Pseudonannolene canastra Gallo & Bichuette, 2020

Gallo, Jessica Scaglione & Bichuette, Maria Elina, 2020, Pseudonannolene canastra sp. nov. (Diplopoda, Spirostreptida) - a new troglobitic millipede from the southwestern state of Minas Gerais, Brazil, Subterranean Biology 35, pp. 33-47 : 33

Pseudonannolene canastra Gallo & Bichuette sp. nov. Figs 3 , 4 , 5 , 6

Materials Examined.

Holotype: Brazil ● ♂; Gruta do Tesouro cave, São Roque de Minas, Minas Gerais, Brazil; 26.IX.2017; Fernandes CS, Gallo JS, von Schimonsky DM leg.; LES15282. Paratypes: Brazil ● 3♀ (two adults and one juvenile); same locality; 15.VIII.2014; by Bolfarini MP and Zepon T leg.; LES15283 ● 1♂ 2♀ (juveniles); same locality, data and collectors as for holotype; LES15284.

Etymology.

The name " canastra " is in allusion to a kind of an ancient chest. This name is also used to refer to the region where the Gruta do Tesouro cave is locate, Serra da Canastra, that is characterized by a chain of mountais shaped like canastra . Here, we use Canastra as a noun in apposition.

Diagnosis.

Pseudonannolene canastra sp. nov. has wide coxa of gonopods resembling those of P. microzoporus Mauriès, 1987, while its solenomerite shape is similar to that of P. maritima Schubart, 1948. However, P. canastra sp. nov. differs from these species in characteristics such as the round shape of the gonopod coxa, the telopodite with a wide base, reduced dentiform processes, different number of spines in the inner part of the coxa (three in the left coxa and four in the right coxa in caudal view), and a divergent pre-femoral process with reduced and flaky pre-femur prolongations. Externally, these species are quite distinct. Pseudonannolene microzoporus , considered troglophilic, has a uniform light brown pigmentation ( Mauriès 1987) while P. maritima , recorded only in epigean environment, is brownish or brownish-black, and the head and the first two segments are always lighter, with nearly yellowish color (Schubart 1948).

Holotype description

(male). Body length 36.26 mm, ring diameter 1.98 mm, with 59 rings (counting the collum and the telson) (Table 2 ) without anterior or posterior tapering of the body; the prozonite is shorter (0.04 mm) than the metazonite (0.33 mm); metazonite has thin striae in the ventrolateral portion of all the rings; the gnathochilarium is typical of the genus Pseudonannolene with longitudinally divided promentum ( Enghoff et al. 2015); head has a posterior suture from the collum to the line of the eyes.

Pigmentation: In life, the pigmentation of the head, antenna, legs, and body rings is light yellow with no difference in the coloration of the prozonite and metazonite; the ommatidia and ozopores are reddish (Figure 4 ). Pigmentation in 70 % ethanol: The head, rings, and legs darken after fixation (brown coloration), the eyes become brown like the head by losing the reddish coloration. Only the antenna maintained the original color (Figure 5 ).

Antenna: Slender (2.3 mm length), covered by fine white setae almost transparent, with some setae larger than others; antennomeres longer than width; the third antennomere is the largest; the sixth antennomere is the widest with a round shape and four sensory cones in the end. The antenna length ratio to the head 1.7 (from the beginning of the suture from labrum) while diameter ratio 1.17.

Eyes: oval-shaped lateral eyes area 0.09 mm², lengths 0.44 mm and 0.43 mm (right and left, respectively); width 0.3 mm; twenty-two ommatidia ( Richter et al. 2010) on the right side and 24 ommatidia on the left side (Table 2 ).

Gonopodium (Figure 6A-D ): The coxa is round, 0.45 mm long and 0.34 mm wide; the dentiform processes reduced in number and size (Figure 3A ) with three internal spines (or processes, Iniesta and Ferreira 2013) on the left side and four on the right side (Figure 3B , one of the spines is not visible in the figure); the solenomerite end rounded and scaly (Figure 3C ) (0.24 mm long, 0.12 mm wide), corresponding to 0.54 and 0.35 of the coxa length and width, respectively; the telopodite smaller than the solenomerite in length (0.122 mm) but larger in width (0.139 mm) and corresponds to 0.51 and 1.17 of the solenomerite length and width respectively; it measures 0.15 mm in length and has a wide base (with thin setae) that narrows gradually (Figure 3D ).

First pair of legs (Figure 6 E-F ): coxa longer than wide (0.58 mm length, 0.28 mm width); setae are concentrated in the distal region of the coxa and few setae are found in the proximal region (Figure 6 D ); the coxa base is slightly narrow; the pre-femur wider (0.18 mm) than length (0.15 mm); strong setae concentrate on the inner side of the pre-femur; pre-femoral process divergent, as small, rounded and scaly extensions in the base of the pre-femur (Figure 3E ); femur (0.27 mm), post-femur (0.15 mm), tibia (0.13 mm), and tarsus (0.22 mm) with thick, elongated setae; the tarsal claw is 0.15 mm long.

Walking legs (mean values): total length 1.79 mm; coxa (0.21 mm), pre-femur (0.26 mm), femur (0.33 mm), post-femur (0.27 mm); tibia (0.23 mm); tarsus (0.34 mm) with setae on the inner side; all podomeres longer than wide; the tarsal claw 0.14 mm length.

Telson: The anal valve has 2 + 2 setae, no sulcus; the pre-anal sclerite does not extend beyond the anal valve; the subanal plate lacks projection (Table 2 ).

Distribution.

An endemic species of Gruta do Tesouro cave, São Roque de Minas, Minas Gerais, Brazil.

Observations.

The juveniles, i.e. individuals that did not present pairs of legs in all segments of the body ( Makarov 2015), show symmetry in the number of ommatidia; eyes are more triangular than oval. The other characteristics of the body are the same as those of the adults. For this species, the females are larger than the males.

Figures

Figure 3. Gonopod an Fist pair of holotype legs by Scannig Electron Microscope (SEM) A caudal view of gonopod B detail of the internal spines and dentiform process C detail of solenomerite e telopodite D caudal view of male first pair of legs E detail of pre-femural process. Photo: LBR Fernandes.

Figure 4. Pseudonannolene canastra sp. nov. live specimens A, B specimens in natural environment C at laboratory, specimen darkened after contact with artificial light. Photos: A DM von Schimonsky and C DJ Tomaz.

Figure 5. Pseudonannolene canastra sp. nov. in left lateral view, preserved in ethanol 70 %. Photo: LBR Fernandes.

Figure 6. Gonopods and first pair of legs of Pseudonannolene canastra sp. nov. A, B scheme and stereomicroscopic photograph of the gonopods in caudal view C, D scheme and photograph in stereomicroscope of the gonopods in oral view E, F schematic and stereomicroscopic photograph of the first pair of legs in oral view. Photo: LBR Fernandes.