Molecular Phylogeny of Pacific Archigregarines (Apicomplexa), Including Descriptions of Veloxidium leptosynaptae n. gen., n. sp., from the Sea Cucumber Leptosynapta clarki (Echinodermata), and Two New Species of Selenidium

Novel cytoskeletal traits in the intestinal parasites (Squirmida, Platyproteum vivax) of Pacific peanut worms (Sipuncula, Phascolosoma agassizii)

The cytoskeletal organization of a squirmid, namely Platyproteum vivax, was investigated with confocal laser scanning microscopy (CLSM) to refine inferences about convergent evolution among intestinal parasites of marine invertebrates. Platyproteum inhabits Pacific peanut worms (Phascolosoma agassizii) and has traits that are similar to other lineages of myzozoan parasites, namely gregarine apicomplexans within Selenidium, such as conspicuous feeding stages, called "trophozoites," capable of dynamic undulations. SEM and CLSM of P. vivax revealed an inconspicuous flagellar apparatus and a uniform array of longitudinal microtubules organized in bundles (LMBs). Extreme flattening of the trophozoites and a consistently oblique morphology of the anterior end provided a reliable way to distinguish dorsal and ventral surfaces. CLSM revealed a novel system of microtubules oriented in the flattened dorsoventral plane. Most of these dorsoventral microtubule bundles (DVMBs) had a punctate distribution and were evenly spaced along a curved line spanning the longitudinal axis of the trophozoites. This configuration of microtubules is inferred to function in maintaining the flattened shape of the trophozoites and facilitate dynamic undulations. The novel traits in Platyproteum are consistent with phylogenomic data showing that this lineage is only distantly related to Selenidium and other marine gregarine apicomplexans with dynamic intestinal trophozoites.

Coinfection of slime feather duster worms (Annelida, Myxicola) by different gregarine apicomplexans (Selenidium) and astome ciliates reflects spatial niche partitioning and host specificity

Individual organisms can host multiple species of parasites (or symbionts), and one species of parasite can infect different host species, creating complex interactions among multiple hosts and parasites. When multiple parasite species coexist in a host, they may compete or use strategies, such as spatial niche partitioning, to reduce competition. Here, we present a host–symbiont system with two species of Selenidium (Apicomplexa, Gregarinida) and one species of astome ciliate co-infecting two different species of slime feather duster worms (Annelida, Sabellidae, Myxicola) living in neighbouring habitats. We examined the morphology of the endosymbionts with light and scanning electron microscopy (SEM) and inferred their phylogenetic interrelationships using small subunit (SSU) rDNA sequences. In the host ‘Myxicola sp. Quadra’, we found two distinct species of Selenidium; S. cf. mesnili exclusively inhabited the foregut, and S. elongatum n. sp. inhabited the mid to hindgut, reflecting spatial niche partitioning. Selenidium elongatum n. sp. was also present in the host M. aesthetica, which harboured the astome ciliate Pennarella elegantia n. gen. et sp. Selenidium cf. mesnili and P. elegantia n. gen. et sp. were absent in the other host species, indicating host specificity. This system offers an intriguing opportunity to explore diverse aspects of host–endosymbiont interactions and competition among endosymbionts.

Pacific marine gregarines (Apicomplexa) shed light on biogeographic speciation patterns and novel diversity among early apicomplexans

Gregarines are the most biodiverse group of apicomplexan parasites. This group specializes on invertebrate hosts (e.g., ascidians, crustaceans, and polychaetes). Marine gregarines are of particular interest because they are considered to be the earliest evolving apicomplexan lineage, having subsequently speciated (and radiated) through virtually all existing animal groups. Still, mechanisms governing the broad (global) distribution and speciation patterns of apicomplexans are not well understood. The present study examines Pacific lecudinids, one of the most species-rich and diverse groups of marine gregarines. Here, marine polychaetes were collected from intertidal zones. Single trophozoite cells were isolated for light and electron microscopy, as well as molecular phylogenetic analyses using the partial 18S rRNA gene. The cytochrome c oxidase subunit 1 gene was used to confirm morphology-based host identification. This study introduces Undularius glycerae n. gen., n. sp. and Lecudina kitase n. sp. (Hokkaido, Japan), as well as Difficilina fasoliformis n. sp. (California, USA). Occurrences of Lecudina cf. longissima and Lecudina cf. tuzetae (California, USA) are also reported. Phylogenetic analysis revealed a close relationship between L. pellucida, L. tuzetae, and L. kitase n. sp. Additionally, clustering among North Atlantic and Pacific L. tuzetae formed a species complex, likely influenced by biogeography.

Dispersal and invasive stages of Urospora eugregarines (Apicomplexa) from brown bodies of a polychaete host

Urosporid eugregarines (Apicomplexa: Urosporidae) are unicellular eukaryotic parasites inhabiting the coelom or the intestine of marine invertebrates such as annelids, molluscs, nemerteans, and echinoderms. Despite the availability of published morphological and phylogenetical analyses of coelomic gregarines, their long-term survival in the host body cavity and dispersal routes into the marine environment remain unclear. Here, we focus on Urospora gametocysts and oocysts with sporozoites, which were found viable inside the so-called brown bodies floating in the body cavity of the polychaete Travisia forbesii. Brown bodies form as a result of host defence where coelomocytes encapsulate dead host cells and foreign objects including potential pathogens. We hypothesise the long-term persistence of Urospora eugregarines in brown bodies through evasion of the host immunity and outline possible pathways for their egress into the marine environment, applicable as dispersal routes for other parasites as well. Unique features revealed by detailed ultrastructural analysis of detected eugregarine stages include asynchronous sporogony, a massive sporozoite secretion apparatus, as well as the presence of free (possibly autoinfective) sporozoites within the gametocyst. The assignment to the genus Urospora and the complete identity with U. ovalis and U. travisiae were confirmed by analysing 18S rDNA sequences obtained from isolated gametocysts. The 18S rDNA phylogeny confirmed the affiliation of Urosporidae to Lecudinoidea and the grouping of all Urospora sequences with Difficilina from nemerteans and environmental sequences from the Artic region. We also enriched the Apicomplexa set by partial 28S rDNA sequences of two Urospora species enabling more complex phylogenetic analyses prospectively.

Evidence for Host Jumping and Diversification of Marine Cephaloidophorid Gregarines (Apicomplexa) Between Two Distantly Related Animals, viz., Crustaceans and Salps

This study examined the evolutionary history and diversity of marine gregarine parasites of pelagic zooplankton, and highlighted a unique example of a host-jumping event of cephaloidophorid gregarines between two distantly related host groups, crustaceans and chordates. Candacia bipinnata Giesbrecht, 1889, a free-living calanoid copepod, and a salp, Salpa fusiformis Cuvier, 1804, were collected on oceanic research cruises in 2018 and 2019, in the West Pacific aboard TRV SEISUI MARU and TOYOSHIO MARU, respectively. A molecular phylogeny based on 18S rDNA nested the gregarine parasite from S. fusiformis among cephaloidophorids, within a clade exclusively comprised of gregarines from crustaceans. The relationship between these groups was underpinned with ultrastructural data including the presence of a septum, and similarities in the apices of the epicytic folds. Subsequently, it was concluded to establish a new combination, Cephaloidophora cf. flava n. comb (Ex. Thalicola flava) and transfer the other two members of the Thalicola (also parasites of salps) to the Cephaloidophora. This study also attempted to ascertain the origin of cephaloidophorids in S. fusiformis. However, the relationship between Cephaloidophora bipinnatae n. sp., and C. cf. flava n. comb. had only modest support.

New gregarine species (Apicomplexa) from tunicates show an evolutionary history of host switching and suggest a problem with the systematics of Lankesteria and Lecudina

Apicomplexa (sensu stricto) are a diverse group of obligate parasites to a variety of animal species. Gregarines have been the subject of particular interest due to their diversity, phylogenetically basal position, and more recently, their symbiotic relationships with their hosts. In the present study, four new species of marine eugregarines infecting ascidian hosts (Lankesteria kaiteriteriensis sp. nov., L. dolabra sp. nov., L. savignyii sp. nov., and L. pollywoga sp. nov.) were described using a combination of morphological and molecular data. Phylogenetic analysis using small subunit rDNA sequences suggested that gregarines that parasitize ascidians and polychaetes share a common origin as traditionally hypothesized by predecessors in the discipline. However, Lankesteria and Lecudina species did not form clades as expected, but were instead intermixed amongst each other and their respective type species in the phylogeny. These two major genera are therefore taxonomically problematic. We hypothesize that the continued addition of new species from polychaete and tunicate hosts as well as the construction of multigene phylogenies that include type-material will further dissolve the currently accepted distinction between Lankesteria and Lecudina. The species discovered and described in the current study add new phylogenetic and taxonomic data to the knowledge of marine gregarine parasitism in ascidian hosts.

Coccidian Parasite in Sea Cucumber (Apostichopus japonicus) Ovaries

We investigated an unknown ellipsoidal body that is sometimes found in the ovaries of the sea cucumber Apostichopus japonicus. Its external morphology, comprising an ellipsoidal dark central body (about 150 µm in length) and a surrounding transparent layer (about 50 µm in thickness), resembled that of a protozoan cyst, particularly an oocyst. Histological observations of the developing A. japonicus ovaries clarified that a small mass of organisms appeared in the cytoplasm of young oocytes, proliferated in these cells through budding, became rod shaped and arranged radially, and, finally, formed an outer layer. These processes were considered to be the formation of a cyst by a protozoan parasite. The small subunit ribosomal RNA (18S rRNA) gene was amplified from the DNA extracted from unknown ellipsoidal bodies by using polymerase chain reaction with universal primers for eukaryote 18S rRNA. The determined sequence was not identical to any of the known sequences in DNA databases, but it clustered in a clade of coccidian species belonging to Eucoccidiorida in phylogenetic analyses. From these results, we concluded that the unknown ellipsoidal body is a cyst (possibly an oocyst) of a coccidian parasite (order Eucoccidiorida) that is formed in the A. japonicus oocyte, though its lower taxonomic position is uncertain. In a survey of the gonads of wild A. japonicus at Esashi, Hokkaido, during the reproductive season, these cysts were detected in more than 50% of females but were never found in males. We consider that the cysts of this parasite can only be formed in A. japonicus ovaries.

Morphology and molecular systematic of marine gregarines (Apicomplexa) from Southwestern Atlantic spionid polychaetes

Gregarines are a common group of parasites that infect the intestines of marine invertebrates, and particularly polychaetes. Here, we describe for the first time four gregarine species that inhabit the intestines of three spionid species: Dipolydora cf. flava, Spio quadrisetosa and Boccardia proboscidea from the Patagonian coast, Argentina, using light and scanning electron microscopy and molecular phylogenetic analyses of small subunit (SSU) rDNA sequences. Even though the spionid species thrive in the same environments, our results showed a high host specificity of the gregarine species. Selenidium cf. axiferens and Polyrhabdina aff. polydorae were both identified from the intestine of D. cf. flava. The new species, Polyrhabdina madrynense sp. n. and Selenidium patagonica sp. n., were described from the intestines of S. quadrisetosa and the invasive species B. proboscidea, respectively. All specimens of D. cf. flava and S. quadrisetosa were infected by gregarines (P = 100%), recording the highest mean intensity values of infection (MI = 80; 60 respectively), in contrast to B. proboscidea (P = 60%; MI = 38). We associated this finding with the recent invasion of this host. It is expected that in the future, an increase of its population density might favour a rising intensity of this gregarine infection.

Fine structure and Molecular Phylogenetic Position of Two Marine Gregarines, Selenidium pygospionis sp. n. and S. pherusae sp. n., with Notes on the Phylogeny of Archigregarinida (Apicomplexa)

Archigregarines are a key group for understanding the early evolution of Apicomplexa. Here we report morphological, ultrastructural, and molecular phylogenetic evidence from two archigregarine species: Selenidium pygospionis sp. n. and S. pherusae sp. n. They exhibited typical features of archigregarines. Additionally, an axial row of vacuoles of a presumably nutrient distribution system was revealed in S. pygospionis. Intracellular stages of S. pygospionis found in the host intestinal epithelium may point to the initial intracellular localization in the course of parasite development. Available archigregarine SSU (18S) rDNA sequences formed four major lineages fitting the taxonomical affiliations of their hosts, but not the morphological or biological features used for the taxonomical revision by Levine (1971). Consequently, the genus Selenidioides Levine, 1971 should be abolished. The branching order of these lineages was unresolved; topology tests rejected neither para- nor monophyly of archigregarines. We provided phylogenies based on LSU (28S) rDNA and near-complete ribosomal operon (concatenated SSU, 5.8S, LSU rDNAs) sequences including S. pygospionis sequences. Although being preliminary, they nevertheless revealed the monophyly of gregarines previously challenged by many molecular phylogenetic studies. Despite their molecular-phylogenetic heterogeneity, archigregarines exhibit an extremely conservative plesiomorphic structure; their ultrastructural key features appear to be symplesiomorphies rather than synapomorphies.

Molecular Phylogenetic Positions and Ultrastructure of Marine Gregarines (Apicomplexa) Cuspisella ishikariensis n. gen., n. sp. and Loxomorpha cf. harmothoe from Western Pacific scaleworms (Polynoidae)

Marine gregarines are unicellular parasites of invertebrates commonly found infecting the intestine and coelomic spaces of their hosts. Situated at the base of the apicomplexan tree, marine gregarines offer an opportunity to explore the earliest stages of apicomplexan evolution. Classification of marine gregarines is often based on the morphological traits of the conspicuous feeding stages (trophozoites) in combination with host affiliation and molecular phylogenetic data. Morphological characters of other life stages such as the spore are also used to inform taxonomy when such stages can be found. The reconstruction of gregarine evolutionary history is challenging, due to high levels of intraspecific variation of morphological characters combined with relatively few traits that are taxonomically unambiguous. The current study combined morphological data with a phylogenetic analysis of small subunit rDNA sequences to describe and establish a new genus and species (Cuspisella ishikariensis n. gen., n. sp.) of marine gregarine isolated from the intestine of a polynoid host (Lepidonotus helotypus) collected from Hokkaido, Japan. This new species possesses a set of unusual morphological traits including a spiked attachment apparatus and sits on a long branch on the molecular phylogeny. Furthermore, this study establishes a molecular phylogenetic position for Loxomorpha cf. harmothoe, a previously described marine gregarine, and reveals a new group of gregarines that infect polynoid hosts.

Archigregarines of the English Channel revisited: New molecular data on Selenidium species including early described and new species and the uncertainties of phylogenetic relationships

Background

Gregarines represent an important transition step from free-living predatory (colpodellids s.l.) and/or photosynthetic (Chromera and Vitrella) apicomplexan lineages to the most important pathogens, obligate intracellular parasites of humans and domestic animals such as coccidians and haemosporidians (Plasmodium, Toxoplasma, Eimeria, Babesia, etc.). While dozens of genomes of other apicomplexan groups are available, gregarines are barely entering the molecular age. Among the gregarines, archigregarines possess a unique mixture of ancestral (myzocytosis) and derived (lack of apicoplast, presence of subpellicular microtubules) features.

Methodology/Principal findings

In this study we revisited five of the early-described species of the genus Selenidium including the type species Selenidium pendula, with special focus on surface ultrastructure and molecular data. We were also able to describe three new species within this genus. All species were characterized at morphological (light and scanning electron microscopy data) and molecular (SSU rDNA sequence data) levels. Gregarine specimens were isolated from polychaete hosts collected from the English Channel near the Station Biologique de Roscoff, France: Selenidium pendula from Scolelepis squamata, S. hollandei and S. sabellariae from Sabellaria alveolata, S. sabellae from Sabella pavonina, Selenidium fallax from Cirriformia tentaculata, S. spiralis sp. n. and S. antevariabilis sp. n. from Amphitritides gracilis, and S. opheliae sp. n. from Ophelia roscoffensis. Molecular phylogenetic analyses of these data showed archigregarines clustering into five separate clades and support previous doubts about their monophyly.

Conclusions/Significance

Our phylogenies using the extended gregarine sampling show that the archigregarines are indeed not monophyletic with one strongly supported clade of Selenidium sequences around the type species S. pendula. We suggest the revision of the whole archigregarine taxonomy with only the species within this clade remaining in the genus Selenidium, while the other species should be moved into newly erected genera. However, the SSU rDNA phylogenies show very clearly that the tree topology and therefore the inferred relationships within and in between clades are unstable and such revision would be problematic without additional sequence data.

A new view on the morphology and phylogeny of eugregarines suggested by the evidence from the gregarine Ancora sagittata (Leuckart, 1860) Labbé, 1899 (Apicomplexa: Eugregarinida)

BACKGROUND

Gregarines are a group of early branching Apicomplexa parasitizing invertebrate animals. Despite their wide distribution and relevance to the understanding the phylogenesis of apicomplexans, gregarines remain understudied: light microscopy data are insufficient for classification, and electron microscopy and molecular data are fragmentary and overlap only partially.

METHODS

Scanning and transmission electron microscopy, PCR, DNA cloning and sequencing (Sanger and NGS), molecular phylogenetic analyses using ribosomal RNA genes (18S (SSU), 5.8S, and 28S (LSU) ribosomal DNAs (rDNAs)).

RESULTS AND DISCUSSION

We present the results of an ultrastructural and molecular phylogenetic study on the marine gregarine Ancora sagittata from the polychaete Capitella capitata followed by evolutionary and taxonomic synthesis of the morphological and molecular phylogenetic evidence on eugregarines. The ultrastructure of Ancora sagittata generally corresponds to that of other eugregarines, but reveals some differences in epicytic folds (crests) and attachment apparatus to gregarines in the family Lecudinidae, where Ancora sagittata has been classified. Molecular phylogenetic trees based on SSU (18S) rDNA reveal several robust clades (superfamilies) of eugregarines, including Ancoroidea superfam. nov., which comprises two families (Ancoridae fam. nov. and Polyplicariidae) and branches separately from the Lecudinidae; thus, all representatives of Ancoroidea are here officially removed from the Lecudinidae. Analysis of sequence data also points to possible cryptic species within Ancora sagittata and the inclusion of numerous environmental sequences from anoxic habitats within the Ancoroidea. LSU (28S) rDNA phylogenies, unlike the analysis of SSU rDNA alone, recover a well-supported monophyly of the gregarines involved (eugregarines), although this conclusion is currently limited by sparse taxon sampling and the presence of fast-evolving sequences in some species. Comparative morphological analyses of gregarine teguments and attachment organelles lead us to revise their terminology. The terms "longitudinal folds" and "mucron" are restricted to archigregarines, whereas the terms "epicystic crests" and "epimerite" are proposed to describe the candidate synapomorphies of eugregarines, which, consequently, are considered as a monophyletic group. Abolishing the suborders Aseptata and Septata, incorporating neogregarines into the Eugregarinida, and treating the major molecular phylogenetic lineages of eugregarines as superfamilies appear as the best way of reconciling recent morphological and molecular evidence. Accordingly, the diagnosis of the order Eugregarinida Léger, 1900 is updated.

Ultrastructure of Selenidium pendula, the Type Species of Archigregarines, and Phylogenetic Relations to Other Marine Apicomplexa

Archigregarines, an early branching lineage within Apicomplexa, are a poorly-known group of invertebrate parasites. By their phylogenetic position, archigregarines are an important lineage to understand the functional transition that occurred between free-living flagellated predators to obligatory parasites in Apicomplexa. In this study, we provide new ultrastructural data and phylogenies based on SSU rDNA sequences using the type species of archigregarines, the Selenidiidae Selenidium pendulaGiard, 1884. We describe for the first time the syzygy and early gamogony at the ultrastructural level, revealing a characteristic nuclear multiplication with centrocones, cryptomitosis, filamentous network of chromatin, a cyst wall secretion and a 9+0 flagellar axoneme of the male gamete. S. pendula belongs to a monophyletic lineage that includes several other related species, all infecting Sedentaria Polychaeta (Spionidae, Sabellaridae, Sabellidae and Cirratulidae). All of these Selenidium species exhibit similar biological characters: a cell cortex with the plasma membrane - inner membrane complex - subpellicular microtubule sets, an apical complex with the conoid, numerous rhoptries and micronemes, a myzocytosis with large food vacuoles, a nuclear multiplication during syzygy and young gamonts. Two other distantly related Selenidium-like lineages infect Terebellidae and Sipunculida, underlying the ability of archigregarines to parasite a wide range of marine hosts.

Wider than Thought Phylogenetic Occurrence of Apicortin, A Characteristic Protein of Apicomplexan Parasites

Apicomplexan parasites cause serious illnesses, including malaria, in humans and domestic animals. The presence of apicortins is predominantly characteristic of this phylum. All the apicomplexan species sequenced contain an apicortin which unites two conserved domains: DCX and partial p25alpha. This paper identifies novel apicortin orthologs in silico and corrects in several cases the erroneous sequences of hypothetical apicortin proteins of Cryptosporidium, Eimeria, and Theileria genera published in databases. Plasmodium apicortins, except from Plasmodium gallinaceum, differ significantly from the other apicomplexan apicortins. The feature of this ortholog suggests that only orthologs of Plasmodiums hosted by mammals altered significantly. The free-living Chromerida, Chromera velia, and Vitrella brassicaformis, contain three paralogs. Their apicomplexan-type and nonapicomplexan-type apicortins might be "outparalogs." The fungal ortholog, Rozella allomycis, found at protein level, and the algal Nitella mirabilis, found as Transcriptome Shotgun Assembly (TSA), are similar to the known Opisthokont (Trichoplax adhaerens, Spizellomyces punctatus) and Viridiplantae (Nicotiana tabacum) ones, since they do not contain the long, unstructured N-terminal part present in apicomplexan apicortins. A few eumetazoan animals possess apicortin-like (partial) sequences at TSA level, which may be either contaminations or the result of horizontal gene transfer; in some cases the contamination has been proved.

Comparative ultrastructure and molecular phylogeny of Selenidium melongena n. sp. and S. terebellae Ray 1930 demonstrate niche partitioning in marine gregarine parasites (apicomplexa)

Gregarine apicomplexans are a diverse group of single-celled parasites that have feeding stages (trophozoites) and gamonts that generally inhabit the extracellular spaces of invertebrate hosts living in marine, freshwater, and terrestrial environments. Inferences about the evolutionary morphology of gregarine apicomplexans are being incrementally refined by molecular phylogenetic data, which suggest that several traits associated with the feeding cells of gregarines arose by convergent evolution. The study reported here supports these inferences by showing how molecular data reveals traits that are phylogenetically misleading within the context of comparative morphology alone. We examined the ultrastructure and molecular phylogenetic positions of two gregarine species isolated from the spaghetti worm Thelepus japonicus: Selenidium terebellaeRay 1930 and S. melongena n. sp. The ultrastructural traits of S. terebellae were very similar to other species of Selenidium sensu stricto, such as having vermiform trophozoites with an apical complex, few epicytic folds, and a dense array of microtubules underlying the trilayered pellicle. By contrast, S. melongena n. sp. lacked a comparably discrete assembly of subpellicular microtubules, instead employing a system of fibrils beneath the cell surface that supported a relatively dense array of helically arranged epicytic folds. Molecular phylogenetic analyses of small subunit rDNA sequences derived from single-cell PCR unexpectedly demonstrated that these two gregarines are close sister species. The ultrastructural differences between these two species were consistent with the fact that S. terebellae infects the inner lining of the host intestines, and S. melongena n. sp. primarily inhabits the coelom, infecting the outside wall of the host intestine. Altogether, these data demonstrate a compelling case of niche partitioning and associated morphological divergence in marine gregarine apicomplexans.

The revised classification of eukaryotes

This revision of the classification of eukaryotes, which updates that of Adl et al. [J. Eukaryot. Microbiol. 52 (2005) 399], retains an emphasis on the protists and incorporates changes since 2005 that have resolved nodes and branches in phylogenetic trees. Whereas the previous revision was successful in re-introducing name stability to the classification, this revision provides a classification for lineages that were then still unresolved. The supergroups have withstood phylogenetic hypothesis testing with some modifications, but despite some progress, problematic nodes at the base of the eukaryotic tree still remain to be statistically resolved. Looking forward, subsequent transformations to our understanding of the diversity of life will be from the discovery of novel lineages in previously under-sampled areas and from environmental genomic information.

Discovery of a diverse clade of gregarine apicomplexans (Apicomplexa: Eugregarinorida) from Pacific eunicid and onuphid polychaetes, including descriptions of Paralecudina n. gen., Trichotokara japonica n. sp., and T. eunicae n. sp

Marine gregarines are poorly understood apicomplexan parasites with large trophozoites that inhabit the body cavities of marine invertebrates. Two novel species of gregarines were discovered in polychaete hosts collected in Canada and Japan. The trophozoites of Trichotokara japonica n. sp. were oval to rhomboidal shaped, and covered with longitudinal epicytic folds with a density of six to eight folds/micron. The nucleus was situated in the middle of the cell, and the mucron was elongated and covered with hair-like projections; antler-like projections also extended from the anterior tip of the mucron. The distinctively large trophozoites of Trichotokara eunicae n. sp. lacked an elongated mucron and had a tadpole-like cell shape consisting of a bulbous anterior region and a tapered tail-like posterior region. The cell surface was covered with longitudinal epicytic folds with a density of three to five folds/micron. Small subunit (SSU) rDNA sequences of both species were very divergent and formed a strongly supported clade with the recently described species Trichotokara nothriae and an environmental sequence (AB275074). This phylogenetic context combined with the morphological features of T. eunicae n. sp. required us to amend the description for Trichotokara. The sister clade to the Trichotokara clade consisted of environmental sequences and Lecudina polymorpha, which also possesses densely packed epicyctic folds (3-5 folds/micron) and a prominently elongated mucron. This improved morphological and molecular phylogenetic context justified the establishment of Paralecudina (ex. Lecudina) polymorpha n. gen. et comb.