Tropostreptus hamatus ( Demange, 1977 )
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: 508-513
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|Tropostreptus hamatus ( Demange, 1977 )|
Tropostreptus hamatus ( Demange, 1977) , comb. nov.
Diagnosis. A medium-sized species of Tropostreptus ( Figs 2 View FIGURE 2 , 11 View FIGURE 11 ). Differs from other species, except T. sigmatospinus , by the combination of size, the presence of two (not three) apical processes (map and bh) on the gonopodal metaplica, and the laterad direction and considerable size of the birdhead-shaped process bh. Differs from T. sigmatospinus by the larger size of the lateral proplical lobe (lpl) and the much longer and more curved antetorsal process (atp) of the telopodite.
Material studied (total: 83 ♂♂, 53 ♀♀, 71 juv.)
All from TANZANIA, all in ZMUC except as noted.
East Usambara Mts : 34 ♂♂, 18 ♀♀, 9 juv. TOPOTYPES, Amani, ca. 1000 m asl, 1970–1992, M. Andersen, H. Enghoff, I. B. Enghoff, C. Griswold, R. Jacobsen, O. Lomholdt, O. Martin, N. Scharff, M. Stoltze & D. Ubick leg. - 2 ♂♂ at Sigi River , 500 m, 7.ii.1977, H. Enghoff, O. Lomholdt, O. Martin leg.
Uluguru Mts: 1 ♂ Morogoro Region, Uluguru South Forest Reserve, forest above Ukwama village , 1450–1550 m asl, 07°11’S, 36°2’E, x. 1993, L. Sørensen leg. GoogleMaps — 1 ♂ Lupanga, East , 1300 m asl, in trunk, 10.vii.1981, M. Stoltze & N. Scharff leg. — 1 ♂, 1 ♀, 2 juv. Morogoro Region, Morogoro District, Mkungwe Forest Reserve. Lowland submontane forest. 6°51’25”S— 6°54’S, 37°54’E— 37°56’E, 400–1000 m asl, viii.2000, Nike Doggart leg., Uluguru Mountains Biodiversity Conservation Project GoogleMaps .— 2 ♂♂, 2 ♀♀ Morogoro Region, Morogoro District, Kasanga Forest Reserve. Taken from leaf litter and rotting logs. 7°10’S, 37°45’E, 27.vii.– 2.viii.2000, Nike Doggart leg., Uluguru Mountains Biodiversity Conservation Project GoogleMaps .
Udzungwa Mts: 1 ♂, 3 ♀♀, 10 juv. Mwanihana Forest above Sanje , 1000 m asl, in tree trunk, 1.viii.1981, M. Stolte & N. Scharff leg. — 3 ♂♂, 2 ♀♀ same data, but 1.viii.1982. — 1 ♂ Iringa District, Mwanihana Forest above Sanje , 3600 ft asl, 5.i.1981, K.M. Howell & S. Stuart leg. (KMH 1723) ( VMNH) .— 1 ♂ Mwanihana Forest Reserve, KMH 2058 ( VMNH) .— 1 ♂ (incomplete) Mwanihana forest N of Ifanre ( VMNH) .—1 ♂, 1 ♀, 4 juv.
Morogoro Region, Mwanihana Forest Reserve, 500–750 m asl, 7–16.ix.1984, lowland rain forest, N. Scharff leg. — 2 ♂♂, 4 ♀♀, Mwanihana Forest Reserve, 1000 m asl, 1.viii.1981, M. Stoltze & N. Scharff leg. — 2 ♂♂ Iringa Region and district: Mwanihana Forest north of Ifakara , 6.iv.1981, J. Kielland leg. ( VMNH). — 4 ♂♂, 2 ♀♀, 2 juv. Morogoro Region, Udzungwa Mts Natl. Park, Mizimu Camp , 1.ix.2013, 7°28’23.40”S, 36°51’07.29”E, 769 m asl, hand collected, T. Pape & N. Scharff leg. GoogleMaps — 2 ♂♂ 1 ♀, Iringa Region, Mahenge District, West Kilombero Forest Reserve, Ndundulu Mts ESE Udekwa Village , 7°47’S, 36°29’E, 1700–1750 m asl, in rotten wood, viii.1993, L.L. Sørensen leg. GoogleMaps — 1 ♂ 4 ♀♀, same data but 1450 m asl, in rotten wood, viii.1993, L.L. Sørensen leg. GoogleMaps — 10 ♂♂, 2 ♀♀ Morogoro Region, Udzungwa Mts Natl Park, Sanje Chini camp, 598 m asl, 07°46’24.6”S, 36°53’47.7”E, hand collected, 17–19.i.2014, T. Pape & N. Scharff leg. GoogleMaps — 4 ♂ ♂ Morogoro Region, Udzungwa Mts Natl Park, Sanje Kati camp & plot, 850 m asl, 07°45’47.6”S, 36°53’10.4”E, hand collected, 20–23.i.2014. Pape & Scharff leg. GoogleMaps — 1 ♂, 1 juv. ♀ Morogoro Region, Udzungwa Mts Natl Park, trail to Mizimu Camp , 250 m asl, hand collected, 3.ix.2012. T. Pape & N Scharff leg. — 3 ♂♂, 2 ♀♀, 13 juv. Morogoro Region, Udzungwa Mts Natl Park, trail to Mizimu Camp , 250 m asl, hand collected, 3.ix.2012. T. Pape & N Scharff leg. — 1 ♂, 5 juv. Morogoro Region, Udzungwa Mts Natl Park, Mito Mitatu , 07°50’16.3”S, 36°50’45.6”E, 800 m asl, 22.iii.2013. Hand collected. T. Pape & N. Scharff leg. GoogleMaps — 2 ♂♂, 5 ♀♀, 2 juv. Morogoro Region, Udzungwa Mts Natl Park, Mizimu Camp , 07°48’23.40”S, 36°51’7.29”E, 769 m asl., 3.ix.2012, and collected. T. Pape & N. Scharff leg. GoogleMaps — 1 ♂ Luhega Forest Reserve ( Udzungwa Scarp ), 35°58’E, 08°23’S, 8–900 m asl, 15.vii.1998, L. A. Hansen leg. GoogleMaps
Kanga Mt.: 1 ♂, 1 ♀ Morogoro Region, Kanga Forest Reserve, 400–500 m asl, 22–25.xi.1984, lowland rain forest, N. Scharff leg.
Rubeho Mts. : 2 ♂♂, 5 ♀♀, 28 juv. forest 5 km SW Madizini, 10–24.ix.1993, M. Andersen leg.
Type locality. TANZANIA: East Usambara Mts, Amani.
Description. Although no consistent morphological differences could be found between specimens from the East Usambara, Kanga, Rubeho Uluguru and Udzungwas Mts there seem to be some colour differences ( Fig. 1 View FIGURE 1 ) and in part also differences in body dimensions. Therefor a separate description is given for specimens from the type locality, Amani (East Usambara Mts) and its immediate surroundings, followed by notes on specimens from the other mountains, focusing on differences vs. the East Usambara population.
Specimens from East Usambara Mts (topotypes). SIZE ( Fig. 11 View FIGURE 11 ). Length 9–11 cm (up to 14 cm according to Sigling  but this may refer to a different species); vertical body diameter 6.6–8.1 mm (males), up to 9.1 mm (females); 53–56 podous rings (one exceptional male with 59 podous rings).
COLOUR ( Fig. 1 View FIGURE 1 A, B). Live specimens ringed in light and dark brown; head and antennae reddish, legs pink. After 24 years in alcohol head and antennae yellow, collum yellow with dark margins, body rings yellowish back to ozopore, then dark brown, then amber, legs light brown, telson yellow.
GONOPODS ( Figs 7 View FIGURE 7 A, 8 A, 12 A). Sternum triangular, not reaching as far distad as paracoxites, lateral edges slightly angled at mid-length, giving the sternum a somewhat “houselike” outline. Proplica ending in blunttriangular mesapical lobe (mpl) separated by conspicuous sinus from large apico-lateral, sub-semicircular lobe (lpl). Mesapical and apico-lateral lobes reaching equally far distad. Metaplica in anterior view basally with straight ridge flanking sternum and continuing ca. to mid-length of coxite, apically with rounded mesal process (map) separated by deep sinus from lateral birdhead-shaped process (bh), lateral “beak” of the latter moderately long, pointed, directed laterad but curving slightly anteriad. Mesal process not reaching as far distad as birdhead-shaped process. Telopodite shortly after emergence from coxa with very long, slender, pointed, antetorsal process (atp) making a broad 180° loop; direction of process first basad, then laterad, then apicad. Telopodite distal to antetorsal process slender, simple, without outgrowths.
Specimens from Udzungwa Mts. SIZE ( Fig. 11 View FIGURE 11 ). Vertical body diameter 5.4–7.1 mm (males), up to 7.7 mm (females); 53–57 podous rings.
Structural characters as in topotypes, with the following exceptions:
COLOUR ( Fig. 1 View FIGURE 1 C). Live specimens dark brown to blackish, telson slightly lighter, legs dark brown to blackish. After 2 years in alcohol head yellow, collum blackish brown, rings yellowish brown back to ozopores, then blackish, then amber. After 3 years in alcohol: overall colour dark brown, anterior half of prozona brownish orange, telson brownish orange, but posterior part of anal valves dark brown to blackish; legs brown.
GONOPODS ( Figs 7 View FIGURE 7 B, 8 B). Sternum triangular, lateral edges tending to be more or less regularly arched, rather than angled. Mesal process of metaplica (map) often separated from lateral birdhead-shaped process (bh) only by narrow sinus and often reaching as far distad as the latter.
Specimens from Uluguru Mts. SIZE ( Fig. 11 View FIGURE 11 ). Vertical body diameter 6–7.9 mm (males), up to 8.6 mm (females), 53–60 podous rings.
Similar to topotypes in all respects, including detailed gonopod shape (except that the lateral margins of sternum are slightly arched in some males).
Specimens from Rubeho Mts. SIZE ( Fig. 11 View FIGURE 11 ). Body diameter 7.6 mm (male), up to 8.7 mm (females), 56–57 podous rings.
Legs yellowish after 23 years in alcohol.
Specimens from Kanga Mt. SIZE ( Fig. 11 View FIGURE 11 ). Body diameter 8.1 mm (male), 8.6 mm (female), 58–59 podous rings.
Similar to topotypes in all respects.
Distribution and habitat. Tropostreptus hamatus is known from the East Usambara, Uluguru, Udzungwa, Rubeho and Kanga Mts., recorded at altitudes 250–1700 (1750?) m asl. Enghoff & Enghoff (1976) most frequently found T. hamatus (recorded as “ Spirostreptus sp. 1”) in decaying wood; several of the newly studied samples were taken in similar microhabitats.
Coexisting congeners. Coexisting with T. austerus in the East Usambara Mts, with T. sigmatospinus in the Uluguru Mts (Lupanga East and Mkungwe Forest Reserve) and the Udzungwa Mts (Mwanihana Forest Reserve / Udzungwa Mts National Park), with T. sigmatospinus and T. severus in Kanga Forest Reserve, Kanga Mt. , and with T. microcephalus in the Udzungwa Mts. (West Kilombero Scarp Forest Reserve).
Infection with Rickia gigas . Several specimens were found to be infected with Rickia gigas . In a sample of 6 ♂♂ and 4 ♀♀ from Amani, all specimens were found to be infected: Two males were quite heavily infected with the long-celled type on the head, antennae, collum, pre-gonopodal and post-gonopodal legs (in one case all the way back to the last pair) and adjacent parts of the body rings. In addition these specimens had many thalli of the shortcelled morphotype on the hind margin of several body rings. The other four males had lighter infections with longcelled R. gigas , confined to pre-gonopodal and anterior postgonopodal legs; two of these also had the short-celled form on posterior body ring margins. The four females all had long-celled R. gigas on some anterior legs, two of them also on adjacent parts of the body rings, one of them also on the head; three of them had the short-celled type on the margin of several body rings. Four further males from Amani were more or less heavily infected with the long-celled type on pre-gonopodal and anterior post-gonopods legs and adjacent parts of the body rings. A male from Udzungwa Mts National Park, Sanje Chini camp, was infected with the long-celled type on pre- and postgonopodal leg back to midbody, on adjacent parts of the body rings and even (just a few thalli) on the gonopods. A female from Udzungwa National Park, trail to Mizimo Camp, had a few long-celled thalli on several anterior legs and adjacent parts of the body rings. A male from Mwanihana Forest Reserve was infected with the long-celled type on pre- and anterior post-gonopodal legs and also had several thalli of the short-celled type on the posterior margin of body rings; a female from the same sample had a few long-celled thalli on anterior legs and some short-celled thalli on posterior margin of body rings. A male from Luhega Forest Reserve (Udzungwa Scarp) had many long-celled thalli on the pregonopodal and anterior post-gonopodal legs, and on adjacent parts of the body rings.
Two males and four females from Rubeho Mts. all had long-celled R. gigas on anterior legs, one of the males also had the short-celled type on the posterior margin of certain body rings.
Notes. The wide distribution and the considerable morphological variability, in combination with the close resemblance between T. hamatus and the even more widespread T. sigmatospinus , suggest that either several species may hide under T. hamatus as here understood, or that T. hamatus and T. sigmatospinus may belong to a single widespread, very variable species. The coexistence of both species at several sites (even in the same samples) however, speaks against conspecificity. Apart from the characters which have been given as diagnostic of the two species recognized here, the generally higher number of body rings in T. hamatus ( Fig. 2 View FIGURE 2 ), and the pink legs which seem to be unique for the East Usambaran population of T. hamatus , no consistent pattern in the variability has been perceived. This complex of large, easily collected millipedes is an obvious candidate for a molecular taxonomic study.
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