Monograph of the Dileptids (Protista, Ciliophora, Rhynchostomatia)

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Language: English

Dileptids are holotrichously ciliated, rapacious ciliates with a conspicuous proboscis carrying a complex ciliary pattern. Most species have a wide or global distribution, occurring in limnetic, marine, and terrestrial environments as well as in benthic and planktonic habitats. Light- and electronmicroscopical investigations suggested the dileptids as strongly derived crown Litostomatea (Gymnostomatea pro parte, Haptoria p.p., Trichostomatia p.p.) because of their complex morphology and ontogenesis. However, recent molecular studies show the opposite: the dileptids form a distinct clade at the base of the litostomateans, supporting the subclass Rhynchostomatia established by Jankowski (1980). The last common ancestor of dileptids and other litostomateans (Haptoria, Trichostomatia) was possibly a rather complex ciliate with a paroral membrane (~ circumoral kinety) and many adoral membranelles (~ preoral kineties).

The genus Dileptus was established by Dujardin (1841). Although afterwards some interesting studies on dileptid biology and diversity were performed, progress was slow during the next ninety years. In 1931, Kahl revised the dileptids recognizing three genera (Dileptus, Paradileptus, Trachelius) and 25 nominal species, including eight new ones. After Kahl's classic study, more protozoologists became interested in the biology and taxonomy of the dileptids, which culminated in the monograph of Dragesco (1963). He revised the genus Dileptus and recognized about 50 species, showing that dileptid diversity doubled between 1931 and 1963. In the following decades, the number of genera and species increased slowly but steadily. In this monograph, the authors recognize 12 genera and 181 nominal species, of which 66 are possibly reliable dileptid taxa; however, only 46 species and subspecies are so well described that their identity is not threatened. They establish two new genera (Apotrachelius and Microdileptus) and 18 new species and subspecies including those recently described by Vïaèný & Foissner (2008a, b): Apodileptus edaphicus, A. visscheri rhabdoplites, Apotrachelius multinucleatus, Dileptus sphagnicola, Dimacrocaryon amphileptoides paucivacuolatum, D. arenicola, D. brasiliense, Microdileptus microstoma, M. semiarmatus, Pseudomonilicaryon brachyproboscis, P. fraterculum, P. gracile antevacuolatum, P. gracile oviplites, P. marinum minimum, Rimaleptus brasiliensis, R. canadensis, R. longitrichus, and R. tirjakovae. Further, the authors redescribe and/or provide additional figures for ten species: Apodileptus visscheri visscheri, Dileptus anatinus, D. costaricanus, Monomacrocaryon polyvacuolatum, M. terrenum, Pelagodileptus trachelioides, Pseudomonilicaryon falciforme, P. thononense, Rimaleptus armatus, and R. binucleatus. The synonymy rate is 27.5% but increases to 60.5% when taxa with "unclear identity" are included.

Monograph of the Dileptids (Protista, Ciliophora, Rhynchostomatia) commences with a detailed general section, showing the dileptid morphology, ultrastructure, resting cysts, ontogenesis, conjugation, ecology, and phylogeny. Further, the authors provide protocols for the methods used in studying the dileptid organization (live observation, silver nitrate impregnation, protargol impregnation, scanning electron microscopy) and a detailed terminology. In the main section of the monograph, they provide, if available, the following data for each species: author, date, and journal page of the original description; a list of synonyms; nomenclatural matters; a morphological treatise including the original description, redescriptions, and all figures published; morphometric data; details on ontogenesis and resting cysts; a comparison with related species; and a detailed compilation of ecological and faunistic data. Monograph of the Dileptids (Protista, Ciliophora, Rhynchostomatia) ends with a carefully prepared reference section and an index to the scientific names mentioned in the text.

Contents

Introduction   3
A. General Section   4
      1 Morphology and Principal Terms   4
      2 Life cycle: Ontogenesis, Conjugation and Resting Cysts   31
      3 Ecology, Occurrence and Geographic Distribution   58
      4 Phylogeny and Evolution   61
      5 Classification   75
      6 Synonymy rate   75
      7 List of Genera and Nominal Species Associated with Dileptids   82
      8 Summary of New Taxa and Nomenclatural Acts   82
      9 Collecting, Culturing, Observing, and Staining of Dileptid Ciliates   86
B. Systematic Section   98
      1 How to Use the Monograph   98
      2 A User-Friendly Flow Chart Key to 66 Dileptid Species   98
            Subclass Rhynchostomatia   109
                  Order Tracheliida   110
                        Family Tracheliidae   110
                              Genus Trachelius (1 species)   111
                              Genus Apotrachelius (1 species)   135
                  Order Dileptida   142
                        Family Dimacrocaryonidae   143
                              Genus Monomacrocaryon (4 species)   143
                              Genus Dimacrocaryon (4 species and subspecies)   161
                              Genus Rimaleptus (18 species)   179
                              Genus Microdileptus (3 species)   242
                        Family Dileptidae   262
                              Genus Dileptus (10 species)   265
                              Genus Apodileptus (3 species and subspecies)   323
                              Genus Monilicaryon (1 species)   343
                              Genus Pseudomonilicaryon (19 species and subspecies)   350
                              Genus Paradileptus (1 species)   437
                              Genus Pelagodileptus (1 species)   451
                  Insufficiently described and doubtful dileptids   465
                        From Various Authors   466
                        From Dumas (1929–1937)   472
Acknowledgements   478
References   478
Systematic Index   516

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