Xangoniscus ceci,

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

publication ID

https://doi.org/10.11646/zootaxa.4819.1.4

publication LSID

lsid:zoobank.org:pub:AB417537-CE48-465A-8C23-5AF0B7602ADC

persistent identifier

http://treatment.plazi.org/id/E55C87AB-FFBD-1A21-C29F-FA2CFA8EFD12

treatment provided by

Plazi

scientific name

Xangoniscus ceci
status

n. sp.

Xangoniscus ceci  n. sp.

Figs. 9–11View FIGURE 9View FIGURE 10View FIGURE 11, 19CView FIGURE 19

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. FerreiraGoogleMaps  . Paratypes: 4 males, 5 females, same data as holotype ( ISLA 77515)GoogleMaps  ; 1 male, 5 females, same locality, 22 January 2015, leg. L.M. Rabelo ( ISLA 14333)GoogleMaps  .

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. 9AView FIGURE 9, 19CView FIGURE 19). Dorsal surface smooth with simple. Cephalon ( Fig. 9BView FIGURE 9) 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. 9AView FIGURE 9). Telson ( Fig. 9CView FIGURE 9) with concave sides, round apex.

Antennula ( Fig. 9DView FIGURE 9) with three articles, second article shortest, distal article with four or five short aesthetascs, three subapical and two apical. Antenna ( Fig. 9EView FIGURE 9) 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. 1FView FIGURE 1), right mandible with one penicil, lacinia mobilis leaf-shaped ( Fig. 1GView FIGURE 1). Maxillula ( Fig. 1HView FIGURE 1) outer branch with 5 + 5 teeth, apically entire, and two thick plumose stalks; inner branch with three penicils. Maxilla ( Fig. 1IView FIGURE 1) with bilobate apex, inner lobe wider than outer lobe with several setae on distal margin. Maxilliped ( Fig. 1JView FIGURE 1) 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. 10AView FIGURE 10) 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. 10BView FIGURE 10) merus and carpus with fringed scales on sternal margin; pereopods 5 and 6 ( Fig. 10CView FIGURE 10) with merus densely setose margin; pereopod 7 ( Fig. 10DView FIGURE 10) basis with scales of water conduction system, merus margin with sparse setae. Genital papilla ( Fig. 10EView FIGURE 10) lanceolate. Pleopod 1 ( Fig. 10EView FIGURE 10) 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. 10FView FIGURE 10) 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. 10GView FIGURE 10) ovoid, concave distal margin with lateral lobe, bearing setae. Pleopods 4 and 5 exopod ( Fig. 10H, IView FIGURE 10) 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. 11AView FIGURE 11). 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. 11BView FIGURE 11). 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. 11CView FIGURE 11). 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, EView FIGURE 11), 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.

R

Departamento de Geologia, Universidad de Chile