Deep Caves Research Articles

Robots that Can Survive the Egg Drop

If you ever did the egg drop challenge, you know it is hard to build something that can protect a fragile egg from crashing into the ground and breaking. Engineers are building soft robots called tensegrity robots, which are designed to survive harsh crashes. The word tensegrity comes from “tension” and “integrity”. It means the robot is made of stiff bars held together with stretchy cables. This flexible structure helps a tensegrity robot absorb the impact from crashes. Someday, these robots might be used to explore dangerous places like deep caves or other planets. These robots could fall off cliffs or into craters. Right now, engineers are making tensegrity robots better and easier to control. In this article, we will explain how tensegrity robots work. We will discuss their advantages, their disadvantages, and what they can be used for.

Evolutionary history of Chinese karst loaches (Nemacheilidae, Karstsinnectes): new insights from mitochondrial-based genomes and description of a new species from Guangxi, China

The genus Karstsinnectes of blind fishes known as karst loaches from China was established in 2023 during a revision of the genus Oreonectes (Nemacheilidae). Six species are recorded in this study and some taxonomic progress has been made; however, the lack of genetic data for some species (e.g., K. anophthalmus) may have weakened our current understanding of Karstsinnectes. This study reassessed the phylogeny and evolutionary history of Karstsinnectes by integrating a combination of previously published and newly sequenced mitochondrial genomic data. A phylogenetic tree was developed that was able to divide Karstsinnectes into two clades corresponding to drainages and clarify the phylogenetic position of K. anophthalmus. Divergence times show that Karstsinnectes originated at the Oligocene/Miocene boundary (~22.37 Mya), with the most recent common ancestor occurring in the early Miocene (~18.87 Mya) and interspecific divergence occurring in the late Miocene. Ancestral area reconstruction suggests that the most recent common ancestor of Karstsinnectes most likely inhabited the Hongshui River basin and dispersed into the Zuojiang-Yujiang, Beipanjiang, and Youjiang river basins during the early Miocene (~18.87 Mya), middle Miocene (~12.78 Mya), and late Miocene (~6.71 Mya), respectively. The dispersal under the influence of orogenesis and a monsoon climate drove the speciation and diverse distribution of Karstsinnectes. Such findings are important for conservation considering that Karstsinnectes strictly inhabits deep caves. Additionally, the taxonomic status of the distributed Karstsinnectes population in Leiping Town, Daxin County, Guangxi, China was revised by combining genetic and morphological differences to describe this population as a new species, Karstsinnectes daxinensis Luo, Zhou & Zhou, sp. nov. The definition of the phylogenetic position of K. anophthalmus emphasizes the importance of using type locality material for the identification of cryptic species.

Prezimovališča velikega podkovnjaka <i>Rhinolophus ferrumequinum</i> (Schreber, 1774): podatki iz štirih globokih jam v Sloveniji

In this paper, we present data on not yet surveyed hibernacula of the greater horseshoe bat (Rhinolophus ferrumequinum) from three deep caves in SE Slovenia (Čaganka, Kaščica, Topli vrh 5) and one in W Slovenia. We found between 161 and 255 overwintering greater horseshoe bats in the caves, in addition to six other species. These data show that some deep caves are still unexplored for bats, although bat sightings have been reported in the past. Targeted survey of caves that are harder to access or those from which larger number of bats have been reported from could contribute not only additional distribution data, but also data on higher concentrations of hibernating bats.

Film, fotografie, feit en fictie in het Pollino-gebergte (Zuid-Italië)

Film, photography, fact and fiction in the Pollino Mountains (Southern Italy)The film “Il Buco” (The Hole, 2022) by Michelangelo Frammartino is about a speleological expedition in the Pollino mountains (northern Calabria, Italy) in 1961. It won the Special Jury Award at the 2022 Venice Film Festival and received excellent reviews in the Dutch press (Volkskrant, Trouw, NRC, VPRO Cinema). In the film, an old shepherd at the end of his life observes a group of speleologists exploring an exceptionally deep cave. The shepherd dies just as the speleologists discover the end of the cave. To situate the death scene, Frammartino reconstructed a typical shepherd’s dwelling used in the days when the transhumance summer camps in the Pollino mountains were still used as shepherds’ summer dwellings. Frammartino based the reconstruction on black-and-white pictures from the archive of Giuseppe De Matteis, a speleologist from Turin, who took part in the expedition. De Matteis took several photographs of such shepherd´s dwellings during the period of the cave exploration, especially at the site of Mandra Vecchia, which is now part of the field study area of the Pollino Archaeological Landscape Project (PALP), led by the authors since 2020. These shepherds’ huts were made of wooden poles and planks and reinforced at ground level with limestone blocks. Other pastoral facilities, such as animal pens and sheds for cheesemaking, were located nearby. Archaeological research on the remains of these summer camps, combined with interviews, is beginning to reveal everyday life in Pollino summer camps. In this paper we bring together fact and fiction based on Frammartino’s documentary from 2021, Giuseppe De Matteis´ photo archive from the 1960s and our own fieldwork in the area.

‘Making-remote’ as an Alternative to Realism in Late Palaeolithic Cave Art: Representations of the Human at the Threshold of Appearance

Abstract I initiate the concept of ‘making-remote’ to capture various strategies for representing the human in late Palaeolithic cave art. Drawing out the role of remoteness within phenomenological accounts of perception (Husserl and Merleau-Ponty), as well as offering an analysis of a wide range of archaeological evidence, I argue that realism does not capture the specificity of these human representations. In contrast to naturalistic animal representations, humans are consistently represented with a high degree of abstraction e.g. schematisation and abbreviation. I also argue for a site-specific distinction between deep caves and rock-shelters. Following Bourdier (2010) and Pinçon (2012), art at sites such as Roc-aux-Sorciers is best understood as stylised ‘public art’. Meanwhile, the highly expressive and realist art of La Marche is domestic in contrast to the exclusively symbolic art of deep caves. In conclusion I argue that ‘making-remote’ in cave art’s human representations exhibits complex relations to self and others.

The geomicrobiology of limestone, sulfuric acid speleogenetic, and volcanic caves: basic concepts and future perspectives.

Caves are ubiquitous subterranean voids, accounting for a still largely unexplored surface of the Earth underground. Due to the absence of sunlight and physical segregation, caves are naturally colonized by microorganisms that have developed distinctive capabilities to thrive under extreme conditions of darkness and oligotrophy. Here, the microbiomes colonizing three frequently studied cave types, i.e., limestone, sulfuric acid speleogenetic (SAS), and lava tubes among volcanic caves, have comparatively been reviewed. Geological configurations, nutrient availability, and energy flows in caves are key ecological drivers shaping cave microbiomes through photic, twilight, transient, and deep cave zones. Chemoheterotrophic microbial communities, whose sustenance depends on nutrients supplied from outside, are prevalent in limestone and volcanic caves, while elevated inorganic chemical energy is available in SAS caves, enabling primary production through chemolithoautotrophy. The 16S rRNA-based metataxonomic profiles of cave microbiomes were retrieved from previous studies employing the Illumina platform for sequencing the prokaryotic V3-V4 hypervariable region to compare the microbial community structures from different cave systems and environmental samples. Limestone caves and lava tubes are colonized by largely overlapping bacterial phyla, with the prevalence of Pseudomonadota and Actinomycetota, whereas the co-dominance of Pseudomonadota and Campylobacterota members characterizes SAS caves. Most of the metataxonomic profiling data have so far been collected from the twilight and transient zones, while deep cave zones remain elusive, deserving further exploration. Integrative approaches for future geomicrobiology studies are suggested to gain comprehensive insights into the different cave types and zones. This review also poses novel research questions for unveiling the metabolic and genomic capabilities of cave microorganisms, paving the way for their potential biotechnological applications.

Deep Ocean and Caves: the Ultimate Frontiers in Tourism

In the ever-shrinking world, the tourism industry is looking for new spaces to explore. It is redefining the known ones and reaching for new ones, which are often located right on geographical peripheries. While it may seem that only space travel remains a challenge for tourism today, terrestrial environments of the deep ocean and deep caves are still beyond the reach of not only mass tourism, but tourism in general. The goal of the article is to identify objective and subjective, stable or variable, external and internal conditions that explain why the deep ocean and caves represent the ultimate frontiers for tourism. The author questions to what extent this situation will continue in the future and discusses the attractiveness and development prospects of various niche forms of tourism based on the features of the underworld and deep waters which, at first sight, constitute barriers or threats to most tourism activities.

Concentrations and dynamics of carbon dioxide, radioactivity and radon in two caves of Italian Classical Karst (Municipalities of Sagrado and Savogna d’Isonzo)

A 13-month monitoring was carried out in two caves that open up in the north-western sector of the Classical Karst (Gorizia Karst): Antro Casali Neri and Grotta Due Piani. In both, ß + γ radioactivity, radon and CO2 have a seasonal pattern, with maximums in summer and minimums in winter, even if their trends are somewhat different, due to the different morphological and thermal conditions. The increases begin when the outside temperature becomes higher than that of the caves and vice versa, decrease is recorded when outside temperature is below the cave temperature. The more modest daily variations of radon, on the other hand, are evident when its concentration is low. Sometimes they are related to meteorological variations or day/night rhythms, but, in other cases, they have no clearly identifiable causes. In Casali Neri cave the maximum radon activity was 50161 Bq/m3, while the CO2 concentration went off the instrument's scale (> 9999 ppm) only in the first days of August 2021. The highest radioactivity value was also recorded in this cave with 0.85 μSv/h (average of 8 minutes of recording), with peaks up to 1.05 μSv/h. In Due Piani cave, on the other hand, the radon activity was lower, with a maximum of 22138 Bq/m3, however, the CO2 values went off the scale from July to the first days of October 2021. In both cases, in the warm months, radon and CO2 appear to come mainly from the fractured rock of epikarstic zone. Further accumulations can then form in points with poor ventilation. Furthermore, research has shown that high concentrations of these two gases are not only typical of large or deep caves, but also of modest and easily accessible caves.

Subterranean Fauna of the Lukina Jama–Trojama Cave System in Croatia: The Deepest Cave in the Dinaric Karst

The Dinaric Karst is a global hotspot for subterranean diversity, with two distinct peaks of species richness in the northwest and southeast, and an area of a lower species richness in the central part. In this article, we present a species list and describe the ecological conditions of the Lukina jama–Trojama cave system, located in the central part of the Dinaric Karst. This cave system is the deepest and one of the most logistically challenging cave systems sampled so far in the Dinaric Karst. Repeated sampling resulted in a list of 45 species, including 25 troglobionts, 3 troglophiles, 16 stygobionts, and 1 stygophile. Most of the recorded species are endemic to the Velebit Mountain, while three species are endemic to the Lukina jama–Trojama cave system. Within the system, species richness peaks in the deepest third of the cave, most likely reflecting the harsh ecological conditions in the upper parts, including ice, cold winds, and occasional waterfalls. Milder and more stable deeper parts of the cave contain a rich subterranean species community, part of which is associated with two very distinct aquatic habitats, the cave hygropetric and the phreatic zone. The newly recognized hotspot of subterranean biodiversity in the central Dinaric Karst, which has emerged between the two known centers of biodiversity, further highlights the species richness in large cave systems, but also challenges the diversity patterns in the Dinaric Karst overall.

A Review of Speleothems as Archives for Paleofire Proxies, With Australian Case Studies

AbstractWildfires affect 40% of the earth's terrestrial biome, but much of our knowledge of wildfire activity is limited to the satellite era. Improved understanding of past fires is necessary to better forecast how fire regimes might change with future climate change, to understand ecosystem resilience to fire, and to improve data‐model comparisons. Environmental proxy archives can extend our knowledge of past fire activity. Speleothems, naturally occurring cave formations, are widely used in paleoenvironmental research as they are absolutely dateable, occur on every ice‐free continent, and include multiple proxies. Recently, speleothems have been shown to record past fire events (Argiriadis et al., 2019, https://doi.org/10.1021/acs.analchem.9b00767; McDonough et al., 2022, https://doi.org/10.1016/j.gca.2022.03.020; Homann et al., 2022, https://doi.org/10.1038/s41467-022-34950-x). Here we present a review of this emerging application in speleothem paleoenvironmental science. We give a concise overview of fire regimes and common paleofire proxies, describe past attempts to use stalagmites to investigate paleofire, and describe the physical basis through which speleothems can record past fires. We then describe the ideal speleothem sample for paleofire research and offer a summary of applicable laboratory and statistical methods. Finally, we present four case studies from southwest Australia which: (a) explore the geochemistry of ash leachates, (b) detail how sulfate isotopes may be a proxy for post fire ecological recovery, (c) demonstrate how a catastrophic paleofire was linked to changes in climate and land management, and (d) investigate whether deep caves can record past fire events. We conclude the paper by outlining future research directions for paleofire applications.

Molecular identification and mapping of mixed root samples to species and individuals.

This article is a Commentary on Osborne et al. (2023), 238: 1305–1317.

Preliminary results from archaeological investigations at Sudwala Caves, Mpumalanga, South Africa

People seldom used deep cave systems during the late Holocene in South Africa. Consequently, excavations were conducted in 2010 to establish the origins of artefacts found during tourist infrastructure developments at Sudwala Caves. These excavations focused on an area near the mouth of the cave where there was, what appeared to be, intact deposit. Four squares were excavated, bearing cultural remains that point to three use episodes. The first use episode, indicated by Marateng pottery, related to the people of Bokoni. The second, characterised by undecorated pottery, could be linked to Swazi speakers, who were known to have used the caves as a refuge during the 1800s. The third use episode, associated with historical objects, signified cave usage during the second half of the 20th century as a tourist attraction. Material culture removed from the caves during the development of tourism infrastructure, however, might point to a much longer use history.

The genome and diet of a 35,000-year-old Canis lupus specimen from the Paleolithic painted cave, Chauvet-Pont d'Arc, France.

The Chauvet-Pont-d'Arc Cave (Ardèche, France) contains some of the oldest Paleolithic paintings recorded to date, as well as thousands of bones of the extinct cave bear, and some remains and footprints of other animals. As part of the interdisciplinary research project devoted to this reference cave site, we analyzed a coprolite collected within the deep cave. AMS radiocarbon dating of bone fragments from the coprolite yielded an age of 30,450 ± 550 RC yr. BP (AAR-19656; 36,150-34,000 cal BP), similar to ages assigned to Paleolithic artwork and cave bear remains from the same cave sector. Using high-throughput shotgun DNA sequencing, we demonstrated a high abundance of canid DNA and lesser amounts of DNA from the extinct cave bear. We interpret the sample as feces from a canid that had consumed cave bear tissue. The high amount of canid DNA allowed us to reconstruct a complete canid mitochondrial genome sequence (average coverage: 83×) belonging to a deeply divergent clade of extinct mitochondrial wolf lineages that are most closely related to coeval (~35 ka) Belgian wolves. Analysis of the nuclear genome yielded a similar coverage for the X chromosome (2.4×) and the autosomes (range: 2.3-3.2×), indicating that the Chauvet canid was a female. Comparing the relationship of the nuclear genome of this specimen with that of a variety of canids, we found it more closely related to gray wolves' genomes than to other wild canid or dog genomes, especially wolf genomes from Europe and the Middle East. We conclude that the coprolite is feces from an animal within an extinct wolf lineage. The consumption of cave bear by this wolf likely explains its intrusion into the dark cave sectors and sheds new light on the paleoecology of a major cave site.

From light to darkness: the duality of influence of habitat heterogeneity on Neotropical terrestrial cave invertebrate communities

ABSTRACT The theory of habitat heterogeneity, which treats one of the global drivers of biodiversity, is valid for several taxonomic groups and distinct ecosystems, including subterranean environments. However, knowledge about the factors that influence the structure of subterranean communities remains limited, especially in Neotropical regions. We sought to understand the main drivers of invertebrate species richness and composition. For that, we compared the substrate elements of twilight and deep-cave zones and their associated invertebrate communities. Variations in habitat heterogeneity were significantly related to richness in the deep cave zone, but had no effect on the fauna associated with the twilight zone. The local heterogeneity enhanced the richness in the deep cave zone due to the increase in the number of available habitats and the effect on decreasing niche overlap. For communities’ composition, the geographic distribution of caves explained the similarity between the twilight zone of different caves. Therefore, nearby caves have a more similar fauna in the entrance regions but conversely, exhibit a higher dissimilarity between communities associated with the deep-cave zone. This study highlights the influence of local habitat heterogeneity on the invertebrate communities associated with different zones of the cave.

Quantifying troglomorphism in hyperspace

Many ecological and evolutionary studies require to quantify the degree of adaptation of subterranean species to caves or other subterranean systems. In 1962, Kenneth A. Christiansen (1924–2017) coined the term “troglomorphism” to illustrate the process of subterranean adaptation and the suite of adaptive traits of organisms (“troglomorphic traits” or “troglomorphies”) (Christiansen 1962). Although this term was proposed in a paper published in French, “troglomorphism” and its derivatives (e.g. “troglobiomorphism”) became widely adopted jargon in subterranean biology. Yet, after decades of work and countless discussions around the subtle meanings of the term, there is still no consensus on how to best quantify troglomorphism in a simple operational way to support eco-evolutionary research. In a recent interview, Boris Sket made the excellent point that “nothing [makes] sense in speleobiology without a comparison of cave animals with the 'normal' epigean ones” (Lučić 2021). Building on this idea, we contend that one could quantify troglomorphism on a continuous scale within a given group of organisms (e.g., family or genus) as the functional distance of each species to the phylogenetically closest surface species or the “average” surface species (depending on whether phylogenetic information is available or not). We illustrate this approach using subterranean spiders in the genus Troglohyphantes, a well-studied group for which both a phylogeny and functional traits are available (Isaia et al. 2017, Mammola et al. 2020). We tested two approaches: i) quantifying adaptation as the morphological distance of each species to the phylogenetically closest surface-dwelling relative; ii) using a kernel density n-dimensional hypervolume (sensu Blonder et al. 2014) to construct the morphospace occupied by all surface-dwelling species of Troglohyphantes, and quantifying the degree of adaptation of subterranean species as their distance from the centroid of this “average” surface species. To test the effectiveness of these alternative methods, we compare how functional distance varies in relation the habitat occupied by each species (deep caves vs cave entrances vs interstitial habitats) and its range size. We suggest our approach could be applied to any group of subterranean organisms for which a surface relative is known, allowing to explore a range of questions on the degree to which the specialization of a given community relates to local environmental conditions, interspecific interactions, and more.

Identification and Evolution of Different Genetic Types of Deep Karst Caves Controlled by Faults—A Case Study in Huanjiang Sag, Guangxi Province, South China

In recent years, it has become more and more common to drill deep karst caves as a part of deep shale gas resource exploration and engineering construction in South China. However, the amount of research on the genesis and development mechanism of deep karst caves is relatively low. Based on drilling core karst morphology analysis and two-dimensional (2D) seismic and wide-field geophysical exploration methods, it is revealed that the deep karst in the Huanjiang area is mainly composed of net cracks, holes expanding along cracks and dolomite honeycomb pores, and that large karst caves are also developed, which are related to NW-trending faults. The deep karst is developed in the hanging wall of the fault, with a width of 500 m and a height of 1500 m, and a linear distribution along NW faults in the region. Based on Th-U dating, inclusion testing and rare earth elements from cave fillings, it is revealed that the development of deep karst space is related to two deep karst genetic types: The first is the hypogene hydrothermal karst, which developed in the Yanshanian period and is related to regional magmatism. The second is the groundwater deep circulation karst, mainly developed after the Himalayan period, which is related to the deep circulation of meteoric water. The genesis of deep karst space is the result of multi-stage karst superposition and is mainly controlled by faults. It is difficult to determine the specific time points of these two types of deep karst transformation, but according to regional tectonic evolution, we speculate that the Yunnan-Guizhou Plateau has been uplifted since the Himalayan period (>3.54 Ma), and the Carboniferous carbonate rocks and early faults in the Huanjiang area have been exposed, leading to the change and evolution of deep karst. Through comprehensive analysis, a fault-controlled hypogene hydrothermal karst pattern and a meteoric water deep karst pattern are established. The genetic pattern of deep karst provides theoretical support for predicting this kind of karst in southern China and for avoiding drilling deep karst caves as a part of resource exploitation.

Foragers or « Feasters ? » Inequalities in the Upper Palaeolithic

Over the last half century, the dominant view in European archaeology has been that Upper Paleolithic societies were highly mobile egalitarian groups. While this model may be accurate for resource poor areas, it is increasingly evident that in some rich refugia like the Dordogne and Charente, more complex societies existed that exhibited transegalitarian types of characteristics including socioeconomic inequalities. Ethnographically, it is in the context of transegalitarian types of societies that unique features occur such as rich burials, prestige items, feasting, complex astronomical observations, elaborate numbering systems, rituals in deep caves, and other special features of the French Southwest Upper Paleolithic. Indeed, due to the socioeconomic dynamics involved, these features make the most sense as part of transegalitarian societies, whereas both the dynamics and these features are rare or are completely lacking among ethnographic egalitarian foragers. This paper re-assesses the status of Upper Paleolithic hunter/gatherers from the transegalitarian perspective. It focuses particular attention on the role and importance of prestige items making the important distinction between communal ritual prestige items and individual status prestige items. Ten other key features are discussed briefly that indicate the existence of complex hunter/gatherers in the Upper Paleolithic.

Biodiversity of the Huautla Cave System, Oaxaca, Mexico

Sistema Huautla is the deepest cave system in the Americas at 1560 m and the fifth longest in Mexico at 89,000 m, and it is a mostly vertical network of interconnected passages. The surface landscape is rugged, ranging from 3500 to 2500 masl, intersected by streams and deep gorges. There are numerous dolinas, from hundreds to tens of meters in width and depth. The weather is basically temperate subhumid with summer rains. The average yearly rainfall is approximately 2500 mm, with a monthly average of 35 mm for the driest times of the year and up to 500 mm for the wettest month. All these conditions play an important role for achieving the highest terrestrial troglobite diversity in Mexico, containing a total of 35 species, of which 27 are possible troglobites (16 described), including numerous arachnids, millipedes, springtails, silverfish, and a single described species of beetles. With those numbers, Sistema Huautla is one of the richest cave systems in the world.

The conquest of the dark spaces: An experimental approach to lighting systems in Paleolithic caves.

Artificial lighting was a crucial physical resource for expanding complex social and economic behavior in Paleolithic groups. Furthermore, the control of fire allowed the development of the first symbolic behavior in deep caves, around 176 ky BP. These activities would increase during the Upper Paleolithic, when lighting residues proliferated at these sites. The physical peculiarities of Paleolithic lighting resources are very poorly understood, although this is a key aspect for the study of human activity within caves and other dark contexts. In this work, we characterize the main Paleolithic lighting systems (e.g., wooden torches, portable fat lamps, and fireplaces) through empirical observations and experimental archeology in an endokarstic context. Furthermore, each lighting system’s characteristic combustion residues were identified to achieve a better identification for the archaeological record. The experiments are based on an exhaustive review of archaeological information about this topic. Besides, we apply the estimated luminous data of a Paleolithic cave with Paleolithic art (Atxurra in northern Spain) in 3D through GIS technology to delve into the archeologic implications of illumination in Paleolithic underground activities.

Hypoxia in Paleolithic decorated caves: the use of artificial light in deep caves reduces oxygen concentration and induces altered states of consciousness

ABSTRACT In this paper, we present a novel hypothesis as to what led humans in the Upper Paleolithic to penetrate and decorate deep, dark caves. Many of the depictions in these caves are located in halls or narrow passages deep in the interior, navigable only with artificial light. We simulated the effect of torches on oxygen concentrations in structures similar to Paleolithic decorated caves and showed that the oxygen quickly decreased to levels known to induce a state of hypoxia. Hypoxia increases the release of dopamine in the brain, resulting in hallucinations and out-of-body experiences. We discuss the significance of caves in indigenous world views and contend that entering these deep, dark environments was a conscious choice, motivated by an understanding of the transformative nature of an underground, oxygen-depleted space. The cave environment was conceived as both a liminal space and an ontological arena, allowing early humans to maintain their connectedness with the cosmos. It was not the decoration that rendered the caves significant; rather, the significance of the chosen caves was the reason for their decoration.