Although Gastrotricha have previously been recorded in bottom sediments of greenhouses as well as in micro-reservoirs of Bromeliaceae, palm houses provide a more specific microhabitat for these animals that often originate from different regions of the world. This paper presents an investigation of gastrotrich assemblages associated with aquatic plants. Eight species of the epiphytic chaetonotids were found in the Jubilee Greenhouse of the Botanical Garden in Kraków (Poland), including three species new to science, Chaetonotus (Chaetonotus) invitatus sp. nov., C. (Hystricochaetonotus) horridus sp. nov. and C. (H.) inaequabilis sp. nov. Two other species are new to Poland, C. (C.) paucisquamatus Kisielewski, 1991 and C. (Zonochaeta) cestacanthus Balsamo, 1990, both recorded here for the first time outside their terra typica. These observations confirm that greenhouses and palm houses provide many ecological niches and favourable conditions for the development of a number of unintentionally introduced species which cannot be found outside their original climate conditions.
Alien species, Chaetonotus, new species, new records, palm house.