Regeneration of ciliary pattern in longitudinal fragments of the hypotrichous ciliate, Stylonychia

Abstract

Longitudinal fragments of the hypotrichous ciliate Stylonychia were studied a t various stages of cortical regeneration by Scanning Electron Microscopy. Analysis showed that (except for the oral primordium) all primordial fields responsible for replacing excised ciliature develop in continuity with existing primordia; i.e., all ciliary primordia are derived from segments originally continuous with the oral primordium. This observation leads to the concept of a single primordial field, a "primordium of the ciliature," possessing the developmental competence of giving rise to a complete set of ciliary structures. Such a concept implies the operation of a reciprocal intra-cortical communication system; i.e., the developmental manifestations of any individual primordium are determined a t least in part by the precise location of morphostatic and/or primordial ciliary structures. An intra-cortical communication system is consistent with the previously proposed "determinative region" (Grimes, '75), the function of which is to serve as the initiation site of a primordium during excystment morp hogenesis.Morphogenesis and control of cortical patterning in ciliates have been subjects of several extensive studies and reviews (e.g., Frankel, '73, '74, '75; Grimes, '72, '73a,b,c, '76; Hammersmith, '76a,b; Hashimoto, '61, '62, '63, '64; '63, '72a,b, '74; '72, '75; '69; Sonneborn, '63, '70, '75; Walker and Grim, '73). In a n attempt to understand the factors which control morphogenesis in hypotrichous ciliates, various studies, most notably those of Hashimoto ('61, '64) and '69, '741, have approached the problem through observation and interpretation of morphogenetic patterns during cortical regeneration (the morphogenetic sequence initiated by cell trauma resulting in the replacement of all missing cortical structures). To date, these studies have employed light microscopy to examine the results of cortical excision and subsequent regeneration.In an attempt to determine the morphogenetic interactions among existing cortical structures and primordia in Stylonychia, longitudinal cell fragments were examined a t various stages of regeneration by Scanning Electron Microscopy (SEMI. The SEM permits a 3-dimensional analysis of external cortical events during morphogenesis without the problems associated with protargol staining (irreproducibility leading to a limited number of well-stained cells). This SEM analysis demonstrates the ability of the oral primordium to participate in the formation of primordial fields which, in the undisturbed cell, would utilize other components of the existing ciliature. These observations and their relation to current theories on morphogenetic mechanisms are discussed. (Grimes, ' 7 3~) . MATERIALS AND METHODSThe anterior portion of one half of individual doublet cells was removed microsurgically, thus inducing cortical morphogenesis in both halves of the doublet (regeneration on the damaged half, morphogenesis comparable to reorganization on the intact half). Cortical reorganization o...

Cortical Morphogenesis during Excystment in Histriculus similis (Hypotrichida: Oxytrichidae)1

“…We have not found continuity between dorsal bristle rows 1, 2, and 3 primordia and the oral or marginal primordia, but we have found that the dorsal bristle rows 1 and 2 primordia initially appear joined at their posterior ends. During regeneration in right longitudinal fragments o f Stylonichia (6), this connection between the dorsal bristle rows 1 and 2 primordia has been described. In this case there is a continuity with the left marginal cirral primordium.…”

“…Our study points out that cortical morphogenesis during excystment of Histriculus similis shows clear differences from cortical morphogenesis during division, regeneration, and reorganization (18,22) with respect to the origin of the cirral primordia. During excystment, the left marginal cirral primordium originates from the oral primordium, as has been described during regeneration of longitudinal fragments in Stylonichia mytilus (6) which lack the old marginal ciliature. 24, 25, 28-34).…”

Physiological reorganization in the hypotrich ciliate Apoamphisiella vernalis (Protista, Ciliophora, Hypotricha)

“…Reorganization of the marginal cirral rows and dorsal kineties had no peculiarities, occurring as in most dorsomarginalians (e.g. Grimes & Adler, 1978;Jerka-Dziadosz & Frankel, 1969;Kamra & Sapra, 1991;Arora et al, 1999;Blatterer & Foissner, 2003).…”

“…Zou & Ng (1991) consider physiological reorganization as an ontogenetic process secondarily derived from divisional morphogenesis. It is responsible for renewing a complete conjunct of ciliary elements in intact, non-dividing individuals (Grimes & Adler, 1978). According to Berger (1999), physiological reorganization usually occurs in response to unfavorable environmental (or culture) conditions, such as starvation or other more subtle changes in the medium.…”

Physiological Reorganization and Post‐Traumatic Regeneration in Stylonychia mytilus: Reflections on Developmental Constraints and the Evolutionary Origin of Alternative Modes of Asexual Morphogenesis

“…They differ-entiated to replace the old ciliature as described by Grimes [ 161 ( Fig. 9, 10, 13,16).…”