Peter Vďačný

The morphology and morphogenesis of a new Australian metopid ciliate, Lepidometopus platycephalus nov. gen., nov. spec., were studied using live observation, various silver impregnation methods, scanning electron microscopy, and morphometry. The new genus is outstanding in having epicortical scales (lepidosomes) and a strongly flattened and distinctly projecting preoral dome. Diagnostic features of L. platycephalus include a small, reniform body carrying an elongated caudal cilium, about 11 ciliary rows, and an adoral zone composed of an average of 11 polykinetids. The morphogenesis of L. platycephalus matches data from other metopids in that (1) the body is drastically re-shaped, (2) the parental oral structures are reorganized but do not contribute to the daughter oral ciliature, (3) the opisthe’s adoral polykinetids originate pleurotelokinetally, (4) the opisthe’s paroral membrane is formed via re-arrangement of the posterior portion of the first two perizonal rows, and (5) the opisthe’s perizonal stripe is made by three parental perizonal rows and two dorsolateral ciliary rows. The morphogenetic data corroborate phylogenetic analyses in that caenomorphids are only superficially similar to metopids; metopids and clevelandellids are closely related; and litostomateans are the best candidates for a sister group of the metopid-clevelandellid assemblage within the SAL superclade.

We investigated interrelationships between four free-living litostomatean lineages, using 18S rRNA gene and ITS region sequences as well as the secondary structure of the ITS2 molecules. Our phylogenetic analyses confirmed the deep split of free-living litostomateans into Rhynchostomatia and Haptoria represented here by Haptorida, Pleurostomatida, and Spathidiida. This bifurcation is also corroborated by the signature of the rhynchostomatian and haptorian ITS2 molecules. Specifically, the consensus stems of helices II and III are longer by one base pair in Rhynchostomatia, while the terminal loops of both helices are longer by one or two nucleotide/-s in Haptoria. A close relationship of Pleurostomatida and Haptorida is favored by quartet likelihood-mapping and supported by a 5’-AG vs. CU-3’ motif in the variable part of helix II and by two morphological apomorphies, i.e., meridionally extending somatic kineties and a non-three-rowed dorsal brush. Although monophyletic origin of Spathidiida is poorly supported in phylogenetic trees, the unique motif 5’-GA vs. UC-3’ present in the consensus helix II stem could be an important molecular synapomorphy of spathidiids, apart from the ancestrally anteriorly curved somatic kineties and the three-rowed dorsal brush. The peculiar family Pseudoholophryidae has very likely found its phylogenetic home among spathidiids, as an early branching lineage.

The response of ciliate communities to cyanobacterial bloom was investigated in a shallow, hypertrophic reservoir in Slovakia, central Europe. Seasonal dynamics of ciliate communities corresponded negatively with course of water bloom formation. The highest numbers and abundances of ciliate species occurred during the spring season when cyanobacterial bloom was not fully developed, while there was an abrupt decrease in both numbers and abundances at the beginning of summer when water bloom culminated. Cyanobacterial blooming thus significantly lowered diversity and equitability of ciliate communities: many rare and sporadic species disappeared and few common taxa flourished and dominated. Nonetheless, these leading ciliates formed a functionally diverse assemblage whose members showed mostly positive contemporaneous and only rarely time-shifted interactions. There were fine filter feeders (Cinetochilum margaritaceum, Dexiotricha granulosa, Paramecium caudatum and Spirostomum teres) grazing heterotrophic bacteria and picocyanobacteria, omnivorous fine to coarse filter feeders (Frontonia leucas) as well as hunters (Coleps hirtus, Holophrya teres and Loxophyllum helus) looking for an individual prey. Also a comparatively rich, anaerobic coenosis comprising various bacterivorous armophoreans and plagiopyleans, developed at the bottom of the reservoir. Our study documents that ciliates form functionally diverse communities with potential to control cyanobacterial blooms in hypertrophic reservoirs.

The morphology and phylogenetic position of a haptorian ciliate, Phialina pupula (Müller, 1773) Foissner, 1983, isolated from microaerobic sandy sediments of the floodplain area of the Boise River, Idaho, U.S.A., were studied using live observation, protargol impregnation, scanning electron microscopy, and the 18S rRNA gene as  well as the ITS region. The Boise population of P. pupula is characterized by a size of about 60–130 × 20–50 μm, an elliptical macronucleus with a single micronucleus, highly refractive dumbbell-shaped inclusions scattered throughout the cytoplasm and concentrated in the anterior body half, a single subterminal/terminal  contractile vacuole, about 10 μm long rod-shaped extrusomes, and an average of 15 ciliary rows. In phylogenetic analyses, the newly obtained sequences from P. pupula and Lacrymaria olor clustered within the family Lacrymariidae with full to moderate statistical support. Neither the genus Phialina nor the genus Lacrymaria was depicted monophyletic both in the single gene and multigene phylogenetic inferences. Specifically, the genus Phialina was shown as a paraphyletic assemblage containing members of the polyphyletic genus Lacrymaria. This indicates that the phialinid bauplan, i.e., an anterior body end differentiated into a head-like structure  directly attached to the trunk, might represent the ground pattern in the family Lacrymariidae. On the other hand, the long highly contractile neck carrying the head-like structure probably evolved later and convergently in multiple Lacrymaria species from Phialina-like ancestors.

The morphology and ontogenesis of a new psilotrichid ciliate, Hemiholosticha pantanalensis, were studied using live observation, protargol impregnation, and scanning electron microscopy. Diagnostic features of the new species include: a medium-sized, almost circular to broadly obovate body with a short anterior projection; two macronuclear nodules with a single micronucleus in between; a total of about 35 cirri arranged in three ventral, one postoral, one right and one left marginal row; three dorsal kineties extending along prominent ribs; an adoral zone occupying about 60% of body length; and intracellular, eyespot-bearing, green algae almost filling the body. The ontogenesis of H. pantanalensis follows the psilotrichid mode, being a mixture of features found not only in various hypotrich taxa but also in other spirotrich groups. Specifically, the oral primordium develops in a deep pouch as in euplotids and oligotrichs, the anlage for the undulating membranes does not produce cirri as in euplotids and some schmidingerothrichids, and the longitudinal ventral cirral row R3 develops from two anlagen as in some amphisiellids and kahliellids. Since psilotrichids are classified in a polytomy of main hypotrich lineages in 18S rRNA gene phylogenies, some of their ontogenetic features might be ancient spirotrich plesiomorphies while others might be homoplasies.

We isolated a relatively unknown haptorian ciliate, Trachelophyllum brachypharynx, in brackish water from the mouth of the Taehwa River, South Korea. The morphology of this isolate was studied using in vivo observation and protargol impregnation, and its evolutionary history was revealed by phylogenetic analysis of the 18S rRNA gene. The main features of T. brachypharynx include (i) a very narrowly fusiform and slightly contractile body about 380 × 40 μm in size; (ii) two ellipsoidal macronuclear nodules typically connected by a fine strand; (iii) a single terminal contractile vacuole; (iv) filiform extrusomes that are typically 30 µm long; (v) an average of 24 ciliary rows, with two of them anteriorly differentiated into an isostichad dikinetidal dorsal brush; and (vi) hat-shaped lepidosomes. Based on the 18S rRNA gene phylogeny, T. brachypharynx clustered together withTrachelophyllum sp. within the order Spathidiida. Furthermore, phylogenetic trees and networks indicate some members from the genera Enchelyodon and Spathidium as the nearest relatives of trachelophyllids. Therefore, based on the present molecular and comparative-morphological analyses, we suggested a hypothesis explaining how trachelophyllids may have evolved from a spathidiid-like ancestor via an enchelyodonid-like stage.

Pleurostomatids are raptorial ciliates that form a very distinct group within the Haptoria. Traditionally, the order Pleurostomatida was divided into two families: the Amphileptidae with two perioral kineties and a suture formed by the right side ciliary rows, and the Litonotidae with three perioral kineties and without suture. However, molecular phylogenies depicted the “traditional” Amphileptidae as a paraphyletic assemblage nesting also the Litonotidae. To overcome this problem we have analyzed genealogy of pleurostomatids using morphological data and 18S rRNA gene sequences, including newly sequenced genera Acineria and Kentrophyllum. Specifically, we have combined a morphological and molecular approach and have used also some other phylogenetic tools such as phylogenetic networks, split spectrum analysis, quartet mapping as well as the likelihood method of tracing history of morphological characters. These analyses show that: (1) there are not two but three distinct pleurostomatid lineages – Epiphyllidae fam. nov., Amphileptidae and Litonotidae; (2) epiphyllids (Epiphyllum + Kentrophyllum) represent a basal pleurostomatid group which is defined by two perioral kineties, by the presence of a suture on both the right and the left side of the body, by the loss of the oral bulge extrusomes, and by the extrusome fringe extending all around the body except for the oral region; (3) the families Amphileptidae and Litonotidae are monophyletic each, and represent sister groups; (4) Acineria belongs to the Litonotidae, as already indicated by morphological data; (5) Loxophyllum is a monophyletic and crown genus of the Litonotidae; and (6) Litonotus is paraphyletic, which could be very likely caused by a rapid radiation event that did not allow primary nucleotide homologies to be fixed.

The present work describes the morphology and morphometry of a freshwater ciliate, Zosterodasys transversus, using live observation and protargol impregnation. The population from the River Ipeľ, Slovakia is designated as a neotype because (i) no type material is available from the species described by Kahl (1928); (ii) the neotype is consistent with Z. transversus as described by Kahl (1928); (iii) the neotype is from the same biogeographic region as Kahl’s (1928) populations; and (iv) there are several similar species (e.g., Z. agamalievi) whose identity is threatened by the species to be neotypified. The main features of Z. transversus are: (i) a body size of 120–240 × 50–115 μm in vivo; (ii) a broadly to narrowly obovate or elliptical body; (iii) a spherical to very narrowly ellipsoidal macronucleus with a single globular micronucleus nearby; (iv) several scattered contractile vacuoles; (v) an average of 82 ciliary rows, most of which are interrupted by a synhymenium incompletely encircling the body; and (vi) an average of 14 nematodesmal rods strengthening walls of the cyrtos. In the well-growing neotype population, a single cell of a mirror-image type was found. Most of the structures of this monster specimen are similar to those from ordinary cells, except for the double cytostome and cyrtos.