THE DEEPEST FINDING OF AN OLM (PROTEUS ANGUINUS): ZAGORSKA PEć, OGULIN, CROATIA NAJGLOBLJA NAJDBA MOčERILA (PROTEUS ANGUINUS): ZAGORSKA PEć, OGULIN, HRVAŠKA Petra KOVAč KONRAD1 & Katarina KOLLER ŠARIć1,* Izvleček UDK 597.92:551.435.85(497.5) Petra Kovač Konrad & Katarina Koller Šarić: Najgloblja najdba močerila (Proteus anguinus): Zagorska peć, Ogulin, Hrvaška Močerila, Proteus anguinus Laurenti, 1768, smo med teren- skim delom našli v sifonu jame Zagorska peć (Hrvaška), na globini 113 m. Poleg izjemne globine najdbe želimo poudariti, da gre za prvi primer opazovanja te jamske dvoživke v nara- vnem okolju, ki so ga jamski potapljači izvedli globlje od 50 m. Ker so tovrstni potopi nevarni in težavni, podatkov o vertika- lni razporeditvi močerila v jamskih sistemih doslej še ni bilo. Nadaljnje raziskave in situ lahko prispevajo k boljšemu pozna- vanju močerilovih prednostnih okolij in vedenja. Ključne besede: globoki potop, jamski sistem, podzemlje, močeril, vertikalna razporeditev. 1 Association Hyla, Lipovac I No. 7, 10 000 Zagreb, Croatia, e-mail: petrakovkon1@gmail.com, katarina.koller@gmail.com Received/Prejeto: 11.06.2017 COBISS: 1.01 ACTA CARSOLOGICA 46/2−3, 347–351, POSTOJNA 2017 Abstract UDC 597.92:551.435.85(497.5) Petra Kovač Konrad & Katarina Koller Šarić: The deepest finding of an olm (Proteus anguinus): Zagorska peć, Ogulin, Croatia During the field work in Zagorska peć cave in Croatia, the olm, Proteus anguinus Laurenti, 1768 was observed in a siphon at depth of 113 m. This was not only the first time that this tro- globiotic amphibian was recorded at such depths but also the first time that its research was done by cave-divers in its natural environment, at depths greater than 50 m. As such research is dangerous and difficult there was no previous data on the verti- cal distribution of the olm in the cave system. Further in situ research will provide valuable insight into species’ environ- mental preferences and behaviour. Key words: deep dive, cave system, subterranean environment, the olm, vertical distribution. INTRODUCTION Croatia has a surface area of 56.594 km2, of which the karst terrain covers 26.000 km2, or 46 % (Gottstein Matočec et al. 2002). There are more than 7.000 registered caves in Croatia (Garašić 1991). Their phreatic parts have been poorly studied, mostly due to the high cost and unavail- ability of diving equipment. Unsystematic cave-diving surveys started in 1959 (Malinar 2015; Kovač Konrad & Buzjak 2011). Since specific and dangerous survey meth- ods are necessary for surveillance of aquatic subterrane- an fauna (i.e. stygofauna) in situ, its research has not been systematically conducted. Alongside many invertebrate groups adapted to subterranean habitats, fish and salamanders are the only obligate subterranean (i.e. troglobiotic) vertebrates (Barr & Holsinger 1985). While approximately 300 troglobi- otic fish species have been reported so far (Romero et al. 2009), only 13 salamander species of the genus Eurycea Rafinesque, 1822, are widely distributed in eastern and south-central North America, and the olm, Proteus an- guinus Laurenti, 1768, inhabits the European Dinaric karst (Chippindale 2000; Wiens et al. 2003).The olm inhabits groundwaters of the Dinaric karst, from Italy, through Slovenia, Croatia, and Bosnia and Herzegovina. (Kletečki et al. 1996; Sket 1997). Prior to the discovery of the first cave fish in the Danube-Aach system (Beh- rmann-Godel et al. 2017), it was the only European tro- globiotic vertebrate (Parzefall et al. 1993). Most of the data about the biology, ecology and behaviour of the olm ACTA CARSOLOGICA 46/2–3 – 2017348 PETRA KOVAč KONRAD & KATARINA KOLLER ŠARIć originate from observations done in an artificial environ- ment (Dumas & Chris 1998; Vuitron et al. 2011). Conse- quently, even basic information about the vertical distri- bution of the olm in subterranean caves is still lacking. While there is some research of vertical distribution of cave invertebrates that live at great depths (Sendra & Re- boleira 2012), there are no data about the vertical distri- bution of vertebrates in the phreatic environment (Sen- dra & Reboleira 2012). In Slovenia, the olm was found in Divje jezero (Idrija) at a depth of approximately 50 m (Krivic et al. 1983). Here we present the first study inves- tigating the vertical distribution of the olm in Zagorska peć Cave in Croatia and the deepest ever record of this cave-dwelling vertebrate. GEOLOGICAL AND GEOGRAPHICAL SETTING Zagorska peć Cave (N: 45.19700⁰; E: 15.21983⁰, 350 m a.s.l.) is situated in the western central part of the Dinaric karst of Croatia, in a part of the Ogulin Zagorje region, Karlovac County, 8 km south from the town of Ogulin (Fig. 1). The whole area is an example of typical karst hydrogeology characterized by permanent springs at the western margin of the area (Kovač Konrad 2011). Within area we can distinguish true hydrogeological barriers, relative barriers, zones of shallow water in fractures, and zones consisting of deep permeable rocks (Bahun 1970). Zagorska peć is one of six caves within the region (Jalžić 2008) where the olm was found. Other localities include: cave Klisura, Rupečica Spring, Rupečica Ponor, cave- spring Zagorska Mrežnica, and Bistrac Spring (Jalžić 2008). Being the deepest cave makes Zagorska peć the most appropriate site to observe the vertical distribution of the olm. The first cave-diving explorations of Zagorska peć Cave were conducted in 1999 when B. Jalžić and D. Lukačić dove to 22 m and confirmed the presence of the olm (Dečak-Barišić et al. 2008). During later cave-diving explorations Zagorska peć Cave and Bistrac Spring were recognised as the only known sites where the olm was found deeper than 50 m (Jalžić 2008). The cave map (Fig. 2) shows that Zagorska peć Cave passages are branched, reaching a total length of 490 m. Main passage has a North-South direction. The pattern of the cave system is characterised by numerous fissures and their mutual intersections. A siphon starts in a lake at a depth of 10 m (Fig. 3), and it continues to a depth of 121 m. In the cave, stable hydrological conditions dominate for relatively long periods, excluding periods of intensive snow-melts or extremely long rainy peri- ods when the cave is partially flooded for several days per year (Bojanić & Ivčić 1981) and it becomes an active spring. fig. 1: Map of Croatia with the location of zagorska peć Cave. ACTA CARSOLOGICA 46/2–3 – 2017 349 THE DEEPEST RECORD OF AN OLM; ZAGORSKA PEć, OGULIN, CROATIA METHODS Field work in Zagorska peć Cave was conducted on 10. 12. 2016 and 31. 1. 2017 by Frederic Swierczynski, Petra Kovač Konrad and Peter Slokan. The research was car- ried out with the main purpose of collecting data for studies of vertical distribution of the olms. For the deep cave dives closed-circuit systems for diving (Innerspace Megalodon Model) and a mixture of helium, oxygen and nitrogen gases were used. The water temperature and depth were measured simultaneously with a diving com- puter (Suunto EON Steel). The depth of each olm was recorded on wet-note. Only olms detected at a 0.5-4 m distance from a safety line (2 mm polypropylene line po- sitioned along the siphon which served as the transect line) were recorded. We recommend such consistent and standardised design of data collection for future dives in this and other caves. fig. 2: Cave Map of zagorska peć Cave, with location of the sam- pling site –siphon (archive of Caving section Željezničar). fig. 3: Lake with syphon (illuminated) in zagorska peć Cave (Photo: M. talaja). tab. 1: Number of the olms, Proteus anguinus, and the depth at which they were recorded. Date (total dive depth) Number of individuals Depth (m) 10. 12. 2016 2 15 (102 m) 1 21 2 30 1 40 1 60 2 70 1 80 31. 1. 2017 2 40 (121m) 2 60 2 80 2 86 1 98 1 113 RESULTS Two successful cave dives deeper than 100 m (102 m, 121 m) were done in Zagorska peć Cave during the data collection. The water temperature during the dives was 8.8 °C. The morphology of the siphon does not change much from its start in the cave lake. It is on average 7×10 m wide, with a slight or no water current. During each dive, 10 adult olms were found along the siphon safety line from 15 m down to a depth of 113 m (Tab. 1; Fig. 4). No individuals were noticed in the cave lake, however, neither on this nor on previous occa- sions. Cave crustaceans (Troglocaris sp., Niphargus sp., Monolistra sp.) were also present all the way down to the deepest parts of the siphon (121 m). ACTA CARSOLOGICA 46/2–3 – 2017350 DISCUSSION This is the first time that the olm, Proteus anguinus, was recorded at such a great depth and also the first time that its observations were done directly by cave divers in its natural environment, at depths greater than 50 m. So far, only two 100 m plus dives have been performed since such observations require long-term preparation and the dive itself is extremely difficult and dangerous. For deeper dives and possible discovery of the olm at greater depths, the continuation of the siphon should be explored first. According to our observations, the depth and food sources (as the potential stress factors) have no substan- tial influence on the proteus’ vertical distribution along the siphon of Zagorska peć Cave. Although caves are of- ten held to be extremely energy-poor environments, this apparently doesn’t apply to the aforementioned cave. In both dives olms were distributed approximately evenly along the safety line, in accordance with abundant inver- tebrates, their main source of food (Bizjak-Mali & Bulog 2004). In both dives the olms were not recorded at the maximum dive depths. A possible reason could be the divers’ complete focus on tying-off the safety line while reaching the maximum dive depth and the planned dis- tance. Nevertheless, since the species was found at such a depth, we could conclude that the olm can withstand significant pressure. Biological structures and processes that allow this creature to dive so deep should also be- come subjects of future research. Last but not least, factors like hydrological activity of certain parts of the cave system, its morphology, and sedimentation conditions, should also be considered in further exploration of the olm’s vertical distribution. fig. 4: Proteus anguinus at the depth of 113 m. ACKNOWLEDGEMENTS We would like to thank Mladen Zadravec (Associa- tion Hyla, Zagreb, Croatia) for his helpful suggestions and comments on the manuscript, Dušan Jelić for do- ing research on Proteus anguinus in Croatia, Branko Jalžić, Damir Lukačić, Dado Podnar, Vedran Jalžić, Alan Kovačević, Zvonimir Švrljuga, Frederic Swierczynski and Peter Slokan for cave diving research of Zagorska Peć Cave. Our thanks also go to cavers of the Caving section Željezničar from Zagreb for providing the cave map and logistic support, Caving section Željezničar from Gospić, Mountain rescue team from Gospić for lending their equipment, the director of Gojak Hydroelectric Power Plant Milan Sabljak for hydrological data and a Director of Water supply and Sewerage Ogulin Zdravko Paušić for logistic support. PETRA KOVAč KONRAD & KATARINA KOLLER ŠARIć ACTA CARSOLOGICA 46/2–3 – 2017 351 Bahun, S., 1970: Geološka osnova krške zavale Ogulin – Plaški.- Krš Jugoslavije, 7, 1, 19-83. Barr, T.C. & J.R. Holsinger, 1985: Speciation in Cave Fau- nas.- Annual Review of Ecology and Systematics, 16, 313-337. Behrmann-Godel, J., Nolte, A.W., Kreiselmaier, J., Berka, R. & J. Freyhof, 2017: The first European cave fish.- Current Biology, 27, 7, 257-258. DOI: https://doi. org/10.1016/j.cub.2017.02.048. Bizjak-Mali, L. & B. Bulog, 2004: Histology and ultra- structure of the gut epithelium of the neotenic cave salamander, Proteus anguinus (Amphibia, Cau- data).- Journal of mophology, 259, 1, 82-89. DOI: https://doi.org/10.1002/jmor.10171 Bojanić, L. & D. Ivčić, 1981: Hidrogeološka istraživanja područja Drežnica, Krakara, Jasenka, Vitunjčice, Risnjaka i Gojačke Dobre. Fond stručne dokument- acije Geološkog zavoda. Dumas, P. & B. Chris, 1998: The olfaction in Proteus an- guinus: a behavioural and cytological study.- Behav- ioural Processes, 43, 2, 107-113. DOI: https://doi. org/10.1016/s0376-6357(98)00002-3. Chippindale, P.T., 2000: Species boundaries and spe- cies diversity in central Texas hemidactyliine plethodontid salamanders, genus Eurycea.- In: Bruce, R., Houck, L. & R. Jaeger (eds.) The biology of plethodontid salamanders. Kluwer Academic/Ple- num, pp. 149-165, New york. Garašić, M., 1991: Morphological and hidrogeological classification of speleological structures (caves and pits) in the Croatian karst area.- Geološki vjesnik, 44, 289-300. Gottstein Matočec, S., Bakran-Petricioli, T., Bedek, J., Bu- kovec, D., Buzjak, S., Franičević, M., Jalžić, B., Ker- ovec, M., Kletečki, E., Kralj, J., Kružić, P., Kučinić, M., Kuhta, M., Matočec, N., Ozimec, R., Rađa, T., Štamol, V., Ternjej, I. & N. Tvrtković, 2002: An overview of the cave and interstitial biota of Croa- tia.- Natura Croatica, 11, 1-112. Jalžić, V., 2008: Speleoronilačka istraživanja na zapadnoj obali akumulacijskog jezera Sabljaci. Projektni elab- orat Hrvatskog biospeleološkog društva u suradnji sa Hrvatskim vodama, 1–7. Kletečki, E., Jalžić, B. & T. Rađa, 1996: Distribution of the olm (Proteus anguinus, Laur.) in Croatia.- Mem- oires de Biospeleologie, 23, 227-231. Kovač Konrad, P., 2011: geomorfološka i hidrološka obilježja izvora zagorske Mrežnice.- Gradua- tion Thesis. Geografski odsjek Prirodoslovno – matematičkog fakulteta Sveučilišta u Zagrebu, pp. 43. Kovač-Konrad, P. & N. Buzjak, 2011: Primijenje- na speleoronilačka istraživanja u zaštiti krških vodonosnika Hrvatske. In: Biondić, D., Holjević, D. & L. Tropan (eds.) zbornik radova 5. hrvatske kon- ferencije o vodama s međunarodnim sudjelovanjem: Proceedings of 5th Croatian water conference with in- ternational participation, 18th- 21th May 2011, Opati- ja, Croatia 561-571, Opatija. Krivic, P., Praprotnik, A. & R. Smerdu, 1983: Potapljaške raziskave Divjega jezera.- Naše jame, 25, 7-10. Malinar, H., 2015: Prvo ronjenje u špilji u Hrvatskoj.- Velebiten, 48, 61 -64. Parzefall, J., Durand, J.P. & B. Sket, 1939: Proteus an- guinus Laurenti, 1768 – Grottenolm. In: Grossen- bacher, K. & Thismeier B. (eds),Schwanzlurche I, handbuch der Reptilien und Amphibien Europas. 4/1 Schwanzlurche (Urodela) I. Wiesbaden, Aula- Verlag, 7–76. Romero, A., Zhao, y. & X. Chen, 2009: The Hypogean fishes of China.- Environmental Biology of Fish- es, 86, 1, 211-278. DOI: https://doi.org/10.1007/ s10641-009-9441-3. Sendra, A. & A.S.P.S. Reboleira, 2012: The world’s deep- est subterranean community – Krubera-Voronja Cave (Western Caucasus).- International Journal of Speleology, 41, 2, 221-230. DOI: https://doi. org/10.5038/1827-806X.41.2.9. Sket, B., 1997: Distribution of Proteus (Amphibia: Urode- la: Proteidae) and its possible explanation.- Journal of Biogeography, 24, 3, 263-280. DOI: https://doi. org/10.1046/j.1365-2699.1997.00103.x. Voituron, y., de Fraipont, M., Issartel, J., Guillaume, O. & J. Clobert, 2011: Extreme lifespan of the human fish (Proteus anguinus): a challenge for ageing mecha- nisms.- Biological Letters, 7, 1, 105-107. DOI: https://doi.org/10.1098/rsbl.2010.0539. Wiens, J.J., Chippindale, P.T. & D.M. Hillis, 2003: When Are Phylogenetic Analyses Misled by Convergence? A Case Study in Texas Cave Salamanders.- Sys- tematic Biology, 52, 4, 501-514. DOI: https://doi. org/10.1080/10635150390218222. REFERENCES THE DEEPEST RECORD OF AN OLM; ZAGORSKA PEć, OGULIN, CROATIA