John C. Clamp

Tachysoma pellionellum Stokes, 1887, a freshwater ciliate isolated from Stone Mountain State Park, North Carolina, was studied in vivo and after staining with protargol. The population was characterized mainly by having the typical 18 frontal-ventral-transverse cirri; posterior ends of left and right marginal rows not confluent; five dorsal kineties and one dorsomarginal kinety; two macronuclear nodules near left cell margin with one or two micronuclei between them; contractile vacuole located at mid-body near left margin. Morphogenesis is characterized as follows: (1) in the proter, the parental adoral zone of membranelles is retained completely; (2) 18 frontal-ventral-transverse cirri are derived from the anlage of the undulating membrane and the five streaks of the frontal-ventral-transverse anlagen; (3) marginal rows develop intrakinetally; (4) anlagen of dorsal kineties 1, 2 and 4 develop in the parental structure and anlagen of dorsal kineties 2 and 4 fragment in the posterior region forming anlagen of dorsal kineties 3 and 5; (5) only one dorsomarginal kinety formed; (6) the two macronuclear nodules fuse into a single mass, which then divides. Phylogenetic analyses based on sequences of the gene coding for SSU RNA revealed a close relationship between T. pellionellum and the Oxytricha clade, both of which grouped with Kleinstyla dorsicirrata and Heterourosomoida lanceolata.

The colonial peritrich ciliate Epistylis anastatica (Linnaeus, 1767) was discovered living as an epibiont on Mesocyclops isabellae Dussart & Fernando, 1988 collected from a pond in Andhra Pradesh state, India. This is the first report of Epistylis on this host, and a description of its morphological characteristics is provided. The biomass of colonies of E. anastatica relative to that of their hosts was relatively high, being greater than that of the host in some cases (8.11 mm3 vs. 1.14 mm3 or less), and this epibiotic burden has the potential to have an impact on the host’s activities. Relationships between epibiotic peritrichs and microcrustaceans like cyclopoid copepods may be much more complex than previously supposed and merit more thorough investigation. Species of Epistylis are commonly found on cyclopoid copepods, but resources for taxonomic identification are limited and scattered; therefore, an annotated checklist of all species reported from cyclopoid copepods and a summary of the diagnostic characteristics of each one is provided as an aid to investigators. Some records of Epistylis spp. from cyclopoid copepods that are accompanied by documentary evidence are misidentifications, raising the suspicion that many other undocumented records also may be erroneous; therefore, it is suggested that authors provide supplementary descriptions and figures.

Chen, X., Clamp, J. C. & Song, W. (2011). Phylogeny and systematic revision of the family Pseudokeronopsidae (Protista, Ciliophora, Hypotricha), with description of a new estuarine species of Pseudokeronopsis. —Zoologica Scripta, 40, 659–671.The family Pseudokeronopsidae is a taxon of hypotrich ciliates with a history of uncertainty regarding its systematic and phylogenetic relationships to other members of the order Urostylida. Phylogenetic analyses of pseudokeronopsids were made using all available molecular and morphological information, and the patterns of morphogenesis of the group were reinvestigated. Results clearly demonstrated that the genera Thigmokeronopsis and Apokeronopsis are not confamilial with Pseudokeronopsis and Nothoholosticha but, instead, must be transferred to the family Urostylidae. A new estuarine species, Pseudokeronopsis erythrina sp. n. was discovered and described using a combination of morphological and molecular characters. Species of Pseudokeronopsis are difficult to characterize but can be distinguished from one another by a combination of morphological and morphogenetic characters. Pseudokeronopsis similis is a freshwater species that has significant morphogenetic differences with other members of the genus and may not be congeneric with them.

The gene encoding 18S small subunit ribosomal RNA (ssu rRNA) was sequenced in the sessiline peritrichs Opisthonecta minima and Opisthonecta matiensis, whose free-swimming, paedomorphic trophonts resemble telotrochs. Using these new sequences, phylogenetic trees were constructed with four different methods to test a previously published association between Opisthonecta henneguyi and members of the families Vorticellidae and Astylozoidae. All trees had similar topologies, with O. minima, O. henneguyi, Vorticella microstoma, and Astylozoon enriquesi forming a well-supported, certainly monophyletic clade. On the basis of genetic evidence, genera of the families Opisthonectidae and Astylozoidae are assigned to the family Vorticellidae, which already includes some species with free-swimming morphotypes. The ssu rRNA sequence of O. matiensis places it in the family Epistylididae; its taxonomic revision will be left to another group of authors. A close association of Ophrydium versatile with members of the family Vorticellidae was confirmed, casting doubt on the validity of the family Ophrydiidae. Epistylis galea, Campanella umbellaria, and Opercularia microdiscum are confirmed as comprising an extremely distinct, monophyletic, but morphologically heterogeneous clade that is basal to other clades of sessiline peritrichs.

The gene coding for 18S small subunit ribosomal RNA (ssu rRNA) was sequenced in seven free-living, marine species of the sessiline peritrich genus Zoothamnium. These were Zoothamnium niveum, Zoothamnium alternans, Zoothamnium pelagicum, and four unidentified species. The ssu rRNA gene also was sequenced in Vorticella convallaria, Vorticella microstoma, and in an unidentified, freshwater species of Vorticella. Phylogenetic trees were constructed using these new sequences to test a previously published phylogenetic association between Zoothamnium arbuscula, currently in the family Zoothamniidae, and peritrichs in the family Vorticellidae. Trees constructed by means of neighbor-joining, maximum parsimony, maximum likelihood, and Bayesian inference methods all had similar topologies. The seven new sequences of Zoothamnium species grouped into three well-supported clades, each of which contained a diversity of morphological types. The three clades formed a poorly supported, larger clade that was deeply divergent from Z. arbuscula, which remained more closely associated with vorticellid peritrichs. It is apparent that Zoothamnium is a richly diverse genus and that a much more intensive investigation, involving both morphological and molecular data and a wider selection of species, will be necessary to resolve its phylogeny. A greater amount of molecular diversity than is predicted by morphological data exists within all major clades of sessiline peritrichs that have been included in molecular phylogenies, indicating that characteristics of stalk and peristomial structure traditionally used to differentiate taxa at the generic level and above may not be uniformly reliable.

Lagenophrys cochinensis is a peritrich ciliate originally reported as an ectocommensal of the wood-boring isopods Sphaeroma terebrans, Sphaeroma triste, and Sphaeroma annandalei and the tanaidacean Apseudes chilkensis in estuaries of southern India. In the present study, it was found to occur also on Sphaeroma quoyanum, Sphaeroma walkeri, and Exosphaeroma planulum. New material was used to make permanent preparations, allowing a comprehensive description of the morphology of L. cochinensis for the first time. The macronucleus of L. cochinensis was found to have an elongate shape that spans the width of the cell body, unlike the compact macronucleus originally described. In addition, the loricae of all samples examined were subcircular or shorter than wide, not longer than wide as originally described. Polykinetid 3 of the infundibular infraciliature consisted of three rows of kinetosomes, only the third species of Lagenophrys found to have more than two rows in polykinetid 3 so far. Samples of L. cochinensis on S. quoyanum from New Zealand and California appeared to represent a population distinct from others. The species has a cosmopolitan distribution, probably owing to the ease with which its hosts are transported from one estuary to another in drifting wood or on hulls of ships.

The loricate peritrich ciliate Lagenophrys maxillaris, a highly specialized ectosymbiont of marine gammarid amphipods, was examined and redescribed by using material from museum collections to make hematoxylin and protargol preparations. The infraciliature is described for the first time, and the shape of the macronucleus was found to differ significantly from the shape given in the original description. Lagenophrys maxillaris is one of only four species of Lagenophrys known to occur on the maxillipeds of amphipods or isopods and differs from the others with respect to the structure of the lips of the lorica aperture and pattern of infundibular polykinetids. It appears to prefer attaching to hosts that live in water deeper than that inhabited by hosts of other known marine species of Lagenophrys and was recorded from one sample of Gammarus locusta taken at a depth of 240–250 m. Lagenophrys maxillaris seems to be restricted to G. locusta and G. oceanicus although three other closely related species of Gammarus are available as hosts. Host specificity is possibly the result of trophic differences, possibly related to depth of habitat, between the two hosts and their congeners.