Bioacoustics of Gaucha ibirapemussu

Description. Male holotype (MPEG 0005). Coloration in 70% ethanol. Prosoma: propeltidium whitish yellow, with central portion pale yellow larger than ocular tubercle in the median region, whitish yellow in the border of the lateral lobes. Ocular tubercle with a narrow longitudinal whitish yellow stripe between the eyes and a black ring surrounding each eye. Peltidium whitish yellow and parapeltidium white. Mesopeltidium and metapeltidium with a brown central stripe and lateral white stripes, each stripe a third of the tergite width ( Fig. 27 ). Chelicerae pale yellow, with three longitudinal, distally fused, white stripes on the ectal face. Pedipalpi and legs pale yellow, with slightly darker ends. Malleollus of the trochanter II grey with large brown spots on the enlarged portion ( Figs. 7 , 17 ) and the remaining malleollus whitish. Opisthosoma: lateral borders of the tergites white, with a wide dark brown stripe on the central half, which is darker near the posterior border of the tergites. White area of the tergites covered by brown bifid setae with brown sockets and scattered brown marks. Pleurites white on the ventral portion, dorsal portion brown. Pale brown translucent bifid bristles in the white portion have sockets shaped into brown spots. Sternites white, lateral borders brownish. Anal segment almost totally brown. First to fourth postspiracular sternites with brown spots which include the sockets of some bifid bristles. All covering bristles and bifid bristles are translucent yellowish. Morphology and chaetotaxy. Prosoma: propeltidium wider than long (Table 1) with some scattered bifid setae, and separated from lateral lobes by dorsal grooves. Ocular tubercle prominent with one transversal row of anteriorly oriented bifid setae and two longitudinal rows between the eyes. Distance between two eyes about 1.5 times eye diameter. Peltidium narrow, with a transverse row of different sized bifid setae. Parapeltidium smooth. Mesopeltidium trapezoidal-shaped, 2.5 times wider than long, with one row of bifid setae on posterior margin. Metapeltidium 1.6 times wider than long. Chelicerae ( Figures 9–10 ; 13–15): stridulatory apparatus on mesal face with seven parallel grooves ( Fig. 13–14 ). Ectal face with several short bristles and setae, both bifid and acuminate. Movable finger with one anterior, one intermediate, and one principal tooth, graded in size from distal to proximal II, III and I ( Figs. 9– 10 , 14 ). Fixed finger with two anterior and two principal teeth graded in size from distal to proximal II, I, IV, III; five ectal fondal teeth, graded in size: I, III, V, II, IV and three mesal fondal teeth, graded in size from distal to proximal I, II, III, the first distal separated from the others by a diastema ( Figs. 9–10 , 14–15 ). Fixed finger bears, centrally on its dorsal face, one very long seta (about the length of femur III) with a prominent socket ( Fig. 14 ). Flagellum ( Figs. 9–10 , 13–16 ): a thin translucent drop-shaped vesicle, laterally flattened as in other mummuciids; with a long longitudinal ectal opening. The attachment of the flagellum is a sclerotized ring placed posteriorly on its ectal face; and its distal portion is irregularly brush-like ( Fig. 16 ). Pedipalp: tarsi immovable, without spines, densely covered by different sized bifid bristles and several short acuminate bristles, with some very long setae in tibiae and femur (about 1.1 times pedipalpal tibial length). Legs: covered by several different sized bifid bristles and some bifid setae (see Fig. 26 ). Some very long setae on the dorsal surface (about 2.6 times the basitarsus IV length). Leg I: thin, without claws and spines. Legs II and III: tibiae with a distal pair of ventral spines; basitarsus with three retrolateral spines and 1.1.2 ventral spines; telotarsi two-segmented with 1.2.2/2.2 ventral spines ( Fig. 5 ). Leg IV: tibia with a distal pair of ventral spines; basitarsus with 1.1.1.2 ventral spines; telotarsi three-segmented, with 2.2.2/2/2.2 ventral spines ( Fig. 6 ). The three segments of the telotarsi IV with some ventral spines can be seen in Figure 26 . Malleoli as in Figures 7 and 17 . Opisthosoma: tergites wider than long ( Figs. 2 , 27 ), with rounded borders, covered by bifid setae and bifid bristles. Genital operculum with central longitudinal opening. Sternites wider than long, densely covered by bifid bristles. Posterior border of 2nd post-spiracular sternite with a row of about 50 ctenidia, more rigid and slightly longer than the bifid bristles in sternites ( Fig. 24 ). Two post-spiracular sternites with several long and acuminate bristles, 1.5 times longer than other sternite bristles. Pleurites as in Figure 3 . Measurements: see Table 1. Female paratype (MPEG 0010). As in male, except for the following features. Morphology and chaetotaxy . Prosoma: Eyes separated by 1.25 times their diameter. Mesopeltidium twice wider than long. Metapeltidium 1.7 times wider than long. Chelicerae ( Figs. 11–12 , 19–22 ): Movable finger with one anterior, one intermediate, and one principal tooth, graded in size from distal to proximal II, III, I ( Figs. 11–12 , 20, 22 ). Fixed finger with two anterior and two principal teeth graded in size from distal to proximal II, I, IV, III; five ectal fondal teeth, graded in size: I, III, V, II, IV ( Figs. 11–12 , 20–21 ). Three (as in males; Fig. 12 ) or two mesal fondal teeth separated by a diastema. Opisthosoma: sternites densely and uniformly covered by bifid bristles, without conspicuous sockets ( Fig. 24 ). Genital operculum ( Fig. 23 ) prominent, round-bordered, with central longitudinal opening. Pleurites as in Figure 4 . Measurements: see Table 1. Intraspecific variation. The white area of the tergites of most of the male paratypes lack the brown scattered marks present on the holotype , probably owing to degradations of the tissue caused by poor preservation of the specimen. The female used for SEM pictures had only four ectal fondal teeth, while the remaining female paratypes have five ectal fondal teeth. TABLE 1. Morphometric characters of Mummucia ibirapemussu n. sp. . Measurements are in millimeters (except propeltidium length/width ratio).