Tropostreptus austerus ( Attems, 1950 ) Attems, 1950

Enghoff, Henrik, 2017, A new East African genus of spirostreptid millipedes (Diplopoda, Spirostreptida, Spirostreptidae), with notes on their fungal ectoparasite Rickia gigas, Zootaxa 4273 (4), pp. 501-530 : 521-522

Tropostreptus austerus ( Attems, 1950) comb. nov.

Figs 2 , 8 G, 10A, 14, 15A

Epistreptus austerus Attems, 1950: 217

Diagnosis. A large species of Tropostreptus ( Fig. 2 ). Differs from other species, except T. severus , by the combination of size and the presence of three apical lobes/processes on the gonopodal metaplica. Differs from T. severus by the smaller size of the lateral proplical lobe (lpl) and the basad(-laterad) curvature of the telopodital antetorsal process (atp).

Material studied (total: 18 ♂♂, 10 ♀♀)

Holotype: ♂ “ Epistreptus austerus Attems, 1950 , E-Afrika Umgebung v. Amani, leg. Bogert” (NMW 2430).

New material: All from TANZANIA, Tanga Region, East Usambara Mts, all in ZMUC: 13 ♂♂, 5 ♀♀ Amani, 5°5.7’S 38°38’E, 950–1000 m asl, 1974–1995, P. Bjørn, I.B. & H. Enghoff, C. Griswold, O. Lomholdt, O. Martin, N. Scharff, L. Sørensen & D. Ubick leg., “on tree stump”, “in decaying wood” etc. ; 1 ♂ Tanga Region, Muheza + Korogwe District , (Nilo Forest Reserve) 940 m asl, 4°56’32.6”S 38°39’38.5”E, trapsite 8 plot 59A, date?, Frontier Tanzania leg. — 4 ♂♂, 4 ♀♀ Muheza district , Nilo Forest Reserve, 1010–1240 m asl, submontane forest, 27.ii.— 21.vi.2001, Frontier Tanzania leg. ; 1 ♀ Muheza District , Nilo Forest Reserve, 4°54’16”S 38°39’45”E, lowland forest, 820 m asl, 10.vi.2000, Frontier Tanzania leg.

Type locality. Environs of Amani, East Usambara Mts.

Description. SIZE ( Fig. 2 ). Length 13–14 cm; vertical body diameter 8.6–10.6 mm (males), up to 11.8 mm (females), 51–57 podous rings.

COLOUR. Live colour dark brown (pers. obs.). After 16 years in alcohol head, antennae, legs and telson orange yellow or brownish, body rings marbled greyish back to suture, then brownish, posterior ca. 10% amber brown; alternatively each body ring dark orange in anterior half, almost black in posterior half.

HEAD. Eyes with more ommatidia than in congeners: up to 60 ommatidia in up to 17 vertical and 8 horizontal rows.

GONOPODS ( Figs 8 G, 14, 15A). Sternum triangular, reaching almost as far distad as paracoxites, lateral edges slightly convex. Proplica ending in blunt-triangular process (map) separated by sinus from large apico-lateral, subsemicircular lobe (lpl). Apico-lateral lobe (lpl) reaching further distad than triangular lobe (mpl). Metaplica in anterior view basally with straight ridge continuing ca. to mid-length of coxite, apically with small mesal process (map) separated by sinus from sub-semicircular mid-distal process which again is separated by deep sinus from lateral birdhead-shaped process (bh), lateral “beak” of the latter long, slender, pointed, directed laterad. Birdheadshaped process reaching further distad than any other part of gonopod. Telopodite shortly after emergence from coxa with very long, slender, pointed, sinuous antetorsal process (atp); overall direction of process basad (the basad-mesad direction seen in Fig. 14 is an artefact due to drying of the gonopods for scanning electron microscopy). Telopodite distal to antetorsal process with subrectangular flange, distal to flange slender, simple, without outgrowths.

Distribution. Known only from lowland and submontane forest in the East Usambara Mts, 820–1010 (1240) m asl. Microhabitat notes include a tree stump and decaying wood.

Coexisting congener. Coexists with T. hamatus in the East Usambara Mts, especially around Amani.

Infection with Rickia gigas . The long-celled type of Rickia gigas was found on the mesal-ventral sides of legpairs 2–7 in males. Most specimens, including the holotype, were found to be infested with the short-celled type of R. gigas on the hind margin of the body rings of both sexes, in some cases on all body rings and even the preanal ring.

Figures

FIGURE 2. Size of Tropostreptus males, expressed as number of podous rings and midbody vertical diameter. Females reach higher diameters than males. See Figs. 11 and 13 for details on T. hamatus and T. sigmatospinus sp. nov.

FIGURE 8. Tropostretus spp., left gonopods, proplica, anterior view. A: T. hamatus, East Usambara Mts, B: T. hamatus, Udzungwa Mts., C: T. sigmatospinus sp. nov., D: T. microcephalus sp. nov., E: T. droides sp. nov., F: T. kipunji sp. nov., G: T. austerus, H: T. severus sp. nov. — not to scale. The apicolateral proplical lobes (apl) are marked with yellow stars.

FIGURE 14. Tropostreptus austerus, gonopods, anterior view. The birdhead-shaped process of the right gonopod is misshapen; the basad-mesad direction of the antetorsal process is due to drying of the gonopods for scanning electron microscopy. Scale 0.5 mm.