Void development on carbonate coasts: creation of anchialine habitats

Anchialine caves in coastal locations develop in two ways: by pseudokarst processes that form talus caves, sea caves, tafoni, fissure caves and lava tubes, and by karst dissolutional processes that form stream caves, flank margin caves, and blue holes. Pseudokarst caves are of minor importance in anchialine cave habitat development, with some lava tubes being notable exceptions. Dissolution caves provide the most extensive, variable, and long-term environments for anchialine habitats. The Carbonate Island Karst Model (CIKM) allows dissolutional cave development in carbonate coasts to be understood as the interplay between freshwater and marine water mixing, sea-level change, rock maturity, and interaction with adjacent non-carbonate rocks. Glacioeustatic sea-level changes of the Quaternary have moved all coastal anchialine cave environments repeatedly through a vertical range of over 100 m, and modern anchialine environments could not develop at their current elevations until ~4,000 years ago when sea level reached its present position. Blue holes form by a variety of mechanisms, but the most common is upward stoping and collapse from deep dissolutional voids. As a result, they provide vertical connection between different levels of horizontal cave development produced by a variety of earlier sea-level positions. Blue holes are overprinted by successive sea-level fluctuations; each sea-level event adds complexity to the habitats within blue holes and the cave systems they connect. Blue holes can reach depths below the deepest glacioeustatic sea-level lowstand, and thereby provide a refugia for anchialine species when cave passages above are drained by Quaternary sea-level fall. Blue holes represent the most significant anchialine cave environment in the world, and may provide clues to anchialine cave species colonization and speciation events.     

Seasonal dynamics of Callibaetis willineri (Ephemeroptera, Baetidae) associated with Eichhornia azurea (Pontedericeae) in Guaraná Lake of the Upper Paraná River, Brazil

The micro-anatomy of the cephalon is described in the troglobic asellotan isopod Craseriella anops from the Nohoch Nah Chich anchialine cave system in southeast Mexico. The cephalon is entirely covered by cuticular scales bordered by marginal spines. The anterior end of the cephalon is bordered by a carina that is wider medially. The isopod is eyeless. The distal seventh portion of the cephalon is characterized by the presence of two sutures and six setae. A suture is found on each side of the distal margin of the cephalon.Each suture is bordered by microtrichs. Two simple setae with a sensory hair, articulated on the base by a socket, are found one on each side of each of the sutures. Two additional setae, similar in shape and size, occur medially on the cephalon. A terminal pore is absent on the sensory hairs of all setae. These setae are suggested to be mechanoreceptors that provide directional sensitivity and enhance the sensibility of turbulent motion, viscosity and changes of hydrostatic pressure.     

Genetic exchange between anchialine cave populations by means of larval dispersal: the case of a new gastropod species Neritilia cavernicola

Despite being limited to caves, many anchialine taxa have disjunct insular distributions, which raises questions about their origins and colonization history. This study deals with the new gastropod Neritilia cavernicola sp. n. (Neritopsina: Neritiliidae) from anchialine caves on two islands in the Philippines that are separated by the deep Bohol Strait and situated 200 km apart along the coastline of Cebu Island. Neritilia cavernicola is an obligate stygobiont and most closely resembles Neritilia littoralis , which lives in interstitial waters of the Nansei-shoto Islands, Japan. Its eggs and larval shells are identical to those of other Neritilia species, despite their different adult habitats. This suggests a marine planktotrophic phase (as occurs in amphidromous riverine species of Neritilia ), and consequent migration between islands via ocean currents. Here we present the first genetic structure for anchialine cave organisms; comparisons of 1276 bp sequences from mitochondrial cytochrome oxidase I show no evidence of genetic isolation between the islands. All individuals evidently are part of a panmictic population and the low vagility of adults and their seemingly isolated cave habitats do not limit gene flow in N. cavernicola . This migration model, based on marine larval dispersal, may be widely applicable to anchialine stygobites with insular distributions, as many such organisms (including shrimps, crabs and fishes) are phylogenetically allied to amphidromous species.     

Phylogeny and historical biogeography of the cave-adapted shrimp genus Typhlatya (Atyidae) in the Caribbean Sea and western Atlantic

Aim To infer phylogenetic relationships among five species of the cave‐adapted shrimp genus Typhlatya in order to test competing hypotheses of dispersal and colonization of the disjunct cave localities occupied by these five species. Location Typhlatya species are found in caves and anchialine ponds across the northern margin of the Caribbean Sea, along the Mediterranean and Adriatic coasts and on oceanic islands in the Atlantic and eastern Pacific oceans. This study focuses on five species, one from Bermuda, one from the Caicos Islands and three from the Yucatan Peninsula of Mexico. Methods Partial sequences (c. 1400 bp) from the mitochondrial cytochrome b, 16S rDNA and COI genes were obtained from representative samples of the five species. Phylogenetic inference was carried out with maximum parsimony and maximum likelihood analyses. Parsimony networks were constructed for the Bermudian species Typhlatya iliffei and one Yucatan species Typhlatya mitchelli, to determine the degree of connectivity among populations inhabiting different cave systems. Results All three land masses were recovered as monophyletic. The two insular marine species from Bermuda and the Caicos Islands formed a clade, while the three continental freshwater species from the Yucatan Peninsula formed another. Within both Bermuda and the Yucatan, shared haplotypes were found in different cave systems, suggesting recent or ongoing gene flow among populations in both locales. Main conclusions The two insular marine Typhlatya species originated from an ancestral marine population, possibly already cave‐adapted, that is suggested to have colonized the Caicos Islands and subsequently dispersed to Bermuda via the Gulf Stream. Divergence estimates suggest that colonization occurred before the formation of present‐day anchialine cave habitat, which did not form on either island until the late Pliocene to early Pleistocene. Divergence estimates also indicate that the Yucatan freshwater species split before the formation of freshwater cave habitat in the Yucatan. These species could have inhabited crevicular marine habitats before the late Pliocene/early Pleistocene in the Yucatan or elsewhere in the Caribbean, and subsequently migrated to freshwater caves once they formed.     

Recently discovered landlocked basins in Indonesia reveal high habitat diversity in anchialine systems

In this article, the variability of physical settings of anchialine systems in Indonesia is discussed together with the consequences these settings have for the environment and biota within the systems. Exploration in two karstic areas (Berau, East Kalimantan and Raja Ampat, West Papua) has resulted in the discovery of 20 previously unknown anchialine systems in Indonesia. Based on parameters such as bathymetry, size, coastline, salinity, water temperature, pH, degree of connection to the sea, and the presence-absence of selected key taxa we distinguish three types of (non-cave) anchialine systems in the Indo-Pacific: (1) Marine lakes with large and deep basins containing brackish to almost fully marine waters. Marine lakes show a range in the degree of connection to the sea with the result that the higher the connection the more the lake resembles a lagoon in both water chemistry and biota, while the more isolated lakes have brackish water and contain unique species that are rarely found in the adjacent sea. (2) Anchialine pools with small and shallow basins containing brackish water and low diversity of macrofauna. (3) Blue pools in chasms that contain water with a clear halocline and are possibly connected to anchialine caves. Study of the many unique features of anchialine systems will enhance our understanding of the physical and ecological processes responsible for diversification in tropical shallow marine environments.     

Systematic status and first description of male of Dujardinia cenotae Pearse, 1936 [= Hysterothylacium cenotae (Pearse, 1936) Moravec et al., 1995] (Nematoda: Anisakidae)

A new collection of adult anisakid nematodes from the intestine of the catfish Rhamdia guatemalensis from two cenotes (= sinkholes) and a cave in the Yucatan Peninsula, southeastern Mexico, has shown that they are conspecific with those inadequately described as Dujardinia cenotae Pearse, 1936. The female is redescribed and the male is described for the first time. The morphology of this species shows that it belongs to the genus Hysterothylacium. This is the only Hysterothylacium species recorded from freshwater fishes in Mexico and it may well be endemic to cenotes and caves of the Yucatan Peninsula.     

Milyeringa Veritas (Eleotridae), a remarkably versatile Cave Fish from the Arid Tropics of Northwestern Australia

The blind cave gudgeon Milyeringa veritas is restricted to groundwaters of Cape Range and Barrow Island, northwestern Australia. It occurs in freshwater caves and in seawater in anchialine systems. It is associated with the only other stygobitic cave vertebrate in Australia, the blind cave eel, Ophisternon candidum, the world's longest cave fish, and a diverse stygofauna comprising lineages with tethyan tracks and widely disjunct distributions, often from North Atlantic caves. The cave gudgeon inhabits a karst wetland developed in Miocene limestones in an arid area. There is an almost complete lack of information on the basic biology of this cave fish, despite it being listed as threatened under the Western Australian Wildlife Conservation Act. Allozyme frequencies and distributions indicate significant population sub-structuring on the Cape Range peninsula such that the populations are essentially isolated genetically suggesting that more than one biological species is present. Further, they suggest that the vicariant events may have been associated with a series of eustatic low sealevels. Analysis of intestinal contents indicates that they are opportunistic feeders, preying on stygofauna and accidentals trapped in the water, at least at the sites sampled which were open to the surface, a conclusion supported by the results of stable isotope ratio analysis. The gudgeons are found in freshwater caves and throughout deep anchialine systems in which they occur in vertically stratified water columns in which there is a polymodal distribution of water chemistries (temperature, pH, salinity, dissolved oxygen, redox, dissolved inorganic nitrogen series, hydrogen sulphide).     

A new species of Typhlatya (Crustacea: Decapoda: Atyidae) from anchialine caves on the French Mediterranean coast

A new species of the thermophylic Tethyan relict prawn Typhlatya is described from two anchialine caves near Perpignan (southern France). The new species is closely related to a congener known only from a freshwater cave at Castellón (eastern Spain), about 400 km to the south-west, differing apparently only in the size and shape of the rostrum and the armature of the dactylus of the fifth pereiopod. Based on palaeogeographical evidence and assuming a sister-group relationship between both species, we suggest that their common ancestor could not be older than early Pliocene in age, and that it was already a stygobiont taxon adapted to live in shallow-water marine crevicular habitats. This ancestor would have vanished from the western Mediterranean after the cooling associated with the onset of northern Hemisphere glaciation, about 3 Mya, as documented for other Mediterranean marine taxa. Indeed, the genus is completely stygobiont and does not occur in fluvial environments. The Pyrenees represent a watershed boundary that eliminates the possibility of the derivation of one species from the other by active dispersal after establishment in continental waters.  © 2005 The Linnean Society of London, Zoological Journal of the Linnean Society , 2005, 144 , 387–414.     

Anchialine Gyprididae (Ostracoda) from the Galapagos Islands, with a review of the subfamily Paracypridinae

The five species of Cyprididae collected from anchialine habitats of the Galapagos Islands include Paracypris crispa, previously described from marine caves and reefs on Bermuda, and the freshwater species Strandesia stocki, which is widely distributed in wells of the West Indies. Three new species, Dolerocypria ensigera, Mungava recta and Hansacypris galapagosensis, contribute to more precise understanding of these circumtropical genera. A review of known soft-anatomical characters for 68 species of Paracypridinae, five of which are transferred to different genera, reveals too many inconsistencies for a simple hypothesis. The current classification of Paracypridinae into three tribes and 18 genera may be overly subdivided, and elevation of Paracypridinae to family rank is not warranted.     

Evolution of cave Axiokebuita and Speleobregma (Scalibregmatidae,Annelida)

The evolutionary history of Axiokebuita and Speleobregma, two poorly known lineages of annelids exclusive from deep‐sea or marine caves but always from crevicular habitats, is explored here. Speleobregma lanzaroteum Bertelsen, 1986, and Axiokebuita cavernicola sp. n. are described from anchialine and marine caves of the Canary Islands using light and electron microscopy. Speleobregma lanzaroteum is previously known only from a single specimen from the water column of an anchialine cave in Lanzarote. Emended diagnosis, details on the ciliary patterns and behavioural observations are provided based on newly collected material and in situ observations. Axiokebuita cavernicola sp. n. is found in Pleistocene gravel deposits in a shallow water marine cave in Tenerife (Canary Islands). The new species is characterized by the presence of dorsal ciliary bands and short knob‐like neuropodial cirri from segment two. The porosity and permeability of the gravelly environment of A. cavernicola sp. n. are shown to be equivalent to the water column or crevices of Speleobregma and other Axiokebuita spp. Phylogenetic analyses of five gene fragments and 44 terminals using maximum‐likelihood and Bayesian methods support a derived position of A. cavernicola sp. n. within Axiokebuita and confirm a sister‐group relationship of Axiokebuita with Speleobregma with high nodal support. The Axiokebuita–Speleobregma clade is morphologically characterized by a globular pygidium with adhesive glands and ventral ungrooved ciliated palps. Our results support two independent cave colonization events, favoured by the preadaptation of the members of Axiokebuita–Speleobregma lineage to crevicular habitats.     

Search for Bermuda’s deep water caves

The mid-Atlantic islands of Bermuda harbor one of the richest and most diverse anchialine communities known from anywhere on Earth. However, all known anchialine caves in Bermuda (maximum depth—26 m) were dry during the last glacial period extending from approximately 9,000 to 115,000 years ago when glacial sea levels were as much as 127 m lower. Since it is highly unlikely that Bermuda’s endemic cave species evolved since the caves were flooded by sea level rise, alternate deeper habitats must have existed to shelter anchiane fauna for prolonged periods of lower sea level during the Pleistocene. In order to systematically search for such now deep water cave habitats, high-resolution multibeam sonar and remotely operated vehicles were used to map and explore the seafloor off Bermuda in 60–200 m depths along the outer shelf break edge of the submarine escarpment surrounding the Bermuda Platform and an adjacent seamount. Specific goals were to discover deep water cave and/or crevicular habitats and to characterize the nature, geological stratification and composition, and sea level history of the platform margin, in particular focusing on features directly relating to Pleistocene low sea stand events. During this sea floor survey, clearly defined paleo-shoreline features generated by wave and current erosion were found to encircle the Bermuda seamount and Challenger Bank at 60 and 120 m depths.     

Biogeography of subterranean decapods in North and Central America and the Caribbean region (Caridea,Astacidea, Brachyura)

A significant number of decapod crustaceans (81 troglobites and 58 other cavernicoles) has been described from various subterranean waters in North and Central America (United States south to Costa Rica) and from the islands in the western north Atlantic and the Caribbean Sea, posing puzzling questions concerning their evolution and biogeography. Of these troglobitic species, 36 are shrimps (1 procarid, 11 atyids, 2 agostocarids, 15 palaemonids, 2 alpheids, 5 hippolytids), 35 are cambarid crayfishes, and 10 are crabs (1 grapsid, 7 pseudothelphusids, 2 trichodactylids). They are known to occur in caves, springs, cenotes, blue holes, anchialine environments, and various crevicular habitats in localized areas throughout the region. Many, if not the majority, of the troglobites appear to have arisen independently from epigean progenitors rather than sharing common subterranean precursors.     

Fish Assemblages of Mediterranean Marine Caves

Fish assemblages associated with 14 marine caves and adjacent external rocky reefs were investigated at four Marine Protected Areas (MPAs) along the coasts of Italy. Within the caves sampling was carried out in different sub-habitats: walls, ceilings, bottoms and ends of caves. On the whole, 38 species were recorded inside the 14 caves investigated. Eighteen species were exclusively found inside the caves: they were mainly represented by speleophilic (i.e. species preferentially or exclusively inhabiting caves) gobids (e.g. Didogobius splechtnai) and nocturnal species (e.g. Conger conger). Forty-one species were censused outside, 20 of which were shared with cave habitats. Apogon imberbis was the most common fish found in all 14 caves investigated, followed by Thorogobius ephippiatus (recorded in 13 caves), and Diplodus vulgaris and Scorpaena notata (both censused in 12 caves). Distinct fish assemblages were found between external rocky reefs and the different cave sub-habitats. New data on the distribution of some speleophilic gobids were collected, showing the existence of a pool of species shared by marine caves on a large scale (i.e. hundreds of km). Considering the uniqueness of cave fishes (18 exclusive species and different assemblage structures), the inclusion of marine caves among the habitats routinely investigated for fish biodiversity monitoring could facilitate the achievement of more comprehensive inventories. Due to their contribution to local species diversity and the shelter they provide to species valuable for conservation, marine caves should be prioritized for their inclusion not only within future MPAs through the Mediterranean Sea, but also into larger management spatial planning.     

How might sea level change affect arthropod biodiversity in anchialine caves: a comparison of Remipedia and Atyidae taxa (Arthropoda: Altocrustacea)

Sea level change influences biodiversity of endemic cave fauna to varying degrees. In anchialine systems, a marine layer flows under less saline layers, each with differing associated fauna. We assess the role of present and historic (last glacial maximum – 18,000 years ago) distance from the ocean in determining species richness and phylogenetic diversity patterns for two groups of anchialine crustaceans: the marine-restricted Remipedia and a subset of groundwater-inhabiting atyid shrimp with greater tolerance for salinity variation. We calculated species richness and phylogenetic diversity per cave based on records of remipede and atyid diversity at 137 locations in the Yucatán Peninsula, Caribbean, Australia, and the Canary Islands. After calculating the distance of each cave’s surface opening from the past and present shoreline, we evaluated how species richness and phylogenetic diversity change with distance from the present and historic ocean. Remipede species richness and phylogenetic diversity declined rapidly with distance from the ocean. Ninety-five percent of the remipedes surveyed were located within 7 km of the present ocean and 18 km of the historic ocean. Atyid species richness and phylogenetic diversity declined more slowly with distance from the ocean than that of remipedes. Atyid shrimp were also distributed over a broader range: 95 % were located within 100 km of the present ocean and 240 km of the historic ocean. Our findings indicate that coastal geomorphology and salinity tolerance influence a clade’s distribution with respect to its distance from the ocean. We also report a possible latent response to sea level change.     

Global biodiversity and phylogenetic evaluation of remipedia (crustacea)

Remipedia is one of the most recently discovered classes of crustaceans, first described in 1981 from anchialine caves in the Bahamas Archipelago. The class is divided into the order Enantiopoda, represented by two fossil species, and Nectiopoda, which contains all known extant remipedes. Since their discovery, the number of nectiopodan species has increased to 24, half of which were described during the last decade. Nectiopoda exhibit a disjunct global distribution pattern, with the highest abundance and diversity in the Caribbean region, and isolated species in the Canary Islands and in Western Australia. Our review of Remipedia provides an overview of their ecological characteristics, including a detailed list of all anchialine marine caves, from which species have been recorded. We discuss alternative hypotheses of the phylogenetic position of Remipedia within Arthropoda, and present first results of an ongoing molecular-phylogenetic analysis that do not support the monophyly of several nectiopodan taxa. We believe that a taxonomic revision of Remipedia is absolutely essential, and that a comprehensive revision should include a reappraisal of the fossil record.     

Nutrient speciation and hydrography in two anchialine caves in Croatia: tools to understand iodine speciation

Despite iodine being one of the most abundant of the minor elements in oxic seawater, the principal processes controlling its interconversion from iodate to iodide and vice versa, are still either elusive or largely unknown. The two major hypotheses for iodate reduction involve either phytoplankton growth in primary production, or bacteria during regeneration. An earlier study intended to exploit the unusual nature of anchialine environments revealed that iodide is oxidised to iodate in the bottom of such caves, whereas reduction of iodate occurs in the shallower parts of the water column. This investigation was made on the hypothesis that study of the nitrogen and phosphorus nutrient systems within the caves might offer a bridge between the iodine chemistry and the marine bacteria which are assumed to be the agent of change of the iodine in the caves. Accordingly, the hydrography, the nutrient chemistry, and some further iodine studies were made of two anchialine caves on the east coast of the Adriatic Sea in Croatia. Iodate and iodide were determined by differential pulse voltammetry and cathodic stripping square-wave voltammetry, respectively. Total iodine was determined indirectly, as iodate, after oxidation of reduced iodine species with UV irradiation and strong chemical oxidants. Nutrient concentrations were measured by spectrophotometry. Nutrient profiles within the well stratified water columns indicate a relatively short-lived surface source of nitrate and phosphate to the caves, with a more conventional, mid-water, nutrient regeneration system. The latter involves nitrite and ammonium at the bottom of the halocline, suggestive of both autotrophic and heterotrophic microbial activity. High iodate/low iodide deep water, and conservative behaviour of total inorganic iodine were confirmed in both systems. Iodate is reduced to iodide in the hypoxic region where nutrient regeneration occurs. The concentrations of organic iodine were surprisingly high in both systems, generally increasing toward the surface, where it comprised almost 80% of total iodine. As with alkalinity and silica, the results suggest that this refractive iodine component is liberated during dissolution of the surrounding karst rock. A major, natural flushing of one of the caves with fresh water was confirmed, showing that the cave systems offer the opportunity to re-start investigations periodically.     

Ecological preferences of neotropical cave bats in roost site selection and their implications for conservation

Bats frequently use caves as roosts due to higher environmental stability and protection. However, species-specific ecological and physiological requirements and conditions of roosts and their surroundings can influence species presence. Little is known on cave choice by bats in the Neotropics, a species- and cave-rich region. Understanding how bats, cave characteristics and the surrounding landscape are related with each other helps the management and conservation of bats and caves. Based on sampling 19 caves using both diurnal observations and captures, we tested (1) whether bat richness was positively related to cave temperature, humidity, size, stability, and heterogeneity of microhabitats, and the preservation and heterogeneity of the surrounding landscape in central Brazil; (2) whether cave and landscape characteristics influenced on species composition; (3) how species responded to cave and landscape variables; and (4) whether these relationships changed between seasons. Temperature was a limiting factor, whereas environmental stability, humidity, and structural attributes of caves favored the occurrence of more species. Larger caves, rich in microhabitats – but more stable than the external environment – supported more species, especially in the dry season. Landscape context did not influence species richness and composition in the caves, but the percentage of vegetation around caves was important for certain species. Our results highlight the influence of environmental variables in the process of cave selection by Neotropical bat species. Moreover, we emphasize the importance of cave protection for bats and provide useful information for decision-making in processes of environmental licensing.     

Shrimps down under: evolutionary relationships of subterranean crustaceans from Western Australia (Decapoda: Atyidae: Stygiocaris)

Background

We investigated the large and small scale evolutionary relationships of the endemic Western Australian subterranean shrimp genus Stygiocaris (Atyidae) using nuclear and mitochondrial genes. Stygiocaris is part of the unique cave biota of the coastal, anchialine, limestones of the Cape Range and Barrow Island, most of whose nearest evolutionary relations are found in coastal caves of the distant North Atlantic. The dominance of atyids in tropical waters and their food resources suggest they are pivotal in understanding these groundwater ecosystems.

Methodology/Principle Findings

Our nuclear and mitochondrial analyses all recovered the Mexican cave genus Typhlatya as the sister taxon of Stygiocaris, rather than any of the numerous surface and cave atyids from Australia or the Indo-Pacific region. The two described Stygiocaris species were recovered as monophyletic, and a third, cryptic, species was discovered at a single site, which has very different physiochemical properties from the sites hosting the two described species.

Conclusions/Significance

Our findings suggest that Stygiocaris and Typhlatya may descend from a common ancestor that lived in the coastal marine habitat of the ancient Tethys Sea, and were subsequently separated by plate tectonic movements. This vicariant process is commonly thought to explain the many disjunct anchialine faunas, but has rarely been demonstrated using phylogenetic techniques. The Cape Range''s geological dynamism, which is probably responsible for the speciation of the various Stygiocaris species, has also led to geographic population structure within species. In particular, Stygiocaris lancifera is split into northern and southern groups, which correspond to population splits within other sympatric subterranean taxa.     

Marine caves of the Mediterranean Sea: a sponge biodiversity reservoir within a biodiversity hotspot

Marine caves are widely acknowledged for their unique biodiversity and constitute a typical feature of the Mediterranean coastline. Herein an attempt was made to evaluate the ecological significance of this particular ecosystem in the Mediterranean Sea, which is considered a biodiversity hotspot. This was accomplished by using Porifera, which dominate the rocky sublittoral substrata, as a reference group in a meta-analytical approach, combining primary research data from the Aegean Sea (eastern Mediterranean) with data derived from the literature. In total 311 species from all poriferan classes were recorded, representing 45.7% of the Mediterranean Porifera. Demospongiae and Homoscleromorpha are highly represented in marine caves at the family (88%), generic (70%), and species level (47.5%), the latter being the most favored group along with Dictyoceratida and Lithistida. Several rare and cave-exclusive species were reported from only one or few caves, indicating the fragmentation and peculiarity of this unique ecosystem. Species richness and phylogenetic diversity varied among Mediterranean areas; the former was positively correlated with research effort, being higher in the northern Mediterranean, while the latter was generally higher in caves than in the overall sponge assemblages of each area. Resemblance analysis among areas revealed that cavernicolous sponge assemblages followed a pattern quite similar to that of the overall Mediterranean assemblages. The same pattern was exhibited by the zoogeographic affinities of cave sponges: species with Atlanto-Mediterranean distribution and Mediterranean endemics prevailed (more than 40% each), 70% of them having warm-water affinities, since most caves were studied in shallow waters. According to our findings, Mediterranean marine caves appear to be important sponge biodiversity reservoirs of high representativeness and great scientific interest, deserving further detailed study and protection.