Abstract
It is known that the freshwater heterotrich ciliate Blepharisma japonicum uses five pigments called blepharismins, stored in its extrusive pigment granules, for both light perception and chemical defense against predators. In this work we focused our attention on the defensive strategies of two additional pigmented species of Blepharisma, B. stoltei and B. undulans. In particular: (1) we observed the predator–prey interactions of B. stoltei or B. undulans against one multicellular and two unicellular predators; (2) we clarified the nature of B. stoltei and B. undulans pigments by means of High Performance Liquid Chromatography (HPLC) and Liquid Chromatography Mass Spectrometry (LC-MS); and (3) we demonstrated and compared the toxicity of the purified pigments on a panel of ciliated protists, and against one metazoan predator. The results indicate that the chemical defense mechanism present in B. stoltei and B. undulans is mediated by the same five blepharismins previously characterized for B. japonicum, although produced in different proportions.
Highlights
Blepharismins (BPs) are multifunctional quinone derivatives identified in the species of heterotrich ciliates belonging to the genus Blepharisma Perty, 1849
In this work: (1) we investigated whether the chemical defense mechanism known in B. japonicum was present in B. stoltei Isquith, 1966 and B. undulans Stein, 1868, exposing both intact cells and pigmentdeficient cells of these two species to unicellular and multicellular predators; (2) we clarified the nature of the pigments produced by B. stoltei and B. undulans using High Performance Liquid Chromatography (HPLC) and Liquid Chromatography Mass Spectrometry (LC-MS) analyses; and (3) we demonstrated and compared the toxicity of the purified pigments on a panel of free-living and raptorial ciliates, and against one microturbellarian predator
It is known that one of the main functions of BPs in B. japonicum is chemical defense against unicellular predators (Harumoto et al 1998; Terazima & Harumoto 2004). To investigate whether this function was present in B. stoltei and B. undulans (Figure 1), we observed the predator–prey interaction of untreated or pigment granule-deficient (PGD) cells of the Blepharisma species against one multicellular (S. sphagnetorum) predator and two unicellular predators (C. hirtus and S. roeseli)
Summary
Blepharismins (BPs) are multifunctional quinone derivatives identified in the species of heterotrich ciliates belonging to the genus Blepharisma Perty, 1849. In B. japonicum Suzuki, 1954, the best-studied photophobic species of the genus, BPs are produced as a mixture of five compounds (BP-A, -B, -C, -D and -E) structurally related to hypericin, a photodynamic toxin of Hypericum perforatum Linnaeus, 1753, and stentorin, produced by Stentor coeruleus Ehrenberg, 1830, another negatively phototactic ciliate (Lobban et al 2007; Matsuoka et al 2010). The step-up photophobic response helps the cells avoid strongly illuminated regions, and lethal damage due to the photodynamic action of BPs (Kato & Matsuoka 1995). It was demonstrated that the photosensitive region is localized in the anterior end of the cell body where only BP-B is present, suggesting that this pigment may represent the photoreceptor mediating the step-up photophobic response (Matsuoka et al 1997)
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