Xangoniscus loboi Campos-Filho, Gallao & Bichuette sp. nov.

Figures 1, 3, 8, 9, 10, 11

Type locality.

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

Type material.

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.

Description.

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.

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.

Etymology.

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

Remarks.

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.

Ecology and behavior.

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.