In this report, dealing with Uronychia transfuga, ultrastructural details of a member of the genus Uronychia are provided for the first time. The most interesting features appear to be: (1) the lack of an alveolar, electrondense material in the cortex. This trait distinguishes Uronychia from the members of the family Euplotidae. (2) The peculiar ciliary arrangement of the massive caudal cirri. (3) The oral membrane (OM) delimited by cytoplasmic laminae of different length; it consists of two components each one formed by semicircular sheets of cilia. The length of the cilia progressively increases from the outermost sheet to the internal one. The kinetosomes are interconnected with each other by a dense material that, proximally, forms peculiar crescent-like structures connecting the kinetosomes to the innermost cytoplasmic lamina. The two components of the OM partially overlap at the apical end; at this level their kinetosomes are interconnected by infraciliary structures. The OM components are able to close the peristomial cavity by flexing toward it and completely overlapping each other. The filter feeding mechanism of Uronychia differs from those of other ciliates and allows the ingestion of large active prey. (4) The endoral membrane, probably stichomonad, is limited to the terminal part of the oral cavity. On the whole, our observations appear consistent with the hypothesis that Uronychia should be placed in its own family.

Ultrastructural features of the peculiar filter feeding hypotrich ciliate Uronychia transfuga

LENZI, PAOLA;ROSATI, GIOVANNA;VERNI, FRANCO
1996

Abstract

In this report, dealing with Uronychia transfuga, ultrastructural details of a member of the genus Uronychia are provided for the first time. The most interesting features appear to be: (1) the lack of an alveolar, electrondense material in the cortex. This trait distinguishes Uronychia from the members of the family Euplotidae. (2) The peculiar ciliary arrangement of the massive caudal cirri. (3) The oral membrane (OM) delimited by cytoplasmic laminae of different length; it consists of two components each one formed by semicircular sheets of cilia. The length of the cilia progressively increases from the outermost sheet to the internal one. The kinetosomes are interconnected with each other by a dense material that, proximally, forms peculiar crescent-like structures connecting the kinetosomes to the innermost cytoplasmic lamina. The two components of the OM partially overlap at the apical end; at this level their kinetosomes are interconnected by infraciliary structures. The OM components are able to close the peristomial cavity by flexing toward it and completely overlapping each other. The filter feeding mechanism of Uronychia differs from those of other ciliates and allows the ingestion of large active prey. (4) The endoral membrane, probably stichomonad, is limited to the terminal part of the oral cavity. On the whole, our observations appear consistent with the hypothesis that Uronychia should be placed in its own family.
Morelli, A; Giambelluca, A.; Lenzi, Paola; Rosati, Giovanna; Verni, Franco
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11568/204269
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