Does the cellular fatty acid and enzyme content of cave bacteria affect the feeding preferences of Enchytraeus crypticus (Oligochaeta, Enchytraeidae)? 1 VÁCLAV KRIŠTŮFEK, DANA ELHOTTOVÁ, VLADIMÍR ŠUSTR, ROBERT LASÁK, LUBOMÍR KOVÁČ, ANDREJ MOCK & PETER LUPTÁČIK Krištůfek, V., Elhottová, D., Šustr, V., Lasák, R., Kováč, L., Mock, A. & Luptáčik, P.: Does the cellular fatty acid and enzyme content of cave bacteria affect the feeding preferences of Enchytraeus crypticus (Oligochaeta, Enchytraeidae)? Contributions to Soil Zoology in Central Europe I. Tajovský, K., Schlaghamerský, J. & Pižl, V. (eds.): 71-75. ISB AS CR, České Budějovice, 2005. ISBN 80-86525-04-X Cellular fatty acid screening (MIDI System) of 93 bacterial strains isolated from the Domica Cave in the Slovak Karst region (Slovakia) showed that three bacterial strains (Chryseobacterium sp., Enterobacter amnigenus, Rhodococcus sp.) produce polyunsaturated fatty acids (PUFA) 18:3ω6 and 20:4ω6. These species (along with a non PUFA producer, Rhizobium sp.) were isolated from the gut content or body surface of Mesoniscus graniger (Frivaldsky, 1865) (Crustacea: Isopoda). Bacterial strains were tested for activity of nine saccharolytic enzymes. Chryseobacterium sp. showed amylase, maltase and cellobiase activity, other bacterial species only had amylase activity. As PUFA and enzymes may be essential for animal growth and development, colonies of the four strains were grown for further use in laboratory food selection and reproduction experiments with E. crypticus. In food selection studies Chryseobacterium sp. was the most attractive species for E. crypticus, Enterobacter amnigenus and Rhodoccocus sp. ranked second and Rhizobium sp. was only selected by a few E. crypticus individuals. Cell mass of all four bacterial species was offered to E. crypticus as a sole nutrient source. The number of E. crypticus individuals per cocoon was the highest when fed Chryseobacterium sp. (13) and second highest when fed Enterobacter amnigenus (10) and Rhodoccocus sp. (11). In contrast to this, only 8 E. crypticus individuals per coccon were counted when Rhizobium sp. or oat flakes was the diet. E. crypticus individuals that fed on Chryseobacterium sp. and Rhodoccocus sp. started to produce coccons 3-6 days sooner than individuals, which fed on the other tested bacteria species. Keywords: Bacteria, karstic caves, enchytraeids, enzymes, isopoda, PUFA. Václav Krištůfek, Dana Elhottová, Vladimír Šustr, Institute of Soil Biology, Academy of Sciences of the Czech Republic, Na sádkách 7, CZ - 370 05, České Budějovice, Czech Republic. E-mail: kristuf@upb.cas.cz Robert Lasák, Andrej Mock, Peter Luptáčik, Institute of Biology and Ecology, Faculty of Science, University of P.J.Šafárik, Moyzesova 11, SK-041 54 Košice, Slovakia. Lubomír Kováč, Institute of Biology and Ecology, Faculty of Science, University of P.J.Šafárik, Moyzesova 11, SK- 04154 Košice, and Institute of Zoology, Slovak Academy of Sciences, Löfflerova 10, SK-040 01 Košice, Slovakia. Presented at the 7th Central European Workshop on Soil Zoology, České Budějovice, April 14-16, 2003 Introduction Caves are usually oligotrophic environments where primary production depends on chemoautotrophic bacteria (Sarbu et al., 1996). However this is not always the case, recent studies of several caves open to the public have found that a considerable input of organic matter supports the growth of heterotrophic bacteria (Groth and Saiz-Jimenez 1999). For example, in Altamira and Tito Bustillo Caves (northern Spain), rock surfaces are coated by diverse microbes and biofilms. Previous studies showed the occurence of different types of heterotrophic bacteria, and particularly actinomycetes (Groth et al. 1999). Similarly, in Domica Cave (Slovak Karst, Slovakia) rock surfaces are coated by organic sediments originating from the cave river, natural filtration and animal excrements. River clay sediment, rotten wood, the excrements and bodies of cave dwelling or stray animals (e.g. bats, invertebrates, foxes, rabbits, frogs) and waste of human activities (e.g. a mattressess) can all be found on the cave floor. In spite of this diversity of substrates, bat guano is the main source of the organic matter in this hypogean habitat (Nováková et al., this volume). The cave does not contain plants and plant litter, which are, except others, source of nutrition important compounds as polyunsaturated fatty acids (PUFA) (Harwood, 1986). PUFAs importance as a source of essential compounds in animal diet was reviewed by Stanley-Samuelson and Pedibholta (1996). Both microorganisms and litter can serve as a source of PUFA in the soil (Zelles et al., 1999) and the quality of litter PUFA can be improved through the development of microflora (Elhottová et al., 2001). Enchytraeus crypticus (Oligochaeta) has been used successfully several times in food selection tests, which