Xangoniscus ceci, Cardoso & Bastos-Pereira & Souza & Ferreira, 2020

Cardoso, Giovanna Monticelli, Bastos-Pereira, Rafaela, Souza, Leila Aparecida & Ferreira, Rodrigo Lopes, 2020, New troglobitic species of Xangoniscus (Isopoda: Styloniscidae) from Brazil, with notes on their habitats and threats, Zootaxa 4819 (1), pp. 84-108 : 93-97

Xangoniscus ceci n. sp.

Figs. 9–11 , 19C

Material examined. Holotype: Male ( ISLA 77514), Minas Gerais , São João da Ponte, Mãe Diná cave, 15.806633ºS, 44.001919ºW, 10 April 2017, leg. R. L. Ferreira . Paratypes: 4 males, 5 females, same data as holotype ( ISLA 77515) ; 1 male, 5 females, same locality, 22 January 2015, leg. L.M. Rabelo ( ISLA 14333) .

Etymology. The specific epithet means ‘mother’ in the Brazilian indigenous language Tupi, referring to the type locality name (Mãe Diná cave—“mãe” meaning mother in Portuguese).

Diagnosis. Antennula with five aesthetascs; antennal flagellum with six articles; pereopods merus longer than wide, with fringed scales on sternal margin of pereopods 1–4 and densely setose on merus sternal margin of pereopods 5 and 6; pleopod 1 exopod triangular with sinuous margin; pleopod 2 exopod subtriangular; pleopod 3 exopod with concave distal margin with lateral lobe; uropod exopod slightly longer than endopod.

Description. Maximum length: male, 10 mm. Colorless, eyes absent ( Figs. 9A , 19C ). Dorsal surface smooth with simple. Cephalon ( Fig. 9B ) with antennary lobes; profrons with V-shaped suprantennal line. Posterior corners of pereonites directed backwards, pereonite 7 not surpassing distal margin of pleonite 2; pleonites 3–5 epimera pos- terior point slightly developed; pleon narrower than pereon ( Fig. 9A ). Telson ( Fig. 9C ) with concave sides, round apex.

Antennula ( Fig. 9D ) with three articles, second article shortest, distal article with four or five short aesthetascs, three subapical and two apical. Antenna ( Fig. 9E ) reaching distal margin of pereonite 2 when extended backwards, fifth article of peduncle shorter than flagellum; flagellum with six articles. Left mandible with two penicils ( Fig. 1F ), right mandible with one penicil, lacinia mobilis leaf-shaped ( Fig. 1G ). Maxillula ( Fig. 1H ) outer branch with 5 + 5 teeth, apically entire, and two thick plumose stalks; inner branch with three penicils. Maxilla ( Fig. 1I ) with bilobate apex, inner lobe wider than outer lobe with several setae on distal margin. Maxilliped ( Fig. 1J ) basis enlarged on distal portion; palp apex with four tufts of setae; endite rectangular, shorter than palp first tuft of setae, outer and medial margins setose, apex with one triangular penicil between two teeth.

Pereopod 1 antennal grooming brush composed by serrated scale setae longitudinally on propodus and carpus. Uropod ( Fig. 10A ) protopod shorter than distal margin of telson; exopod slightly longer than endopod, exopod with proximal insertion.

Male. Pereopods merus longer than wide; pereopods 1–4 ( Fig. 10B ) merus and carpus with fringed scales on sternal margin; pereopods 5 and 6 ( Fig. 10C ) with merus densely setose margin; pereopod 7 ( Fig. 10D ) basis with scales of water conduction system, merus margin with sparse setae. Genital papilla ( Fig. 10E ) lanceolate. Pleopod 1 ( Fig. 10E ) exopod triangular with fine setae on distal margin, sinuous margin; endopod as long as exopod, with narrow basal article and flagelliform distal article; protopod distal margin shorter than exopod. Pleopod 2 ( Fig. 10F ) exopod subtriangular, round distal margin, bearing one seta; endopod of two articles, basal article rectangular, shorter than exopod, distal article wrench-like, transverse pointed process on apex, directed outwards, with lateral membrane. Pleopod 3 exopod ( Fig. 10G ) ovoid, concave distal margin with lateral lobe, bearing setae. Pleopods 4 and 5 exopod ( Fig. 10H, I ) rhomboidal wider than long, with distal margin rounded and bearing setae.

Remarks. X. ceci n. sp. presents modifications on pereopods 5 and 6 merus, that are longer than wide with densely setose margins, thus differing from X. dagua n. sp. and X. lundi n. sp. that show pereopods 5 and 6 merus enlarged. Moreover, X. ceci n. sp. presents modification on pereopod 4 and scale setae on distal sternal margin. The pleopod 1 exopod is triangular with distal margin prominent as X. lundi n. sp.; and the pleopod 2 exopod is subtriangular as X. dagua n. sp. and X. lundi n. sp. The uropod with exopod longer than endopod can also be seen in X. aganju , while in the other species such as X. dagua n. sp. and X. itacarambiensis , the exopod and endopod are subequal in length, and in X. odara the endopod is longer than exopod.

Habitat and threats. Mãe Diná cave is the only known habitat of X. ceci n. sp. until the present. This cave presents a single entrance associated with an extremely altered landscape. Although many forest fragments occur in the area, they are mainly associated with the limestone outcrops ( Fig. 11A ). However, Mãe Diná cave entrance is not located in a typical outcrop in the region, but in a small limestone outcrop associated with a slope of a valley mainly covered by pasture ( Fig. 11B ). After entering the cave, a conduit leads to a chamber located in the innermost part. From this chamber onwards, several small conduits irradiate in distinct directions, given the cave a labyrinthine aspect. One of those conduits is trespassed by an intermittent small drainage that form ponds in some areas, with the biggest one associated with the main chamber ( Fig. 11C ). Specimens of X. ceci n. sp. were only found in this previously mentioned biggest pond. Despite the fact that this pond is connected to other smaller ponds occurring on the conduit that leads to the cave entrance ( Fig.11D, E ), no specimens were found in any other area of the cave, in both visits. The stream leaves the cave through the entrance, and since it constitutes an autogenic drainage (formed by percolating water), there were no signs of strong floods inside the cave.

Some conduits of the cave present clear signs of digging, probably caused by extraction of saltpeter, which was a common activity in Brazil in the 19 th century. However, although the external landscape is severely altered by human activities in the present, the cave itself is currently well preserved and no signs of modern human presence was observed. It is important to highlight that the severe habitat changes in the external landscape surrounding the cave represents a concern both by the risks of making the cave drier and the risks of reducing organic supply.

Figures

FIGURE 1. Xangoniscus lundi n. sp., male paratype. A, habitus, dorsal view; B, cephalon, frontal view; C, telson and uropod, dorsal view; D, antennula; E, antenna; F, left mandible; G, right mandible; H, maxillula; I, maxilla; J, maxilliped. Scale bars: A: 1 mm; B–J: 0.2 mm.

FIGURE 9. Xangoniscus ceci n. sp., male paratype. A, habitus, dorsal view; B, cephalon, frontal view; C, telson, dorsal view; D, antennula; E, antenna; F, left mandible; G, right mandible; H, maxillula; I, maxilla; J, maxilliped. Scale bars: A: 1 mm; B–J: 0.2 mm.

FIGURE 10. Xangoniscus ceci n. sp., male paratype.A, uropod; B, pereopod 1; C, pereopod 6; D, pereopod 7; E, genital papilla and pleopod 1; F, pleopod 2; G, pleopod 3 exopod; H, pleopod 4 exopod; I, pleopod 5 exopod. Scale bar: 0.2 mm.

FIGURE 11. Xangoniscus ceci n. sp. A, Surroundings of Gruta Mãe Diná cave; B, entrance of the cave from the inside; C, entrance of the cave, view from the outside; D, collection site; E, specimen in the natural habitat.

FIGURE 19. A, X. lundi n. sp.; B, X. dagua n. sp.; C, X. ceci n. sp.; D, X. ibiracatuensis n. sp.; E, X. santinhoi n. sp. Scale bar: 1 mm.