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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

[ref. ID; 4692 (Foissner, 1985)]

Class: Colpodea Small & Lynn, 1981

Subclass I. Bryometopia nov. subcl.

Order I. Bryometopida nov. ord.

Subclass II. Colpodia nov. subcl.

Order I. Sorogenida nov. ord.

Order II. Bryophryida De Puytorac et al. 1979

Order III. Cyrtolophosidida Foissner, 1978

Order IV. Grossglocknerida Foissner, 1980

Order V. Colpodida De Puytorac et al. 1974

Order VI. Bursariomorphida Fernandez-Galiano, 1978

(Bursaridium, Bursaria, Paracondylostoma)

The classification and phylogeny of the Colpodea are discussed. This review considers the hitherto known light microscopical, fine structural, morphogenetical, and ecological results. The Colpodea probably evolved from haptorid ancestors. This hypothesis is supported by the observation that the silverline system is formed like in Platyophrya and the somatic kineties are organized dikinetally in the area of the "dorsal brush" of many Haptorida. A comparable situation still exists with the Sorogenidae, very likely rather primitive Colpodea, which performed only a limited morphological radiation because of their highly specialized mode of life. Some families formerly considered to be heterotrichs or to be of uncertain systematic position, i.e. the Kreyellidae, Bryometopidae, and Thylakidiidae are included into the Colpodea. This is based on the following observations: a) The somatic kineties consist of ciliated dikinetids only. b) The oral structures and the morphogenesis are similar to those of the Cyrtolophosidida. c) The fine structure of the somatic kineties of Bryometopus is colpodid. d) The silverline system and the mode of life of these families are similar to other "true" colpodids. The Sorogenidae possess a colpodid somatic fine structure and are raised to the ordinal rank, Sorogenida nov. ord., because of their primitive oral structures and their spezialized way of life. The Colpodea are splitted into 2 subclasses: The Bryometopia nov. subcl., nov. ord. are diagnosed as having a kreyellid to slightly platyophryid silverline system and curved or slightly spiralized somatic kineties. The Colpodia nov. subcl. are defined as having a platyophryid to colpodid silverline system and usually strongly spiralized somatic kineties. The oral structures and partly the silverline system too show similar evolutionary trends within these subclasses. This may be due to convergence because the Bryometopia have a kreyellid and the Bursariomorphida a colpodid silverline system. The Grossglocknerida and the Bursariomorphida are considered as specialized branches of the Colpodida. This orders contain the smallest (Nivaliella) and the biggest (Bursaria) ciliate species known which is a good example for the extreme ecological and morphological radiation of the Colpodea. The Bryophryida are a quickly evolving branch of the Cyrtolophosidida. Pure and mixed colpodid and platyophryid silverline systems occur within the Cyrtolophosidida. Although that may be due to convergence this and the fine structure of the oral apparatus could indicate even a rather close relationship between the Grossglocknerida and the Cyrtolophosidida.

[ref. ID; 4841 (Foissner, 1995)]

Family Colpodidiidae nov. fam.

Diagnosis

Medium-sized Nassulida with conspicuous buccal cavity in middle ventral third of cell containing 1 complete and 2 more or less distinctly reduced adoral organelles.

Remarks

Puytorac et al. (1983) also suggested a new family for Colpodidium. However, they did not provide any characterization for their "?Colpodidiidae fam. nov.", which is thus invalidated by the Int. Code of Zool. Nomenclature. Wilbert (1982) assigned Colpodidium to the family Colpodidae (class Colpodea) because of its paired cilia and the rather deep vestibulum near mid-body, containing an upper and lower ciliary field. Foissner (1985) followed Wilbert (1982). However, a reinvestigation of the type species showed that Wilbert's description contains serious mistakes and misinterpretations (Foissner 1990 and below). The reinvestigation of C. caudatum and observations on a new genus, Pedohymena, related to Colpodidium showed that both are near the family Furgasoniidae within the order Nassulida. The evidence for this new classification can be summarized as follows (for details see species descriptions). (1) The somatic ciliature consists of monokinetids except of a few postoral dikinetids; (2) the oral ciliature is composed of a dikinetidal paroral membrane at the right margin of the buccal cavity and of 1-3 triple-rowed adoral organelles on the bottom of the buccal cavity; (3) the contractile vacuole pore and the cytopyge have the same spatial relationship as in many nassulids i.e. are on the postoral ventral surface; (4) The cortex is thick and inflexible and contains a tightly and irregularly meshed silverline system, as e.g., in Parafurgasonia (Foissner & Adam 1981); (5) Division occurs in free-swimming condition; (6) the few ontogenetic stages observed are highly reminiscent of those described by Eisler & Bardele (1986) in Furgasonia and Nassula. The general organization of Colpodidium and Pedohymena suggests that their nearest relatives are Parafurgasonia (1 adoral organelle, paroral membrane conspicuous) and Furgasonia (3 adoral organelles, paroral membrane inconspicuous). However, these genera and all other nassulids s.str., e.g. Nassula and Obertrumina, have a conspicuous cytopharyngeal basket and the oral apparatus located subapically on the cell surface, i.e. do not have the distinct buccal cavity so characteristic of COlpodidium and Pedohymena. These characters of Colpodidium and Pedohymena are highly reminiscent of microthoracid nassulids, which, however, have a reduced somatic ciliature (Kahl 1931). It is thus reasonable to separate Colpodidium and Pedohymena at family level.

Type genus

Colpodidium Wilbert, 1982

[ref. ID; 6945 (Foissner, 1990)]

Key to the genera of the Colpodidae

The separation of the colpodid genera is not easy. I am, however, now able to provide a reliable key, based on the present results and on a monograph about colpodid ciliates that is in preparation.