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Home , Hydra oligactis, Vjetrenica Cave

Zagmajster et al.

Freshwater hydrozoans in with report on new records

Maja Zagmajster1, Megan L. Porter2, Daniel W. Fong3

1 Department of Biology, Biotechnical Faculty, University of Ljubljana, Ljubljana, , email: [email protected] 2 Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD, USA, e-mail: [email protected] 3 Department of Biology, American University, Washington, D.C., USA, e-mail: [email protected]

Key Words: , , sp.; Smoke Hole , Blowhole Cave, West Virginia, USA; Cueva de la Curva, ; Pajsarjeva jama, Kompoljska jama, Slovenia; Engelbrecht Cave, South ; new records.

1 Introduction

Most of the cnidarians in subterranean waters are found in marine or brackish waters1. Only some species in the class Hydrozoa occur in freshwater2,3. Few are found in subterranean habitats like hyporheic waters, sinking rivers, and residual lakelets1,4. For example, freshwater hydrozoans were found in interstitial habitats near large rivers in Slovenia (Hydra sp.)5, (Hydra vulgaris Pallas, 1766)6, (Hydra (»fusca«) sp., Hydra oligactis Pallas, 1776)7,8, (Hydra viridissima Pallas, 1766)9 and (Hydra (»fusca«) sp.)10. Chappuis11 reported H. viridissima from a well near Basel in . As for cave habitats, information is scarce and mostly derived from records from the first part of the 20th century12,13,14. Reports included Hydra vulgaris, H. oligactis and H. viridissima from caves and an artificial mine. However, most of the reports in the literature did not give species identification.

Only one species, Velkovrhia enigmatica Matjašič & Sket, 1971, in the family Bougainvilliidae, is considered an obligate cave dweller (aquatic troglobiont)15,16. It was described from the cave Planinska jama in SW Slovenia15 and was later found in additional caves in the Dinarides in the western Balkans4,17.

In this contribution we provide an overview of all published records of hydrozoans from cave environments that were available to the authors. Additionally, we report new findings from cave systems in North America, Europe and Australia. We suggest that hydrozoans may be more common in subterranean waters, yet due to difficulties in finding the and lack of taxonomic investigations they are underrepresented in the literature.

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2 Records of hydrozoans from caves

Hydrozoans were found in caves in Europe, North America and Australia (Table 1, Fig. 1). We do not include the report of Hydra pellucida from two caves in Slovenia, given by Joseph18. This author often gave unreliable records of cave animals, according to reports in the literature12,15.

The only currently described aquatic troglobiotic hydrozoan, V. enigmatica, was found in four caves in the Dinarides17. The type locality, Planinska jama (jama = cave), is a large cave with about 6.7 km of passages, and two subterranean rivers join together inside the cave. V. enigmatica was found only in the Rak River channel, attached to permanently submerged as well as occasionally exposed river stones15. Specimens of V. enigmatica were collected in Krška jama in a sample of material from the river just before the resurgence, in Tounjčica cave on stones in small pools, and in Vjetrenica cave from a sample of stones17. Another undetermined epigean hydrozoan is reported from some sites of the Pivka River in Planinska jama15 and was observed in other parts of Postojna Planina Cave System (Boris Sket, University of Ljubljana, pers. Comm.).

Reports on hydrozoans from other countries are mostly from up to the first half of the 20th century. They were found in caves in Germany19,20,21, in the 12,21, Austria22,23 , Mexico24 and Florida in the USA25 . Furthermore, we give information on new records of freshwater hydrozoans in caves that were observed in the recent decade.

In Slovenia, there are two new localities where hydrozoans were observed (Boris Sket, University of Ljubljana, pers. comm.). Pajsarjeva jama, near Vrhnika, is a 555 m long cave with a subterranean stream forming permanent lakelets and resurging from the cave. In October 1999, a polyp of Hydra sp. was collected from the benthos and interstitial samples of the stream about 100 m before the resurgence from the cave. Kompoljska jama near Dobrepolje has 525 m of passages and many permanent lakes. In May 2002, two polyps, each with buds, were collected in the larger puddle–syphon of the cave, about 50 m from the resurgence of the stream from the cave. In the first case specimens were preserved in 70%, and in the second in 96% ethanol.

In October 2004, a Hydra sp. was found in a sample from the lake in Engelbrecht Cave in Mount Gambier in South Australia (Boris Sket, University of Ljubljana, pers. comm.). The cave consists of a few large chambers ending with lakes that lead to submerged chambers regularly entered by divers. The specimen was preserved in 70% ethanol.

Freshwater hydrozoans were observed in two caves in Pendleton County, West Virginia in USA. In May 2006, they were observed in Smoke Hole Cave. The cave

2011 Speleobiology Notes 3: 4-10 5 Zagmajster et al. consists of a series of small rooms connected by narrow slots. The shadows of a forest of hydroids were observed in one small mud-bottomed rimstone pool (about 1 cm deep and 15 cm in diameter) when illuminated from the side. We collected some of the hydroids by using a baster to collect the substrate and animals. The substrate and mixture was left in a plastic container overnight. About 8 hydroids were seen standing erect with extended tentacles the next morning. The bodies of the hydroids were about 2 mm tall and the tentacles were about 1.5 mm long. However, no approriate supplies were available to preserve these specimens or to keep them alive at the field camp. In November 2006, hydrozoans were observed in Blowhole Cave. This is a cave system with many large rooms. Seventeen hydroids were observed in a muddy-bottom rimstone pool (about 1 cm deep and 5 cm in diameter) up on one sidewall of a passage about 30 cm from the cave ceiling, detected again by sidelighting the pool. They were similar in appearance to the ones observed in Smoke Hole Cave. No other organisms were present in the pool or on its surface. We did not collect these specimens.

Figure 1. Localities where hydrozoans have been observed in freshwaters in caves. For the list of localities and details see Table 1.

In March 2009, hydrozoans were observed in Cueva de la Curva near Ciudad Valles, San Luis Potosi, Mexico. The cave consists of a narrow passage, with the upper parts being former stream passages with water present only in the lowest parts of the channel. The specimens were found attached to rocks in pools of the cave stream in the lower levels. The cave fish Astyanax mexicanus was also present in the stream. We collected the hydroids with forceps directly from the surface of the rocks, keeping some specimens alive for several days. Some specimens were preserved in 96% ethanol and some in 4% formalin. Molecular investigations and characterizations of the specimens are ongoing (Daniel Martinez, Pomona College, California, pers. comm.)

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Table 1. Previously known and new cave localities of hydrozoans (see also Fig. 1). No Locality Lat Long Altitude Species Reference [m]

1 Cueva de la Curva, Ciudad 21.98131N 98.92370W 132 Hydra sp. New (13th March Valles, San Luis Potosi, 2009) Mexico 2 Cueva de los Sabinos, 22.09194N 98.95794W 240 Hydra sp. 24 Ciudad Valles, San Luis Potosi, Mexico 3 Little River Spring, Branford, 29.99686N 82.96635W 25 Cordylophora 25 Suwannee County, Florida, lacustris USA 4 Smoke Hole Cave, Brushy 38.84333N 79.29167W 510 Hydra sp. New (May 2006) Run, Pendleton County, West Virgina, USA 5 Blowhole Cave, Franklin, 38.66111N 79.41472W 1091 Hydra sp. New (November 2006) Pendleton County, West Virgina, USA 6 Gruben von Clausthal, 51.80141N 10.33831E 555 Hydra sp. 21 Clausthal-Zellerfeld, Goslar, Germany 7 Hilgershauser Höhle, 51.27110N 8.89888E 263 Hydra sp. 20,21 Hilgershausen, Bad Saalen- Allendorf, Nordhessen, Germany 8 Amselhöhle, Sachsen, 51.10227N 13.19451E na Hydra sp. 19 Germany* 9 Byci Skala Cave, Adamov, 49.30745N 16.69433E 350 Hydra sp. 12,21 Brno, Czech Republic 10 Semriach Lurhöhle, 47.21660N 15.38330E 410 Hydra sp., 22,23 Semriach, Peggau, Hydra viridissima

11 Planinska jama, Planina, 45.81990N 14.24566E 453 Velkovrhia 15,17 Postojna, Slovenia enigmatica, Hydra sp. 12 Krška jama, Krka, Ivančna 45.88999N 14.77126E 280 Velkovrhia 17 Gorica, Slovenia enigmatica 13 Pajsarjeva jama, Podlipa, 45.99765N 14.26575E 325 Hydra sp. New (19th October Vrhnika, Slovenia 1999)

14 Kompoljska jama, 45.79950N 14.73094E 425 Hydra sp. New (12th May 2002) Dobrepolje, Slovenia 15 Spodnja Klevevška jama, 45.90671N 15.23341E 179 Hydra sp. 26 Škocjan, Novo mesto, Slovenia 16 Tounjčica Cave, Tounj, 45.24882N 15.32263E 230 Velkovrhia 17 Ogulin, Croatia enigmatica 17 Vrelo Bosne (cave-spring), 43.81927N 18.26724E 500 Hydra sp. 27 Ilidža, Sarajevo, Bosnia and 18 Vjetrenica Cave, Zavala, 42.84572N 17.98391E 250 Velkovrhia 17,28 Popovo , Bosnia and enigmatica Herzegovina 19 Engelbrecht Cave, Mount 37.82053S 140.77242E 45 Hydra sp. New (18th October Gambier, South Australia, 2004) Australia *The coordinates refer to the middle point of Sachen county.

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3 Rare or overlooked?

There are relatively few reports of hydrozoans from cave environments. This may be partly due to difficulties in finding the animals. Very likely, hydrozoans are commonly overlooked during faunal surveys due to their small, transparent nature. They have been collected mostly as detached specimens in samples of benthos from cave streams15. It may be that sampling of sediments would reveal more hydrozoans from more caves. The rare reports from subterranean habitats in the literature may also be due to the lack of species identification. An additional reason could be that some aquatic areas in caves are difficult to access.

To evaluate whether any of the hydrozoans found in caves could be considered troglobiotic, studies in surface waters should also be conducted. Some indications of whether specimens are isolated from surface habitats can be made from observing the water situation in caves. The colonial Cordylophora lacustris from Florida25 is a wide spread surface species that was found in the cave after flooding events that reversed the water flow at the spring. On the other hand, the passage where hydroids were collected in Cueva de la Curva in Mexico is perched at least 78 m above the resurgence, and most likely receives water from rising ground water only during extremely wet periods29,30. This is supported by the presence of a troglobiotic population of the cave fish, Astyanax mexicanus, that does not show any sign of hybridization with surface populations, implying that connections with surface waters can be considered none or minimal (W.R. Jeffery, University of Maryland, pers. comm.).

Detailed taxonomic analyses may also aid in the determination of troglobiotic species, but requires that materials be properly preserved. Matjašič & Sket15 stored their specimens for morphological study in formaline and Bouin's. In the case of the finding in Mexico, we stored some specimens in 96% ethanol for molecular study. The V. enigmatica were successfully bred in cave-like conditions for a year15,17,31. Some specimens we collected in Cueva de la Curva in Mexico survived for a few weeks in small water containers. Specialists (Daniel Martinez, Pomona College, California, pers. comm.) have advised that, if possible, some speciments should be delivered alive to taxonomic experts.

Our recent findings suggest that the occurrence of hydrozoans in caves may be more common than currently known. In some cases, additional work is needed to determine whether the newly discovered populations are isolated from the surface and whether they reproduce underground. Further studies could reveal additional cave populations, which should be combined with studies on the surface.

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4 Acknowledgements

We are very grateful to Boris Sket (University of Ljubljana, Slovenia) for contributing data on new, recent observations from Slovenia and Australia. Katharina Dittmar (University of Buffalo, New York) organised the cave research expedition to Mexico in 2009. Funding was partly provided through an NSF SGER grant (0827365). Comments from two anonymous reviewers and Steve Taylor greatly improved this manuscript. We appreciate the support and inspirations given by DCBDC (Washington, D.C.) members during regular weekly meetings.

5 Literature cited

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