Diverging Cave- and River-Dwelling Newts Exert the Same Mate Preference in their Native Light Conditions

When colonizing a new habitat, populations must adapt their sexual behaviour to new ecological constraints. Because caves display drastically different conditions from surface habitats and cave animals are deprived from visual information, hypogean populations are expected to have modified their mate preference and signalling behaviour after cave colonization. Here, we experimentally examined the female preference and the sexual behaviour of brook newts Calotriton asper from different cave and river populations, either in light or in darkness. Our results suggest that females prefer large individuals in both hypogean and epigean populations, but that this preference is only expressed in the light conditions of their native habitat. Hence, some mate choice criteria would be maintained across genetically divergent populations and throughout dissimilar habitats. However, this sexual behaviour is likely to be expressed via a different sensory pathway in the different habitats, suggesting that a sensory shift has occurred in cave populations, enabling animals to communicate through a non-visual channel.     

Ecotone delimitation: Epigean–hypogean transition in cave ecosystems

Abstract The ecotone zone between epigean and hypogean environments has been delimited for two limestone caves using a new method proposed herein. The richness and the diversity of the ecotone, epigean and hypogean environments and their similarities have also been determined. The ecotones were delimited using a similarity matrix between the inner and outer sectors of each cave. The ecotone of Dona Rita's cave was estimated to be 12 m long and the ecotone of Retiro's cave 16 m. The richness (S) of arthropods in Dona Rita's cave was higher in the ecotone (S = 131), intermediate in the epigean environment (S = 75) and lower in the hypogean system (S = 45). The invertebrate diversity (H′) was lower in the hypogean environment (H′ = 2.89) and not statistically different between the epigean environment and the ecotone (H′ = 3.56 and H′ = 3.76, respectively). The richness in Retiro's cave was higher in the ecotone (S = 86), intermediate in the epigean environment (S = 39) and lower in the hypogean system (S = 12). The invertebrate diversity was lower in the hypogean environment (H′ = 0.48), intermediate in the ecotone (H′ = 3.02) and higher in the epigean region (H′ = 3.29). Species migration patterns, differential environmental barriers and determination of accidental versus trogloxenes/troglophylous species are topics that are primarily approached by establishing ecotone zones in caves. The aim of the present paper is to establish the delimitation of theses zones.     

Niche partitioning in orbweaving spiders Meta menardi and Metellina merianae (Tetragnathidae)

Hypogean habitats are relatively simple exhibiting low diversity, low production and relative constancy of environmental factors, and are therefore appropriate for studying species coexistence in situ. We investigated the coexistence of two closely related, similarly sized orb-weaving spider species, Meta menardi and Metellina merianae, living syntopically in a Slovenian cave. We studied the annual dynamics of both species within a mixed population, and the impact of the ambient temperature, relative humidity, airflow and illumination, and compared their trophic niches to legacy data on prey of both species from 55 caves in Slovenia. We predicted a large overlap in their spatial niches and substantial differences in their temporal and trophic niches. We found that their spatial niches overlap greatly with few exceptions, mostly on the dates of notable meteorological changes in the cave but that their temporal niches differ significantly with r-strategy resembling epigean annual dynamic in M. merianae and a steady low abundance course in M. menardi within the cave. We also found that different predatory strategies significantly segregate their trophic niches: M. merianae uses a typical orb-weaving hunting strategy, while M. menardi combines web hunting with off-web hunting. Our findings suggest that both the diverse dynamics and trophic niches enable the coexistence of M. menardi and M. merianae despite their similar spatial niches, and that M. menardi, in particular, is optimally adapted to the epigean/hypogean ecotone.     

Locomotory,ventilatory and metabolic responses of the subterranean Stenasellus virei (Crustacea,Isopoda) to severe hypoxia and subsequent recovery

The locomotory and ventilatory activities and the intermediary and energy metabolism modifications of the hypogean aquatic isopod crustacean Stenasellus virei were investigated in severe hypoxia (Po₂ < 0.03 kPa) and subsequent recovery. The aims of this study were i) to determine why the subterranean species displayed a greater tolerance of hypoxia than numerous other epigean crustaceans, ii) to confirm previous results obtained with four hypogean and epigean crustaceans, iii) to compare the responses to severe hypoxia in hypogean amphipods and isopods, and iv) to better understand the ecological problems of the hypogean organisms survival in subterranean habitats. S. virei responded to experimental long-term, severe hypoxia with classical anaerobic metabolism mainly characterized by a decrease in adenosine triphosphate (ATP) and phosphagen, utilization of glycogen and glutamate, and accumulation of lactate and alanine. Lactate was also largely excreted by this organism, which is unusual for crustaceans in general. Compared to most other epigean crustaceans, the isopod S. virei showed high amounts of stored glycogen and arginine phosphate. These differences in glycogen and phosphagen stores, and the ability to reduce energetic expenditures linked to locomotion and ventilation, extended the survival of S. virei under experimental anaerobiosis. During recovery, the isopod S. virei showed a higher capacity for glyconeogenesis from lactate and a faster and total replenishment of ATP and arginine phosphate levels than epigean crustaceans. Data concerning responses to hypoxia and subsequent recovery in S. virei are similar to those previously obtained with two other hypogean amphipods, except that this isopod did not synthesize succinate in anaerobiosis.     

Morphology and reproduction of the cavefish Trichomycterus chaberti and the related epigean Trichomycterus cf. barbouri

Hypogean and epigean populations of Trichomycterus catfishes inhabit streams from different environments (cave, headwater, canyon and valley) in the Torotoro National Park in the Andes, Bolivia. A significant reduction in the diameter of the eyes and in the surface area of the mesencephalon was observed in subterranean populations, along with an increase in the surface area of the telencephalon. Contrary to expectations, the barbel did not appear to be longer in hypogean populations. The observed pattern of modification of the other variables (pigmentation, eye asymmetry, surface area of the cerebellum and rhombencephalon, fecundity and egg diameter) corresponded to a gradient of values from valley to canyon, headwater and subterranean populations. This result argues not for a simple distinction between epigean and hypogean populations but for an adaptation to an environmental gradient of constraints in which caves correspond to an extreme situation.     

Biotic and abiotic interactions between surface and interstitial systems in rivers

Water chemistry and community assemblages of surface and interstitial invertebrates were studied at seven sues on the French Rivers Rhône and Am at surface and at 50 cm depth into the bed sediments Chemical factors allowed differentiation of surface water from groundwater and detection of water exchanges defining clear downwelling and upwelling zones At some sites, interstitial water showed both surface and phreatic conditions, characterizing the underflows of the Rhone or of the Am In the interstitial area, most taxa showed no significant correlations with water chemistry Some epigean and hypogean fauna showed correlations with certain factors Clear relationships appeared between the water exchanges and the distribution of surface and interstitial faunas In interstitial samples, epigean and some hypogean species characterized the downwelling zones while others seemed to be strictly linked to the upwelling zones In surface samples, the presence of hypogean species was associated with regions of groundwater upwelling     

Shape variation in surface and cave populations of the armoured catfishes Ancistrus(Siluriformes: Loricariidae) from the São Domingos karst area, upper Tocantins River, Brazil

Body shape of four distinct populations of Ancistrus cryptophthalmus from different caves in the São Domingos karst area and the local epigean (surface) Ancistrus species were compared using geometric morphometrics. Angélica and Bezerra catfishes were closer to each other and successively to the studied sample of epigean catfishes than to Passa Três and São Vicente I catfishes. Greater similarity between catfishes from the Angélica‐Bezerra cave system to epigean catfishes than to other cave catfishes may represent a plesiomorphic feature. On the other hand, the present analyses allowed the distinction between Passa Três and São Vicente I catfishes, which inhabited the same cave system. Topographic isolation due to the presence of several waterfalls interposed between the stream reaches where these catfishes live may explain such morphological differentiation. Also, the presence of a waterfall downstream of the reach where the Angélica sample was obtained may have contributed to the partial isolation of these catfishes from those living in Bezerra Cave. Differences in population sizes probably influenced the degrees of morphological differentiation observed among the cave populations. The mosaic distribution of character states indicated that the four populations of A. cryptophthalmus have evolved rather independently, but the continuous variation suggests a recent connection between these populations, perhaps with a limited gene flow. Considering other features such as reduction of eyes and pigmentation, and changes in body shape, a separate species status for the epigean and hypogean Ancistrus species from the São Domingos karst area has been maintained.     

Regional Risk Assessment of a Brazilian Rain Forest Reserve

The objective of this study was to identify subareas inside and near an Atlantic Rain Forest reserve, the Parque Estadual Turístico do Alto Ribeira (PETAR), most likely to be affected by land use in the vicinity of the area. In addition, the study aimed to compare risks per stressor source (agriculture, human settlements and mining) to both epigean (surface) and hypogean (subterranean) aquatic fauna. The methodological approach included the relative vulnerability of endpoints to the stressors (pesticides, metals, nutrients, and particles) and ranking of stressor sources and habitats (epigean and hypogean streams) based on their relative distribution in 14 subareas within the catchment areas of the main rivers that cross PETAR: Pilões, Betari and Iporanga. Four subareas presented high risk for both epigean and hypogean fauna. Three of those areas were located inside the Betari catchment area, where most of the settlements and abandoned lead mines are located. The fourth area was situated in the headwaters of the Pilões River, where agricultural activities are intense. Agriculture and human settlements were the activities most likely to cause impacts on aquatic ecosystems. Uses of risk assessment results include management of the PETAR and communication to stakeholders by the Park Administration.     

Metabolic rates of a hypogean and an epigean species of copepod in an alluvial aquifer

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Phylogeography of cave pseudoscorpions in southern Australia

Aim  To investigate molecular phylogenetic divergence and historical biogeography of the cave-dwelling pseudoscorpion genus Protochelifer.
Location  Caves and nearby epigean habitats in southern Australia were sampled from western Victoria, Naracoorte Caves, Flinders Ranges, Kangaroo Island, Nullarbor Plain and south-west Western Australia.
Methods  Allozyme electrophoresis (57 individuals) and a 569-base-pair section of the mtDNA COI gene (22 individuals) were used to reconstruct phylogenetic relationships among four cave species and three epigean species from 13 locations.
Results  Phylogenetic reconstruction using the allozyme and mtDNA sequence data revealed a similar topology, showing recent speciation of several Protochelifer populations in caves from Naracoorte to the Nullarbor Plain. Naracoorte Caves contained a single species, Protochelifer naracoortensis , found in four separate caves, while all other cave species appear to be restricted to single caves.
Main conclusions  At a local scale, as indicated by the four Naracoorte caves, dispersal is thought to occur via micro- and mesocaverns, and possibly by phoresy using insect or bat vectors. With current data we are unable to determine if cavernicolous species of Protochelifer have arisen from a single cave colonization event followed by phoretic dispersal on bats to other caves, or multiple cave-invasion events from independent epigean ancestors. Genetic heterogeneity among Protochelifer populations from Nullarbor caves suggest that P. cavernarum , the only species presently recorded from this region, is likely to constitute a species complex requiring further study to fully resolve its relationships.     

Troglomorphic Sculpins of the Cottus Carolinae Species Group in Perry County, Missouri: Distribution, External Morphology, and Conservation Status

The existence of cavernicolous sculpin (here allocated to Cottus carolinae, banded sculpin, and referred to as grotto sculpin), in the karst regions of Perry County, Missouri, first came to our attention in 1991. Examination of 35 caves in Missouri, 96 in Illinois, 17 in Tennessee, two in Indiana, and 11 in Arkansas revealed that banded sculpin are common in cave habitats; however, grotto sculpin are limited to two karst areas of Perry County, Missouri, where they are known from only six cave systems. These caves and their streams are extensive and apparently provide a unique habitat compared to other karst systems; this may be a critical factor in the present restricted distribution of the grotto sculpin. Grotto sculpin occupy pools and riffles of cave streams, and occur over a variety of substrates, from sediment to breakdown. Density estimates in Mystery and Running Bull caves were 0.29 and 0.63 individuals m^-2, respectively. Grotto sculpin have small eyes (1–6% SL vs. 6–10% SL in epigean samples), significantly reduced pigmentation (including nearly complete loss of dorsal saddles), a reduction in pelvic fin ray number (from 4+4 elements to often 4+3 , or 3+3), and enlarged cephalic lateralis pores (e.g., mandibular pores of cavernicolous samples are 2–3 times those of epigean stream samples). Multivariate analyses of body shape revealed statistically significant separation of epigean and hypogean samples, with eye size highly variable, but smallest in the Running Bull Cave population. We interpret these results as representative of losses associated with long-term cave habitation. Caves of Perry County provide ample habitat for grotto sculpin, but because the caves are located downgradient of the city of Perryville and an intensively farmed landscape, point and non-point source pollution threaten their continued existence. Escape of farm-pond fishes through the extensive sinkhole network in Perry County has increased potential predation pressure on grotto sculpin by channel catfish, Ictalurus punctatus, and other species normally excluded from cave environments.     

Is the reduced metabolism of hypogean amphipods solely a result of food limitation?

The epigean amphipod Gammarus lacustris possessed a rate of oxygen uptake (MO2) three times greater that of the hypogean amphipod Stygobromus sp. While much of the difference between these two species could be attributed to different feeding regimes, the hypogean amphipod still exhibited a lower rate of metabolism than the epigean species. This suggests that there can be both a genetic and an environmental (reduced food availability and/or hypoxia) component to the reduced metabolism characteristic of many hypogean animals. The results of this study have re-emphasised the pitfall of making species comparisons without knowledge of the extent of physiological variation within a species. This revised version was published online in July 2006 with corrections to the Cover Date.     

Predation of a cave fish (Poecilia mexicana, Poeciliidae) by a giant water-bug (Belostoma, Belostomatidae) in a Mexican sulphur cave

Abstract.  1. Caves are often assumed to be predator-free environments for cave fishes. This has been proposed to be a potential benefit of colonising these otherwise harsh environments. In order to test this hypothesis, the predator–prey interaction of a belostomatid (predator) and a cave fish (prey) occurring in the Cueva del Azufre (Tabasco, Mexico) was investigated with two separate experiments.
2. In one experiment, individual Belostoma were given a chance to prey on a cave fish, the cave form of the Atlantic molly ( Poecilia mexicana ), to estimate feeding rates and size-specific prey preferences of the predator. In the other experiment, population density of Belostoma was estimated using a mark–recapture analysis in one of the cave chambers.
3. Belostomatids were found to heavily prey on cave mollies and to exhibit a prey preference for large fish. The mark–recapture analysis revealed a high population density of the heteropterans in the cave.
4. The absence of predators in caves is not a general habitat feature for cave fishes. None the less predation regimes differ strikingly between epigean and hypogean habitats. The prey preference of Belostoma indicates that cave-dwelling P. mexicana experience size-specific predation pressure comparable with surface populations, which may have implications for life-history evolution in this cave fish.     

Electron transport system activity and oxygen consumption of two amphibious isopods,epigean Ligia italica Fabricius and hypogean Titanethes albus (Koch), in air and water

Electron transport system (ETS) activity and oxygen consumption (i.e. respiration, R) were measured in two amphibious isopods, epigean Ligia italica and hypogean Titanethes albus. The measurements were made in air and in water to estimate the exploitation of metabolic potential for actual metabolism in the two media. Oxygen consumption was measured in animals in air before their transfer to water, in water and again after their transfer back to air. Both species showed greater oxygen consumption during submergence in water than in air. Although epigean L. italica had higher oxygen consumption and ETS activity than hypogean T. albus, both species exhibited high and variable ETS/R ratios. A high and variable ETS/R ratio is one of the characteristics of amphibious isopods that enables them to cope with specific environmental conditions in their habitats.     

Review of winter trophic relations of soricine shrews

This paper attempts to review all those factors that affect the winter trophic relations of soricines in northern, Holarctic areas, from physiological and ecological aspects to prey and predators. Winter is generally a time of food scarcity and low temperatures, often accompanied by snow cover. Winter shrews are characterized by decreased metabolic rates, longer periods in the nest, short foraging periods and the subsequent decreased need to forage. In smaller species the diet generally consists of epigean fauna, while in larger species hypogean fauna is also included, the proportions of which vary seasonally. In areas of snow cover their diets are derived from the subnivean fauna, i.e. soil and litter fauna, overwintering on the soil surface, and consist of many insects, especially beetles, arachnids, small vertebrates and carrion. Their predators include owls and, to a lesser extent, weasels and foxes.     

Distribution and phylogenetic relationships of Australian glow-worms Arachnocampa (Diptera, Keroplatidae)

Glow-worms are bioluminescent fly larvae (Order Diptera, genus Arachnocampa) found only in Australia and New Zealand. Their core habitat is rainforest gullies and wet caves. Eight species are present in Australia; five of them have been recently described. The geographic distribution of species in Australia encompasses the montane regions of the eastern Australian coastline from the Wet Tropics region of northern Queensland to the cool temperate and montane rainforests of southern Australia and Tasmania. Phylogenetic trees based upon partial sequences of the mitochondrial genes cytochrome oxidase II and 16S mtDNA show that populations tend to be clustered into allopatric geographic groups showing overall concordance with the known species distributions. The deepest division is between the cool-adapted southern subgenus, Lucifera, and the more widespread subgenus, Campara. Lucifera comprises the sister groups, A. tasmaniensis, from Tasmania and the newly described species, A. buffaloensis, found in a high-altitude cave at Mt Buffalo in the Australian Alps in Victoria. The remaining Australian glow-worms in subgenus Campara are distributed in a swathe of geographic clusters that extend from the Wet Tropics in northern Queensland to the temperate forests of southern Victoria. Samples from caves and rainforests within any one geographic location tended to cluster together within a clade. We suggest that the morphological differences between hypogean (cave) and epigean (surface) glow-worm larvae are facultative adaptations to local microclimatic conditions rather than due to the presence of cryptic species in caves.     

Phototactic response and light sensitivity in an epigean and a hypogean population of a barb (Garra barreimiae, Cyprinidae)

We investigated the response of two populations of the barb Garra barreimiae to different light intensities (0.5–2000 lx) from a light source. Adults of both the surface (epigean) and cave (hypogean) G. barreimiae populations show photophobic behavior. A photophobic response in the cave form was seen only at higher light intensities because the cavefish are eyeless and rely on extra-retinal light receptors to detect light. In contrast, juveniles (surface and cave) showed photophilic behavior, and their preference for the photic zone of the test tank decreased with increasing age. We discuss the potential role played by photophobic behavior for the colonization of caves by previously surface-dwelling fishes.     

Comparative study of electron transport system activity and oxygen consumption of amphipods from caves and surface habitats

1. Respiratory electron transport system (ETS) activity and oxygen consumption were measured at 10 °C for the hypogean amphipods Niphargus stygius (from two epikarst locations) and N. krameri (from a sinking river in a cave) and the epigean amphipod Gammarus fossarum (inhabiting a spring and a river). 2. ETS activity and oxygen consumption were compared between caves and the two surface locations, and between hypogean and epigean amphipods. ETS activities were found not to differ between animals from different locations, or between epigean and hypogean amphipods. As expected, the oxygen consumption of N. krameri and N. stygius was lower than that of G. fossarum. 3. The high ratio between ETS activity and oxygen consumption (ETS/R ratio) showed that N. krameri and N. stygius possess high metabolic potential that can be exploited for energy recovery and rapid restoration of body reserves immediately following the appearance of favourable conditions (food and/or oxygen). In contrast, G. fossarum exhibited a low ETS/R ratio, indicating exploitation of a great proportion of the metabolic potential for standard metabolism. 4. Feeding in N. stygius increased oxygen consumption but not ETS activity, and thus fed N. stygius had a much lower ETS/R ratio than starved ones. 5. A relatively high metabolic potential (i.e. high ETS/R ratio) may be an adaptation to hypogean life in amphipods, in that it improves survival under poor food and/or oxygen conditions.     

Effects of spates on the vertical distribution of the interstitial community

The effect of hydrological variations on the vertical distribution of interstitial organisms was studied in a by-passed channel of the Rhône River(France) in terms of the distortion and recovery of community structure over a 480-day period that included 9 spates. The hypogean and epigean components of the interstitial assemblages were studied, the latter at four depths (50, 100, 150 and 200 cm) within the substratum, during a succession of artificially regulated spates and periods of low flow. Interstitial fauna were obtained with a Bou-Rouch sampler through permanent standpipes at intervals of one, seven and seventeen days after each spate. A strong relationship was demonstrated between disturbance intensity (amplitude and duration of spates) and the magnitude of changes in the vertical distribution of the fauna. Both hypogean and epigean organisms were displaced vertically after each spate, resulting in an increase in the numbers of epigean organisms in interstitial layers. Recovery of vertical distribution of the interstitial fauna to pre-spate conditions, consisted of a decrease of epigean and an increase of hypogean fauna with the substratum, mainly at intermediate sampling depths (100, 150 cm). The effect of spates on community structure and rate of recovery varied in relation to 1) the combination of spate amplitude and duration (i.e. the shape of the discharge pattern), 2) the disturbance regime (i.e. the recent hydrological past) and 3) season (temperature and biological cycle).