Groundwater is a hidden global keystone ecosystem.

Groundwater is a vital ecosystem of the global water cycle, hosting unique biodiversity and providing essential services to societies. Despite being the largest unfrozen freshwater resource, in a period of depletion by extraction and pollution, groundwater environments have been repeatedly overlooked in global biodiversity conservation agendas. Disregarding the importance of groundwater as an ecosystem ignores its critical role in preserving surface biomes. To foster timely global conservation of groundwater, we propose elevating the concept of keystone species into the realm of ecosystems, claiming groundwater as a keystone ecosystem that influences the integrity of many dependent ecosystems. Our global analysis shows that over half of land surface areas (52.6%) has a medium-to-high interaction with groundwater, reaching up to 74.9% when deserts and high mountains are excluded. We postulate that the intrinsic transboundary features of groundwater are critical for shifting perspectives towards more holistic approaches in aquatic ecology and beyond. Furthermore, we propose eight key themes to develop a science-policy integrated groundwater conservation agenda. Given ecosystems above and below the ground intersect at many levels, considering groundwater as an essential component of planetary health is pivotal to reduce biodiversity loss and buffer against climate change.

Environmental Drivers of the Moonmilk Microbiome Diversity in Some Temperate and Tropical Caves.

Moonmilk is a cave deposit that was used for medical and cosmetic purposes and has lately raised interest for its antimicrobial potential. We studied five moonmilk samples from four caves with different microclimatic conditions, two temperate in north-western and northern Romania (Ferice, Fața Apei, and Izvorul Taușoarelor caves) and one tropical in Minas Gerais, Brazil (Nestor Cave). The physicochemical and mineralogical analyses confirmed the presence of calcite and dolomite as the main phase in the moonmilk. A 16S rRNA gene-based metabarcoding approach showed the most abundant bacteria phyla Proteobacteria, GAL15, Actinobacteriota, and Acidobacteriota. The investigated caves differed in the dominant orders of bacteria, with the highest distance between the Romanian and Nestor Cave samples. Climate and, implicitly, the soil microbiome can be responsible for some differences we found between all the samples. However, other factors can be involved in shaping the moonmilk microbiome, as differences were found between samples in the same cave (Ferice). In our five moonmilk samples, 1 phylum, 70 orders (~ 36%), and 252 genera (~ 47%) were unclassified, which hints at the great potential of cave microorganisms for future uses.

Cave conservation priority index to adopt a rapid protection strategy: a case study in Brazilian Atlantic rain forest.

Cave environments are characterized by possessing specialized fauna living in high environmental stability with limited food conditions. These fauna are highly vulnerable to impacts, because this condition can frequently be easily altered. Moreover, environmental determinants of the biodiversity patterns of caves remain poorly understood and protected. Therefore, the main goal of this work is to propose a cave conservation priority index (CCPi) for a rapid assessment for troglobiotic and troglophile protection. Furthermore, the troglobiotic diversity, distribution and threats have been mapped in the Brazilian Atlantic forest. To propose the CCPi, the human impacts and richness of troglobiotic and troglophile species of 100 caves were associated. Data related to troglomorphic/troglobiotic fauna from another 200 caves were used to map the troglobiotic diversity and distribution. The CCPi reveals extremely high conservation priority for 15% of the caves, high for 36% and average for 46% of the caves. Fourteen caves with extremely high priorities should have urgent conservation and management actions. The geographical distribution of the 221 known troglobiotic/troglomorphic species allowed us to select 19 karst areas that need conservation actions. Seven areas were considered to have urgent priority for conservation actions. The two richest areas correspond to the "iron quadrangle" with iron ore caves (67 spp.) and the "Açungui limestone group" (56 spp.). Both areas have several caves and are important aquifers. The use of the CCPi can prevent future losses because it helps assessors to select caves with priorities for conservation which should receive emergency attention in relation to protection, management and conservation actions.

Stemmiulus brasiliensis n. sp., a new species of millipede from Brazilian iron ore caves (Diplopoda: Stemmiulida: Stemmiulidae).

A new species of Stemmiulus Gervais, 1844 is described from Amazonian iron ore caves located in Pará State, Brazil. The new species differs from the other Brazilian species by gonopod morphology, especially the angiocoxite and colpocoxite, and for the first pairs of legs of males. A key for the species of Stemmiulus found in Brazil is included.

Ultrastructural analysis and polymorphisms in Coarazuphium caatinga (Coleoptera: Carabidae: Zuphiini), a new Brazilian troglobitic beetle.

Coarazuphium caatinga sp. n. occurs in limestone caves located in Campo Formoso municipality, in the Brazilian Caatinga (Bahia, Brazil). The new species is close to C. formoso although they are morphologically distinct by the elytra sinuosity, which is more pronounced in C. caatinga; the aedeagus is more tapered at the tip in this last species. Important traits found in C. caatinga are the variable size presented by the eyes, and the remarkable variability of body pigmentation among specimens; both traits do not seem to be correlated. Coarazuphium Gnaspini, P., Vanin, S.A. & Godoy, N.M., 1998, species exhibit advanced troglomorphic characters in comparison to other Brazilian cave beetles, as are increased extra-optic sensory structures, presence of particular sensilla, and sensory and gustatory receptors. These characters are not detected under routine microscopy and thus require ultrastructural methods for their study.

A new troglobiotic species of Hyalella (Crustacea, Amphipoda, Hyalellidae) with a taxonomic key for the Brazilian species.

The freshwater crustaceans from the order Amphipoda occur mainly in cold and temperate climates. However, in the tropics, these animals can be more abundant in subterranean environments, where the temperatures are milder than in surface. Despite being accepted that the number of species of freshwater amphipods in South America is lower when compared to other regions, recent descriptions have shown that its diversity is certainly underestimated. In this study, a new species of the genus Hyalella is described for Brazil, the fourth troglobiotic species of Hyalella for the country and the sixth in the world. The new species was found on the epikarst of a cave in São Paulo state, Southeastern Brazil. Besides, the new species shows typical characteristics from organisms adapted to the subterranean environments, a pattern also observed in the other troglobiotic species of the genus.

Two new subterranean species of Hyalella Smith, 1874 (Crustacea: Amphipoda: Hyalellidae) from Brazil.

Two new species of Hyalella from Brazil are described. Hyalella veredae sp. n. shows the following characters: eyes reduced or absent in some specimens; antenna 1 and antenna 2 of similar size, and a curved seta on the inner ramus of male uropod 1. Hyalella formosa sp. n. is characterized by the absence of eyes, antenna 1 longer than antenna 2 and a curved seta on the inner ramus of male uropod 1. The species were found on caves located in two private properties, both under the impact of agricultural activities, which demonstrates a potential threat to these subterranean environments.

The ticking clock in the dark: Review of biological rhythms in cave invertebrates.

Circadian clocks, internal mechanisms that generate 24-hour rhythms, play a crucial role in coordinating biological events with day-night cycles. In light-deprived environments such as caves, species, particularly isolated obligatory troglobites, may exhibit evolutionary adaptations in biological rhythms due to light exposure. To explore rhythm expression in these settings, we conducted a comprehensive literature review on invertebrate chronobiology in global subterranean ecosystems, analyzing 44 selected studies out of over 480 identified as of September 2023. These studies revealed significant taxonomic diversity, primarily among terrestrial species like Coleoptera, with research concentrated in the United States, Italy, France, Australia, and Brazil, and a notable gap in African records. Troglobite species displayed a higher incidence of aperiodic behavior, while troglophiles showed a robust association with rhythm expression. Locomotor activity was the most studied aspect (>60%). However, approximately 4% of studies lacked information on periodicity or rhythm asynchrony, and limited research under constant light conditions hindered definitive conclusions. This review underscores the need to expand chronobiological research globally, encompassing diverse geographical regions and taxa, to deepen our understanding of biological rhythms in subterranean species. Such insights are crucial for preserving the resilience of subsurface ecosystems facing threats like climate change and habitat loss.

A new cave-dwelling species of Charinus (Amblypygi: Charinidae) from northern Brazil.

We present the description and illustration of a new species within the genus Charinus Simon, 1892, discovered in a cave located in the state of Tocantins, situated in the northern region of Brazil. Charinus tocantinensis sp. nov., can be distinguished from its congeners by the following combination of distinctive characters: pedipalp femur with four dorsal spines and four ventral spines; well-developed median eyes and median ocular tubercle; female gonopods sucker-like, slightly longer than wide, opening rounded and margins with fold with each a small posterior slit; cheliceral claw with ten denticles. In addition to the species description, we have included a key for identifying Charinus species in Brazil, along with a distribution map that highlights the known species in the country. This newly described species marks the first formal documentation of a Charinus species within the state of Tocantins. With the addition of this species, the global tally of recognized Charinus species now stands at 98, and Brazil, in particular, is home to a total of 44 formally described species within this genus.

Synopsis of the Ptiloneuropsis Roesler, 1940 (Psocodea: Psocoptera: Ptiloneuridae), with a new cave-dwelling species from Brazil.

A new cave-dwelling species of Ptiloneuropsis from southeastern Brazil, is here described based on both sexes, illustrated and named as: Ptiloneuropsis krenaki sp. nov. This new species differs from Ptiloneuropsis immaculata Roesler, 1940 and Ptiloneuropsis diamantina Silva-Neto, Garca Aldrete & Rafael, 2018 in details of the hypandrium and phallosome. In addition to the third new species of the Ptiloneuropsis, descriptions of variation in the fore and hindwings veins are also given. The diagnosis of Ptiloneuropsis is updated, and P. immaculata is redescribed. Furthermore, the first identification key for Ptiloneuropsis species, based on males, is presented.

Two new species of Pseudonannolene Silvestri, 1895 from Brazilian iron ore caves (Spirostreptida: Pseudonannolenidae).

Pseudonannolene gogo sp. n. and Pseudonannolene rolamossa sp. n. are described from individuals collected from Brazilian iron ore caves, Minas Gerais state. The family Pseudonannolenidae is exclusively Neotropical and frequently found in caves of Brazil, from which 23 species are known. The new species are compared with its congeners and with other Brazilian cave-dwelling species.

Two new species of Pseudonannolene Silvestri, 1895 from Brazilian limestone caves (Spirostreptida: Pseudonannolenidae): synotopy of a troglophilic and a troglobiotic species.

Pseudonannolene ambuatinga n. sp. and Pseudonannolene saguassu n. sp. are described from individuals collected in limestone caves in the municipality of Pains, Minas Gerais, Brazil, which comprises a scenario of great conflict between speleological preservation and limestone extraction. The two species differ in their gonopod morphology and in size and color. Pseudonannolene ambuatinga n. sp. is regarded as the second troglobite species known for the family. This is the first report for Brazil of syntopy in two congeneric species in the same cave.

The first troglobitic Cryptops (Trigonocryptops) (Chilopoda: Scolopendromorpha) from South America and the description of a non-troglobitic species from Brazil.

Cryptops (Trigonocryptops) iporangensis n. sp., and C. (T) hephaestus n. sp. are described from SE Brazil. C. (T) iporangensis n. sp. presents highly troglomorphic characters and is described from a remarkable cave system located in Sao Paulo State, the Areias cave system, from were other 16 troglobitic species are also known. C. (T) hephaestus n. sp. was described on specimens collected in three caves of the "Quadrilátero Ferrifero" (Iron quadrangle), in Minas Gerais State, but does not presents a clear specialization to subterranean habitat. The new troglobitic species can be separated from other species of Cryptops (T.) from Brazil and all troglobitc species of the genus Cryptops by presenting incomplete paramedian sutures on tergites, antennal article 1 with an inverted Y-shaped suture on its proximal part and distal spinose processes on ultimate leg. C. (T.) hephaestus differs from the other species of Cryptops (Trigonocryptops) from Brazil by presenting anterior oblique sutures on tergites 2-7 and posterior oblique sutures on tergites 1-3. Cryptops (Cryptops) galatheae Meinert, 1886 is moved here to the subgenus Trigonocryptops.

The first troglobitic Pseudonannolene from Brazilian iron ore caves (Spirostreptida: Pseudonannolenidae).

Pseudonannolene spelaea n. sp. is the first strictly cave-dwelling species described for the family Pseudonannolenidae. It is found in iron ore caves in the Brazilian Amazon. The family Pseudonannolenidae is exclusively Neotropical and frequently found in caves of Brazil, from which 20 species are known. The new species is compared with its congeners and with related cave-dwelling species. The family Pseudonannolenidae is discussed, and comments are presented on the conservation status of the caves where the species is found, which potentially may be the target of anthropogenic impacts resulting from iron ore extraction.

Description of Mitogoniella mucuri sp. nov. (Opiliones: Gonyleptidae) and considerations on polymorphic traits in the genus and Gonyleptidae.

Mitogoniella mucuri sp. nov. is described for some caves in Minas Gerais, Brazil. This species differs from other Mitogoniella species by large tubercles on the ocularium that have fused bases and free apices (or almost fully fused tubercles with bifurcated apices), and by a large dry-mark between tubercles on the longitudinal groove of area III. Mitogoniella species are hard to recognize: their males lack any armature on leg IV (normally an important diagnostic character among gonyleptid species), and they also present many polymorphisms in coloration (dry-mark), male secondary sex characters, the number of dorsal scutal granules, and the shapes of tubercles on the ocularium. The patterns of these polymorphisms are discussed for the genus and for the family. The present work also presents new occurrences for all the species of the genus, and their biogeography is discussed.

A new species of Charinus Simon, 1892 from northeastern Brazil with comments on the potential distribution of the genus in Central and South Americas (Arachnida: Amblypygi: Charinidae).

A new species of the genus Charinus Simon, 1892 is described from caves in the Rio Grande do Norte, Brazil. This is the first record of the genus for the state. This paper presents a map of the Charinus species distribution in Brazil with new records and a map of potential distribution of the genus in South and Central Americas. An updated key for Charinus species from Brazil is also presented.

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).

A new cave-restricted species of Benthana and two cave-restricted species of Benthanoides are described from iron-ore caves located in the Serra dos Carajás complex, Pará state, in the Amazon biome. Benthana alba n. sp. occurs only in one cave in the south of Serra Norte, in the plateau N5 (cave N5SM2_0077); Benthanoides amazonicus n. sp. occurs in several caves in the north of Serra Norte, in the plateau N1; and Benthanoides tarzan n. sp. occurs in several caves in the Serra do Tarzan. This record represents an important distribution data for Benthana that typically occurs in the Brazilian Atlantic Forest, indicating that such species may represent a relict lineage of this genus. Additionally, efforts must be directed towards the conservation of these species, all of which are associated with caves occurring in areas of intense mining activity.

The first cave-dwelling species of Whiteheadiana Perrault, 1994 (Carabidae: Clivinini) from Brazil.

The new species Whiteheadiana thaisae sp. nov., is described and illustrated. This is the first species of the genus known for Toca do Gonalo cave, located in Campo Formoso municipality, Bahia state, northeastern Brazil. The new species differs from the other species of the genus by presenting frontal lateral projections two times longer than eyes; frons with two parallel carinae deeply notched near the clypeus, shallow toward the gena, and it is a restricted eventual cave-restricted. Ecological notes about habitat and conservation issues are provided.

Two new species of Endecous Saussure, 1878 (Orthoptera: Grylloidea: Phalangopsidae) from caves in central-western Brazil, with the proposition of a new subgenus to accommodate E. vitreus Bolfarini & Campos, 2023.

The genus Endecous (Orthoptera, Grylloidea, Phalangopsidae) encompasses over 20 species, grouped into four subgenera: E. (Endecous), E. (Pedroecous), E. (Notendecous), and E. (Ramalhoecous). In this study, we present the description of two novel species belonging to the subgenus Endecous (Endecous) Saussure, 1878 (Phalangopsidae) discovered in caves located within the Serra da Bodoquena region of Mato Grosso do Sul state, Brazil. The descriptions are based on the distinguishing male genitalia characteristics, among other traits. Furthermore, we introduce a new subgenus, namely Endecous (Bodoquenaecous), specifically created to accommodate the recently discovered species E. vitreus, also found in caves within the same area. Initially, E. vitreus was placed under the subgenus Endecous; however, due to its numerous distinct traits, the establishment of a new subgenus became justified. In this study, we also introduce the first pictorial key for the subgenera within the genus Endecous. Additionally, we briefly discuss observed troglomorphic adaptations in species belonging to this genus. Finally, comprehensive ecological observations and conservation status assessments are provided for both newly described species, as well as for E. vitreus.

Three new cricket species and a new subgenus of Endecous Saussure, 1878 (Grylloidea: Phalangopsidae) from caves in northeastern Brazil.

The genus Endecous (Orthoptera, Grylloidea, Phalangopsidae), commonly found in caves, comprises more than 20 species, grouped into three subgenera: E. (Endecous), E. (Pedroecous) and E. (Notendecous). In this study, from differences observed mainly in the male genitalia, we describe a new subgenus-Endecous (Ramalhoecous) n. sp.-as well as three new species-E. (R.) infernalis n. sp., E. (E.) zin n. sp. and E. (E.) zaum n. sp.-all of them collected in caves in the Serra do Ramalho region, Northeastern, Brazil. We also briefly discuss some troglomorphisms verified in one of the new species: E. (R.) infernalis n. sp.