Phylum CILIOPHORA

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Introduction

At present this section of the Australian Faunal Directory deals only with the free-living ciliates.

Summary
In developing this section on free-living ciliates, all published reports of ciliated protozoan species free-living in Australia have been compiled into a taxonomic catalogue and cross-referenced bibliography. Records were extracted from 126 publications and are listed (with taxonomic authorities, synonyms, sizes, habitats and geographic locations) for ~570 ciliate species belonging to 275 genera in 126 families, 42 orders and 10 classes. Only free-living ciliate species are recorded from aquatic and terrestrial habitats (those living in association with a host are listed in another catalogue). Studies on ciliates in Australia have been sparse and fragmentary for such a vast and diverse continent, thus knowledge about the biodiversity and ecology of our ciliate fauna is limited and often speculative.

Introduction
Ciliated protozoa (phylum Ciliophora) are unique amongst the unicellular eukaryotes because they are the only group to exhibit nuclear dualism. Individual cells possess two different types of nuclei; vegetative macronuclei and reproductive micronuclei. Asexual reproduction occurs by transverse binary fission across rows of cilia (homothetogenic fission) whereas some species exhibit sexual reproduction by the phenomenon of conjugation (temporary fusion of two conjugates which exchange micronuclei).

As their common name implies, ciliates are also characterised by the possession of simple cilia, or compound ciliary organelles, in at least one stage of their life cycles (compound subpellicular infraciliature is universally present even when cilia are absent). Cilia are elongate hair-like extensions of the cell membrane with an internal microtubular core (universal 2+9 configuration = 2 single central microtubules surrounded by 9 peripheral doublets). They are organelles of motility used for locomotion and/or feeding. Cilia (singular, cilium) are similar in ultrastructure to flagella (singular, flagellum), and they are collectively often called undulipodia (singular, undulipodium) because both use cross-linked proteins (dynein-walking mechanism) to undulate about their basal kinetosome (unlike the rotary motion unique to flagella in bacteria).

Ciliates, together with dinoflagellates and apicomplexans, have subpellicular alveoli which are membrane-bound sacs beneath the plasma membrane. Alveoli are thought to serve many varied functions: ranging from support (helping maintain body shape, act as fulcrum for undulipodia); metabolism (storage); osmoregulation (mucocysts); excretion (extrusomes); protection (toxicysts, trichocysts); and even hunting (haptocysts).

Most ciliate species are free-living in aquatic or terrestrial habitats but many are commensals in vertebrate or invertebrate hosts and some are parasitic. Early classification systems recognised three main classes of ciliates mainly on the basis of their patterns of somatic (body) and buccal (oral) ciliation. The ‘lower holotrichs’ have simple body and oral ciliature; most are free-living species but some are highly specialized symbionts aiding cellulose digestion in herbivores. The ‘higher holotrichs’ have simple body ciliature but more specialized oral ciliature forming membranelles; most occur as free-living organisms but some live as commensals or parasites in a range of animals. The ‘spirotrichs’ have reduced body ciliation but well-developed oral ciliature forming an adoral zone of membranelles; most are bactivores living in aquatic and terrestrial habitats.

More recently, 10 major monophyletic lineages were recognised on the basis of their infraciliature, i.e. the ultrastructural organization of their kinetids (comprising basal bodies (= kinetosomes) and associated microtubular ribbons and fibrils). These lineages (ranked as classes) are well supported by modern molecular biological studies using several gene sequences. The classification scheme used in this document follows that of
Lynn & Small (2000).

The subphylum Postciliodesmatophora contains ciliates that have somatic dikinetids with postciliodesmata or overlapping postciliary microtubular ribbons. Two classes are recognised: the Heterotrichea (‘different hair’) in which the left oral polykinetid does not encircle the body and the macronuclei do not divide; and the Karyorelictea (‘surviving nucleus’) which exhibit simple nuclear dualism and when the macronucleus divides, microtubules occur outside the macronuclear envelope. The subphylum Intramacronucleata is a diverse group, whose members are united by the presence of microtubules inside the macronuclear envelope during division. Eight classes are recognised: the Spirotrichea (‘coiled hair’) with conspicuous oral membranelles (previously known as polyhymenophoreans); the Litostomatea (‘simple mouths’) with a noncurved tubular cytopharngeal apparatus (rhabdos); the Phyllopharyngea (‘leaf throated’) with cytopharyngeal phyllae; the Colpodea (‘breast shaped’) with reniform body profiles; the Prostomatea (‘before mouth’) with simple apical mouths; the Nassophorea (‘pot bearer’) with curved tubular cytopharngeal apparatus (cyrtos or nasse); the Plagiopylea (‘misshapen marker’) with twisted oral tubes; and the Oligohymenophorea (‘few membrane-bearer’) with an adoral zone of three membranelles.

Notes on the database
Names and data included in this checklist are taken from a checklist provided to ABRS by Professor Peter O'Donoghue, University of Queensland. In entering the data into the AFD, ABRS has interpreted it within the structure and constraints of the AFD data fields. Thus, contrary to the usual method used by Protozoologists of citation of attributions for names and changed combinations of those names, the author and reference for the changed combinations are given separately. The 'site of occurrence' given in the checklist as drainage basins has been translated into IBRA and IMCRA regions on the maps. Otherwise data have been entered faithfully and the following notes from the O'Donoghue checklist hold true.

"All records given in this catalogue have the following format: Taxon + authority [synonyms]; size; habitat; region; reference. Where information is unavailable, [it is indicated as 'not necorded']. All taxa are listed as genus and species names, immediately followed by their taxonomic authorities (where, by convention, brackets indicate revision by the subsequent authority) … When provided in the publication, ciliate size is given as the ranges in length by breadth (in micrometres). The habitat is listed for each record as freshwater, salt lake, marine (including oceanic and estuarine habitats), moss, soil (including exposed lake sediment), leaf-litter or tree-bark."

Diagnosis

Ciliates; with nuclear dualism, conjugation, alveoli, cilia.

General References

Lynn, D.H. & Small, E.B. 2000. Phylum Ciliophora Doflein, 1901. pp. 371-656 in Lee, J.J., Leedale, G.F. & Bradbury, P. (eds). An Illustrated Guide to the Protozoa. Lawrence, Kansas : Society of Protozoologists, Allen Press Inc. Vol. I.