Stemmiulus brasiliensis Iniesta & Ferreira

Iniesta, Luiz Felipe Moretti & Ferreira, Rodrigo Lopes, 2015, Stemmiulus brasiliensis n. sp., a new species of millipede from Brazilian iron ore caves (Diplopoda: Stemmiulida: Stemmiulidae), Zootaxa 3964 (5), pp. 546-552 : 548-550

Stemmiulus brasiliensis Iniesta & Ferreira , sp. nov.

( Figs 2–5 )

TYpe. Holotype male ( ISLA 5681), SL22 cave (Serra Leste 5°57’39.14’’S, 49°38’03.51’’N), Curionópolis/PA, Brazil, 2010, leg. M. P. Oliveira.

Paratypes: 2 males ( ISLA 3701, 5682), SL51 and SL22 caves, Curionópolis/PA, Brazil, 2010; 2 females ( ISLA 5683), SL22 cave, Curionópolis/PA, Brazil, 2010, all leg. M. P. Oliveira.

Name. To emphasize Brazil, the terra typica.

Comparative diagnosis. Stemmiulus brasiliensis sp. nov. is distinguished from the other Brazilian species by the peculiar cephalic chaetotaxy pattern of the male and the different gonopod structure (cf. Mauriès 1984). The species S. adisi , S. amazonicus and S. wellingtoni all show complex gonopod conformations compared to S. brasiliensis sp. nov. The differences are especially clear in angiocoxite (Ag) and colpocoxite (K) structure. The species S. wellingtoni has a trifurcate Ag tip while the latter in the other species is either bifid or, like in S. brasiliensis sp. nov., unipartite. In S. adisi , the tip of Ag is wider distally and shortened laterally while S. amazonicus has a diagonal/digitiform tip and a wider apex. In S. brasiliensis sp. nov., Ag is highly distinctive, being tiny and devoid of a differentiated tip. K in the new species is also different, elongated, irregular in shape and membranous at apex, versus wide and with some apical projections in S. adisi , rounded and thin in S. amazonicus or thin and more strongly curved mesad in S. wellingtoni .

Measurements. Length from 8.33 to 12.15 mm; maximum midbody diameter between 0.68 to 0.92 mm; body with 35–41 rings, plus 1–2 apodous before telson.

Description of adults. General characteristics: Head and body brownish. Head with different chaetotaxy patterns in male ( Fig. 3 A) and female ( Fig. 3 B). One large ocellus on each side of head. In length, antennomere 1 <3 = 4 ≈ 5 = 6 <2. Ozopores located dorsolaterally and starting with fifth body ring. Lateral region of tergites with parallel striations, including above ozopore. Telson with 3+3 evident spinnerets. Gnatochilarium rounded in male: stipes enlarged and curved, mentum triangular, lamellae linguales striated, with 1+1 setae; females with a square gnatochilarium: stipes straight, mentum subtriangular, lamellae linguales non-striate. Trunk with a dorsal axial suture and line; a clear lateral line on each side.

Male characteristics: First to third pairs of legs modified. Legs 1 with enlarged coxae, these apparently fused to prefemur, also beset with long ventral setae; femur elongated, with short ventral setae and one especially long seta; postfemur and tibia similar, with long ventral setae; tarsus elongated, with a ventral row of short setae reaching the claw. Legs 2 ( Fig. 4 A, B) with a coxosternal lobe (Lcs) beset with short setae; Lcs rounded and supporting some long distal setae in oral view; telopodite (1°, 2° Tp) elongated and digitiform, beset with short setae; coxosternal process (Pcs) acute and elongated. Legs 3 ( Fig. 4 C, D) with a non-enlarged Cx; Pf, F, Psf and Tb with long ventral setae and square in shape; T with long dorsal setae, nine ventral spatulate setae (Ss) and four long setae around the tarsal claw. No paragonopods (ninth pair of leg) were found, perhaps vestigial (reduced) or non-existent in this species. Gonopods elongated ( Fig. 5 A, B), with basal section wider than distal one; Cx fused to sternum, with two large, rounded, gonopodal processes. Distal region with two well-developed extensions: a long and slender angiocoxite (Ag) resembling a thin shell adhered to colpocoxite (K) and carrying short setae in distal portion. K with curved setae in the latter portion; tip with a membranous area (Ma) surrounding the end of a seminal groove (Sg). Sg visible at K beginning with junction of gonopodal segments. Both Ag and K with thick edges.

Notes. The new species can be recognized, in males, by a slight difference in head chaetotaxy. In the Brazilian species, the first row of setae is close to the occipital suture, the row being composed of 4 setae, as observed in S. brasiliensis sp. nov., S. amazonicus and S. wellingtoni , or 2 setae (maybe 2+2 dislocated), as in S. adisi (cf. Mauriés 1984). Furthermore, there are other, straight or diagonal rows. These setae are arranged mainly near the suture on the clypeus, on the frons and labrum ( Silvestri 1916; Mauriès 1984).

As regards the gonopod, the genus Stemmiulus shows remarkable variation between the species, mainly in Ag and K structure ( Chamberlin 1952; Loomis 1964; Hoffman 1977; Mauriés 1979, 1989; Mauriès & Golovatch 2006; Mauriès et al. 2010). According to Mauriès (1989), most of the American species have a distolaterally expanded Ag. The species S. amazonicus , S. wellingtoni and S. adisi share this trait ( Mauriés 1984), but the new species has no evident expansion. The Ag structure in S. brasiliensis sp. nov. seems to serve as a lateral shield to K.

In the Brazilian species of Stemmiulus , males generally show no meaningful differences in leg structure, although there is some variation in the second and third pairs. All Brazilian species are similar in leg 1 conformation. The second pair is the most strongly reduced. In S. brasiliensis sp. nov., Cx is very different from that in the other species. Both S. adisi and S. amazonicus show a kind of shoulder while such a structure is absent from S. brasiliensis sp. nov. In all Brazilian species, Cx is large, yet without Lcs in S. adisi , S. amazonicus and S. wellingtoni , while Tp digitiform. However, its outline slightly varies between the species. In leg 3 structure, S. brasiliensis sp. nov. is notably different, mainly in Pf and F which are not enlarged.

The size and number of body segments can vary between species. In the Brazilian species, this number ranges from 42 to 53 ( Mauriés 1984). In S. brasiliensis sp. nov., the body is with 35–41 rings. This variation is common within the order, with extremes found in S temmiulus annulatus Silvestri, 1916 (38 segments, regardless of the new species described herein) and S. diversicolor Loomis, 1964 (54 segments) ( Silvestri 1916; Loomis 1964). Although there are few studies concerning stemmiulidan ontogeny, the development can be recognized as euanamorphotic ( Mauriés 1984; Enghoff et al. 1993).

Figures

FIGURE 2. Stemmiulus brasiliensis sp. nov., A) live paratype female; B) anterior part of body, a fixed paratype female.

FIGURE 3. Schematic drawings of head of Stemmiulus brasiliensis sp. nov. A) Male paratype; B) Female paratype.

FIGURE 4. Microscopic images of male paratype of Stemmiulus brasiliensis sp. nov. (ISLA 3701). A) Second pair of legs in oral view and B) Second pair of legs in caudal view; C) Third pair of legs; D) Detail of tarsus of third pair. Scale bar: 0.1 mm. Abbreviations: Cx = coxae; Pf = prefemur; F = femur; Psf = postfemur; Tb = tibia; T = tarsus; Ss = spatulate setae; Cs = coxosternite; Lcs = coxosternal lobe; Pcs = coxosternal process; 1 ° Tp = first telopoditomere; 2 ° Tp = second telopoditomere. Scale bar: 0.1 mm. The roman numbers indicate the sequence of spatulate setae.

FIGURE 5. Microscopic images of male paratype of Stemmiulus brasiliensis sp. nov. (ISLA 3701). A) and B) gonopod. Abbreviations: Sg = seminal groove; Ag = angiocoxite; K = colpocoxite; Ma = Membranous area. Scale bar: 0.5 mm.