Showing papers in "Acta Protozoologica in 2016"
TL;DR: The discovery of so many new species from only one very specific habitat (Microcystis colonies) from a rather restricted geographical area indicates that the diversity of planktonic naked amoebae is much higher than previously appreciated.
Abstract: The colonies of Microcystis, one of the most common bloom-forming cyanobacteria worldwide, harbor a diverse community of microorganisms. Among these, naked amoebae feeding on Microcystis cells can strongly influence natural Microcystis population dynamics. In this study, we investigated the species diversity of these amoebae based on 26 Microcystis-associated amoebae (MAA) strains from eutrophied water bodies in Belgium and elsewhere in western Europe. A detailed morphological characterization in combination with 18S rDNA (SSU) phylogenies revealed the presence of no less than 10 species. Nine of these belonged to the known genera Vannella (2 species), Korotnevella (2), Copromyxa (2), Vexillifera (1), Cochliopodium (1) and the recently described Angulamoeba (1). Only two were previously described, the others were new to science. One taxon could not be assigned to a known genus and is here described as Schoutedamoeba gen. n., representing a new variosean lineage. The discovery of so many new species from only one very specific habitat (Microcystis colonies) from a rather restricted geographical area indicates that the diversity of planktonic naked amoebae is much higher than previously appreciated and that only a tiny fraction of the total diversity of naked amoebae is currently known.
18 citations
TL;DR: It is documents that ciliates form functionally diverse communities with potential to control cyanobacterial blooms in hypertrophic reservoirs.
Abstract: 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.
15 citations
TL;DR: It is put forward the hypothesis that the differences in testate amoebae diversity across the Arctic hint to the existence of protozoological arctic regions, with emphasis on two arctic flagship species.
Abstract: Forty different sites, represented by 1483 samples, ranging from Alaska eastwards to Siberia, have been studied to assess the circumpolar testate amoebae species diversity. A total of 378 species have been recorded. The most common taxa are cosmopolitan and are widely distributed across various arctic habitats. Statistical analysis of testate amoebae species at sites across the Arctic have yielded geographic clusters of sampling sites that have been matched with climatic regions in the Arctic. We put forward the hypothesis that the differences in testate amoebae diversity across the Arctic hint to the existence of protozoological arctic regions. The problems concerning the question of the origin of the testate amoebae in the Arctic are also discussed, with emphasis on two arctic flagship species.
14 citations
TL;DR: The history of the discovery of T. diaptomi in different parts of the world was used and it was concluded that it is a cosmopolitan species, exclusively associated with copepods of the order Calanoida.
Abstract: Members of the genus Trichodina are mostly found on fish, but have also been recorded from a variety of other aquatic organisms, including calanoid copepods. So far, it appears that all the trichodinid populations collected from calanoids in various parts of the world are the same species, i.e. Trichodina diaptomi Sramek-Husek, 1953. This paper reports on a new record of T. diaptomi from Metadiaptomus meridianus in a large reservoir in South Africa, as well as on a new host species, Metadiaptomus transvaalensis, and the first record of T. diaptomi from pools in an ephemeral river in northern Botswana, therefore adding a new country to the distribution of this species. We used the history of the discovery of T. diaptomi in different parts of the world and came to the conclusion that it is a cosmopolitan species, exclusively associated with copepods of the order Calanoida. Based on existing information, T. diaptomi does not appear to have a reservoir host. Against this background, we provide a discussion on the possibility that, although no dormant stage has been recorded for any trichodinid, it may be possible that T. diaptomi possesses some form of diapause and that this might be related to that of calanoid copepods.
9 citations
TL;DR: In addition to cyst formation, naked amoebae may survive harsh, frozen winter soil in a dormant or resting stage that is capable of rapid resumed growth in spring, thus gaining an immediate competitive advantage in exploiting food and other environmental resources early after the winter thaw.
Abstract: Experimental evidence is presented to support a hypothesis that terrestrial naked amoebae, collected during late autumn from cold, moist temperate soil, develop a non-encysted, freeze-thaw resistant stage that is capable of surviving winter frozen soil. Therefore, in addition to cyst formation, naked amoebae may survive harsh, frozen winter soil in a dormant or resting stage that is capable of rapid resumed growth in spring, thus gaining an immediate competitive advantage in exploiting food and other environmental resources early after the winter thaw.
9 citations
TL;DR: A new protosteloid amoeba, Luapeleamoeba hula, cultured from dead leaves of mamaki from the Manuka Natural Area Reserve, Hawaii, USA, is described, which is unique in both itsAmoebal and fruiting body morphology.
Abstract: We describe a new protosteloid amoeba, Luapeleamoeba hula. Protosteloid amoebae, sometimes called protostelids, are sporocarpic amoebae that make fruiting bodies that consist of a stalk and one to a few spores. This new taxon was cultured from dead leaves of mamaki (Pipturus albidus) from the Manuka Natural Area Reserve, Hawaii, USA. Light microscopic examination showed that this amoeba has a short, rigid stalk with a small apophysis and a spore that changes shape continuously until it is shed and crawls away from the stalk. In addition, this amoeba was initially observed to maintain a diurnal rhythm in which fruiting body formation occurred primarily in the late afternoon. This new species is unique in both its amoebal and fruiting body morphology. Spore deciduousness appears to be a result of shape changes in the spore itself. This is the fourth species of protosteloid amoeba described with a clearly described diurnal rhythm. In addition, previous molecular phylogenetic analyses suggested that this new species has SSU rRNA gene sequences that clearly separate it from any other protosteloid amoebae and place it as sister to Protacanthamoeba bohemica among the Acanthamoebidae family in Centramoebida of Amoebozoa. Because this new amoeba species does not fit into any of the centramoebid genera, we have proposed a new genus Luapeleamoeba.
8 citations
TL;DR: The occurrences of the new species in environmental DNA and RNA samples correspond well to its distribution inferred from the microscopic study.
Abstract: Psammophaga fuegia is a new monothalamid foraminifera discovered in surface sediment samples in the Beagle Channel, South America. The species is a member of the important, globally distributed genus Psammophaga , which has the ability to ingest and store mineral particles inside the cytoplasm. Its shape is ovoid to pyriform, the size varies from 250 to 600 µm in length and from 200 to 400 µm in width. Like other Psammophaga species P. fuegia has a single aperture. It was found in multiple samples across the Beagle Channel area at water depths of 4 to 220 meters and in environments as variable as fjords, the main channel, and the harbour of Puerto Williams (Chile). The occurrences of the new species in environmental DNA and RNA samples correspond well to its distribution inferred from the microscopic study.
8 citations
TL;DR: The results emphasised that the evaluated environmental resources are important as assembly factors to shell traits in testate amoebae community.
Abstract: Shell composition is considered an important functional trait in testate amoebae community. Differences in the composition of shells may represent adaptations of these organisms to changes in the availability of environmental resources. We aimed to evaluate the influence of these environmental resources on the presence of different testate amoeba species, based on observation of one important functional trait (shell composition), in floodplain environments. We hypothesised that species diversity would increase with increased availability of food (chlorophyll-a; a critical environmental requirement). We also predicted that a higher concentration of suspended inorganic material would contribute to the occurrence of species that have an exogenous shell. Testate amoeba samples were taken between 2002 and 2011 in plankton of ten floodplain environments. A significant positive correlation was noted between the concentration of chlorophyll-a and the diversity of testate amoeba species according to a simple regression analysis. Furthermore, non-metric multidimensional scaling showed distinct groups with lower and higher concentration of suspended inorganic material. The occurrence of testate amoeba species with smaller exogenous shells was the most influenced by environments with higher concentrations of suspended inorganic material. Thus, our results emphasised that the evaluated environmental resources are important as assembly factors to shell traits in testate amoebae community.
7 citations
TL;DR: Molecular phylogenetic tree supports the previously reported polyphyly of the genus Anteholosticha, and morphological features of related species are compared and discussed to confirm the validity of the new species.
Abstract: The soil ciliate Anteholosticha rectangula nov. spec. was discovered on King George Island in maritime Antarctica. Morphology and the nuclear SSU rDNA sequence were used to describe and infer the phylogenetic position of the new species. Anteholosticha rectangula is morphologically similar to A. bergeri and A. verrucosa , differing primarily by the morphology of the nuclear apparatus and dorsal kineties, respectively. The morphological features of related species are compared and discussed to confirm the validity of the new species. Molecular phylogenetic tree supports the previously reported polyphyly of the genus Anteholosticha .
7 citations
TL;DR: A new microsporidian parasite of the adipose and connective tissue cells of Megacyclops viridis (Jurine, 1820) (Copepoda: Cyclopidae) is described, characterized by a complex decorated exospore.
Abstract: Lanatospora costata sp. n., a new microsporidian parasite of the adipose and connective tissue cells of Megacyclops viridis (Jurine, 1820) (Copepoda: Cyclopidae) is described. It was isolated from a woodland pool with a rich and diverse fauna of microsporidiainfected small crustaceans and insect larvae. The parasite is structurally similar to the genus Lanatospora Voronin, 1989, characterized by a complex decorated exospore. In the described species the exospore is armoured by a conspicuous layer of interwoven ribs forming labyrinth on the spore surface. SSU rRNA phylogeny places the organism in the “aquatic outgroup” of microsporidia (Vossbrinck et al. 2004), which includes a number of microsporidia from aquatic microcrustacea of the classes Copepoda and Cladocera. The increasing number of available SSU rRNA gene sequences of these microsporidia allows a more detailed interpretation of their developmental histories.
6 citations
TL;DR: This study uses a large dataset from sites in Russia, Switzerland and Italy to demonstrate that testate amoebae in this epilithic mosses and lichens habitat are both abundant and diverse and adds to the evidence that moisture availability is a critical factor in structuring testateAmoeba communities across habitats.
Abstract: The testate amoebae (TA) of many potential habitats around the world have been barely investigated but data on species presence and abundance is essential to answering big questions about microbial biogeography and the diversity of protist life. One such habitat lacking basic data is epilithic mosses and lichens with only a small number of samples analysed in previous studies and no systematic attempt to understand potential environmental controls. We use a large dataset (n = 81) from sites in Russia, Switzerland and Italy to demonstrate that testate amoebae in this habitat are both abundant and diverse. The community of our samples was dominated by ubiquitous taxa and differed between the northern (Russia) and southern (Switzerland and Italy) sites, perhaps due to differences in climate or air quality. Community composition, concentration and diversity were explained by moisture content but not by elevation above the ground surface and there were no significant differences between communities of mosses and lichens. Surprisingly our data showed a significant difference between communities of epiphytic and epilithic lichens in the same region sampled at the same time. Our study adds to the evidence that moisture availability is a critical factor in structuring testate amoeba communities across habitats and highlights the paucity of knowledge of TA in many environments.
TL;DR: A conspicuous new species, Arcella gandalfi sp.
Abstract: Arcellinida are free-living lobose amoebae that produce an outer shell (test). Here, we describe a conspicuous new species, Arcella gandalfi sp. nov, from Brazilian continental waters, along with a morphological and biometrical characterization. Test diameter and test height are on average 81 and 71 respectively. This new species has an apical conical extension, which differentiates it from other Arcella species. A. gandalfi seems to be closely-related to A. brasiliensis, due to the distinct marginal ring (test brim) present only in these two species. Since A. gandalfi is easily identified by morphological features and due to its apparent geographic restriction to South America, we discuss its possible use as a new flagship species.
TL;DR: A new peritrich species highly tolerant to ammonium and nitrite, Epistylis camprubii n.
Abstract: A new peritrich species highly tolerant to ammonium and nitrite, Epistylis camprubii n. sp., was found adhered to the biofilm of two advanced wastewater treatment plants treating high ammonium-loaded wastewater in Rubi, Spain. Its morphology, oral infraciliature and phylogenetic position in the peritrich clade were studied. The new species is a vase-shaped peritrich, constricted below the peristomial lip, with an in vivo average length of 58.7 ± 10.1 µm, average width of 32.0 ± 5.4 µm, and a longitudinally striated, compact stalk that occasionally exhibits uneven thickness and rarely shows transverse segments. The peristomial disc is commonly rounded or pointed, and rarely umbilicated. The C-shaped macronucleus is located in the adoral half of the body, and the only contractile vacuole lies in the adoral third of the zooid. The molecular analysis of the 18s gene sequence clustered E. camprubii n. sp. together with the other Epistylis, with the exception of Epistylis galea.
TL;DR: The isolate (GFP151sc) is phylogenetically sister to but unique from the freshwater environmental flamellid clone from Borok, Yaroslavl region, Russia originally published in 2006 and placed into a new species, Flamella piscinae n.
Abstract: We isolated and identified a freshwater amoebozoan species that belongs to the genus Flamella Schaeffer, 1926 by single cell isolation and light microscopy. Our specific strain was isolated from a water sample obtained on the cover of a swimming pool in Petal, Mississippi, USA collected during the winter of 2015. Morphologically, our isolate is a fan-shaped amoeba with a large, frontal hyaloplasm and distinctive granuloplasm. It is capable of encystment and trophozoites occasionally have two nuclei. The isolate (GFP151sc) is phylogenetically sister to but unique from the freshwater environmental flamellid clone from Borok, Yaroslavl region, Russia originally published in 2006. Here we describe and place this isolate into a new species, Flamella piscinae n. sp.
TL;DR: Overall, high densities of naked amoebae in the winter soils of Japanese knotweed, some as resting cells capable of forming rapidly activated trophic stages, likely increase soil fertility and strengthen the species’ invasive capacity.
Abstract: Among the most prolific invasive plant species posing threats to the ecological balance of ecosystems in North America and Europe is Japanese knotweed (Fallopia japonica). In order to identify the potential role of protists in the invasive capacity of Japanese knotweed the winter abundances of naked amoebae in soils from three roadside thickets of Japanese knotweed were compared to nearby non-invaded sites. Japanese knotweed soils had higher abundances (t = 5.43, df, 16, p < 0.001) of amoebae than comparison sites. This is one of the first studies to document higher abundances of soil naked amoebae associated with an invasive plant, and may indicate more generally that below-ground abundances of amoebae can promote soil fertility and support the successful adaptation and expansion of some invasive plant species. Moreover, analysis of encysted vs. trophic forms of naked amoebae in the winter soil, provided evidence of freezeresistant, amoeba resting cells in soil samples from the natural environment in support of prior findings that were based solely on laboratory experimental evidence. Overall, high densities of naked amoebae in the winter soils of Japanese knotweed, some as resting cells capable of forming rapidly activated trophic stages, likely increase soil fertility and strengthen the species’ invasive capacity.
TL;DR: A new microsporidia Glugea sardinellensis n.
Abstract: A new microsporidia Glugea sardinellensis n. sp. found in the teleost fish Sardinella aurita Valenciennes collected from the Tunisian coasts. The parasite develops in a large xenomas measuring 1–16 mm in diameter and is generally visible with naked eye in the connective tissue around the pyloric caeca of the host. Xenoma were often rounded, but would be occasionally ovoid or irregular shape, generally creamy but rarely opaque, and filled with mature spores. The spores were unikaryotic pyriform measuring 5–5.5 (5.25±0.24) µm in length and 2.5–3 (2.75±0.24) µm in width. The posterior vacuole was large and occupied more than half of the spore. Ultrastructural study indicated that the mature spore has 13–14 coils of polar filament arranged in one layer, and a rough exospore. Intermediate stages were rare and randomly distributed in the xenoma. Merogonial and sporogonial stages were uni or binucleate. The plasma membrane surrounding the meront was irregular and indented. The mean prevalence was 18.3% and it varied according to season and locality. The distribution of prevalence according to fish size indicated that small fish were primarily affected. Phylogenetic analysis using the partial sequence of the SSU rDNA showed consistent association with species of the genus Glugea. The most closely related species was Glugea atherinae Berrebi, 1979 with 98.5% similarity.
TL;DR: Birojimia soyaensis nov. spec. as mentioned in this paper is characterized by the following features: body slender, elongate, and somewhat twisted; body size in vivo 170-200 μm × 40-50 μm; contractile vacuole located at middle of left cell margin; cortical granules present; 37-48 adoral membranelles; 3 frontal and 2 frontoterminal cirri present; III/2 and buccal cirrus present; midventral pairs only; 1 left and 4 right marginal rows, including 3 compound rows
Abstract: A new soil urostylid ciliate, Birojimia soyaensis nov. spec. was discovered from Soya Island, Incheon, South Korea. The species is described based on live and stained specimen observations, and 18S ribosomal RNA gene sequence analysis. Birojimia soyaensis nov. spec. is characterized by the following features: body slender, elongate, and somewhat twisted; body size in vivo 170–200 μm × 40–50 μm; contractile vacuole located at middle of left cell margin; cortical granules present; 37–48 adoral membranelles; 3 frontal and 2 frontoterminal cirri present; III/2 and buccal cirrus present; midventral pairs only; pretransverse ventral and transverse cirri present; 1 left and 4 right marginal rows, including 3 compound rows; 5 long dorsal kineties with 3 additional shortened kineties in anteriorly compound rows; 8–11 caudal cirri; 53–69 macronuclear nodules; and 2 or 3 micronuclei. Birojimia soyaensis nov. spec. is distinguished from B. terricola by cortical granule size (0.4–1.2 μm in diameter vs. 2–3 μm × 1–2 μm), cortical granule shape (mostly spherical vs. broadly ellipsoid to lenticular, respectively); number of caudal cirri (8–11 vs. 2–7), and number of dorsal bristle rows (8 vs. 6–7). Phylogenetic analysis suggests this new species is most closely related to the genus Hemicycliostyla.
TL;DR: Two new species of centrohelids Acanthocystis lyra sp.nov.
Abstract: Two new species of centrohelids Acanthocystis lyra sp. nov. and A. siemensmae sp. nov. from the Pismenka River in the South Urals, Russia, have been studied with scanning electron microscopy. Cells of these species have both long and short spine scales with hollow shafts and circular basal plates. A. lyra has the long spine scales divided into two curved S-shaped branches possessing small teeth on their inner surface. The short spine scales have primary and secondary bifurcations. Every secondary branch ends with two teeth. A. siemensmae has both long and short scales with funnel-like apices, which possess small teeth. Based on the scale morphology A. lyra has been attributed to the A. turfacea species group, whereas A. siemensmae has been attributed to the A. pectinata species group, both according to classification proposed by Mikrjukov, 1997. Similarities and differences of the new species with other members of the genus Acanthocystis have been discussed.
TL;DR: The specimens of newly erected genus Meisterfeldia are characterised by ovoid shell, which is bilaterally symmetrical and laterally compressed, composed of proteinaceous material without mineral particles.
Abstract: The review on the systematics of the suborder Phryganellina is presented. The diagnosis of newly erected genus Meisterfeldia is provided. Three new species, namely Meisterfeldia chibisovi, Meisterfeldia wegeneri and Meisterfeldia polygonia, of testate amoeba family Cryptodifflugiidae are described. Two species, namely Meisterfeldia vanhoornei and Meisterfelsia turfacea are transferred from the genus Cryptodifflugia. The specimens of new genus are characterised by ovoid shell, which is bilaterally symmetrical and laterally compressed, composed of proteinaceous material without mineral particles; circular subterminal aperture placed on ventrally and obliquely cut apertural end, or it is situated on a well developed or poorly expressed neck inclined ventrally.
TL;DR: A new species of Papposphaera heldalii sp.
Abstract: In an attempt to establish a taxonomy for the polar contingent of lightly calcified coccolithophores, we are currently dealing with species of Papposphaera . Here we describe a new species, Papposphaera heldalii sp. nov., based on material from Svalbard. The species is unique in terms of calyx design, which is an elegant modification of the standard P. sagittifera theme, and also in terms of the absence of central area calcification in body coccoliths. The species thus occupies a further step in a sequence of five Arctic forms ranging from P. sagittifera via P. sarion , P. arctica and P. iugifera to P. heldalii showing a gradual reduction of central area calcification in body coccoliths. P. heldalii is unique also in the sense that the species has not been found during any of the major Arctic TEM nanoplankton surveys conducted during the last decades.
TL;DR: The ultrastructural aspects observed, together with the formation of a cyst-like, suggest that the parasite belongs to the genus Pleistophora, and this taxonomic positioning was confirmed by the molecular analysis of the SSU rRNA gene and Maximum-likelihood inference.
Abstract: A new microsporidian, Pleistophora beebei sp. nov., parasitizing the freshwater benthopelagic teleostean fish Brachyhypopomus beebei Schultz, 1944 (fam. Hypopomidae) collected from the Amazon River is described based on molecular and morphological studies. The parasite develops in the skeletal muscle of the abdominal cavity, forming a whitish cyst-like containing several groups of two types of spores (macrospores and microspores), which were observed in close contact with the myofibrils. Small groups of macrospores (ovoid elongate, tapering more anteriorly than posteriorly and measuring about 7.8 ± 0.4 × 4.7 ± 0.2 µm) were observed among the numerous microspores (lightly pyriform to ellipsoidal with rounded ends, measured about 4.7 ± 0.3 × 2.8 ± 0.4 µm). Both types of spores possessed a single large posterior vacuole containing flocculent material. The ultrastructural aspects observed, together with the formation of a cyst-like, suggest that the parasite belongs to the genus Pleistophora. This taxonomic positioning was confirmed by the molecular analysis of the SSU rRNA gene and Maximum-likelihood (ML) inference. Comparison to similar species previously described, recognized this as a new species, herein named Pleistophora beebei sp. nov.
TL;DR: The re-examination of the lightly calcified Arctic coccolithophore species, Papposphaera sagittifera, has some inherent challenges due to the research history, and the species description based on just a single specimen does not adequately account for the true identity of this taxon.
Abstract: The re-examination of the lightly calcified Arctic coccolithophore species, Papposphaera sagittifera, has some inherent challenges due to the research history on this taxon. It is thus obvious in retrospect that the species description based on just a single specimen does not adequately account for the true identity of this taxon. Today we are aware of the existence of at least three species of Papposphaera that have basically the same calyx design while being differentiated based on patterns of central area calcification. In order to remedy this we emend here the description of P. sagittifera and provide an epitype for the species. When realizing that species pairs of Papposphaera and Turrisphaera share a life history, the new combination, P. borealis, was established to accommodate P. sagittifera and T. borealis. However, it turns out that ‘sagittifera’ is in fact the senior epithet by a few months, which means that the correct name for the species is P. sagittifera with T. borealis added as a synonym. While the P. sagittifera HET and HOL morphological variability across Arctic sites clearly leaves the impression of a single, fairly well defined species, the situation is different with respect to the occurrence of P. sagittifera in Antarctic waters. While there are obvious similarities between P. sagittifera HET across the Polar Regions there are also subtle differences, and most importantly it has been found that the Antarctic P. sagittifera shares a life history with a species of Turrisphaera that is markedly different from T. borealis. While awaiting molecular evidence the Antarctic material is tentatively referred to as P. sagittifera cfr.
TL;DR: The potential for improved estimation of microbial CO2 emission from organically enriched freshwater ecosystems with respect to carbon dioxide emissions is investigated.
Abstract: Microbial respiration of organic carbon in freshwater microcosms: The potential for improved estimation of microbial CO2 emission from organically enriched freshwater ecosystems
TL;DR: This study is the first formal report of these trichodinids from South America, and the description of two new species, based on dry silver nitrate-impregnated specimens.
Abstract: During surveys of parasites of the pepper cory Corydoras paleatus Jenyns, 1842 and sided-livebearer Jenynsia multidentata Jenyns, 1842 from Samborombon River, Argentina, Trichodina corydori n. sp., Trichodina cribbi Dove and O’Donoghue, 2005 and T. jenynsii n. sp. were morphologically studied. Taxonomic and morphometric data for these trichodinids based on dry silver nitrate-impregnated specimens are presented. Trichodina corydori is characterized by a prominent blade apophysis, the section connecting the blade and central part is short, and the adoral ciliary spiral makes a turn of 370–380°. Trichodina jenynsii is characterized by curved blades and prominently-shaped denticle rays that are characteristically extremely long, tapering to thin sharp points in adult specimens. This study is the first formal report of these trichodinids from South America, and the description of two new species.
TL;DR: The astomatous metaradiophryids are ciliates which live endosymbiotically in earthworms (Annelida, Lumbricidae), and a detailed description of different parts of the hook apparatus exists in older literature, including a hypothesis on how these elements interact with each other to function as a holdfast device.
Abstract: The astomatous metaradiophryids are ciliates which live endosymbiotically in earthworms (Annelida, Lumbricidae). Their prominent hook apparatus is demonstrated in detail in light micrographs of living organisms as well as in scanning electron micrographs of Parducz-fixed cells. Since it was first observed, this structure has been interpreted as a ‘holdfast’ organelle preventing ciliates from being expelled prematurely from the intestine of the worm along with its excrements. No active movement of the hook has been reported in earlier papers or in our recent studies. Nevertheless, a detailed description of different parts of the hook apparatus exists in older literature, including a hypothesis on how these elements interact with each other to function as a holdfast device – without any experimental evidence. The suspected mode of function of this structure is questioned and critically discussed.
TL;DR: The first molecular data based on small subunit (SSU) rRNA gene sequences of Oxytoxum and Corythodinium, including the type species (O. scolopax and C. tessellatum), were obtained, suggesting the need of new combinations for species that were described as Oxyt oxum and possessed the characteristics of CorythODinium.
Abstract: The dinoflagellate genera Oxytoxum and Corythodinium that account for more than fifty species are widespread in warm oceans. These genera have been considered synonyms and thecal plate designations varied among authors. Several planktonic and sand-dwelling genera have been placed within the Oxytoxaceae. We obtained the first molecular data based on small subunit (SSU) rRNA gene sequences of Oxytoxum and Corythodinium, including the type species (O. scolopax and C. tessellatum) and C. frenguellii and C. cristatum. The three species of Corythodinium branched together a strong support [bootstrap (BP) of 98%]. This formed a sister clade with moderate support (BP 75%) with O. scolopax that supported the generic split. Oxytoxaceae should exclusively remain for Oxytoxum and Corythodinium, as an independent group, unrelated to any other known dinoflagellate. Oxytoxum was characterized by spindle-shaped cells with an anterior narrow epitheca, an apical spine and little cingular displacement. Corythodinium exhibits relatively broad cell shapes, with wider epitheca and greater cingular displacement, and an obovate or pentangular anterior sulcal plate that noticeably indented the epitheca. This suggested the need of new combinations for species that were described as Oxytoxum and possessed the characteristics of Corythodinium.