Combined uranium-series and electron spin resonance dating from the Pliocene fossil sites of Aves and Milo's palaeocaves, Bolt's Farm, Cradle of Humankind, South Africa.

Bolt's Farm is the name given to a series of non-hominin bearing fossil sites that have often been suggested to be some of the oldest Pliocene sites in the Cradle of Humankind, South Africa. This article reports the results of the first combined Uranium-Series and Electron Spin Resonance (US-ESR) dating of bovid teeth at Milo's Cave and Aves Cave at Bolt's Farm. Both tooth enamel fragments and tooth enamel powder ages were presented for comparison. US-ESR, EU and LU models are calculated. Overall, the powder ages are consistent with previous uranium-lead and palaeomagnetic age estimates for the Aves Cave deposit, which suggest an age between ~3.15 and 2.61 Ma and provide the first ages for Milo's Cave dates to between ~3.1 and 2.7 Ma. The final ages were not overly dependent on the models used (US-ESR, LU or EU), which all overlap within error. These ages are all consistent with the biochronological age estimate (<3.4->2.6 Ma) based on the occurrence of Stage I Metridiochoerus andrewsi. Preliminary palaeomagnetic analysis from Milo's Cave indicates a reversal takes place at the site with predominantly intermediate directions, suggesting the deposit may date to the period between ~3.03 and 3.11 Ma within error of the ESR ages. This further suggests that there are no definitive examples of palaeocave deposits at Bolt's Farm older than 3.2 Ma. This research indicates that US-ESR dating has the potential to date fossil sites in the Cradle of Humankind to over 3 Ma. However, bulk sample analysis for US-ESR dating is recommended for sites over 3 Ma.

Bacterial diversity and geomicrobiology of Winter Wonderland ice cave, Utah, USA.

The Winter Wonderland ice cave, located at an elevation of 3140 m above sea level in the Uinta Mountains of northern Utah, USA, maintains a constant sub-zero temperature. Seasonal snowmelt and rain enter the cave, freeze on the surface of the existing ice, and contribute to a 3-m-thick layered ice mass. This ice mass contains organic matter and cryogenic cave carbonates (CCCs) that date back centuries. In this study, samples of ice, liquid water, and exposed CCCs were collected to examine the bacterial communities within the cave and to determine if these communities vary spatially and between sample types. Flow cytometry showed that cell counts are an order of magnitude higher in liquid water samples than in ice. Epifluorescence microscopy and scanning electron microscopy imaging revealed potential coccoid and bacillus microbial morphologies in water samples and putative cells or calcite spherules in the CCCs. The diversity of bacteria associated with soil, identified through sequence-based analysis, supports the hypothesis that water enters the cave by filtering through soil and bedrock. A differential abundance of bacterial taxa was observed between sample types, with the greatest diversity found in CCCs. This supports a geomicrobiological framework where microbes aggregate in the water, sink into a concentrated layer, and precipitate out of the ice with the CCCs, thereby reducing the cell counts in the ice. These CCCs may provide essential nutrients for the bacteria or could themselves be products of biomineralization.

Combining traceological analysis and ZooMS on Early Neolithic bone artefacts from the cave of Coro Trasito, NE Iberian Peninsula: Cervidae used equally to Caprinae.

Few studies have combined the analysis of use-wear traces, traceology, and the proteomic taxonomic identification method Zooarchaeology by Mass Spectrometry (ZooMS). Traceology provides information on the usage, in this case, of bone artefacts, while ZooMS allows for taxonomic identifications where diagnostic features are otherwise gone. The approaches therefore offer complementary information on bone artefacts, allowing for insights into species selection strategies in bone tool manufacture and their subsequent use. Here we present a case study of 20 bone artefacts, mainly bone points, from the Early Neolithic cave site of Coro Trasito located on the southern slope of the Central Pyrenees. Hitherto, studies on Early Neolithic bone artefacts from the Iberian Peninsula have suggested based on morphological assessments that Ovis aries/Capra hircus constituted the majority of the bone material selected for bone tool production. However, the taxonomic identification in this study suggests that, at this site, Cervidae was selected equally to that of O. aries/C. hircus. Furthermore, bone artefacts made from Cervidae specimens seem to be utilised in a wider range of artefact types compared to O. aries/C. hircus. Coro Trasito's bone artefact species composition is probably site-specific to some degree, however, morphological assessments of bone artefacts might not be representative and could be biased towards certain species. Therefore, research on bone artefacts' usage could possibly gain new insights by implementing ZooMS in combination with traceology.

Disturbance of hibernating bats due to researchers entering caves to conduct hibernacula surveys.

Estimating population changes of bats is important for their conservation. Population estimates of hibernating bats are often calculated by researchers entering hibernacula to count bats; however, the disturbance caused by these surveys can cause bats to arouse unnaturally, fly, and lose body mass. We conducted 17 hibernacula surveys in 9 caves from 2013 to 2018 and used acoustic detectors to document cave-exiting bats the night following our surveys. We predicted that cave-exiting flights (i.e., bats flying out and then back into caves) of Townsend's big-eared bats (Corynorhinus townsendii) and western small-footed myotis (Myotis ciliolabrum) would be higher the night following hibernacula surveys than on nights following no surveys. Those two species, however, did not fly out of caves more than predicted the night following 82% of surveys. Nonetheless, the activity of bats flying out of caves following surveys was related to a disturbance factor (i.e., number of researchers × total time in a cave). We produced a parsimonious model for predicting the probability of Townsend's big-eared bats flying out of caves as a function of disturbance factor and ambient temperature. That model can be used to help biologists plan for the number of researchers, and the length of time those individuals are in a cave to minimize disturbing bats.

Old World Fruit Bats (Pteropodidae, Chiroptera) from the Pleistocene of Vietnam.

Isolated teeth of a lesser short-nosed fruit bat Cynopterus brachyotis (Müller, 1838), a fulvous fruit bat Rousettus leschenaultii (Desmarest, 1820), and a dawn bat Eonycteris spelaea (Dobson, 1871) are described from the Middle Pleistocene Tham Hai cave locality in northern Vietnam (Lang Son Province). These are the first fossil findings of the Old World fruit bats in Vietnam. The Middle Pleistocene association of Pteropodidae from the Tham Hai locality may largely reflect the composition of species that roosted in local caves.

Ancient and remote quartzite caves as a novel source of culturable microbes with biotechnological potential.

Quartzite caves located on table-top mountains (tepuis) in the Guyana Shield, are ancient, remote, and pristine subterranean environments where microbes have evolved peculiar metabolic strategies to thrive in silica-rich, slightly acidic and oligotrophic conditions. In this study, we explored the culturable fraction of the microbiota inhabiting the (ortho)quartzite cave systems in Venezuelan tepui (remote table-top mountains) and we investigated their metabolic and enzymatic activities in relation with silica solubilization and extracellular hydrolytic activities as well as the capacity to produce antimicrobial compounds. Eighty microbial strains were isolated with a range of different enzymatic capabilities. More than half of the isolated strains performed at least three enzymatic activities and four bacterial strains displayed antimicrobial activities. The antimicrobial producers Paraburkholderia bryophila CMB_CA002 and Sphingomonas sp. MEM_CA187, were further analyzed by conducting chemotaxonomy, phylogenomics, and phenomics. While the isolate MEM_CA187 represents a novel species of the genus Sphingomonas, for which the name Sphingomonas imawarii sp. nov. is proposed, P. bryophila CMB_CA002 is affiliated with a few strains of the same species that are antimicrobial producers. Chemical analyses demonstrated that CMB_CA002 produces ditropolonyl sulfide that has a broad range of activity and a possibly novel siderophore. Although the antimicrobial compounds produced by MEM_CA187 could not be identified through HPLC-MS analysis due to the absence of reference compounds, it represents the first soil-associated Sphingomonas strain with the capacity to produce antimicrobials. This work provides first insights into the metabolic potential present in quartzite cave systems pointing out that these environments are a novel and still understudied source of microbial strains with biotechnological potential.

Gypsum Cave Biofilm Communities are Strongly Influenced by Bat- And Arthropod-Related Fungi.

The Gypsum Karst of Sorbas, Almeria, southeast Spain, includes a few caves whose entrances are open and allow the entry and roosting of numerous bats. Caves are characterized by their diversity of gypsum speleothems, such as stalactites, coralloids, gypsum crusts, etc. Colored biofilms can be observed on the walls of most caves, among which the Covadura and C3 caves were studied. The objective was to determine the influence that bat mycobiomes may have on the fungal communities of biofilms. The results indicate that the fungi retrieved from white and yellow biofilms in Covadura Cave (Ascomycota, Mortierellomycota, Basidiomycota) showed a wide diversity, depending on their location, and were highly influenced by the bat population, the guano and the arthropods that thrive in the guano, while C3 Cave was more strongly influenced by soil- and arthropod-related fungi (Ascomycota, Mortierellomycota), due to the absence of roosting bats.

The evolution of olfactory sensitivity, preferences, and behavioral responses in Mexican cavefish is influenced by fish personality.

Animals are adapted to their natural habitats and lifestyles. Their brains perceive the external world via their sensory systems, compute information together with that of internal states and autonomous activity, and generate appropriate behavioral outputs. However, how do these processes evolve across evolution? Here, focusing on the sense of olfaction, we have studied the evolution in olfactory sensitivity, preferences, and behavioral responses to six different food-related amino acid odors in the two eco-morphs of the fish Astyanax mexicanus. To this end, we have developed a high-throughput behavioral setup and pipeline of quantitative and qualitative behavior analysis, and we have tested 489 six-week-old Astyanax larvae. The blind, dark-adapted morphs of the species showed markedly distinct basal swimming patterns and behavioral responses to odors, higher olfactory sensitivity, and a strong preference for alanine, as compared to their river-dwelling eyed conspecifics. In addition, we discovered that fish have an individual 'swimming personality', and that this personality influences their capability to respond efficiently to odors and find the source. Importantly, the personality traits that favored significant responses to odors were different in surface fish and cavefish. Moreover, the responses displayed by second-generation cave × surface F2 hybrids suggested that olfactory-driven behavior and olfactory sensitivity is a quantitative genetic trait. Our findings show that olfactory processing has rapidly evolved in cavefish at several levels: detection threshold, odor preference, and foraging behavior strategy. Cavefish is therefore an outstanding model to understand the genetic, molecular, and neurophysiological basis of sensory specialization in response to environmental change.

De novo transcriptomes of cave and surface isopod crustaceans: insights from 11 species across three suborders.

Isopods are a diverse group of crustaceans, that inhabit various environments, including terrestrial, freshwater, and marine, both on the surface and in the underground. The biological mechanisms underlying their wide range of adaptations to diverse ecological niches remain elusive. In order to unravel the molecular basis of their adaptability, we generated a comprehensive RNAseq dataset comprising 11 isopod species belonging to the three different suborders: freshwater Asellota, marine, brackish and freshwater Sphaeromatidea, and terrestrial Oniscidea, with representatives from families Asellidae, Sphaeromatidae, and Trichoniscidae, respectively. Representatives of each family were collected from both cave and surface environments, representing at least three independent cave colonization events. Three biological replicates were sequenced from each species to ensure data robustness. The 11 high-quality RNAseq datasets will serve as a valuable resource for understanding cave-specific adaptations, comparative and functional genomics, ecological annotation as well as aid in conservation efforts of these non-model organisms. Importantly, transcriptomes of eight featured species have been made publicly accessible for the first time.

Black surfaces on ancient leather tefillin cases and straps from the Judean Desert: Macroscopic, microscopic and spectroscopic analyses.

Tefillin are Jewish ritual artifacts consisting of leather cases, containing inscribed slips, which are affixed with leather straps to the body of the tefillin practitioner. According to current Jewish ritual law, the tefillin cases and straps are to be colored black. The present study examines seventeen ancient tefillin cases discovered among the Dead Sea Scrolls in caves in the Judean Desert. All seventeen cases display grain surfaces with a very dark, nearly black appearance. We start with a hypothesis that the cases were intentionally colored black in antiquity using either a carbon-based or iron-gall-based paint or dye. The aim of this study is to test this hypothesis by subjecting these tefillin cases to a battery of examinations to assess the presence of carbon and iron used as pigments, and of organic materials which may have been used as binding agents in a paint. The tests deployed are: (1) macroscopic and microscopic analyses; (2) multispectral imaging using infrared wavelengths; (3) Raman spectroscopy; (4) Fourier transform infrared spectroscopy (FTIR); and (5) scanning electron microscope (SEM) and energy dispersive X-ray (EDX) spectroscopy. The results of these tests found no traces of carbon-based or iron-gall-based pigments, nor of organic compounds which may have served as binders in a paint. These results suggest that our posited hypothesis is unlikely. Instead, results of the SEM examination suggest it more likely that the black color on the surfaces of the tefillin cases is the result of natural degradation of the leather through gelatinization. The Judean Desert tefillin likely represent tefillin practices prior to when the rabbinic prescription on blackening tefillin was widely practiced. Our study suggests that the kind of non-blackened tefillin which the later rabbis rejected in their own times may well have been quite common in earlier times.

The role of turnover in structuring subterranean aquatic communities in Southeastern Brazil.

Similarly to other animal communities, the diversity of subterranean aquatic fauna is influenced by several factors and processes, such as habitat fragmentation, dispersion, environmental heterogeneity, and physical and chemical water characteristics. Here, we studied cave aquatic communities of the Alto Ribeira hydrographic basin, regarding troglobitic and non-troglobitic species, located in a single karst area to evaluate the influence of sub-basins in fauna differentiation. We investigated how abiotic variables (flow, electrical conductivity, temperature, pH, and substrate) influence the fauna composition and the contribution of beta diversity components (nestedness and turnover) in explaining communities' dissimilarities. Fauna composition differed between sub-basins, as most species did not co-occur in different caves. Caves with higher flow and substrate diversity were the richest. In addition, each cave community was influenced by a unique set of abiotic variables. Dissimilarity among caves was mainly explained by turnover, and our findings suggest the restricted species distribution could be due to ecological (e.g., limited dispersion capacity, tolerance to abiotic variables), hydrogeological (e.g., dispersion barriers, isolation of sub-basins), and historical (e.g., colonization, paleoclimatic events) factors and processes. Therefore, different elements are responsible for determining the composition of cave aquatic communities in different sub-basins, reflecting the variability within a single karst area.

Environmental specificity of karst cave habitats evidenced by diverse symbiotic bacteria in Opiliones.

BACKGROUND: Karst caves serve as natural laboratories, providing organisms with extreme and constant conditions that promote isolation, resulting in a genetic relationship and living environment that is significantly different from those outside the cave. However, research on cave creatures, especially Opiliones, remains scarce, with most studies focused on water, soil, and cave sediments. RESULTS: The structure of symbiotic bacteria in different caves were compared, revealing significant differences. Based on the alpha and beta diversity, symbiotic bacteria abundance and diversity in the cave were similar, but the structure of symbiotic bacteria differed inside and outside the cave. Microorganisms in the cave play an important role in material cycling and energy flow, particularly in the nitrogen cycle. Although microbial diversity varies inside and outside the cave, Opiliones in Beijing caves and Hainan Island exhibited a strong similarity, indicating that the two environments share commonalities. CONCLUSIONS: The karst cave environment possesses high microbial diversity and there are noticeable differences among different caves. Different habitats lead to significant differences in the symbiotic bacteria in Opiliones inside and outside the cave, and cave microorganisms have made efforts to adapt to extreme environments. The similarity in symbiotic bacteria community structure suggests a potential similarity in host environments, providing an explanation for the appearance of Sinonychia martensi in caves in the north.

From darkness to discovery: evolutionary, adaptive, and translational genetic insights from cavefish.

How genotype determines phenotype is a well-explored question, but genotype-environment interactions and their heritable impact on phenotype over the course of evolution are not as thoroughly investigated. The fish Astyanax mexicanus, consisting of surface and cave ecotypes, is an ideal emerging model to study the genetic basis of adaptation to new environments. This model has permitted quantitative trait locus mapping and whole-genome comparisons to identify the genetic bases of traits such as albinism and insulin resistance and has helped to better understand fundamental evolutionary mechanisms. In this review, we summarize recent advances in A. mexicanus genetics and discuss their broader impact on the fields of adaptation and evolutionary genetics.

Origin and modern microbial ecology of secondary mineral deposits in Lehman Caves, Great Basin National Park, NV, USA.

Lehman Caves is an extensively decorated high desert cave that represents one of the main tourist attractions in Great Basin National Park, Nevada. Although traditionally considered a water table cave, recent studies identified abundant speleogenetic features consistent with a hypogenic and, potentially, sulfuric acid origin. Here, we characterized white mineral deposits in the Gypsum Annex (GA) passage to determine whether these secondary deposits represent biogenic minerals formed during sulfuric acid corrosion and explored microbial communities associated with these and other mineral deposits throughout the cave. Powder X-ray diffraction (pXRD), scanning electron microscopy with electron dispersive spectroscopy (SEM-EDS), and electron microprobe analyses (EPMA) showed that, while most white mineral deposits from the GA contain gypsum, they also contain abundant calcite, silica, and other phases. Gypsum and carbonate-associated sulfate isotopic values of these deposits are variable, with δ34SV-CDT between +9.7‰ and +26.1‰, and do not reflect depleted values typically associated with replacement gypsum formed during sulfuric acid speleogenesis. Petrographic observations show that the sulfates likely co-precipitated with carbonate and SiO2 phases. Taken together, these data suggest that the deposits resulted from later-stage meteoric events and not during an initial episode of sulfuric acid speleogenesis. Most sedimentary and mineral deposits in Lehman Caves have very low microbial biomass, with the exception of select areas along the main tour route that have been impacted by tourist traffic. High-throughput 16S rRNA gene amplicon sequencing showed that microbial communities in GA sediments are distinct from those in other parts of the cave. The microbial communities that inhabit these oligotrophic secondary mineral deposits include OTUs related to known ammonia-oxidizing Nitrosococcales and Thaumarchaeota, as well as common soil taxa such as Acidobacteriota and Proteobacteria. This study reveals microbial and mineralogical diversity in a previously understudied cave and expands our understanding of the geomicrobiology of desert hypogene cave systems.

Microbial consortium involved in ferromanganese and francolite biomineralization in an anchialine environment (Zinzulùsa Cave, Castro, Italy).

Tidally-influenced subterranean settings represent natural geomicrobiological laboratories, relatively unexplored, that facilitate the investigation of new biomineralization processes. The unusual water chemistry of Zinzulùsa Cave and its oligotrophic and aphotic conditions have allowed the development of a unique ecosystem in which complex bacterial activities induce rare biomineralization processes. A diversified microbial community develops on centimeter-thick crusts that form in the submerged part of the cave. The crusts are formed of Ca-phosphate minerals, mostly carbonate-fluoroapatite (francolite), covered by a black crust, few microns in thickness, composed of ferromanganiferous oxides (hematite and vernadite). Diffuse coccoidal and filamentous bacteria and amorphous organic matter are mixed with the minerals. The micromorphologies and comparative 16S rRNA gene-based metabarcoding analyses identify a "core microbiota" also common to other natural environments characterized by FeMn and Ca-phosphate mineralization. The microbiota is characterized by nitrifying, sulfide/sulfur/thiosulfate-oxidizing and sulfate/thiosulfate/sulfur-reducing bacteria. In addition, manganese-oxidizing bacteria include the recently described "Ca. Manganitrophus noduliformans" and an abundance of bacteria belonging to the Planctomycetes-Verrucomicrobia-Chlamydiae (PVC) superphylum, as well as Haliangiales (fruiting body-forming bacteria) and Hyphomicrobiales (stalked and budding bacteria) that are known to produce extracellular polymers that trap iron and manganese oxides. 16S rRNA gene metabarcoding analysis showed the presence of bacteria able to utilize many organic P substrates, including Ramlibacter, and SEM images revealed traces of fossilized microorganisms resembling "cable bacteria", which may play a role in Ca-phosphate biomineralization. Overall, the data indicate biomineralization processes induced by microbial metabolic activities for both ferromanganiferous oxide and francolite components of these crusts.

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.

Middle through late Holocene long-distance transport of exotic shell personal adornments in Central West Patagonia (southern South America). The archaeomalacological assemblage of Baño Nuevo 1.

The exchange of information and social interactions on broad spatial scales between human groups in the past can be studied through the provenance of key indicators of distant origin recorded at archaeological sites. The remains of shells of mollusk species, especially when crafted as elements of personal ornaments, express aspects of the behaviors and valuations for the populations that selected, transformed, and exchanged such items. In the southern cone of South America, past hunter-gatherer groups traveled long distances and interacted with communities distributed throughout the territory to acquire goods for technological use, visual display or considered highly valued materials. When recorded at distant locations, these goods of extra local origin are very informative regarding the differences between commonly used home ranges and the occasional access to remote spaces. We present the results of the analysis of the archaeomalacological assemblage of the Baño Nuevo 1 site, a cave with exceptional preservation conditions in Central West Patagonia. This site has yielded a diverse group of artifacts made of shells with origins from multiple distances, as well as evidence of the use of marine, freshwater, and terrestrial species. Its deposits, which extend over the last 11,000 years, reveal an antiquity of at least the middle Holocene for the acquisition, manufacture, use and transport of goods as personal ornaments from shells in the macroregion.

Past anthropogenic impacts revealed by trace elements in cave guano.

Natural and human-induced toxic elements can accumulate in the environment, posing significant risks to human health and ecosystems. This study explores cave bat guano, an unconventional and relatively under-researched environmental repository, to reveal historical pollution trends and sources. Through trace elements analysis of a 1.5-m-thick guano deposit from Zidita Cave (Romania), we track changes in mining and metallurgy from 1000 CE-2012. We identified substantial pollution primarily from porphyry copper and Au-Ag-Te mines, but also impacts from usage of leaded gasoline and agricultural practices. Our record shows disruptions caused by the Bubonic plague around 1250 CE and a major surge âˆ¼ 1500 CE. After the decline triggered by the European silver market collapse in 1525 CE, our study reveals a brief mining revival. This resurgence was followed by a continuous decline lasting until the early 1800s, driven by socio-economic upheavals and recurrent outbreaks of the bubonic plagues. The Industrial Revolution sparked prolonged growth that lasted until 1989 CE, only briefly interrupted by the Great Depression and World War II. Consequently, cave bat guano proves to be a critical resource for understanding spatial pollution patterns, both locally and regionally, and for identifying specific pollution sources.

Blind cavefish evolved higher foraging responses to chemo- and mechanostimuli.

In nature, animals must navigate to forage according to their sensory inputs. Different species use different sensory modalities to locate food efficiently. For teleosts, food emits visual, mechanical, chemical, and/or possibly weak-electrical signals, which can be detected by optic, auditory/lateral line, and olfactory/taste buds sensory systems. However, how fish respond to and use different sensory inputs when locating food, as well as the evolution of these sensory modalities, remain unclear. We examined the Mexican tetra, Astyanax mexicanus, which is composed of two different morphs: a sighted riverine (surface fish) and a blind cave morph (cavefish). Compared with surface fish, cavefish have enhanced non-visual sensory systems, including the mechanosensory lateral line system, chemical sensors comprising the olfactory system and taste buds, and the auditory system to help navigate toward food sources. We tested how visual, chemical, and mechanical stimuli evoke food-seeking behavior. In contrast to our expectations, both surface fish and cavefish did not follow a gradient of chemical stimulus (food extract) but used it as a cue for the ambient existence of food. Surface fish followed visual cues (red plastic beads and food pellets), but, in the dark, were likely to rely on mechanosensors-the lateral line and/or tactile sensor-as cavefish did. Our results indicate cavefish used a similar sensory modality to surface fish in the dark, while affinity levels to stimuli were higher in cavefish. In addition, cavefish evolved an extended circling strategy to forage, which may yield a higher chance to capture food by swimming-by the food multiple times instead of once through zigzag motion. In summary, we propose that ancestors of cavefish, similar to the modern surface fish, evolved extended food-seeking behaviors, including circling motion, to adapt to the dark.