Benthana alba Cardoso & Ferreira 2023, n. sp.

Benthana alba n. sp. (Figures 3B, 4 and 5) Type material. Holotype: male (ISLA 96766 in slide), Brazil, Pará state, municipality of Parauapebas, cave N5 SM2 _ 0077: GEM1762 (-6.124548º -50.131116º), 12.iii.2011, leg. M. P. A. Oliveira. Paratypes: 2 males, 1 juvenile (ISLA 96767), same data as holotype. Diagnosis. Pleonites 3–5 with well-developed posterior point; eyes with seven ommatidia; antennula with 19+2 aesthetascs; male pleopod 1 exopod rounded with lateral protrusion prominent acute and lobe on inner distal margin. Description. Maximum body length: male 9.5 mm. Colorless in ethanol. Body convex, outline as in Fig. 4A. Dorsal surface smooth bearing few long triangular scale-setae (Fig. 4B); noduli laterales long, one line per side with d/c coordinates reaching maximum on pereonite 4; b/c coordinates gradually decreasing (Fig. 4C, D). Cephalon (Fig. 4E) with suprantennal line bent downwards in middle, no frontal line and lateral lobes; eyes composed of seven small ommatidia arranged in two rows. Pereonites 5–7 with postero-lateral corners gradually more acute; pleon narrower than pereon, pleonites 3–5 with well-developed posterior point acute (Fig. 4A). Telson (Fig. 4F) triangular, lateral sides straight. Antennula (Fig. 4G) of three articles, distal article longest bearing 17 lateral aesthetascs in five rows, plus apical pair. Antenna (Fig. 4H) long, reaching pereonite 4 when extended backwards, distal article of peduncle longer than flagellum; flagellum of three articles, distal article longest, apical organ short. Mandibles with molar penicil of 11–13 branches, left mandible (Fig. 4I) with 2+1 penicils, and right mandible (Fig. 4J) with 1+1 penicils. Maxillula (Fig. 4K) inner endite with two penicils; outer endite with 4+5 teeth (5 pectinate), plus one short and simple. Maxilla (Fig. 4L) inner lobe wider than outer lobe, covered with thick setae; outer lobe distal margin sinuous, covered with thin setae. Maxilliped (Fig. 4M) with rectangular basis; endite rectangular, medial seta surpassing distal margin, two hooks on distal margin, dorsal face with longitudinal ridge bearing dense setae plus one short triangular seta; proximal article of palp with two setae, one longer. Pereopods slender; carpus 1 with transverse antennal grooming brush, distal seta with hand-like apex; dactylus inner claw shorter than outer claw, dactylar and ungual setae simple, not surpassing outer claw. Uropod (Fig. 4F) protopod subquadrangular, protopod and exopod grooved on outer margin bearing glandular pores; exopod longer than endopod; endopod inserted at same level. Male. Pereopods 1–3 (Fig. 5A, B) merus and carpus with brushes of setae on sternal margin. Pereopod 7 (Fig. 5C) without sexual dimorphism. Genital papilla (Fig. 5D) with triangular ventral shield and two subapical orifices. Pleopod 1 (Fig. 5D, E) exopod rounded (ratio z:y= 1.7) lateral protrusion prominent acute, lobe on inner margin; endopod longer than exopod, stout and straight, distal portion with line of short setae. Pleopod 2 (Fig. 5F) exopod triangular, outer margin concave with three setae; endopod slender, longer than exopod. Pleopods 3 and 4 exopods as in Fig. 3G, H, respectively. Pleopod 5 exopod (Fig. 5I) triangular, outer margin sinuous with three setae and transverse plumose fringe. Etymology. From the latin: alba = white. The name refers to the lack of pigmentation in the new species. Morphological remarks. Benthana alba n. sp. presents some troglomorphic traits such as the lack of pigmentation and the reduction in the number of ommatidia. Benthana alba n. sp. is similar to B. iporangensis in the lack of pigmentation, in the shape of male pleopod 1 exopod, but it differs by the number of ommatidia (7 vs. 18 in B. iporangensis); by the number of aesthetascs on the antennula (19+2 vs. 11+2); and the articles proportion on the antenna (distal article longest vs. first article longest). Ecological remarks. Specimens of Benthana alba n. sp. were only found in the N5SM2_0077 cave (also known as cave GEM-1762), in the plateau N5 (Serra Norte complex) (Fig. 1). This cave comprises a small cavity with 13,5 meters of horizontal projection. It is inserted on the “canga” formation (a topmost ferruginous breccia) with its entrance located inside the forest. The external area surrounding the cave features large trees and sparse understory, in addition to abundant undergrowth. The cave is, in general, a shelter under a high external environmental influence and without completely aphotic zones. The entrance is wide (around 3.5 x 8 m) and presents a large amount of organic matter; the floor (composed of many collapsed blocks) descends through the internal wings after an abrupt drop. Inside the cave, the floor is predominantly flat and composed of granulated sediment with some pebbles and sparse boulders, and a small pile of hematophagous bat guano was observed. In the iron-ore outcrop where the N5SM2_0077 cave is located there are several other caves that were also sampled (at least twice, in both dry and rainy periods) but specimens of B. alba n. sp. were only recorded in this cave. However, in the ferruginous subterranean systems this fact does not mean that it is restricted or rare, since many invertebrate species associated with the ferruginous subterranean systems use the interstitial voids such as the canaliculi network (Ferreira et al. 2018) (Fig. 2E). Therefore, specimens of Benthana alba n. sp. may be randomly found in macrocaverns, and this is at least partially reinforced by the small size of this cave (and consequently low environmental stability) where the specimens were found. On the other hand, one could think that the species is not restricted to subterranean habitats; however, external surveys for soil invertebrates accomplished in the Carajás region never revealed this species, thus indicating it should be considered as troglobitic. It is worth mentioning that the canaliculi network is usually very superficial, what causes such habitats to become highly vulnerable to the mining processes that advance over the region. Therefore, even considering the lack of information about the real distribution and population density of this species, it is plausible to consider it as highly threatened due to its specific habitat, and effective loss of habitat caused by activities related to the iron ore exploitation on its occurrence area.Published as part of Cardoso, Giovanna Monticelli & Ferreira, Rodrigo Lopes, 2023, New troglobitic species of Benthana Budde-Lund, 1908 and Benthanoides Lemos de Castro, 1958 from iron-ore caves and their important record in the Amazon biome (Crustacea: Isopoda: Philosciidae), pp. 548-562 in Zootaxa 5319 (4) on pages 550-552, DOI: 10.11646/zootaxa.5319.4.5, http://zenodo.org/record/820330