Ammodesmus granum Cook, 1896

VandenSpiegel, Didier & Golovatch, Sergei, 2012, The millipede family Ammodesmidae (Diplopoda, Polydesmida) in western Africa, ZooKeys 221, pp. 1-17 : 5-9

Ammodesmus granum Cook, 1896 Figs 1-27

Ammodesmus granum Cook, 1896

Cenchrodesmus volutus Cook, 1896 syn. n.

Type material.

Neotype ♂ (MRAC 21667), Liberia, Bong Range Forest, 06°49'N, 010°17'W, rainforest, pitfall trapping, 13.III.2005, leg. D. Flomo.

This male specimen has been chosen as neotype, because it is in perfect condition and represents a near-topotype. A neotype of Cenchrodesmus volutus has also been selected to substantiate this taxon as well.

Other material.

1 ♂, 2 ♀ (ZMUM), 1 ♂ (MNHN), same locality, date and collector; 6 ex. (MRAC 21966) GUINEA, Mt Nimba, Gouela forest, 07°37'N, 008°21'W, Winkler extraction, 12.X.2008; 39 ex. (MRAC 21981), including a ♀ neotype of Cenchrodesmus volutus , same locality, Winkler extraction, 15-17.X.2008; 6 ex. (MRAC 21991), same locality, Winkler extraction, 13-15.X.2008; 4 ex. (MRAC 22004), same locality, Winkler extraction, 17-19.X.2008; 12 ex. (MRAC 22045), same locality, Winkler extraction, 13-16.X.2008; 4 ex. (MRAC 22007), Mt Nimba, Zié forest, 07°40'N, 008°22'W, Winkler extraction, 16-18.X.2008; 2 ex. (MRAC 22040), same locality, Winkler extraction, 14-16.X.2008; 2 ex. (MRAC 22050), Mt Nimba, Ziela forest, 07°43'N, 008°21'W, litter, Winkler extraction, 19.X.2008; all leg. D. VandenSpiegel; 1 ♂, 1 ♀ (MRAC 22284), Taï forest, 05°50'N, 007°21'W, Winkler extraction, 01-03.IX.2010; 1 ex. (MRAC 22285), same locality, Winkler extraction, 13-15.X.2010; 4 ex. (MRAC 22286), same locality, Winkler extraction, 01-03.IX.2010; 2 ex. (MRAC 22288), same locality, Winkler extraction, 01-03.IX.2010; 1 ex. (MRAC 22289), same locality, Winkler extraction, 01-03.IX.2010; 2 ex. (MRAC 22290), same locality, Winkler extraction, 13-15.X.2010, all leg. A. Kablan; 3 ex. (MRAC 22287), same locality, forest on clayey soil, Winkler extraction, 22-24.II.2010; 4 ex. (MRAC 22291), Taï forest, Ecological Research Centre, 05°50'N, 007°21'W, secondary forest, Winkler extraction, 21-22.II.2010, all leg. M. Diarassouba & R. Jocqué.

Diagnosis.

Minute polydesmidans (1.4-2.0 mm in length) showing evident sexual dimorphism in tergal structure: ♂ with a transverse row of up to ten ovoid tubercles arising from posterior part of each metatergum, ♀ with nearly smooth metaterga. Gonopod with a small globular coxa reaching in length only about one-third of telopodite; the latter slender, flattened and twisted mesad in distal part, with a small sac-shaped outgrowth laterally at base.

Redescription.

♂ ca 1.9 mm long; maximum width, 0.9 mm. Entire dorsal surface covered with a thin layer of secretions (= cerategument), under which the body integument is light brown to pinkish with metaterga of each segment brownish (Fig. 1). Body with 18 or 19body rings (16 or 17+1+T), shape as in Figs 1, 2 & 3, with caudal body end tapering towards a relatively small telson not concealed by paraterga (Fig. 6).

Head small, only partly concealed under front edge of collum (Figs 7, 11); preceding half of head densely granular, lower part smooth and densely setose (Figs 7, 8). Interantennal isthmus about as wide as antennomere 1, surmounted by a small tubercle (Fig. 8). Antennae as in Fig. 7. Collum covered with low rounded tubercles (Fig. 11), tergum 2 as usual, hypertrophied, with strongly enlarged, spatuliform paraterga concealing the head in lateral view, ventral edge with a line of granules (Fig. 3). Limbus smooth; 2nd and following metaterga with 7-10 large oblong tubercles along caudal margin (Figs 1, 2, 4, 5, 6, 13). Each tubercle surmounted by a short seta (Fig. 17). Prozona rugose anteriorly, with a row of square areas along anterior edge of metatergum (Figs 13, 15), these square areas being reduced in ♀ or absent in juveniles (Fig. 3). Paraterga set at segments’ midheight just below a deep pit (Fig. 16, pt), continuing the highly convex outline of dorsum, their ends rounded, projecting far below venter/coxae (Fig. 14), increasingly angular towards telson (Figs 5, 6). Anteroventral edges of paraterga 3 to 15 with a notch forming a groove for paratergum 2 to hinge into during volvation (Figs 18, 19, g). Ozopore formula: 5, 7, 9, 10, 12, 13, 15, 17; ozopores opening flush on tergal surface about midheight of paraterga, most of openings concealed by preceding paraterga (Fig. 16). Telson small (Fig. 6).

Legs rather slender, but short, barely reaching tips of paraterga (Fig. 14); femoral and tarsal segments longest, subequal in length; claw normal, simple, very slightly curved ventrad (Fig. 22); first pair of legs in ♂ with modified setae (Figs 20, 21); last pair of ♂ legs modified, typical of Ammodesmus (Fig. 23).

Gonopods (Figs 24, 25) relatively simple. Coxae rather small, globular, scaly, without setae. Telopodite long and well exposed beyond small gonocoxae; apical part of the main body of telopodite (= solenomere) smooth, flattened, pointed and twisted medially, devoid of a hairy pulvillus; a small, sac-shaped, lateral outgrowth at base of telopodite.

♀ usually slightly larger than ♂, segments rather smooth, without metatergal tubercles. Vulva small, poorly sclerotized, edge of bursa supplied with long setae (Figs 26, 27).

Distribution.

Known from Liberia, Guinea and the Ivory Coast. It is noteworthy that at Mt Nimba this species occurs parapatrically with the new congener described below.

Remarks.

Ammodesmus granum is striking in being perhaps the only species in Polydesmida in which both sexes vary in the number (18 or 19) of body rings. Infraspecific variations in the number of body segments in this order are usually quite rare, always being stable per sex. Thus, in such cases males always have fewer body rings (18 or 19) than females (19 or 20), a situation not too uncommon, e.g., in Haplodesmidae ( Golovatch et al. 2009a, 2009b, 2010) and, especially, Opisotretidae ( Golovatch 1988).

Neotype designations for both Ammodesmus granum and Cenchrodesmus volutus are necessary, because the original types can be presumed as being lost. A special search undertaken among Cook’s diplopod collections, currently housed in the Smithsonian Institution, National Museum of Natural History, Washington, D.C., had failed already before the description of Elassystremma pongwe by Hoffman and Howell (1981).