Bioacoustics of Zebragryllus aphonus

Diagnosis Specimens dark ( Figs 1A–B , 4A–B ). Tympana reduced or absent ( Fig. 2A–F ). All femora entirely ochre, without the ‘zebra’ pattern ( Fig. 2A–C, G–K ). Males dorsally with head, pronotum, tegmina, and first abdominal tergite black ( Fig. 1A–E ); without stridulatory apparatus ( Fig. 1E ). Comparatively, all the other known species of Zebragryllus are easily distinguished for having stridulatory apparatus on the male tegmina. Male genitalia: pseudepiphallic median lophi elongated, conspicuously produced hind- and upwards, very narrow, and apically acute, ventrally with a sharp keel. Pseudepiphallic lateral lophi acute. Pseudepiphallic paramere surpassing the lateral lophi; in ventral view, slightly arched. Ectophallic fold very thin, not reaching the level of the pseudepiphallic paramere apex ( Fig. 3A–D ). Female with the black coloration extending till the second abdominal tergite ( Fig. 4A–D ); remaining tergites dark brown; ovipositor straight and almost as long as the hind femora ( Fig. 4A, H–I ). Female genitalia: copulatory papilla with posterior margin of dorsal surface widely concave, and the anterior margin with medial process emarginated, flanking the spermatheca duct ( Fig. 4L ); ventral surface acute anteriorly ( Fig. 4M ); in lateral view, posterior portion taller than anterior one ( Fig. 4N ).

Description Male COLORATION . Specimens very dark ( Figs 1A–E , 4A–D ). Cephalic capsule, pronotum, and tegmina black ( Fig. 1A–E ). Abdominal tergites dark brown and posteriorly black ( Figs 1B , 4B ), each with midline of black punctuations extending from lateral to the dorsolateral portion. Some whitish spots sometimes present on head dorsum ( Fig. 1B ). Eyes black, ocelli whitish. Scapus and pedicel yellowish, flagellomeres brown. Clypeus and labrum dark brown. Mandibles proximally black and mediodistally reddish-brown ( Fig. 1C ). Maxillary palpi dark brown, except for whitish ventral areas on mediodistal portion and apex ( Fig. 1G ). Two first segments of labial palpi dark brown, and last ochre, with tip and ventrodistal portion whitish. Femora entirely ochre, and tibiae dark brown ( Fig. 2A–C, G–K ) – fore tibia with two inner whitish circular areas on most proximal portion ( Fig. 2G ). Ventral sclerites of thorax and abdomen ochre, except for brown sternite 8 and male subgenital plate, which are brown ( Fig. 1F, I ). HEAD . In frontal view ( Fig. 1C ), semicircular, almost as wide as high, with eyes slightly produced laterally; ocelli circular and almost aligned to eyes dorsal margin – median ocellus slightly lower. Antennal pits located low on frons, near epistomal suture, and almost on same level as eyes’ most ventral border (these last also close to subgenal suture). Clypeus dorsal area notably separated from ventral area by clypeal suture. Ventral area conspicuously constricted laterally, almost half as wide as dorsal area, with median white stripe and transverse dark line on sides. Labrum circular, with pair of incomplete transverse mediolateral sutures. First two segments of maxillary palpi subequal in length; third and fourth as long as first and second together; fifth longer than any other segment, ventrally truncated on mediodistal area ( Fig. 1G ). In lateral view ( Fig. 1D ), head convex, with frons slightly tumescent; eyes ovoid, higher than wide. In dorsal view ( Fig. 1B ), eyes protruding; fastigium subtriangular and apically convex. Scapus wide, almost as wide as half fastigium apex. THORAX . Pronotum wider than long, bearing bristles on margins, with both anterior and posterior dorsal margins slightly concave ( Fig. 1B ). Lateral lobes almost squared, with anterior and posterior margins almost straight and ventral margin obliquely straight ( Fig. 1A, D ). Prosternum reduced, triangular, and continuous with conjoint cervical sclerites. Mesosternum sub-squared, with posterior margin slightly bilobed. Metasternum hexagonal, with posterior margin slightly incised ( Fig. 1F ) LEGS . All femora covered by fine pubescence and some longer bristles ( Fig. 2A–C, G–K ). Fore and mid tibia with two apical spurs on outer side ( Fig. 2A–C, H ) and one on inner side ( Fig. 2G, I ). Tympana reduced ( Fig. 2A–B, D–E ) or absent ( Fig. 2C, F ) (different development levels can be found in same specimen). Hind tibia with 6–7 external and 5–6 internal dorsal spurs and three apical spurs on each side ( Fig. 2J–K ); externally, dorsal and ventral apical spurs equal in length, mid one twice longer; internally, dorsal and mid spurs same-lengthened, ventral one at least three times smaller ( Fig. 2J–K ). Fore and mid basitarsi covered by strong setae on ventral side ( Fig. 2A–C, G–I, L ). Hind basitarsi ventrally with setae, dorsally with two rows of spines, and apically with two spurs, outer one smaller ( Fig. 2J–K ). WINGS . Tegmina short, reaching up to the third tergite, without stridulatory apparatus or transverse veins; lateral field with six longitudinal veins ( Fig. 1A–B, D–E ). Hind wings absent. ABDOMEN . Cylindrical, covered with bristles. Male supra-anal plate triangular, medially incised posteriorly and with transverse suture ( Fig. 1H ). Subgenital plate slightly longer than wide, with widely rounded posterior margin ( Fig. 1I–J ). GENITALIA . Pseudepiphallic median lophi conspicuously elongated, notably produced hind- and upwards, very narrow, apically acute ( Fig. 3A–B, D ), and ventrally with sharp keel ( Fig. 3C ). Pseudepiphallic lateral lophi triangular, apically acute ( Fig. 3D ). Pseudepiphallic parameres elongated, surpassing lateral lophi; in ventral view, slightly arched, with rounded apex ( Fig. 3B ). Pseudepiphallic apodemes acute, incurved ( Fig. 3A ). Ectophallic fold very thin, not reaching level of pseudepiphallic paramere apex ( Fig. 3B ). Ectophallic arc very thin and notably curved; in dorsal view, forming ‘W’ with ectophallic apodemes ( Fig. 3A ). Rami basally bifid and notably arched along its length, contiguous, and medially incised ( Fig. 3A–B ). Female Similar to males in very dark coloration, with head, pronotum, tegmina, and first two abdominal tergites blackish ( Fig. 4A–B ). Tegmina reduced, reaching only first abdominal tergite, with only longitudinal veins ( Fig. 4C–D ). Supra-anal plate notably triangular, with transverse suture ( Fig. 4E ). Subgenital plate short; in ventral view, wider than long, with posterior margin slightly concave medially ( Fig. 4G ); in lateral view, higher than long, with posterior margin truncated ( Fig. 4F ). Ovipositor almost straight, with triangular apex. Dorsal valves dorsally sulcated ( Fig. 4H–K ). GENITALIA . Copulatory papilla with posterior margin of dorsal surface widely concave, and anterior margin with medial process emarginated, flanking spermatheca duct ( Fig. 4L ); ventral surface acute anteriorly ( Fig. 4M ); in lateral view, posterior portion taller than anterior one ( Fig. 4N ). Nymphs In life, bearing same black coloration as head and pronotum of adults, but abdomen and legs gray ( Fig. 5A ). When preserved in alcohol, gray body parts become ochre ( Fig. 5B–D ). MEASUREMENTS (mm). ♂ , holotype . TL: 11.0; LP: 2.0; WP: 3.0; Tg: 2.5; HF: 6.0; HT: 4.0. ♂ , paratype . TL: 9.5; LP: 2.0; WP: 2.5; Tg: 3.0; HF: 7.0; HT: 4.0. ♀ , paratype . TL: 9.0; LP: 2.0; WP: 3.0; Tg: 1.5; HF: 7.0; HT: 4.0; Ov: 6.5.

Remarks Zebragryllus aphonus Tavares, Oya & Cadena-Castañeda sp. nov. has quite a unique feature. It is the only known species of the genus in which the male has no stridulatory apparatus. The different development levels of the tympana are also singular to this species. These two characteristics may be adaptations to the caves in which they were found. Still, it is hard to ensure since no phylogenetic study was made and ecological data are lacking. The shape of the pseudepiphallic median lophi is similar to that of Z. nauta . However, it differs by the presence of conspicuous pseudepiphallic lateral lophi, which are very reduced and almost inconspicuous in Z. nauta . These two species may be related. We believe this species is facultative to a cave-dwelling way of life or caviculous (sensu Desutter-Grandcolas et al. 1998 ), foraging on forest ground during the nights and passing the day inside the caves or cavities at ground level. We believe in this assumption since adult and immature stages were found inside caves as field work was carried out during the day. This species may also inhabit or take refuge in pores or voids on the soil, characteristic microhabitats of the environment where it was collected. The structure of the landscape is known as Banded Ferruginous Formations, which are iron formations composed of alternated bands of jaspilite and ore bodies rich in iron. In this area, extensive iron ore plateaus are formed, comprising superficial ferrugineous breccia, also known as canga formation. A metallophilic savannah covers the canga formations on the plateaus and mountains, while typical tropical vegetation of the Amazon rainforest covers the slopes. The highly porous canga formations result from the removal of silica and carbonates due to the tropical rains, which causes the dissolution and chemical change found in iron ore, forming several interconnected small spaces in the canga formations – the voids ( Ferreira et al. 2018 ). Zebragryllus aphonus Tavares, Oya & Cadena-Castañeda sp. nov. was collected in seven caves in the municipality of Canaã dos Carajás, located in the east region of Pará State , Brazil ( Fig. 16A–C ). The caves are coded as S11C-0033, S11C-0037, S11C-0050, S11C-0066, S11C-0092, S11C-0110, S11C-0121. They are situated in the Amazon rainforest and are part of the federal conservation unit “Floresta Nacional de Carajás” (FLONA) ( Carmo & Kamino 2015 ). They are located within the “Grão-Pará” geological group, known for its iron-ore lithology. This region is popularly known as “Serra dos Carajás”, which comprises vast plateaus separated by depressions in the landscape, dividing it into three regions: Serra Norte, Serra Leste, and Serra Sul ( Carmo & Kamino 2015 ). The seven caves where the specimens were collected are situated in the “Serra Sul” plateaus region ( Fig. 16 ).