Diploexochus obscurus, B & B & B, 2023

B, Giovanna Monticelli Cardoso, B, Rafaela Bastos-Pereira & B, Rodrigo Lopes Ferreira, 2023, Cave-dwellers Diploexochus (Isopoda, Armadillidae): new species and new records of the genus from Brazil, Nauplius (e 2023008) 31, pp. 1-15 : 9-10

Diploexochus obscurus sp. nov.

( Figs. 7 – 10 )

Zoobank: urn:lsid:zoobank.org:act:E2B21901-1FE9-4731-B8B0-B00C3FA56987

Typematerial. Holotype: male ( ISLA77539 , part in slide), Brazil, Bahia State, municipality of Carinhanha , Água Escura I cave (-13.817694º -43.950366º), 17 September 2021, G.M. Cardoso and R.L. Ferreira coll. Paratypes: 3 females (1 in slide) ( ISLA 77540 ), same data as holotype .

Diagnosis. Dorsal surface covered with acute and rectangular tubercles; pereonites2–7 with11 tubercles in 2 rows; pleonite 3 with 4 tubercles, pleonites 4, 5 and telson with 2 paramedian tubercles; uropod exopod inserted medially, endopod around threefold exopod length.

Description. Body length: ♂ 7.5 mm, ♀ 6 mm. Body gray with depigmented spots; antenna 5 th article and flagellum yellowish ( Fig. 7A ). Endoantennal conglobation. Dorsal surface covered with acute and rectangular tubercles disposed as follows ( Fig. 8A,B ): cephalon with 12 tubercles in 3 rows; pereonite 1 with 21 tubercles in 3 rows; pereonite 2 with 13 tubercles in 2 rows; pereonites 3–7 with 11 tubercles in 2 rows; pleonite 3 with 4 tubercles, pleonites 4 and 5 with 2 paramedian tubercles, telson with 2 tubercles. Dorsal surface with short semi-circular scale-setae ( Fig. 7C ). Cephalon ( Figs. 7B , 8C, D ) with frontal shield prominent, protruding above vertex, distal margin straight; eye with about16 ommatidia.Pereonites with epimera flattened and directed backwards; pereonite 1 strongly grooved on lateral margin, inner lobe of schisma rounded ( Fig. 8C, E ); pereonite 2 with triangular ventral lobe; pereonites 5–7 with oblique ventral ridge. Pleonites 3–5 ( Fig.8F ) with epimera well developed, quadrangular with round distal margin, slightly directed outwards. Telson hourglass-shaped, base wider than distal part, distal margin straight. Antennula ( Fig. 7D ) of 3 articles, proximal and distal articles subequal in length, distal article with 2 lateral and 5 apical aesthetascs. Antenna ( Fig.8G ) short, not surpassing distal margin of pereonite 1; flagellum of 2 articles, distal article about fourfold longer than first, with 1 row of aesthetascs. Mandible ( Fig. 8H, I ) molar penicil simple; left mandible with 2 + 1 and right mandible with 1 + 1 free penicils. Maxillula ( Fig. 8J ) outer branch with 4 + 5 simple teeth. Maxilla ( Fig. 8K ) bilobate, outer lobe twice wider than inner lobe, covered with thin setae. Maxilliped ( Fig. 8L ) endite with medial seta surpassing distal margin, distal margin slightly rounded with 2 short triangular setae; palp with 2 setae on basal article. Pereopod 1 with longitudinal antennal grooming brush, dactylus inner claw not surpassing outer claw, dactylar organ and ungual seta simple, with longitudinal scale-field ( Fig. 9A ). Pleopods 1–5 with monospiracular lungs. Uropod ( Fig. 7D ) protopod flattened, distal part subrectangular, exopod short inserted medially, endopod stout, short, not reaching the insertion of exopod, around threefold exopod length.

Male: pereopods 1 and 7 ( Fig. 9A, B ) with no particular modifications. Genital papilla with triangular ventral shield, papilla slightly surpassing ventral shield with apical orifices ( Fig.9C ). Pleopod 1 ( Fig. 9C ) exopod small, triangular, wider than long; endopod about 4 times longer than exopod, distal part straight. Pleopod 2 ( Fig. 9D ) exopod triangular, outer margin strongly concave bearing setae;endopod longer than exopod. Pleopods 3 and 4 exopods as in Fig. 9E, F .

Etymology. The specific epithet “obscurus ” refers to the cave where the species was collected, Água Escura (that in Portuguese means dark water).

Habitat and ecological remarks. Specimens of D. obscurus sp. nov. were found in a limestone cave (Água Escura I cave) located in the region of “Serra do Ramalho”, northeastern Brazil. This area has hundreds of caves and several cave-restricted species (e.g., Baptista and Giupponi, 2002; Kamimura and Ferreira, 2018; Hellmann et al., 2020). Although many other caves in the area were also inventoried, specimens of D. obscurus sp. nov. were only found in this cave. Although this cave is peripheral to the main subterranean drainage in the area, it can be considered part of the Água Clara cave system, which comprises the richest hotspot of subterranean biodiversity in South America ( Souza-Silva et al., 2021). The Água Escura I cave presents a single entrance, located at the base of a limestone outcrop ( Fig. 10A ). The cave presents two main conduits (one intercepting the other), which were extremely dry during the samplings ( Fig. 10C ). However, the cave conduits are located at a lower level when compared to the surface, so that the water from f loods can enter the cave, submerging part of its chambers during strong rains ( Fig. 10B ). According to Köppen’s climate classification system, the local climate is “Aw”, with dry winter and an average annual rainfall of 640 mm 3 ( Alvares et al., 2013). Only four specimens of D. obscurus sp.nov. were found in the cave ( Fig. 10D, E ), all sheltered under big rocks, in which microhabitats still retained some moist content on the subjacent f loor ( Fig. 10C ). The cave surroundings are severely impacted ( Fig. 10A ), mainly by deforestation and fires, although cattle and goat breeding were also observed. As mentioned for D. spinatus sp. nov., the cave is likely being used by D. obscurus sp. nov. as a refuge, considering the highly impacted area surrounding the cave.

Figures

Figure 7.Diploexochus obscurus sp.nov.,female paratype.A, Habitus, lateral view; B, cephalon and pereonite 1, frontal view; C, scale setae; D, antennula; E, uropod. Scale bars: A, B: 1 mm; C: 50µm; D: 100µm; E: 300µm.

Figure 8. Diploexochus obscurus sp. nov., female paratype. A, Habitus, lateral view; B, disposition of dorsal tubercles; C, cephalon and pereonite 1, frontal view; D, cephalon and pereonite 1, dorsal view; E, epimera 1–4 ventral view; F, pleonites 3-5, uropods and telson, dorsal view. Male paratype: G, antenna; H, right mandible; I, left mandible; J, maxillula; K, maxilla; L, maxilliped. Scale bars: A: 1 mm; C–L: 0.2 mm.

Figure 9.Diploexochus obscurus sp.nov.,male paratype.A, Pereopod 1; B, pereopod 7; C, pleopod 1and genital papilla; D, pleopod 2; E, pleopod 3 exopod; F, pleopod 4 exopod. Scale bar: 0.2 mm.

Figure 10. A, Karstic area surrounding Água Escura I cave; B, entrance of Água Escura I cave; C, conduitwhere the specimens were found; D, live specimenof Diploexochus obscurus sp.nov.in lateralview;E, live specimen ofDiploexochus obscurus sp.nov.in dorsalview.