New records of ostracods (Crustacea, Ostracoda) from groundwater habitats in Italy, with faunistic and biogeographical notes

Groundwater ecosystems host highly specialised and frequently endemic faunas, yet their biodiversity remains poorly explored. Although Italy is recognised as a hotspot of subterranean diversity, knowledge of its stygobitic ostracods (i.e., species that are obligate inhabitants of subterranean waters) remains fragmentary. Here we report new data on ostracods collected from 15 natural caves, a mine and an aquifer across mainland Italy and Sicily between 2009 and 2018, with the aim of documenting new occurrence records from poorly investigated subterranean sites, discussing their taxonomic implications, and reassessing the diversity and endemism of Italian stygobitic ostracods in a broader European context. Nineteen taxa belonging to 12 genera and five families were identified, several of which are regarded as strictly stygobitic. These include representatives of Mixtacandona (Candonidae), among which several putative undescribed species of the laisi-chappuisi group were detected. Particularly noteworthy is the occurrence of Mixtacandona cf. botosaneanui in southern Italy: if its identity with the nominal species is confirmed, this record would considerably extend its known geographical range and provide the first description of the male, thereby adding important taxonomic information for a poorly known subterranean lineage. We also report a new record of Typhlocypris cf. eremita and specimens referable to Pseudolimnocythere, further expanding the known distribution of these genera within Italian subterranean habitats. Although some specimens could be assigned only tentatively because well-preserved adults were scarce, the new records substantially refine current knowledge of Italian groundwater ostracod diversity and distribution patterns at both regional and European scales. An updated checklist raises the number of Italian stygobitic ostracods to more than 30 taxa, representing approximately 30% of the currently known European groundwater ostracod diversity. This proportion is remarkable given the limited extent of Italian territory, and the high frequency of endemic and potentially undescribed species further highlights the Italian peninsula and its islands as important centres of diversification for subterranean ostracods. These results emphasize the need for continued biospeleological surveys and integrative taxonomic approaches combining morphology and molecular data to resolve species boundaries, phylogenetic relationships and colonization histories in subterranean lineages.

Becher J, Englisch C, Griebler C, Bayer P, 2022. Groundwater fauna downtown - Drivers, impacts and implications for subsurface ecosystems in urban areas. J Contam Hydrol 248:104021. DOI: https://doi.org/10.1016/j.jconhyd.2022.104021

Bottazzi E, Bruno MC, Mazzini M, Pieri V, Rossetti G, 2008. First report on Copepoda and Ostracoda (Crustacea) from northern Apenninic springs (N Italy): a faunal and biogeographical account. J Limnol 67:56-63. DOI: https://doi.org/10.4081/jlimnol.2008.56

Bottazzi E, Bruno MC, Pieri V, Di Sabatino A, Silveri L, Carolli M, Rossetti G, 2011. Spatial and seasonal distribution of invertebrates in Northern Apennine rheocrene springs. J Limnol 70:S77-92. DOI: https://doi.org/10.4081/jlimnol.2011.s1.77

Boulton AJ, 2020. Conservation of groundwaters and their dependent ecosystems: integrating molecular taxonomy, systematic reserve planning and cultural values. Aquat Conserv 30:1-7. DOI: https://doi.org/10.1002/aqc.3268

Boutin CL, Coineau N, 1990. [Regression model, modèle biphase d'évolution et origine des micro-organismes stygobies interstitiels continentaux].[Article in French]. Rev Micropaleontol 33:303-322.

Bruno MC, Bottazzi E, Rossetti G, 2012. Downward, upstream or downstream? Assessment of meio- and macrofaunal colonization patterns in a gravel-bed stream using artificial substrates. Ann Limnol 48:371-381. DOI: https://doi.org/10.1051/limn/2012025

Castillo-Escrivà A, Baltanás Á, Camacho A, Horne DJ, Pretus JL, Mesquita-Joanes F, 2023. IMOST: a database for non-marine ostracods in the Iberian Peninsula, the Balearic Islands and Macaronesia. J Limnol 82:2115. DOI: https://doi.org/10.4081/jlimnol.2023.2115

Colin JP, Danielopol DL, 1980. [Sur la morphologie, la systématique, la biogéographie et l'évolution des ostracodes Timiriaseviinae (Limnocytheridae)].[Article in French]. Paleobiol Continent 11:1-52.

Crema S, Ferrarese U, Golo D, Modena P, Sambugar B, Gerecke R, 1996. [Ricerche sulla fauna bentonica ed interstiziale di ambienti sorgentizi in area alpina e prealpina].[in Italian]. Centro di Ecologia Alpina, Trento, Report 8:1-104.

Culver DC, Pipan T, 2019. The biology of caves and other subterranean habitats. Oxford University Press, Oxford. DOI: https://doi.org/10.1093/oso/9780198820765.001.0001

Danielopol DL, 1973. [Sur la morphologie des aesthetascs chez quelques ostracodes hypogés de la sous-famille des Candoninae (Cyprididae, Podocopida)].[Article in French]. Ann Speleol 28:233-245.

Danielopol DL, 1977/78. [Ostracodes hypogés du Sud de la France. 1. Mixtacandona juberthiae].[in French]. Int J Speleol 9:235-249. DOI: https://doi.org/10.5038/1827-806X.9.3.3

Danielopol DL, 1980. An essay to assess the age of the freshwater interstitial ostracods of Europe. Bijdr Dierkd 50:243-291. DOI: https://doi.org/10.1163/26660644-05002001

Danielopol DL, 1981. [Mixtacandona cottarellii n sp, un ostracode interstitiel de Sardaigne].[Article in French]. Boll Mus Civ St Nat Verona 8:419-425.

Danielopol DL, 1982. Three groundwater Candoninae (Ostracoda) from Romania. Int J Speleol 12:83-102. DOI: https://doi.org/10.5038/1827-806X.12.1.9

Danielopol DL, Cvetkov L, 1979. [Trois nouvelles espèces du genre Mixtacandona (Ostracoda, Cyprididae, Candoninae)].[Article in French]. Hydrobiologia 67:249-266. DOI: https://doi.org/10.1007/BF00023181

Danielopol DL, Hartmann G, 1986. Ostracoda. Part I: Stigobiont Ostracoda from inland subterranean waters, p. 266-279. In: Botosaneanu L (ed.), Stygofauna Mundi. EJ Brill. DOI: https://doi.org/10.1163/9789004631977_032

Danielopol DL, Pospisil P, Rouch R, 2000. Biodiversity in groundwater: a large-scale view. Trends Ecol Evol 15:223-224. DOI: https://doi.org/10.1016/S0169-5347(00)01868-1

Ficetola GF, Canedoli C, Stoch F, 2019. The Racovitzan impediment and the hidden biodiversity of unexplored environments. Conserv Biol 33:214-216. DOI: https://doi.org/10.1111/cobi.13179

Galassi DMP, Stoch F, Fiasca B, Di Lorenzo T, Gattone E, 2009. Groundwater biodiversity patterns in the Lessinian Massif of northern Italy. Freshwater Biol 54:830-847. DOI: https://doi.org/10.1111/j.1365-2427.2009.02203.x

Ghetti PF, McKenzie KG, 1981. [Ostracodi (Crustacea, Ostracoda). Guide per il riconoscimento delle specie animali delle acque interne italiane].[in Italian]. Consiglio Nazionale delle Ricerche, Rome; 83 pp.

Gibert J, Danielopol DL, Stanford JA, 1994. Groundwater ecology. Academic Press, San Diego.

Griebler C, Avramov M, 2015. Groundwater ecosystem services: a review. Freshw Sci 34:355-367. DOI: https://doi.org/10.1086/679903

Halse SA, 2018. Subterranean fauna of the arid zone, p. 215-241. In: H. Lambers (ed.), On the ecology of Australia’s arid zone. Springer, Cham. DOI: https://doi.org/10.1007/978-3-319-93943-8_9

Hanken J, 2025. Subterranean salamanders lean into mechanical sense following vision loss. Proc Natl Acad Sci USA 122:e2512732122. DOI: https://doi.org/10.1073/pnas.2512732122

Hotèkpo SJ, Schön I, Martens K, 2024. An endemic species flock of Candonidae Kaufmann, 1900 (Crustacea, Ostracoda) from wells in Benin (Africa), with the description of a new subfamily, a new genus and five new species. Zootaxa 5503:1-72. DOI: https://doi.org/10.11646/zootaxa.5503.1.1

Howarth FG, Moldovan OT, 2018. The ecological classification of cave animals and their adaptations, p. 41-67. In: O. Moldovan, L. Kováč, S. Halse (eds.), Cave Ecology. Springer. DOI: https://doi.org/10.1007/978-3-319-98852-8_4

Iannella M, Fiasca B, Di Lorenzo T, Di Cicco M, Biondi M, Mammola S, Galassi DM, 2021. Getting the ‘most out of the hotspot’ for practical conservation of groundwater biodiversity. Glob Ecol Conserv 31:e01844. DOI: https://doi.org/10.1016/j.gecco.2021.e01844

Iepure S, Wysocka A, Sarbu SM, Kijowska M, Namiotko T, 2023. A new extremophile ostracod crustacean from the Movile Cave sulfidic chemoautotrophic ecosystem in Romania. Sci Rep 13:6112. DOI: https://doi.org/10.1038/s41598-023-32573-w

Iriarte E, Revelles J, Finsinger W, Mesquita-Joanes F, Rodrigo MA, Burjachs F, Saña M, 2023. Youngest Iberian Holocene volcanic eruptions and paleoenvironmental evolution of a barrier-paleolake in the Garrotxa Volcanic Field (NE Spain). Holocene 33:939-959. DOI: https://doi.org/10.1177/09596836231169989

Issartel C, Marmonier P, 2025. Description of five new species of Schellencandona Meisch, 1996 (Ostracoda: Candoninae) from the southern French Alps, a highly diversified area for groundwater ostracods. Eur J Taxon 1022:85-133. DOI: https://doi.org/10.5852/ejt.2025.1022.3083

Juan C, Guzik MT, Jaume D, Cooper SJB, 2010. Evolution in caves: Darwin’s “wrecks of ancient life” in the molecular era. Mol Ecol 19:3865-3880. DOI: https://doi.org/10.1111/j.1365-294X.2010.04759.x

Kalbe J, Jagher R, Pümpin C, 2016. The spring of Nadaouiyeh Aïn Askar - Paleoecology of a Paleolithic oasis in arid central Syria. Palaeogeogr Palaeoclimatol Palaeoecol 446:252-262. DOI: https://doi.org/10.1016/j.palaeo.2016.01.030

Karanovic I, Pesce GL, 2000. Trapezicandona italica n sp from the underground waters of southern Italy. Fragmenta Entomol 32:213-224.

Karanovic I, Pesce GL, 2001. Ostracods (Crustacea, Ostracoda) from underground waters of Puglia (Southern Italy), with redescription of Pseudolimnocythere hypogaea Klie, 1938. Thalassia Salentina 25:11-39.

Klie W, 1931. [Zwei neue Arten der ostracoden-Gattung Candona aus unterirdischen Gewassern im sudostlichen Europa].[Article in German]. Zool Anz 96:161-169.

Klie W, 1938. [Ostracoden aus unterirdischen Gewässern in Süditalien].[Article in German]. Zool Anz 123:148-155.

Knight LRFD, Mori N, 2022. An updated review of the Ostracoda known from subterranean habitats in the British Isles. Cave Karst Sci 49:57-64.

Linhart J, Brauneis W, Neubauer W, 2007. Morphomatica, Computer Program, version 1.6.0.1.

Malard F, Boutin C, Camacho AI, Ferreira D, Michel G, Sket B, Stoch F, 2009. Diversity patterns of stygobiotic crustaceans across multiple spatial scales in Europe. Freshwater Biol 54:756-776. DOI: https://doi.org/10.1111/j.1365-2427.2009.02180.x

Malard F, Hervant F, 1999. Oxygen supply and the adaptations of animals in groundwater. Freshwater Biol 41:1-30. DOI: https://doi.org/10.1046/j.1365-2427.1999.00379.x

Mammola S, 2019. Finding answers in the dark: caves as models in ecology fifty years after Poulson and White. Ecography 42:1331-1351. DOI: https://doi.org/10.1111/ecog.03905

Mammola S, Altermatt F, Alther R, Amorim IR, Băncilă RI, Borges PA, Malard F, 2024. Perspectives and pitfalls in preserving subterranean biodiversity through protected areas. NPJ Biodivers 3:2. DOI: https://doi.org/10.1038/s44185-023-00035-1

Mammola S, Cardoso P, Culver DC, Deharveng L, Ferreira RL, Fišer C, Zagmajster M, 2019. Scientists' warning on the conservation of subterranean ecosystems. BioScience 69:641-650. DOI: https://doi.org/10.1093/biosci/biz064

Martens K, Horne DJ, 2000. Preface: Ostracoda and the four pillars of evolutionary wisdom. Hydrobiologia 419:7-11. DOI: https://doi.org/10.1023/A:1003994820756

Mazzini I, Marrone F, Arculeo M, Rossetti G, 2017. Revision of Recent and fossil Mixtacandona Klie 1938 (Ostracoda, Candonidae) from Italy, with description of a new species. Zootaxa 4221:323-340. DOI: https://doi.org/10.11646/zootaxa.4221.3.3

Meisch C, 2000. Freshwater Ostracoda of Western and Central Europe. Spektrum Akademischer Verlag, Heidelberg; 522 pp.

Meisch C, Smith RJ, Martens K, 2024. An updated subjective global checklist of the extant non-marine Ostracoda (Crustacea). Eur J Taxon 974:1-144. DOI: https://doi.org/10.5852/ejt.2024.974.2767

Meisch C, 1996. Contribution to the taxonomy of Pseudocandona and four related genera, with the description of Schellencandona nov. gen., a list of the Candoninae genera, and a key to the European genera of the subfamily (Crustacea, Ostracoda). Bull Soc Nat luxemb 97:211-237.

Moldovan OT, 2018. An overview on the aquatic cave fauna, p. 173-194. In: O. Moldovan, L. Kováč, S. Halse (eds.), Cave Ecology. Springer. DOI: https://doi.org/10.1007/978-3-319-98852-8_8

Montanari A, Cerveau N, Fiasca B, Flot JF, Galassi D, Mainiero M, et al., 2021. Stygobitic crustaceans in an anchialine cave with an archeological heritage at Vodeni Rat (Island of Sveti Klement, Hvar, Croatia). Int J Speleol 50:1-14. DOI: https://doi.org/10.5038/1827-806X.50.1.2342

Mori N, Meisch C, 2012. Contribution to the knowledge on the distribution of Recent free-living freshwater ostracods (Podocopida, Ostracoda, Crustacea) in Slovenia. Natura Sloveniae 14:5-22. DOI: https://doi.org/10.14720/ns.14.2.5-22

Mori N, Vehovar Ž, Brad T, Balázs G, Englisch C, Fišer C, Zagmajster M, 2025. A comprehensive occurrence dataset for European Ostracoda inhabiting groundwater and groundwater-dependent ecosystems. Glob Ecol Biogeogr 34:e70065. DOI: https://doi.org/10.1111/geb.70065

Namiotko T, Danielopol DL, Meisch C, Gross M, Mori N, 2014. Redefinition of the genus Typhlocypris Vejdovský, 1882 (Ostracoda, Candonidae). Crustaceana 87:952-984. DOI: https://doi.org/10.1163/15685403-00003338

Pesce GL, 1985. The groundwater fauna of Italy: a synthesis. Stygologia 1:129-159.

Pesce GL, Fusacchia G, Maggi D, Tete P, 1978. [Ricerche faunistiche in acque freatiche del Salento (Contributo alla conoscenza della fauna delle acque sotterranee dell'Italia centro-meridionale: V)].[Article in Italian]. Thalassia Salentina 8:3-51.

Pesce GL, Pagliani T, 1997. [Gli ambienti anchialini della Puglia e la loro fauna].[Article in Italian]. Thalassia Salentina 23:89-102.

Peterson DE, Finger KL, Iepure S, Mariani S, Montanari A, Namiotko T, 2013. Ostracod assemblages in the Frasassi Caves and adjacent sulfidic spring and Sentino River in the northeastern Apennines of Italy. J Cave Karst Stud 75:12-27. DOI: https://doi.org/10.4311/2011PA0230

Petrov BV, 2013. Ostracods (Ostracoda, Crustacea) of Fruška Gora mt (Serbia), p. 19-25. In: Invertebrates (Invertebrata) of the Fruška Gora mountain. Matica srpska, Novi Sad.

Pieri V, Caserini C, Gomarasca S, Martens K, Rossetti G, 2007. Water quality and diversity of the Recent ostracod fauna in lowland springs from Lombardy (northern Italy). Hydrobiologia 585:79-87. DOI: https://doi.org/10.1007/s10750-007-0630-9

Pieri V, Marrone F, Martens K, Rossetti G, 2020. An updated checklist of recent ostracods (Crustacea: Ostracoda) from inland waters of Sicily and adjacent small islands with notes on their distribution and ecology. Eur Zool J 87:714-740. DOI: https://doi.org/10.1080/24750263.2020.1839581

Pieri V, Martens K, Meisch C, Rossetti G, 2015. An annotated checklist of the Recent non-marine ostracods (Ostracoda: Crustacea) from Italy. Zootaxa 3919:271-305. DOI: https://doi.org/10.11646/zootaxa.3919.2.3

Pipan T, Culver DC, 2012. Convergence and divergence in the subterranean realm: a reassessment. Biol J Linn Soc 107:1-14. DOI: https://doi.org/10.1111/j.1095-8312.2012.01964.x

Popa I, Brad T, Vaxevanopoulos M, Giurginca A, Baba ŞC, Iepure S, et al., 2019. Rich and diverse subterranean invertebrate communities inhabiting Melissotrypa Cave in central Greece. Trav Inst Spéol Émile Racovitza 58:65-78.

Ramirez-Llodra E, Brandt A, Danovaro R, De Mol B, Escobar E, German CR, Vecchione M, 2010. Deep, diverse and definitely different: unique attributes of the world's largest ecosystem. Biogeosciences 7:2851-2899. DOI: https://doi.org/10.5194/bg-7-2851-2010

Rohde MM, Albano CM, Huggins X, Klausmeyer KR, Morton C, Sharman A, Stella JC, 2024. Groundwater-dependent ecosystem map exposes global dryland protection needs. Nature 632:101-107. DOI: https://doi.org/10.1038/s41586-024-07702-8

Rohlf FJ, 2009. TpsDig, digitize landmarks and outlines, version 2.14. State University of New York, Stony Brook.

Rossetti G, 2021. Crustacea Ostracoda (freshwater). In: M.A. Bologna, M. Zapparoli, M. Oliverio, A. Minelli, L. Bonato, F. Cianferoni, F. Stoch (eds.), Checklist of the Italian Fauna. LifeWatch Italy.

Rossetti G, Martens K, Meisch C, Tavernelli S, Pieri V, 2006. Small is beautiful: diversity of freshwater ostracods (Crustacea, Ostracoda) in marginal habitats of the province of Parma (Northern Italy). J Limnol 65:121-131. DOI: https://doi.org/10.4081/jlimnol.2006.121

Rossetti G, Mazzini I, Bruno MC, 2025b. On the occurrence of the genus Schellencandona (Ostracoda, Candonidae) in Italy, with the description of a new species. Zootaxa 5723:189-208. DOI: https://doi.org/10.11646/zootaxa.5723.2.2

Rossetti G, Pieri V, Bolpagni R, Nizzoli D, Viaroli P, 2020. Variability in environmental conditions strongly impacts ostracod assemblages of lowland springs in a heavily anthropized area. Water 12:3276. DOI: https://doi.org/10.3390/w12113276

Rossetti G, Pieri V, Martens K, 2005. Recent ostracods (Crustacea, Ostracoda) found in lowland springs of the provinces of Piacenza and Parma (Northern Italy). Hydrobiologia 542:287-296. DOI: https://doi.org/10.1007/s10750-004-2566-7

Rossetti G, Sarbu SM, Ștefan A, Motoc R, Mazzini I, 2025a. Mixtacandona thessalica, a new species of ostracod (Crustacea, Ostracoda) from a sulfidic cave in central Greece. Subterr Biol 52:111-133. DOI: https://doi.org/10.3897/subtbiol.52.142113

Rossetti G, Stoch F, Mazzini I, 2022. A reassessment of the origin and distribution of the subterranean genus Pseudolimnocythere Klie, 1938 (Ostracoda, Loxoconchidae), with description of two new species from Italy. Subterr Biol 43:33-60. DOI: https://doi.org/10.3897/subtbiol.43.82158

Rossetti G, Stoch F, Mazzini I, 2026. The occurrence of the genus Marmocandona (Ostracoda, Candoninae) in Italy, with the description of two new species. Zool Stud 65:16.

Saccò M, Mammola S, Altermatt F, Alther R, Bolpagni R, Brancelj A, Reinecke R, 2024. Groundwater is a hidden global keystone ecosystem. Glob Change Biol 30:e17066. DOI: https://doi.org/10.1111/gcb.17066

Sanna L, Chiarini V, De Waele J, 2023. Underground geodiversity of Italian show caves: An overview. Geoheritage 15:126. DOI: https://doi.org/10.1007/s12371-023-00876-z

Schornikov EI, Zenina MA, Ivanova EV, 2014. Ostracods as indicators of the aquatic environmental conditions on the Northeastern Black Sea shelf over the past 70 years. Russ J Mar Biol 40:455-464. DOI: https://doi.org/10.1134/S1063074014060200

Stoch F, 1993a. [Indagini faunistiche sui crostacei delle acque sotterranee della Val Torre (Italia nordorientale)].[Article in Italian]. Gortania 14:167-183.

Stoch F, 1993b. [Indagini sulla fauna acquatica delle grotte del Trentino (Italia settentrionale)].[Article in Italian]. Studi Trentini Sci Nat Acta Biol 74:117-132.

Stoch F, 1997.[ La fauna delle acque carsiche sotterranee delle Valli del Natisone].[Article in Italian]. Mem Ist Ital Speleol 9:89-100.

Stoch F, 2001. Mapping subterranean biodiversity: structure of the database, mapping software (CKMAP), and a report of status for Italy, p. 29-35. In: D.C. Culver, L. Deharveng, J. Gibert, I.D. Sasowsky (eds.), Mapping Subterranean Biodiversity. Karst Waters Institute.

Stoch F, 2004. [Prime osservazioni sulla fauna delle acque carsiche sotterranee delle Alpi Carniche].[Article in Italian]. Mem Ist Ital Speleol 15:87-95.

Stoch F, 2008. [La fauna cavernicola delle Prealpi Giulie settentrionali].[Article in Italian]. Mem Ist Ital Speleol 20:97-121.

Stoch F, 2017. [Il Lacus Timavi: la fauna acquatica sotterranea, con particolare riguardo alle risorgive del Fiume Timavo].[Article in Italian]. Atti Mem Comm Grotte E Boegan 47:173-203.

Stoch F, Dolce S, 1994. [Progetto Timavo: risultati delle indagini sulla fauna delle acque sotterranee].[Article in Italian]. Atti Mem Comm Grotte E Boegan 31:59-71.

Stoch F, Gerecke R, Pieri V, Rossetti G, Sambugar B, 2011. Exploring species distribution of spring meiofauna (Annelida, Acari, Crustacea) in the south-eastern Alps. J Limnol 70:65-76. DOI: https://doi.org/10.4081/jlimnol.2011.s1.65

Wagenleitner H, 1990. Morphology and evolution of Cypria cavernae n sp (Ostracoda, Crustacea). Bull Soc Nat Luxemb 90:199-226.