Diploexochus spinatus B & B & B 2023, sp. nov.
Creators: name: B, Giovanna Monticelli Cardoso
name: B, Rafaela Bastos-Pereira
name: B, Rodrigo Lopes Ferreira
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Isopoda
Armadillidae
Diploexochus
Diploexochus spinatus

description: Diploexochus spinatus sp. nov.
(Figs. 3 – 6)
Zoobank: urn:lsid:zoobank.org:act: 7A394BCA- F660-4424-A8A3-5AE58475F71C
Type material. Holotype: male (ISLA 77536), Brazil, Bahia State, municipality of Iuiu, Lapa do Honorato cave (-14.4628º -43.5931º), 19 October 2021, R. L. Ferreira coll. Paratypes: 2 males (1 in slide), 7 females (ISLA 77537), same data as holotype.
Additional material. 1 female (ISLA 77537), Brazil, Bahia State, municipality of Malhada, Tapera d’Água cave (-14.517270º -43.682842º), 18 October 2021, R.L. Ferreira coll.
Diagnosis. Dorsal surface covered with acute and rectangular tubercles; pleonites 3–5 with 2 paramedian tubercles, telson with 2 tubercles or smooth; pereonites epimera f lattened directed backwards; pleonites epimera quadrangular with round distal corner.
Description. Body length: ♂ 10 mm, ♀ 12 mm.Body dark gray with depigmented spots, antenna yellowish (Fig. 3A). Endoantennal conglobation (Fig. 4A, B). Dorsal surface covered with acute and rectangular tubercles disposed as follows(Fig. 4B): cephalon with 11 tubercles in 3 rows; pereonite 1 with 21 tubercles in 3 rows; pereonites 2–6 with 13 tubercles in 2 rows; pereonite 7 with 11 tubercles in 2 rows; pleonites 3–5 with 1 row of 2 paramedian tubercles each, telson smooth (holotype) or with 2 small tubercles. Dorsal surface with short semi-circular scale-setae, one nodulus lateralis on the second line of tubercles far from lateral margin, on outer distal margin (Fig. 3B). Cephalon with frontal shield prominent, distal margin slightly curved, protruding above vertex; eye with about 20 ommatidia (Figs. 3B; 4C, D). Pereonites with epimera flattened and directed backwards; pereonite 1 strongly grooved on lateral margin, inner lobe of schisma rounded (Figs. 3B, 4C–E), pereonite 2 with triangular ventral lobe; pereonites 5–7 with oblique ventral ridge (Fig. 4E). Pleonites 3–5 with well-developed epimera, quadrangular with round distal corner slightly directed outwards (Fig. 4F). Telson hourglass-shaped, base broader than distal part, distal margin straight (Fig. 4F). Antennula (Figs. 3C, 4G) with 3 articles, proximal and distal articles subequal in length, distal article with 9 apical aesthetascs. Antenna (Fig. 4H) short, not surpassing distal margin of pereonite 1; f lagellum with 2 articles, distal article about 2 times longer than first, with 1 row of aesthetascs.Mandibles (Fig. 4I, J) molar penicil simple, right mandible with 1 + 1, left mandible with 2 + 1 free penicils.Maxillula (Fig. 4K) outer branch with 4 + 5 simple teeth; inner branch with 2 long penicils. Maxilla (Fig. 4L) bilobate, outer lobe twice wider than inner lobe, covered with thin setae. Maxilliped (Fig. 4M) endite with medial seta surpassing distal margin, distal margin slightly rounded with 2 short triangular setae; palp with 2 setae on basal article. Pereopod 1 with longitudinal antennal grooming brush (Fig. 5A), dactylus inner claw not surpassing outer claw, dactylar organ and ungual seta simple, with longitudinal scale-field (Fig. 3E). Pleopods 1–5 with monospiracular lungs (Fig. 3E–I). Uropod (Fig. 3J) protopod f lattened, distal part subrectangular with round apex, exopod short inserted medially; endopod stout, short, not reaching the insertion of exopod, around 2 times exopod length.
Male: pereopods 1 and 7 (Figs. 3D; 5A, B) with no particular modifications. Genital papilla with triangular ventral shield, papilla slightly surpassing ventral shield with apical orifices (Fig. 5C). Pleopod 1 (Fig. 5C)exopod small, triangular, wider than long; endopod about threefold longer than exopod, distal part slightly bent outwards. Pleopod 2 (Fig. 5D) exopod triangular, outer margin strongly concave bearing setae; endopod longer than exopod. Pleopods 3–5 exopods as in Fig. 5E–G.
Etymology. The specific epithet “ spinatus ” refers to the morphology of the dorsal tubercles, which in this species are like spines.
Morphological remarks. The specimens from Honorato cave showed variations in the tubercle development on the telson, being very reduced in relation to the tubercles on pleonites (in 4 specimens) or absent (in 5 specimens); while on the female from Tapera D’água cave these tubercles are as long as those on pleonites 3–5 (Fig. 6D, E). Furthermore, the female from Tapera D’água cave presents the cephalon with seven tubercles and pereonites and pleonite epimera with posterior points well-developed, curved and directed outwards, in a pattern similar to D. echinatus (Fig. 6E).
Habitat and ecological remarks. Specimens of D. spinatus sp. nov. were found in two caves in the municipality of Iuiú, a region with several caves and cave-restricted endemic species (Souza et al., 2015; Souza and Ferreira, 2018; Cardoso et al., 2020; 2021). Other caves in the area were also inventoried, however specimens of D. spinatus sp. nov. were only found in these two caves. This area is located in the Caatinga domain, the only xeric biome of Brazil with xeromorphic and deciduous vegetation (Fig. 6A). Several specimens of D. spinatus sp. nov. were found in Honorato cave, a limestone cave with 150 meters of horizontal projection. This cave has a single entrance leading to a wide chamber (Fig. 6B), partially trespassed by an intermittent stream that occurs in the cave main conduit. During dry periods, only a few ponds are observed inside the cave, while during rainy periods the stream can f low, especially after strong rains. Several specimens were found from the middle portion of the cave to the deepest chamber (Fig. 6D). In all cases, they were sheltered under rocks on the cave f loor distant from the potentially f looded areas. Although three samplings have been performed in this cave (in 2008, 2012, and 2021), specimens of D. spinatus sp. nov. were only found in the last sampling event, although body remnants potentially belonging to this species were observed in 2008. It is worth mentioning that in the first two samplings, there was a forested area surrounding the cave. In the last sampling, however, this forest was no longer present, and a considerable area of exposed soil was observed.
The presence of living specimens of D. spinatus sp. nov. only in the last sampling may have occurred due to their migration from the external area to the cave environment, seeking more suitable habitat. Considering that the species lacks any troglomorphic traits, it is likely that it exhibits external populations and their occurrence in caves may be related to the presence of impacts (such as deforestation) in the epigean environments. A single specimen was observed in Tapera D’água cave, located around 11.5 km away from Honorato cave. This cave presents around 300meters of horizontal projection, trespassed by a stream. The single specimen (Fig. 6E) was also found under a rock on the cave floor, in a chamber located in the deep portion of the cave (Fig. 6C), far from the potentially f looded areas. The surrounding area of this cave is more preserved, although there are signs of human impacts in the past (like deforested areas and some abandoned water reservoirs). In this sense, several suitable habitats seem to exist for the species in the cave surroundings.
description: Published as part of B, Giovanna Monticelli Cardoso, B, Rafaela Bastos-Pereira & B, Rodrigo Lopes Ferreira, 2023, Cave-dwellers Diploexochus (Isopoda, Armadillidae): new species and new records of the genus from Brazil, pp. 1-15 in Nauplius (e 2023008) (e 2023008) 31 on pages 3-9, DOI: 10.1590/2358-2936e2023008, http://zenodo.org/record/10904946