Morphology, Morphogenesis and Systematic Position of the Sorocarp Forming Ciliate Sorogena Stoianovitchae Bradbury & Olive, 1980

Abstract

Reinvestigation of the type population of the sorocarp‐forming ciliate Sorogena stoianovitchae Bradbury & Olive, 1980 using the Fernández‐Galiano technique and various electron‐microscopy techniques (scanning electron microscopy, freeze‐fracture and ultrathin sections) expands the observations reported in the original description of the species, Sorogena stoianovitchae is a colpodid ciliate with oral ciliature consisting of 25 ciliated paroral dikinetids on the right and 3‐5 small adoral organelles on the left of an elongated and domed oral slit, resembling that of the genus Platyophrya. Sorogena stoianovitchae divides in the free swimming condition and not in a division cyst, as is the case in the colpodids sensu stricto (s. str.), e.g. Colpoda, Bresslaua. or Tillina, As shown in a detailed light‐microscopy study, morphogenesis in S. stoianovitchae is of the stomatic mode typical for certain colpodid ciliates. Based on the wealth of new information the phylogenetic position of S. stoianovitchae is discussed at some length and arguments are given in favor of the following classifications: S. stoianovitchae Bradbury & Olive, 1980 currently sole member of the family Sorogenidae Bradbury & Olive, 1980; order Sorogenida Foissner, 1985;subclassColpodiaFoissner, 1985; class Colpodea Small & Lynn, 1981. This investigation facilitates the discovery of further members of this genus reported primarily from the tropical and subtropical zone.

Phylogenetic Relationships between Prostome and Colpodean Ciliates Tested by Small Subunit rRNA Sequences

“…Detailed observations by both light and electron microscopy have provided important data that have served to properly relate certain genera. For example, after using both light and electron microscopy, Bardele et al (1991) transferred the sorocarp-forming ciliate Sorogena stoianovitchae from the prostomes to the class Colpodea. Huttenlauch and Bardele (1987) used these techniques to transfer the genus Coleps from the subphylum Rhabdophora to the subphylum Cyrtophora sensu Small (1976).…”

Phylogenetic Relationships of Orders Within the Class Colpodea (Phylum Ciliophora) Inferred from Small Subunit rRNA Gene Sequences

“…Ultrastructural study of the somatic kinetids as a complement to light microscopy corroborated newly discovered genera as colpodean: Bresslauides (Platt and Hausmann 1993), Cosmocolpoda (Foissner and Foissner 1994), Grossglockneria (Aescht et al 1991), Kuklikophrya (Njiné 1979), andPseudoplatyophrya (de Puytorac et al 1983). Finally, ultrastructural data have provided evidence of colpodean somatic kinetids in ciliates previously placed in different classes but now considered to be colpodean: Cyrtolophosis (Detcheva 1976;Didier et al 1980), formerly an oligohymenophorean; Sorogena (Bardele et al 1991), formerly a kinetofragminophorean (Bradbury and Olive 1980); and Bursaria (Gerassimova et al 1979;Lynn 1980;Perez-Paniagua et al 1980; and Bryometopus (Wirnsberger et al 1985), formerly heterotrichid spirotricheans. Bardele (1989) expressed doubts about the monophyly of the class Colpodea because this assemblage of species showed diversity in the kinds of intramembranous particle arrays in their ciliary membranes, features Bardele (1989) considered strongly indicative of common ancestry.…”

Analysis of Fruiting Body Development in the Aggregative Ciliate Sorogena stoianovitchae (Ciliophora, Colpodea)

“…Although Sorogena is clearly a ciliate, this life cycle is atypical of the ciliates and is similar to that of the cellular slime molds. Ultrastructural analysis of the infraciliature (Bardele, Foissner, and Blanton 1991) and the small subunit (SSU) rDNA phylogeny (Lasek‐Nesselquist and Katz 2001) place Sorogena in the class Colpodea. Pioneering works by Olive (1978) and Olive and Blanton (1980) revealed some requirements for triggering the fruiting body formation, including mild starvation, high cell density, and light‐dark cycle.…”