Varelasminthurus , Silva, Diego Dias Da, Palacios-Vargas, José G. & Bellini, Bruno Cavalcante, 2015
Silva, Diego Dias Da, Palacios-Vargas, José G. & Bellini, Bruno Cavalcante, 2015, A new genus and a new species of Sminthuridae (Collembola: Symphypleona) from Atlantic Forest of Brazil, Zootaxa 3990 (3), pp. 410-418: 411-417
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Varelasminthurus gen. nov.
Diagnosis. Head and body presenting only smooth and thin sharp chaetae; 8 + 8 subequal eyes lenses ( Figs 1 CView FIGURE 1 A – H and 2View FIGURES 2 – 4); head frontal area with row C with 2 + 2 chaetae ( Fig. 2View FIGURES 2 – 4); tibiotarsi bearing only normal chaetae and 1 oval organ each ( Figs 5–8View FIGURES 5 – 11); pretarsal chaeta present only anteriorly ( Figs 9–11View FIGURES 5 – 11); unguis with tunica and cuticular granulation, one anterior external deep cavity, one posterior external crest with 6 teeth and with finely serrated inner edge ( Figs 1 FView FIGURE 1 A – H and 9–11View FIGURES 5 – 11); unguiculi shorter than unguis, with external cavity and microserrations; tenent hairs absent ( Figs 9– 11View FIGURES 5 – 11); rami of tenaculum bidentate, with basal appendix ( Fig. 1 GView FIGURE 1 A – H); trochanter III with 2 trochanteral organs ( Fig. 1 DView FIGURE 1 A – H) and 1 posterior spine; anterior dental chaetae formula 3, 2, 1 … 1 ( Fig. 12View FIGURES 12 – 16); mucronal edges almost smooth, with proximal heel-like structure developed and striated ( Fig. 1 HView FIGURE 1 A – H); trichobothrium B short, trichobothria C and D longer than A ( Fig. 14View FIGURES 12 – 16); female with some thicker circumanal chaetae, subanal appendage smooth and elbowed ( Fig. 15View FIGURES 12 – 16).
Type species. Varelasminthurus potiguarus gen. nov. sp. nov.
Etymology. The genus is named after deceased Prof. Adalberto Antônio Varela Freire, for his important contributions to the University of Rio Grande do Norte, Brazil.
Remarks. The interpretation of Betsch (1980) and Richards (1968) were considered for the tenaculum rami, which recognizes the basal tooth as coming from the basal appendix present in other groups of Symphypleona. In the other hand, the analysis of Bretfeld (1999) suggests tridentate tenaculum as a synapomorphy for Sminthuroidea, which also fits the morphology seen in Varelasminthurus gen. nov. with rami bidentate and basal appendix projected laterally.
The new genus clearly belongs to the family Sminthuridae due to the position of thricobothria A, B and C; Ant. IV longer than Ant. III and elbowed between these two segments; 8 + 8 eye lenses; and the presence of a long ventral tube ( Bretfeld 1999). However, it presents a set of morphological features which obscure its position within one of the two subfamilies of this family, sensu Betsch (1980). It differs from most other Sminthuridae by the presence of only one pretarsal chaeta (instead of two) and smooth mucronal edges (instead of serrated). Indeed, the study under SEM revealed there is a kind of vestigial serrated area in inner edge of mucro ( Fig. 1 GView FIGURE 1 A – H), which may have been derived from the original serrated condition of other Sminthuridae .
Even though the particular morphology of Varelasminthurus gen. nov., here we consider this new genus within Sminthurinae sensu stricto because its antennae are relatively long, the Ant. IV has well defined subsegments, there is no neosminthuroid chaetae, it has a long anterior dental formula, and mucro is not sharp or notched. Also, all other Sminthuridae genera presenting unguis with cavity belong to this subfamily.
Due to unguis morphology, Varelasminthurus gen. nov. is probably close related to other four genera of Sminthurinae ( Gisinurus, Songhaica, Dietersminthurus and Soqotrasminthurus ), but can be readily separated from them by the lack of posterior pretarsal chaetae. Also, the following combination of characters is only seen in the new genus: 1 + 1 tenaculum chaetae; only 7 anterior dental chaetae; smooth mucronal edges; and absence of neosminthuroid chaetae (a detailed comparison among cited genera provided in Table 1). Finally, another important diagnostic feature of Varelasminthurus gen. nov. is the peculiar chaetotaxy of line C on cephalic frontal area, with 2 + 2 chaetae and without axial substitution, a disposition of chaetae not seen in any other genera of the family ( Betsch & Waller 1994).
Type material. Holotype: female on slide, Brazil, Rio Grande do Norte State, Tibau do Sul, Parque Estadual Mata de Pipa, pitfall traps, 8.ii. 2013. Silva, D. coll. Paratypes: 1 allotype and other male on same slide as holotype; 7 females in different slides, same data as holotype. Type material deposited at Collembola Collection of DBEZ / UFRN, number 1002.
Description. Habitus sminthuroid ( Figs 1 A –BView FIGURE 1 A – H). Holotype female total length (head+body) 0.82 mm; body 0.71 mm; longitudinal head 0.31 mm; antenna 0.64 mm; furca 0.46 mm. Allotype male total length (head+body) 0.64 mm; body 0.53 mm; longitudinal head 0.23 mm; antenna 0.57 mm, furca 0.37 mm.
Color in alcohol. Body pale yellow with light blue pigment covering clypeal region of head, antennae and distal legs, and dark pigment covering eye patches; dorsal surface of body with a characteristic pattern of black and brown spots ( Figs 1 A –BView FIGURE 1 A – H).
Head. 8 + 8 eyes, eye patches with one interocular acuminated chaeta ( Fig. 2View FIGURES 2 – 4); labral chaetotaxy: a: 4; m: 5; p: 5; pl: 4; clypeal, interantennal and frontal area of head with acuminate chaetae, arranged as in Fig. 2View FIGURES 2 – 4; mandibles and maxillae subequal in size.
Antennae ( Fig. 3View FIGURES 2 – 4). Holotype (female) antennal segmentation ratio: 1: 1.42; 4.01; 9.53, allotype (male): 1: 1.51; 5.21; 8.53. Ant. I with 5 chaetae; Ant. II with 16 chaetae; Ant. III with 37-40 chaetae, apical organ with 2 sense rods within invagination, Aai as a microsensillum ( Fig. 4View FIGURES 2 – 4); Ant IV with 11 subsegments; without apical bulb.
Leg I ( Fig. 5View FIGURES 5 – 11). Coxa with 1 chaeta; trochanter with 2 chaetae in proximal and 2 in medial position; femur with 15 chaetae; tibiotarsus with smooth and acuminated chaetae; primary chaetae missing: Iai, IIai, Iae, Ip, secondary chaetae present: 3 ai, 4 ai 1, Vai, FSai, 3 a, 4 a 1, FSa, 2 ae, 3 ae, 4 ae 1, FSe↑, FSpe↓, 3 p, 4 p1, 3pi, 4 pi 1, Vpi, FSpi, oval organ O 4 pe present ( Fig. 6View FIGURES 5 – 11); anterior pretarsal chaeta present; unguis with tunica and cuticular granulation, one anterior external deep cavity, one posterior external crest with 6 teeth, finely serrated (with 10–13 teeth) in inner side ( Fig. 9View FIGURES 5 – 11); unguiculus shorter than unguis, with one external cavity and finely serrated (with 4–5 teeth); ratio unguis: unguiculus 1: 0.7.
Leg II ( Fig. 7View FIGURES 5 – 11). Coxa with 2 chaetae; trochanter with 2 chaetae in proximal, 2 in medial and 1 in distal position; femur with 15 chaetae; tibiotarsus with smooth and acuminated chaetae, primary chaetae missing: Iai, IIai, Iae, Ip, Vp, secondary chaeta present: 3 ai, 4 ai 1, Vai, FSai, 3 a, 4 a 1, FSa, 2 ae, 3 ae, 4 ae 1, FSe↑, FSpe↓, 3 p, 4 p1, 3pi, 4 pi 1, Vpi, FSpi, oval organ O 4 pe present; anterior pretarsal chaeta present; unguis and unguiculus with similar morphology seen in leg I ( Fig. 10View FIGURES 5 – 11); ratio unguis: unguiculus 1: 0.7.
Leg III ( Fig. 8View FIGURES 5 – 11). Coxa with 4 chaetae; trochanter with 5 chaetae, 2 trochanteral organs ( Fig. 1 DView FIGURE 1 A – H) and one thick acuminated spine on posterior side ( Fig. 8View FIGURES 5 – 11); femur with 16 chaetae; tibiotarsus with smooth and acuminated chaetae, primary chaetae missing: Iai, IIai, Iae, Ip, Vp, IIpi, secondary chaetae present: 3 ai, 4 ai1, 4ai 2, Vai, FSai, 2 a, 3 a, 4 a 1, FSa, 2 ae, 3 ae, 4 ae 1, FSe↑, FSpe↓, 2 p, 3 p, 4 p1, 3pi, 4 pi 1, Vpi, FSpi, 3 i, 4 i 1, oval organ O 4 pe present; anterior pretarsal chaeta present ( Fig. 1 EView FIGURE 1 A – H); unguis and unguiculus with similar morphology seen in leg I ( Fig. 1 E –FView FIGURE 1 A – H and 11View FIGURES 5 – 11); ratio unguis: unguiculus 1: 0.7.
Ventral tube with smooth sacs, lateral papillae and two pairs of chaetae ( Fig. 13View FIGURES 12 – 16). Each ramus of tenaculum bidentate, with basal appendix; corpus with 2 apical chaetae ( Fig. 1 GView FIGURE 1 A – H). Furca: manubrium dorsally with 6 + 6 posterior chaetae; dorsal dens chaetotaxy as shown in Figure 12View FIGURES 12 – 16; anterior dental chaetae formula 3, 2, 1 … 1, chaetae Vpi and VIpi thicker than others; mucro spatulate; mucronal edges smooth, with proximal heel-like structure developed and striated ( Fig. 1 HView FIGURE 1 A – H); ratio mucro: dens: manubrium 1: 2.4; 1.9.
Great abdomen. Dorsal chaetae smooth and acuminate; thorax without any visible segmentation; thoracic chaetotaxy as in Figure 14View FIGURES 12 – 16; trichobothria A/B/C in inverted pattern sensu Richards (1968), almost in line ( Fig. 14View FIGURES 12 – 16); trichobothria B shorter than C.
Small abdomen. Female chaetotaxy as shown in Figure 15View FIGURES 12 – 16; trichobothria D present and very long; 2 + 2 oval organs present; chaetae ms 1, ms 3, mps 1, mps 3, mpi 1 and mpi 2 slightly thicker than others; subanal appendage smooth, acuminated and apically turned toward anal opening; male chaetotaxy and genital opening as in Figure 16View FIGURES 12 – 16.
Etymology. “Potiguar” refers to the native indigenes from the type locality, Rio Grande do Norte State, Brazil.
Distribution and Habitat. The specimens were collected during the dry season from leaf litter in two Atlantic Forest remnants, at coordinates: S 06° 22 ' 10 " W 35 °00' 28 " and S 06° 14 ' 56.11 " W 35 ° 3 ' 29.01 ", from Rio Grande do Norte State, Northeastern Region of Brazil; Good’s biogeographic zone 27 ( Good 1974).
Remarks. Specimens of Varelasminthurus potiguarus gen. nov. sp. nov. run in Gisinurus Dallai, 1970 , following the key to genera proposed by Bretfeld (1999, page: 172). In fact there are many resemblances between both taxa, some of them presented in Table 1. The most notable feature shared by them is the peculiar shape of unguis, with a cavity and with some internal serration. However the genera differ in the shape of this structure. Also in Gisinurus the antennae are as long as body (versus shorter than body); Ant. IV bears 13 intermediate subsegments (versus 9); the posterior dental chaetae formulae is 3,2,2,2,2,1, 1 (versus 3,2, 1 … 1); and the mucronal edges are coarsely serrate (versus smooth).
The unguis shape and other morphological features (especially chaetotaxy) suggest phylogenetic proximity of Varelasminthurus gen. nov. and Gisinurus, Songhaica, Dietersminthurus and Soqotrasminthurus (comparison in Table 1). However, only a detailed phylogenetic analysis can provide a clear understating of the validity of these characters in evolutional approaches, and the relations of these genera among each other and among the Sminthurinae .
The discovery of a new genus of Sminthurinae in the Atlantic Forest, within an area never studied before and clearly disturbed by human colonization points out how little is known about the Brazilian fauna and how potentially rich in number of collembolan taxa the Neotropical Region is. Even though the type locality of Varelasminthurus gen. nov., “Parque Estadual Mata de Pipa”, is an small area of environmental protection, it is located in Pipa Beach, Tibau do Sul, a highly visited region due to international tourism. This contrasting conditions show how urgent is the necessity to unveil the Brazilian fauna and to create better policies to protect it.
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