Xangoniscus aganju Campos-Filho, Araujo & Taiti, 2014, by original designation.

Bahia, Feira da Mata, Gruna Boca da Lapa cave (13°56'46.4"S, 44°11'12.0"W).

Holotype male (LES 27734), Bahia, Feira da Mata, Gruna Boca da Lapa cave, 15 October 2020, leg. ME Bichuette, DF Torres, JS Gallo, L Senna-Horta & JE Gallão. Paratypes 1 male (parts in slides), 2 females (LES 27735); 1 male, 3 females (one female with parts in slides) (LES 27736), same data as holotype.

Body length: ♂ 8.0 mm, ♀ 9.3 mm. Body unpigmented, slightly robust, lateral sides slightly convex (Figs 2C, D, 4A–C). Dorsal surface smooth with scattered fringed scale setae (Fig. 5A). Pereonite 1 epimera with distal corners slightly developed frontwards, not surpassing cephalon, posterior corners right-angled; pereonite 2–4 epimera gradually directed backwards, posterior corners progressively more acute; pleon slightly narrower than pereon, pleonites 3–5 epimera well-developed and falciform (Figs 4B, 5C). Cephalon (Figs 4C, 5B) with large quadrangular antennary lobes; vertex with lateral depression to fit antennae when extended backwards, profrons with V-shaped suprantennal line; eyes absent. Telson (Fig. 5C) with well pronounced concave sides and broadly rounded apex. Antennula (Fig. 5D) of three articles, medial and distal articles subequal in length, second article bearing one long seta on inner margin, distal article with two long apical aesthetascs. Antenna (Fig. 5E) with fifth article of peduncle longer than flagellum; flagellum of three articles, first article longest, distal article bearing tuft of free sensilla. Left mandible (Fig. 5F) with two penicils, right mandible (Fig. 5G) with one penicil and lacinia mobilis leaf-shaped with rounded apex. Maxillula (Fig. 5H) outer branch with 5 + 5 teeth, apically entire, and two thick plumose stalks; inner branch with three penicils, proximal one longer than two apical. Maxilla (Fig. 5I) with setose and bilobate apex, outer lobe smaller. Maxilliped (Fig. 5J) basis enlarged on distal portion bearing fringe of fine setae; first article of palp with two setae, distal articles fused bearing distal tufts of several thin setae; endite rectangular, outer and medial margins setose, apically with two triangular teeth and large rounded penicil. Uropod (Fig. 6A) branches inserted at same level, endopod slightly longer than exopod. Pereopods 1–7 gradually elongated, pereopods 1–7 merus, carpus, and propodus bearing sparse setae and fringed scales (discernible over 200× magnification) on sternal margin, pereopod 7 basis with scales of water conduction system; dactylus of one claw bearing many setae on inner and outer margins.

Figure 4. 

Xangoniscus lapaensis sp. nov. A habitus, lateral view B habitus, dorsal view C cephalon and pereonites 1–4, dorsal view. Scale bar: 2 mm (A, B); 1 mm (C).

Figure 5. 

Xangoniscus lapaensis sp. nov. Male A dorsal scale-setae C pleonites 4 and 5, telson and uropod. Female B cephalon, frontal view D antennula E antenna F left mandible G right mandible H maxillula I maxilla J maxilliped.

Figure 6. 

Xangoniscus lapaensis sp. nov. Male A uropod B pereopod 1 C pereopod 2 D pereopod 3 E pereopod 4 F pereopod 5 G pereopod 6 H pereopod 7.

Male. Pereopods 1–6 (Fig. 6B–G) merus with proximal portion bearing fringed scales and thin setae on sternal margin. Pereopod 1 (Fig. 6B) carpus with large antennal grooming brush. Pereopod 5 (Fig. 6F) slightly depressed on distal sternal margin. Pereopod 6 (Fig. 6G) ischium flattened on sternal portion bearing brush of fine setae. Pereopod 7 (Fig. 6H) ischium with straight sternal margin, merus and carpus with no distinct modifications. Genital papilla (Fig. 7A) lanceolate, enlarged on median portion, apical part narrow. Pleopod 1 (Fig. 7B) exopod subtriangular bearing two short setae; endopod longer than exopod, narrow basal article and flagelliform distal article; basipod with triangular medial part fringed with fine and long setae on outer and distal margins, distal margin strongly sinuous. Pleopod 2 (Fig. 7C) exopod triangular, median portion narrower, distal margin almost straight bearing three setae; endopod of two thickset articles, second article about three times as long as first, with complex apical part: distal margin subquadrangular with narrow transverse process, subapical triangular lobe strongly folded. Pleopod 3 exopod (Fig. 7D) subtriangular, longer than wide, covering pleopods 1 and 2, bearing many short setae, distal external margin straight. Pleopod 4 and 5 exopods (Fig. 7E, F) subrectangular, wider than long, with distal portion bearing many short setae.

Figure 7. 

Xangoniscus lapaensis sp. nov. Male A genital papilla B pleopod 1 C Pleopod 2 D pleopod 3 exopod E pleopod 4 exopod F pleopod 5 exopod.

The new species is named after the locality where the specimens were collected, Gruna Boca da Lapa, an important cave discovered and mapped by Grupo Bambuí de Pesquisas Espeleológicas (GBPE) in 1991 and only now is it studied in relation to its cave fauna.

Xangoniscus lapaensis sp. nov. resembles X. aganju in the shape of the male pleopod 2 endopod; however, it differs in the vertex of the cephalon that lacks a frontal groove, and with a more pronounced suprantennal line that surpasses the antennule insertion (not surpassing in X. aganju). Also, the male pereopod 6 carpus lacks any modification (strongly modified in X. aganju, see Campos-Filho et al. 2014); the male pleopod 1 exopod is not elongated, and the male pleopod 2 exopod is narrower on inner portion. Moreover, X. lapaensis sp. nov. differs in the uropod endopod slightly longer than exopod (opposite in X. aganju) and the compact triangular shape of the male pleopod 1 exopod (elongated in X. aganju).

Xangoniscus lapaensis sp. nov. occurs in travertine pools fed by infiltration of water through the limestone rock, dripping from the cave ceiling, and in isolated pools along the cave (Fig. 2B, C), distributed from the twilight until the aphotic zone, something that demonstrates that its distribution is related to pools formed by infiltration water, i.e., its special habitat is available. The microhabitat is composed of rocky substrate, with little silt and sand sediment. The water is clear, with a very slow current, and a depth varying from 0.05 m to 0.15 m (Fig. 2B–D). Physicochemical variables were typical of karst aquifers that have high pH values: pH = 8.5–9.0, T = 23.5 °C, very different from the conditions in the base-level river (pH = 7.5, T = 25 °C). A small quantity of organic and particulate matter was observed in the small pools. Population density in the pools was high, ranging 6.5 to 32 individuals.m^-2 and the abundance was 74 individuals in an area of 2.8 m². The locomotor behavior was very particular, exhibiting fast and effective walking movements when submerged. However, when emerging from water, individuals showed a slow walking behavior on terrestrial substrate (see Supplementary Online Material 1). Xangoniscus lapaensis sp. nov. did not show photophobic behavior (indifferent to flashlight of about 600 lumens), and also seemed to exhibit intraspecific interactions, with no agonistic behavior. Adults and juveniles were observed in the pools, representing possible recruitment at the end of the dry season. It appears that X. lapaensis sp. nov. occurs preferentially in microhabitats fed by infiltration water, since no individual was recorded in the stream of the cave, a base-level river. This is very specific and unique, and probably the main habitat of this species is the spaces in the rocks filled by water.

Bahia, Feira da Mata, Gruna da Pingueira II cave (14°12'04.3"S, 44°24'39.1"W).

Holotype male (LES 27737), Bahia, Feira da Mata, Gruna da Pingueira II cave, 14 October 2020, leg. ME Bichuette, DF Torres, JS Gallo & JE Gallão. Paratypes 2 males, 3 females (one female with parts in micropreparations) (LES 27738), 6 males (one male in micropreparations), 4 females (LES 27739), same data as holotype.

Body length: ♂ 12 mm, ♀ 10 mm. Body unpigmented, slender and elongated, lateral sides almost parallel (Figs 3C, E, 8A–C). Dorsal surface smooth with scattered fringed scale setae (Figs 8C, 9A). Pereonite 1 epimera with distal corners not developed frontwards, posterior corners right-angled; pereonites 2–4 epimera gradually directed backwards, posterior corners progressively more acute; pleon slightly narrower than pereon, pleonites 3–5 epimera very short, slightly visible on dorsal view (Figs 8A, 9C). Cephalon (Figs 8D, 9B) with large quadrangular antennary lobes; vertex with slightly lateral depression to fit antennae when extended backwards, profrons with V-shaped suprantennal line, not surpassing antennule insertion; eyes absent. Telson (Fig. 9C) with well pronounced concave sides and broadly rounded apex. Antennula (Fig. 9D) of three articles, proximal and distal articles subequal in length, second article bearing short setae on inner margin, distal article with five aesthetascs. Antenna (Fig. 9E) with fifth article of peduncle longer than flagellum; flagellum of four articles, first article longest, distal article bearing tuft of free sensilla. Left mandible (Fig. 9F) with two penicils, right mandible (Fig. 9G) with one penicil and lacinia mobilis leaf shaped. Maxillula (Fig. 9H) outer branch with 5 + 5 teeth, apically entire, and two thick plumose stalks; inner branch with three penicils, proximal one longer than two apical. Maxilla (Fig. 9I) with setose and bilobate apex, outer lobe smaller bearing one strong seta. Maxilliped (Fig. 9J) basis enlarged on distal portion bearing fringe of fine setae; first article of palp with two setae, distal articles fused bearing distal tufts of fine setae; endite rectangular, outer and medial margins setose, apically with one triangular teeth and large triangular penicil. Uropod (Fig. 10A) branches inserted at same level, endopod and exopod subequal in length. Pereopods 1–7 gradually elongated, pereopods 1–7 merus, carpus and propodus bearing sparse setae and fringed scales (discernible over 200× magnification) on sternal margin, pereopod 7 basis with scales of water conduction system; dactylus of one claw bearing many setae on inner and outer margins.

Figure 8. 

Xangoniscus loboi sp. nov. A habitus, lateral view B habitus, dorsal view C habitus, lateral view D cephalon and pereonite 1, frontal view. Scale bar: 2 mm (A-C); 1 mm (D).

Figure 9. 

Xangoniscus loboi sp. nov. Male A dorsal scale-seta B cephalon, frontal view C pleonites 4, 5 and telson D antennula E antenna F left mandible G right mandible H maxillula I maxilla J maxilliped.

Figure 10. 

Xangoniscus loboi sp. nov. Male A uropod B pereopod 1 C pereopod 2 D pereopod 3 E pereopod 4 F pereopod 5 G pereopod 6 H pereopod 7.

Male. Pereopods 1–3 (Fig. 10B–D) merus with proximal lobe bearing fringed scales and fine setae on sternal margin. Pereopods 4–6 (Fig. 10E-G) merus with dense field of short setae on sternal margin. Pereopod 6 (Fig. 10G) merus bearing brush of setae on sternal margin. Pereopod 7 (Fig. 10H) ischium straight on sternal margin, merus, and carpus with no distinct modifications. Genital papilla (Fig. 11A) lanceolate, enlarged on median portion, apical part narrow and pointed. Pleopod 1 (Fig. 11B) exopod subtriangular, longer than wide, inner and outer margins bearing fringe of fine setae; endopod slightly longer than exopod, narrow basal article and flagelliform distal article; basipod with stout and broadly rounded medial part bearing fringe of fine setae along outer and distal margins. Pleopod 2 (Fig. 11C) exopod triangular, median portion narrower, distal margin almost straight bearing three setae; endopod of two thickset articles, second article about three times as long as first, with complex apical part: distal margin rounded with two narrow transverse processes, subapical circular lobe strongly folded. Pleopod 3 exopod (Fig. 11D) triangular, slightly longer than wide, covering pleopods 1 and 2, bearing many short setae on distal margin. Pleopod 4 exopod (Fig. 11E) subrectangular, wider than long, distal portion bearing many short setae. Pleopod 5 exopod (Fig. 11F) subtrapezoidal, distal margin rounded bearing many short setae.

Figure 11. 

Xangoniscus loboi sp. nov. Male A genital papilla B pleopod 1 C Pleopod 2 D pleopod 3 exopod E pleopod 4 exopod F Pleopod 5 exopod.

The new species is named after Alexandre Lobo for all his contributions for knowledge and conservation of the Brazilian speleological heritage.

Xangoniscus loboi sp. nov. differs from all other species of the genus in having the proximal lobe of male pereopods 1–3 merus covered with scales and fine setae, and in the shape of the distal complex apparatus of the male pleopod 2 endopod.

Xangoniscus loboi sp. nov. occurs in a small stream formed by infiltration water in the limestone rock (Fig. 3). The small stream crosses an extension of about 9 m through the cave entrance and the twilight zones, with width varying from 0.2 to 1.2 m and depth from 0.05 to 0.25 m. Along the stream, two small waterfalls (ca. 0.6 m of length) with a rocky substrate were observed. In these stretches, the individuals were seen constantly climbing the substrate (see Supplementary Online Material 2). The bottom of the stream is composed mainly of rocky substrate (concretions and small pebbles), with silt and sand sediment in the bottom, offering rich shelter for the isopods (Fig. 3 C, E–H). The water is clear, with a very slow current. Physicochemical variables are typical of karst aquifers (high pH values), pH = 8.0–8.5, T = 24.1 °C. A low load of organic and particulate matter was observed in the stream, with some seeds of fruits in the sector close to the cave entrance. The population density in three sectors of the stream were: 54 inds.m^-2, 67 inds.m^-2 and 342 inds.m^-2; minimal abundance was 455 individuals in an area of ca. 5.0 m². As observed for X. lapaensis sp. nov., the locomotor behavior was very particular. Xangoniscus loboi sp. nov. shows an efficient walking behavior when submerged (see Supplementary Online Material 3) and climbs vertical stretches (upstream direction) in the stretches with relatively strong water flow. They are clumsy out of water (they do not perform as well as in the submersion behavior), but they adhere very well on dry rock. We also observed copulation: three different couples in reproductive behavior, mated for several minutes (at least 5 min.) (see Supplementary Online Material 4 and 5). Several adults and juvenile individuals were observed along the stream, representing possible recruitment at the end of the dry season. Other interesting behaviors are the indifference to light, even under strong flashlight (ca. 600 lumens), and the interactions among several individuals, touching each other, showing no signs of agonistic behavior. In relation to feeding behavior, some individuals were observed foraging on vegetal debris and seeds (see Supplementary Online Material 6). It appears that X. loboi sp. nov. occurs preferentially in microhabitats fed by infiltration water in the limestone. This is very specific and unique, and probably the main habitat of this species is the spaces in rocks filled by water.