Scolopendropsis duplicata, Chagas-Junior, Amazonas, Edgecombe, Gregory D. & Minelli, Alessandro, 2008

Chagas-Junior, Amazonas, Edgecombe, Gregory D. & Minelli, Alessandro, 2008, Variability in trunk segmentation in the centipede order Scolopendromorpha: a remarkable new species of Scolopendropsis Brandt (Chilopoda: Scolopendridae) from Brazil, Zootaxa 1888, pp. 36-46 : 40-45

Scolopendropsis duplicata n. sp.

Figs. 1–14 .

Diagnosis: Thirty-nine or 43 trunk segments; paramedian sutures of T1 incomplete anteriorly, extending ¾ of length; posterior border of coxopleuron usually bearing single short spine caudal to posterolateral corner of pore field; ultimate leg prefemur with two ventromedial and one to three dorsomedial spines in longitudinal rows (when multiple), the dorsomedial row aligned with prefemoral process; latter with two or three apical spines; flattened medial face of prefemur variably bearing one to six small spines that, when maximally developed, are aligned in two rows; posterior halves of ultimate leg prefemur and femur with sulcus-like longitudinal depression dorsad.

Type specimens: Segment number (39 or 43) indicated in parentheses. Holotype MNRJ 15258, 1 ex., Tocantins State, Porto Nacional, 10.0589°S 48.412°W, 22L 0 783671 UTM 8886955, 29.IX–07.X.2001, D. Pavan (43). Paratypes all from type locality, leg. D. Pavan unless indicated otherwise: paratype MNRJ 15259, 1 ex., 29.IX–07.X.2001 (39); MNRJ 15305, 1 ex., 29.X–07.X.2001 (43); MNRJ 15306, 6 ex., 29.IX– 07.X.2001 (39); IBSP 1519, 1 ex., Ribeirão Santa Luzia, Fazenda Sandoval, 2000, Equipe Investco/Ulbra (43); IBSP 1498, 1 ex., 07–11.VIII.2000, I. Knysak, R. Martins & G. Puorto (43); IBSP 2406, 1 ex., Ribeirão Santa Luzia, Fazenda Sandoval, 10–13.VII.2000, Equipe Investco/Ulbra (39); IBSP 2843, 1 ex., Fazenda Sandoval, 11.VIII.2000, I. Knysak, R. Martins & G. Puorto (43); IBSP 2392, 2 ex., Fazenda Sandoval, 5– 10.V.2000, I. Knysak, R. Martins & G. Puorto (43); NMNH, 1 ex., 29.IX–07.X.2001 (39); MCZ, 1 ex., 29.IX– 07.X.2001 (39); NCSM, 2 ex., 29.IX–07.X.2001 (43, 39); MZSP, 3 ex., 29.IX–07.X.2001 (43, 39); BMNH, 2 ex., 29.IX–07.X.2001 (39).

Etymology: The specific name refers to the near doubling of trunk segment numbers compared to the most closely related species.

Description: Length of 39-segmented individuals ranging from 31–74 mm; that of 43-segmented individuals from 53–78 mm. Cephalic plate, trunk and legs yellow in specimens preserved in alcohol; forcipulae and ultimate legs orange. Cephalic plate: smooth, 1.3 times as long as wide, distinctly narrower than T1, with four ocelli on each side. Posterior longitudinal median suture extending for ½–¾ of length ( Fig. 6 ), difficult to detect in juveniles. Posterior border overlain by T1; basal plates at posterolateral corners delimited by continuous suture across posteromedial margin. Antennae: short, usually reaching backwards to midlength of T1; with 17 articles, basal six glabrous/sparsely hirsute. Coxosternum: tooth plates about 1.3 times as long as wide ( Figs. 3 , 7 ); inner teeth fused, with two ill-defined cusps, lateral teeth isolated, apices slightly caudad to inner teeth; basal sutures approximately transverse. Longitudinal median suture bifurcating posteriorly into inverted Y-shape, crossed at or near division point by a subtransverse suture curving anteriad laterally and extending to forcipular bases ( Figs. 2 , 7 ). Process of forcipular trochanteroprefemur with two blunt apical denticles. Second maxilla: symmetrical accessory claws on each side of apical claw. Coxosternum with complete median sulcus. Tergites: smooth; T1 with paramedian sutures on posterior ¾ ( Fig. 6 ); TT2-38 or TT2-42 with complete paramedian sutures; ultimate tergite (T39 or T43) about 1.5 times as long as penultimate, with complete median longitudinal suture ( Figs. 5 , 8 ). Margination on ultimate tergite only. Pretergites usually present on the posterior segments. Sternites: smooth; complete paramedian sutures present on SS2-38 or SS2-42 ( Fig. 14 ). Ultimate sternite considerably longer than wide ( Figs. 4 , 9 ), lateral margins gently converging caudad, with median longitudinal depression; posterior margin gently convex or straight. Spiracles: on segments 3, 5, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38 of all specimens; those with 43 trunk segments additionally bear spiracles on segments 40 and 42. Anteriormost spiracle enlarged relative to others, nearly half length of T3; second spiracle (segment 5) only slightly larger than those immediately more posterior. Longitudinal pleurites parallel to trunk axis ( Fig. 12 ). Coxopleura: longer than wide, pore field half as wide as coxopleuron, separated from pore-free part of pleuron by well-incised longitudinal sulcus; posterior border of coxopleuron bearing short spine immediately caudal to posterolateral corner of pore field ( Fig. 4 ), usually present on only one side, sometimes absent in specimens with 39 leg-bearing segments. Posterior border of coxopleuron abruptly truncated, coxopleural process absent. Legs: tarsi composed of two articles. Tarsus 1 shorter than tarsus 2. Spur present on tarsus 1 of legs 1–37 or 1–41; ultimate and penultimate legs lacking spur. Pretarsus longer or equal in length to tarsus 2; proximal 1/3 pale, distal 2/3 strongly pigmented with concave ventral surface bounded on each side by sharp marginal ridge; pretarsi of legs 1–38 or 1–42 with two accessory spurs about ¼ as long as pretarsi on anterior segments, increasing to about 1/3 length of pretarsi on posterior segments. Ultimate legs: thickened, forcipulate, with relatively short articles; prefemora with two ventromedial and one to three dorsomedial spines in longitudinal rows (when multiple), the dorsomedial row aligned with distomedial process ( Figs. 5 , 10 ); the latter conical, bearing two or three small apical spines. Medial face of prefemur flattened, variably bearing one to six small spines that, when maximally developed, are aligned in two rows. Posterior halves of prefemur and femur with sulci-like longitudinal depressions on dorsal side ( Fig. 10 ). Pretarsus with one basal accessory spur, shorter than those on ambulatory legs; ventral surface of pretarsus with serrated ridge bearing numerous small, sharp teeth.

Distribution: Brazil, Tocantins State. Scolopendropsis duplicata is restricted to typical “cerrado” vegetation, and is known only from its type locality ( Fig. 15 ).

Discussion: Despite the fact that this new species differs from all other Scolopendromorpha with respect to a character (trunk segment number) that is routinely used to diagnose genera or families within the order, the highly detailed similarity to Scolopendropsis bahiensis in all morphological characters apart from trunk segmentation leads us to favour its congeneric classification. We note the paradox that variability in scolopendromorph segmentation is a remarkable discovery, and yet S. duplicata and S. bahiensis are so similar in other respects and their sister group relationship so highly corroborated that generic separation is unwarranted. The discovery of segmental polymorphism in S. duplicata suggests that Schileyko (2006) was correct in interpreting S. bahiensis as also polymorphic. More evidence is now available demonstrating that segmental polymorphism is indeed possible in a scolopendromorph species and more specifically is known within this restricted clade.

Because the genitalia are concealed beneath the genital sternite, we have not amassed an adequate sample size to determine how segmental polymorphism correlates with sex. Dissected individuals with 39 segments include ones with spermatophores, confirming that at least some are males. Spermatophores are lacking in dissected 43-segmented specimens, but we have not ascertained whether they are invariably females. Even if some exceptions are eventually found to the possible rule that males in this species have 39 segments and females have 43, S. duplicata is likely to represent the first example of sexual dimorphism in segment number in non-geophilomorph centipedes.

Most specimens of S. duplicata were found in pitfall traps for reptiles and amphibians in the dry, xeric “cerrado”, a vegetation typical of central Brazil. All specimens were collected before flooding of the Luis Eduardo Magalhães hydroelectric power plant, in the Tocantins River, and the type locality is now under water. Vegetation around the lake is the same as that at the now submerged type locality. An expedition organized by the first author in June 2007 failed to discover any specimens of S. duplicata , even though a forest patch 500 m away from the type locality was sampled. Thus, the original habitat of this species may have been impacted by the flooding of the hydroelectric power plant, and further expeditions are needed to seek additional individuals of this remarkable Brazilian species. Also noteworthy is the fact that a closely related species, Rhoda spinifer ( Kraepelin, 1903) , occurs sympatrically on the left bank of the Tocantins River.

Figures

FIGURE 1. Scolopendropsis duplicata n. sp. Paratype MNRJ 15306. Lateral view. Scale bar, 1 mm.

FIGURES 2 – 5. Scolopendropsis duplicata n. sp. Holotype MNRJ 15258. 2, forcipulae; 3, tooth plates (tp) and processes of trochanteroprefemora (pr) of forcipulae; 4, sternite and coxopleurae of segment 43; 5, segment 43 and ultimate legs, dorsal view. Scale bars, 0.5 mm. Additional abbreviations: dp, distomedial prefemoral process; ld, longitudinal depression on femur; ls, longitudinal sulcus delimiting pore field; sp, spine at posterior border of coxopleuron.

FIGURES 6 – 11. Scolopendropsis duplicata n. sp. Paratype MNRJ 2392. 6, cephalic plate and T 1; 7, forcipular coxosternum; 8, segment 43 and ultimate legs, dorsal view; 9, segment 43 and ultimate legs, ventral view; 10, ultimate legs, dorsal view; 11, ultimate legs, ventral view. Scale bars, 1 mm.

FIGURES 12 – 14. Scolopendropsis duplicata n. sp. Paratype MNRJ 2392. 12, trunk segments 3 – 5, lateral view; 13, trunk segments 7 – 12, dorsal view; 14, trunk segments 7 – 11, ventral view. Scale bars, 1 mm.

FIGURE 15. South America, with dot indicating type locality of Scolopendropsis duplicata n. sp. (Brazil: Tocantins State: Porto Nacional). The distribution of S. bahiensis (Brandt, 1841) is indicated by black squares.