Chaimowiczia: a new Iuiuniscinae genus from Brazil (Oniscidea, Synocheta, Styloniscidae) with the description of two new troglobitic species

A new genus of Styloniscidae, Chaimowiczia gen. nov., is described with two new species: Chaimowiczia tatus sp. nov. from Gruta do Padre cave (Santana, Bahia) and Chaimowiczia uai sp. nov. from Lapa d’água do Zezé cave (Itacarambi, Minas Gerais). The new genus and species were allocated into the subfamily Iuiuniscinae, hitherto monotypic, by the pronounced rectangular-shaped lateral pereonites epimera, dorsal surface smooth, body outline continuous without a gap between pereon and pleon, and pleonites 3 to 5 developed forming tips. The two species of Chaimowiczia gen. nov. differ in the shape of cephalon antennal lobes, pereonite 1 epimera, pleonite 5 posterior margin and uropod exopod and endopod proportion.

We present a new genus of Styloniscidae allocated into the subfamily Iuiuniscinae, with the description of two new species found in Brazilian caves. In addition to the taxonomic descriptions, this paper provides ecological and conservation information related to the new species and the subterranean ecosystems where they were found.

Materials and methods
The specimens were manually collected and fixed in 70% ethanol. They were measured and photographed with a ZEISS Axio ZoomV16 stereomicroscope coupled with an Axio Cam 506 Color camera, dissected and mounted in slides using Hoyer's medium in the Center of Studies on Subterranean Biology of the Federal University of Lavras (CEBS-UFLA, Lavras, Brazil). Drawings were made either from photographs or with the aid of a camera lucida coupled with the microscope Leica DM750. Illustrations were prepared using the software GIMP (v. 2.8) (Montesanto 2015(Montesanto , 2016. For analysis of the dorsal cuticular structures, pictures were taken using the scanning electron microscope Hitachi TM4000. Holotype and paratypes of the new species were deposited in the Subterranean Invertebrate Collection of Lavras (ISLA) in the Federal University of Lavras.
Diagnosis. Body non-volvational. Cephalon with antennal lobes, distinct suprantennal line bent in middle, vertex with lateral grooves. Body outline continuous with pereonites epimera well developed, widely separated, pleonites 1 and 2 bridge the gap between pereon and pleon, pleonites 3-5 with epimera well developed. Telson with subtriangular distal half depressed with rounded apex. Antennula of three articles covered with setae, distal article with two apical aesthetascs. Antenna with flagellum of three distinct articles covered with setae. Mandibles pars molaris large and projected. Maxillula outer ramus with entire teeth and two long and thick setose stalks; inner ramus with three penicils at apex. Maxilla inner lobe wider than outer lobe. Maxilliped basis trapezoidal; endite bearing one penicil between two strong teeth. Pereopods with unbranched dactylar setae. Genital papilla lanceolate. Male pleopod 1 exopod and endopod subequal in length, endopod two-jointed, with flagelliform distal article. Male pleopod 2 endopod with two thickset articles, distal one tapering apically.
Etymology. The genus is named after Dr Flavio Chaimowicz, a physician who provided important contributions for the Brazilian speleology. Gender feminine.
Remarks. The diagnosis of Styloniscinae, Notoniscinae and Kuscheloniscinae has been presented in old publications that unfortunately include few characters of their members (Vandel 1952;Strouhal 1961). Meanwhile, more details have been provided for Iuiuniscinae (Souza et al. 2015). According to Vandel (1952: 95), Styloniscinae exhibit i. body smooth or tuberculated, without longitudinal ribs, and ii. pleon-epimera 1-5 narrow, with a gap between the pereon and pleon. For Notoniscinae, Vandel (1952: 95-96) noted i. pereonites dorsum tuberculated or with longitudinal ribs (sometimes with conspicuous protuberances also on the pleonites); ii. pleon-epimera 3-5 or 4-5 well developed, reducing the gap between the pereon and pleon; iii. genital tract of styloniscid type; iv. eyes with 3 ommatidia. For Kuscheloniscinae Strouhal (1961: 217) indicated the following: i. outline of pleon continuous with that of pereon; ii. pleonepimera 3-5 very reduced; iii. anterior pereonites with protuberances and lateral ribs. Finally, Iuiuniscinae are characterized by i. dorsal integument smooth or without ribs or large protrusions; ii. enlarged epimera; iii. pereopod 1 much shorter than the others flanking the head; iv. pleon-epimera forming acute tips; v. telson distal half lower than the proximal half, and vi. habit to build mud shelters to molt and to protect juveniles (Souza et al. 2015). Chaimowiczia gen. nov. can be promptly distinguished from all the already described Styloniscidae by the pronounced rectangular-shaped lateral projections of pereonites, which is not observed in other members of this family. Moreover, tubercles are absent and the body outline is continuous without a gap between pereon and pleon. Epimera are developed in pleonites 3 to 5 forming tips, and telson distal half is narrower than the proximal half. Based on these characters, Chaimowiczia gen. nov. was allocated into the subfamily Iuiuniscinae.
Chaimowiczia gen. nov., as well as Iuiuniscus, occurs in the São Francisco River Basin and the caves are in the limestone plateaus of the Bambuí Group (Auler et al. 2001) (Fig. 1). The new genus resembles Iuiuniscus by the widely separated pereonites 1-7 epimera directed outwards, pleonites 3-5 epimera well developed; mandibles pars molaris large and projected. However, Chaimowiczia gen. nov. is not able to build mud shelters as Iuiuniscus. These genera also differ in the number of aesthetascs in antennula distal article (Iuiuniscus 12 versus 2 in Chaimowiczia gen. nov.), in the number of articles in antennal flagellum (Iuiuniscus 8 versus 3 in Chaimowiczia gen. nov.), teeth morphology in the maxillula outer ramus (outer group with curved teeth in Iuiuniscus versus straight in Chaimowiczia gen. nov.; inner group with two longer teeth in Iuiuniscus versus subequal in Chaimowiczia gen. nov.), male pleopod 1 exopod and endopod proportion (exopod longer than endopod in Chaimowiczia gen. nov. versus the opposite in Iuiuniscus), shape of male pleopod 1 exopod, shape of male pleopod 2 exopod (triangular in Iuiuniscus versus semicircular in Chaimowiczia gen. nov.), and notably by the morphology of pereon and pleon (with very prominent and very acute tips in pereon and pleon epimera in Iuiuniscus versus not so prominent nor so acute tips in Chaimowiczia gen. nov.).  Diagnosis. Chaimowiczia tatus sp. nov. is characterized by pereonite 1 epimera directed sideways; quadrangular antennal lobes; pleonites 3-5 epimera tips well developed, pleonite 5 short, not surpassing the apex of telson; and uropods endopod and exopod subequal in length.
Etymology. The epithet "tatus" refers to the "Tatus II project", an experiment of human permanency inside a cave held in 1987, conducted in Gruta do Padre cave.
During the experiment, a group of speleologists stayed for 21 days inside the cave performing topographic and speleology surveys (Chaimowicz, 1987).
Ecological remarks. Gruta do Padre comprises an extensive cave with 16,400 m of horizontal projection and is currently considered the fifth longest cave in Brazil (Rubbioli et al. 2019). It presents two entrances and three distinct levels. A river flows in the lowest level, which is the most extensive. The main entrance comprises a huge rock shelter (Fig. 5A) that connects to a descending set of flowstones (Fig. 5A, B). Specimens of Chaimowiczia tatus sp. nov. were observed in a single chamber in the second level (ca. 500 m from the main cave entrance), in clayish sediment pools (Fig. 5C-E). Two other troglobitic styloniscid species occur in this cave: one terrestrial (Pectenoniscus santanensis Cardoso, Bastos-Pereira, Souza & Ferreira, 2020a) and one new amphibious species. A peculiar condition is observed regarding the distribution of the two styloniscid species. While one species is amphibious, occurring in both aquatic and moist terrestrial habitats, C. tatus sp. nov. was observed exclusively underwater. The ponds where C. tatus sp. nov. occurs are devoid of the amphibious species, suggesting they might avoid each other. There are dozens of ponds along the lower conduit formed by the river overflow or by percolating water (especially in the case of travertine pools), where hundreds of individuals of the amphibious species were observed. However, no specimens of C. tatus sp. nov. were observed in the lower level coexisting with the other styloniscid. The ponds in which specimens of C. tatus sp. nov. occur usually present the substrate full of traces made by these individuals (Fig. 5C) indicating their high motility and activity. Since no visible organic matter was observed within the ponds (like bat guano or vegetal debris), they may be feeding on the substrate itself, which might be rich in microorganisms. Gruta do Padre Cave presents other troglobitic species: the beetle Coarazuphium tessai (Godoy & Vanin, 1990), the amphipod Spelaeogammarus santanensis Koenemann & Holsinger, 2000, and the millipede Phaneromerium cavernicolum Golovatch & Wytwer, 2004. All of them were discovered during the Tatus II experiment, demonstrating the relevance of this cave regarding the biota. Although some alterations were caused during the Tatus II experiment (in both the cave interior -a camping area was established inside the cave -and the external area), no impacts from past actions are currently visible. The external environment surrounding the cave was altered by the replacement of the native vegetation by pastures or crops. On the other hand, the inner portion of the cave is well preserved. Since the huge extension of the cave and the fact that only a few speleologists visit it each year (especially due to the difficult access), C. tatus sp. nov. does not seem to be currently threatened. Diagnosis. Chaimowiczia uai sp. nov. is characterized by the concave shape of pereonites epimera, with pereonite 1 epimeron directed frontward; round antennal lobes; pleonites 3-5 epimera with tips well developed, pleonite 5 surpassing apex of telson; and uropods endopod longer than exopod. Description. Maximum length: male, 8 mm. Colorless, eyes absent (Fig. 6A,  7A, B). Dorsal surface smooth covered with scale setae with long base (reaching half the total length) and free sensory hair (Fig. 7C). Cephalon (Fig. 7A, B) vertex with lateral grooves; frons with distinct suprantennal line, downward in middle; round antennal lobes. Body convex; pereonite 1 postero-lateral corners well developed and projected forward, lateral margin concave; pereonite 7 slightly surpassing distal margin of pleonite 2; pleon 3-5 epimera well developed, pleonite 5 surpassing telson apex (Fig. 6A). Telson (Fig. 6B) with distal half subtriangular depressed, rounded apex. Antennula (Fig. 6C) with three articles covered with setae, distal article as long as second article, with two apical aesthetascs. Antenna (Fig. 6D) surpasses pereonite 1 when extended backwards, fifth article of peduncle shorter than flagellum; flagellum with three articles. Left mandible with two penicils (Fig. 6E); right mandible with one penicil (Fig. 6F). Maxillula (Fig. 6G) outer ramus with 5 + 5 teeth, apically entire, and two thick plumose stalks; inner ramus with three penicils, two of them stout. Maxilla (Fig. 6H) with bilobate apex, inner lobe wider than outer lobe with several setae on distal margin. Maxilliped (Fig. 6I) basis distal portion slightly wider than basal; palp apex with tufts of setae; endite rectangular, shorter than palp, setose, apex with one rounded penicil between two strong teeth, inner tooth longer. Pereopod 1 (Fig. 8C) antennal grooming brush composed by pectinate scales longitudinally on frontal face of propodus and carpus, dactylus with one claw; pereopod 7 basis with water conducting system scale rows. Uropod (Figs 6B, 7F) protopod surpasses distal margin of telson, covered with pectinate scales; endopod longer than exopod, inserted at the same level.
Etymology. The epithet "uai" refers to the word often used by people from the state of Minas Gerais, Brazil, to express doubt, astonishment or surprise.
Ecological remarks. Lapa D'Água do Zezé cave is located at the border of Cavernas do Peruaçu National Park. Although most of the outcrop where the cave is inserted within the limits of the park, the cave entrance is outside the park's limit. The external landscape is composed of a well-preserved deciduous forest on the limestone outcrop and surroundings (Fig. 9A), which is inserted in a transition between two phytogeographic domains, Cerrado (Brazilian savannah) and Caatinga (mesophytic and xeromorphic forests). Lapa D'Água do Zezé is a labyrinthine cave with one horizontal entrance (main entrance, Fig. 9C) and at least two vertical openings. The cave presents perennial water bodies with different conditions. The first one comprises the only accessible part of the water table, a narrow passage in the base of a diaclasis (Fig. 9B) close to one of the cave's vertical openings (Fig. 9C). The second area comprises a very small drainage, apparently originated by the water table overflow. Some physical and chemical parameters of the water were measured during one visit (January 2015): dissolved oxygen 3.46 mg/L, temperature 25.35 °C, pH 8.45, electrical conductivity 0.565 µS/ cm, total dissolved solids 0.359 g/L. This cave also harbors two other stygobitic species and one troglobitic species: the amphipod Spelaeogammarus uai (Bastos-Pereira & Ferreira, 2017), which is easily observed in the water table (accessible through the small passage) and seldom at the small drainage; the isopod Xangoniscus santinhoi Cardoso, Bastos-Pereira, Souza & Ferreira, 2020b, which is only observed in the drainage; and the hydrometrid Spelaeometra gruta Polhemus & Ferreira, 2018. Considering the presence of the amphipod on the drainage, it is possible to infer that both water bodies are connected. Each species seems to present specific preferences. Only a few amphipods were observed in the drainage during several visits to the cave. They seem to avoid this area due to the water flow. Interestingly, specimens of C. uai sp. nov. were only found in the water table, sharing the habitat with amphipods, while no specimens were observed in the drainage (Fig. 9D, E). As mentioned for C. tatus sp. nov., C. uai sp. nov. seems to avoid other styloniscid isopods, which are quite abundant along the drainage and very rare at the water table. This apparent avoidance may have resulted from competition between species, and this certainly deserves further investigation. Organic debris is seasonally transported to the water table (during the rainy periods) due to the proximity to the vertical entrance. Accordingly, the observed organic matter is mainly composed of vegetal debris.
Local farmers have installed a gravitational pump inside the cave in order to drag water from the cave for consumption and irrigation (Fig. 9C) (Bastos-Pereira and Ferreira 2017). Hence, the drainage was partially altered and is disturbed by farmers, who periodically remove the sediment to allow water flow. Such intervention occurs with low frequency (once in a year, according to the farmer), and only in a few parts of the drainage. It does not seem to affect the cave communities, especially considering that a great part of the populations may be in inaccessible areas of the cave. Lastly, although the vegetation seems well preserved in the surroundings of the cave entrance, the original forests were severely altered in many areas around the outcrops and the landscape is mainly composed of pastures and crops.
Chaimowiczia gen. nov. was allocated into the subfamily Iuiuniscinae. Iuiuniscinae was created to include Iuiuniscus iuiuensis Souza, Ferreira & Senna, 2015, a species with unique behavior in Oniscidea: it builds semi-spherical shelters using clay. This behavior represents an evolutionary novelty that probably could support the subfamily as a clade (or support a least inclusive group in which this characteristic has arisen), even if other possible species of Iuiuniscinae, such as the new species of Chaimowiczia gen. nov. described here, do not exhibit this characteristic.
Good character interpretation is essential to achieve more robust results in phylogenetic analysis. In taxonomy, primary homology hypotheses are made when taxa are comparatively described. It is not possible to start a phylogenetic analysis without resorting to descriptive works. Improvement of descriptive works such as Campos-Filho et al. (2019) did for Iuiuniscus and Taiti and Montesanto (2020) did for Thailandoniscus Dalens, 1989 is important. Morphological characters can indicate kinship, which may be investigated in future phylogenetic analyses. Thus, hypotheses of primary homologies provided in taxonomic works can be tested and confirmed (or not) as synapomorphies through phylogenetic analyses. Therefore, evolutionary reasonings should be developed in taxonomic works, in addition to character description. However, based on the premises mentioned, it is necessary to amend some arguments provided by Campos-Filho et al. (2019). The illustration provided by these authors for the male pleopod 2 endopod confirms what was established by Souza et al. (2015: 10): "the morphology of the distal part pleopod 2 endopodite of male... is in part similar to Spelunconiscus". Campos-Filho et al. (2019) suggested that such similarity might indicate kinship. This could invalidate Iuiuniscinae along with the similarity between the male exopod 3 of Xangoniscus, Spelunconiscus, and Iuiuniscus. Such similarity might be symplesiomorphic instead. The character states have not been established yet, so such similarities can be considered superficial until future phylogenetic analyses are carried out.
An important morphological trait observed in both species of Chaimowiczia gen. nov. are the rectangular-shaped lateral projections of pereonites epimera and somewhat acute in pleonites. These projections of pereonites and pleonites may be, another synapomorphies of Iuiuniscinae, in addition to the behavioral characteristic already mentioned. These lateral projections differ from the lateral projections in Iuiuniscus, especially considering the pleonites. The presence of morphological modifications (as some sort of spines) in subterranean crustaceans is well documented, and evidences associate them to mechanical defense mechanisms preventing predation (Jugovic et al. 2010;Souza et al. 2015). In some cases, exaggerated spines can be observed, like in the stenasellid Acanthastenasellus forficuloides Chelazzi & Messana, 1985 from Somalia, which shares the habitat with the troglobitic cyprinid predator fish Phreatichthys andruzzii Vinciguerra, 1824 (Messana et al. 2001). The distinct morphology observed in Chaimowiczia gen. nov. species may be related to this tendency. However, no potential predators were observed in their habitats. Hence, a question rises on the origin of these body lateral expansions. Connell (1980) proposed the term "ghost of competition past" to describe one possible reason for observed niche differentiations among species. The theory suggests that competing species may present a lower fitness compared to species that avoids competition by occupying non-overlapping niches. As such, natural selection would favor the non-competing species since their population could increase in contrast to the competing species population. The observed differentiation might be the result from a past competition, the called ghost of competition past. Further studies tested such concept, observing that natural selection reduced interaction strength among cooccurring species, facilitating coexistence and population persistence (Steiner et al. 2007). Sheriff et al. (2010) proposed that the lack of recovery of reproductive rates of the snowshoe hare (Lepus americanus Erxleben, 1777) during the early low phase of the reproductive cycle may be a result from impacts of intergenerational, maternally inherited stress hormones caused by high predation risk during the population decline phases. Following the idea firstly presented by Connell (1980) and posteriorly corroborated by other authors, past predation could have selected some traits in a given population along a time period, but later this selective force may have ceased by the predator disappearance from the habitat. Despite the lack of any direct evidence (as a fossil record, for example), the morphology observed in Chaimowiczia gen. nov. may be a product of a "ghost predation past" in a period when the ancestor populations could be under a predator selective pressure. After ceased the selection, the morphology was kept in an intermediate state, which is currently observed as the pereonite and pleonites 3-5 epimera well developed in Chaimowiczia gen. nov. It is important to stress that such hypothesis deserves further investigation.
The here described genus raises to 17 the number of Styloniscidae living genera in the world, nine of them with occurrence in Brazil. Brazilian caves currently shelter 20 described species of Styloniscidae, while five other are found in epigean habitats (Campos-Filho et al. 2018;Cardoso et al. 2020a, b). The subterranean species deserves special attention regarding conservation actions due to their short-ranged geographical distribution (most of them are restricted to a single cave) and surrounding landscape being frequently threatened by anthropic activities.