcus termini sp. nov., posterior view. White oval = basomere, blue oval = torsotope, red oval = telomere, yellow = solenomere (slm), green = proximal spine of solenomere (ps), pxl = proximal lobe of telomere, st = main stem of telomere, st’ = shallow lobe of st. B–C. Torsotope (left gonopod) with torsotope process (tp). B. C. vilici sp. nov., mesal-anterior view. C. C. netus sp. nov., posterior view. D. Solenomere (C. dabagaensis) to show longitudinal fluting. E. Tip of solenomere (C. netus sp. nov.) to show spinulation. Scales: 0.1 mm (A– D), 0.01 mm (E).

Fig. 10. Chaleponcus netus sp. nov., left gonopod, coloured. — A. Posterior view. B. Ventral view. Orange = coxite, blue = torsotope, yellow = solenomere (slm), green = proximal spine of solenomere (ps), pink = telomere. pxs = spine on proximal telomeral lobe, st = main stem of telomere. Scales 0.1 mm.