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In this study we test three hypotheses. (1) Secretory hairs in the arms and the distal part of the neck of the carnivorous plant Genlisea (Lentibulariaceae) have a different principal function than the digestive hairs in the digestive chamber, that is, prey attraction. (2) Only bacteria and other organisms inside the trap and on the external trap surface lure prey. (3) Substances produced by the plant have a minor influence on prey attraction; more important is trap shape and morphology, because protozoa and microfauna may move to the small interspaces (traps or capillaries) by accidental, nonspecific wandering. We studied the structure of secretory hairs (glands) in the arms and the distal and proximal parts of the trap neck using light, fluorescence and electron microscopy. We tested the hypotheses with several experiments using sterile Genlisea traps as well as glass tubes acting as a Genlisea trap model, and various organisms as prey (Blepharisma sp., Paramecium bursaria, Euglena sp.). Hairs in the arms and the distal part of the Genlisea trap neck represent polysaccharide-protein-secreting hairs. Prey still moved to cleaned traps without chemical attractants. In the proximal part of the neck the secretory hairs have the same ultrastructure as digestive hairs in the digestive chamber of Genlisea. Sterile traps do not need commensals for catching prey. The results of the behavioral experiments reported here support the hypothesis that prey can move to the traps or capillaries by accidental, nonspecific wandering to small objects filled with water. Thus, the complex structure of the Genlisea trap with long arms may help catch prey simply by providing a large surface with many small openings which mimic the interspaces between soil particles, and the plant does not need special mediators for prey attraction.
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The results of the internal transcribed spacer (ITS2) of extrachromosomal rDNA and the chloroplast SSU rDNA sequence analysis presented here confirmed elevated genetic polymorphism revealed earlier by RFLP and RAPD for seven clones of the cosmopolitan species - Euglena agilis Carter. High diversity among these clonal strains was not reflected by morphological criteria, with the exception of the only one character - the ability of the cell in its non-motile dividing states (palmella) to produce mucus and form a slimy envelope. Evolutionary adaptation as formation of slimy envelope may be attributed to different survival strategy of the species by which it adapts to life in a highly variable environment.
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