Search

A new chytrid genus and species was isolated and cultured from samples obtained in the Baltic Sea during a dinoflagellate bloom event. This species is characterized by having a spherical sporangium without papillae and zoospores of 2–3 µm in diameter that are released through 3 discharge pores. Molecular phylogeny based on ribosomal operon showed its sister position to the Dinomyces cluster in Rhizophydiales. Zoospores lack fenestrated cisternae but contain a paracrystalline inclusion, found in a Rhizophydiales representative for the first time. Additionally, the kinetid features are uncommon for Rhizophydiales and only observed in Dinomyces representatives so far. These morphological features and its phylogenetic relationships justify the description of the new genus and speciesParadinomyces triforaminorum gen. nov. sp. nov. belonging to the family Dinomycetaceae. The chytrid was detected during a high-biomass bloom of the dinoflagellate Kryptoperidinium foliaceum. Laboratory experiments suggest this species is highly specific and demonstrate the impact it can have on HAB development. The chytrid co-occurred with three other parasites belonging to Chytridiomycota (Fungi) and Perkinsea (Alveolata), highlighting that parasitic interactions are common during HABs in brackish and marine systems, and these multiple parasites compete for similar hosts

Perkinsea is a phylogenetic group of protists that includes parasites of distantly related hosts. However, its diversity is still mainly composed of environmental sequences, mostly obtained from freshwater environments. Efforts to isolate and culture parasitoids of dinoflagellates have led to the description of several phylogenetically closely related species constituting the Parviluciferaceae family. In this study, two new parasitoid species infecting dinoflagellates during recurrent coastal blooms are reported. Using the ribosomal RNA (rRNA) gene phylogenies, we show that both cluster within Perkinsea, one of them at the base of Parviluciferaceae and the other in a distinct branch unrelated to other described species. The establishment of host-parasite lab cultures of the latter allowed its morphological characterization, resulting in the formal description of Maranthos nigrum gen. nov., sp. nov. The life-cycle development of the two parasitoids is generally the same as that of other members of the Parviluciferaceae family but they differ in the features of the trophont and sporont stages, including the arrangement of zoospores during the mature sporangium stage and the lack of specialized structures that release the zoospores into the environment. Laboratory cross-infection experiments showed that the parasitoid host range is restricted to dinoflagellates, although it extends across several different genera. The maximum prevalence reached in the tested host populations was lower than in other Parviluciferaceae members. The findings from this study suggest that Perkinsea representatives infecting dinoflagellates are more widespread than previously thought

Parasites in aquatic systems are highly diverse and ubiquitous. In marine environments, parasite-host interactions contribute substantially to shaping microbial communities, but their nature and complexity remain poorly understood. In this study, we examined the relationship between Perkinsea parasitoids and bloom-forming dinoflagellate species. Our aim was to determine whether parasite-host species interactions are specific and whether the diversity and distribution of parasitoids are shaped by their dinoflagellate hosts. Several locations along the Catalan coast (NW Mediterranean Sea) were sampled during the blooms of five dinoflagellate species and the diversity of Perkinsea was determined by combining cultivation-based methods with metabarcoding of the V4 region of 18S rDNA. Most known species of Parviluciferaceae, and others not yet described, were detected, some of them coexisting in the same coastal location, and with a wide distribution. The specific parasite-host interactions determined for each of the studied blooms demonstrated the host preferences exhibited by parasitoids in nature. The dominance of a species within the parasitoid community is driven by the presence and abundances of its preferred host(s). The absence of parasitoid species, often associated with a low abundance of their preferred hosts, suggested that high infection rates are reached only under conditions that favour parasitoid propagation, especially dinoflagellate blooms

Many fungi have been identified as pathogens of marine algae. Among them, Chytridiomycota have been revealed as relatively highly abundant, but much of the diversity known within these groups is almost entirely based on environmental sequencing data. Here, we present a novel chytridiomycete genus and species, characterized by light microscopical observations, ultrastructure, and molecular phylogenetic analysis of the parasitic chytrid of brackish-water dinoflagellate Kryptoperidinium foliaceum from the Baltic Sea. Phylogenetic analysis of rDNA sequences and the ultrastructure of the strain reveals that it represents a new family in the order Rhizophydiales. Ericiomyces syringoforeus gen. et sp. nov. is a parasitoid with a life cycle composed by zoospores, which attach to the host, encyst, and produce a rhizoidal system (haustorium). Unlike typical Rhizophydiales chytrids, sporangium develops as a lateral outgrowth of the encysted zoospore. The ultrastructural study revealed at least two unique traits: the syringe-like organelle in the cyst, which supposed to paralyze the host, and funnel-shaped structure anchoring sporangium in the host wall. Sporangium matures and produces new zoospores within 3 days. Multiple infections are common and then the life cycle is 1–2 days shorter compared to the duration when a single infection occurred. Cross-infection experiments showed that E. syringoforeus could only infect dinoflagellates, being K. foliaceum highly susceptible to infection by the chytrid parasitoid. The effects of some fungal epidemics on populations of Kryptoperidinium are discussed

Perkinsea is a phylogenetic group of protists that includes parasites of distantly related hosts. However, its diversity is still mainly composed of environmental sequences, mostly obtained from freshwater environments. Efforts to isolate and culture parasitoids of dinoflagellates have led to the description of several phylogenetically closely related species constituting the Parviluciferaceae family. In this study, two new parasitoid species infecting dinoflagellates during recurrent coastal blooms are reported. Using the ribosomal RNA (rRNA) gene phylogenies, we show that both cluster within Perkinsea, one of them at the base of Parviluciferaceae and the other in a distinct branch unrelated to other described species. The establishment of host-parasite lab cultures of the latter allowed its morphological characterization, resulting in the formal description of Maranthos nigrum gen. nov., sp. nov. The life-cycle development of the two parasitoids is generally the same as that of other members of the Parviluciferaceae family but they differ in the features of the trophont and sporont stages, including the arrangement of zoospores during the mature sporangium stage and the lack of specialized structures that release the zoospores into the environment. Laboratory cross-infection experiments showed that the parasitoid host range is restricted to dinoflagellates, although it extends across several different genera. The maximum prevalence reached in the tested host populations was lower than in other Parviluciferaceae members. The findings from this study suggest that Perkinsea representatives infecting dinoflagellates are more widespread than previously thought

Perkinsea are a group of intracellular protist parasites that inhabit all types of aquatic environments and cause significant population declines of a wide variety of hosts. However, the diversity of this lineage is mostly represented by environmental rDNA sequences. Complete descriptions of Perkinsea that infect marine dinoflagellates have increased in recent literature due to the identification, isolation and culturing of representatives during bloom events, contributing to expand the knowledge on the diversity and ecology of the group. Shallow coastal areas in the Baltic Sea suffer seasonal dinoflagellate blooms. In summer 2016, two parasitoids were isolated during a Kryptoperidinium foliaceum bloom in the Baltic Sea. Morphological features and sequences of the small and large subunit of the ribosomal DNA gene revealed these two parasitoids were new species that belong to the genus Parvilucifera. This is the first time that Parvilucifera infections are reported in the Inner Baltic Sea. The first species, Parvilucifera sp. has some morphological and phylogenetic features in common with P. sinerae and P. corolla, although its ultrastructure could not be studied and the formal description could not be done. The second new species, named Parvilucifera catillosa, has several distinct morphological features in its zoospores (e.g. the presence of a rostrum), and in the shape and size of the apertures in the sporangium stage, which are larger and more protuberant than in the other species of the genus. Infections observed in the field and cross-infection experiments determined that the host range of both Parvilucifera species was restricted to dinoflagellates, each one showing a different host preference. The coexistence in the same environment by the two closely related parasitoids with very similar life cycles suggests that their niche separation is the preferred host

Muchas de las especies que parasitan las floraciones algales están aún por descubrir. Las zonas costeras de todo el mundo se ven a menudo afectadas por episodios de proliferaciones algales nocivas. Estos episodios los causan mayormente microalgas del grupo de los dinoflagelados, los cuales tienen un efecto nocivo tanto para el propio ecosistema como para la economía y la salud humana debido a su toxicidad. Aunque estas proliferaciones y sus causas han sido ampliamente estudiadas, algunos de sus enemigos naturales, los parásitos, han pasado inadvertidos. El pequeño tamaño de su fase infectiva (entre 2 y 5 micrómetros) y la heterogeneidad de morfologías que adquieren durante su ciclo biológico hacen de estos parásitos los pequeños grandes desconocidos del ecosistema marino costero. El uso de novedosas técnicas moleculares ha permitido determinar el importante papel que desempeña el parasitismo en las comunidades de protistas marinos. Combinadas con las técnicas de microscopía más avanzadas, han empezado a desvelar la enorme diversidad de los parásitos de microalgas, de los que se han descrito un gran número de especies nuevas. Los parásitos, que acaban matando a la microalga en la que se hospedan para completar su ciclo biológico, pertenecen a grupos filogenéticos diversos. Pueden actuar como ecto o endoparásitos según si infectan a su huésped adhiriéndose a él desde el exterior o si penetran en su interior. En nuestro grupo de investigación nos dedicamos a estudiar la diversidad y ecología de los parásitos de dinoflagelados en el medio marino. La determinación de su impacto en las floraciones algales y el estudio de las interacciones que se establecen entre el parásito y el huésped a escala molecular permitirán una mejor comprensión de la función que cumplen estos diminutos organismos en el ecosistema marino

During summer, when oligotrophic conditions prevail offshore in the Mediterranean Sea, enhanced phytoplankton stripes are often observed in nearshore waters. In this study, we examine the cross-shore hydrographic variability and the associated microbial plankton communities in this zone. Detailed cross-shore underway sampling at 47 coastal sites spread along the Balearic and Catalan coasts revealed the widespread existence of narrow bands of warm and decreased salinity water beholding high phytoplankton biomass (up to 50-fold vs. offshore chlorophyll). Most intense physical and biological anomalies along these transects were generally constrained to the first hundred meters from the shoreline (i.e., a transition zone starting at ~400 m). We use Principal Component Analysis (PCA) and k-means cluster analysis to categorize temperature, salinity and chlorophyll (T, S and Chl) in three main types of cross-shore trends. Prevalence of exponential-shaped Chl trends was observed particularly in areas with shoreward directed winds (B1-type). The other two trends (B2 and B3) presented variations offthe coast produced by alongshore structures like river plumes, city outfalls and other features. Exponential-shaped cross-shore chlorophyll distribution (B1-type) accumulated 90% of the total transect Chl variation in the first 367 ± 190 m from the shoreline, whereas this distance was variable in the other profile types. Repeated daily sampling at one site with this transect typology revealed that wind forcing variations produced fast response on cross-shore T and S properties. Chl was less sensitive to changes at this time-scale. Phytoplankton communities exhibited site-dependent responses to the nearshore environment. Pico- and nanoplankton assemblages, typically dominating coastal assemblages during summer in the Mediterranean Sea, showed lower cross-shore variation. Conversely, larger response to nearshore conditions was observed in microplankton populations. These larger cells

El curs se centra en l'estudi de les espècies de microorganismes dels ecosistemes marins i els factors que regulen la seva abundància. Concretament, s'abordaran els factors que regulen l’estructura de la comunitat de microorganismes i com la variabilitat del clima i les pertorbacions humanes afecten els ecosistemes marins de la zona costanera del Mediterran

[CAT] El parasitisme és una interacció generalitzada, que ha evolucionat pràcticament en totes les branques de l’arbre de la vida. Històricament no s’ha tingut en compte en l’estudi dels sistemes microbians marins, limitant el coneixement de les xarxes tròfiques marines i dels ciclesbiogeoquímics. Recentment, les eines moleculars han revelat moltes associacions hoste-paràsit fins ara desconegudes, situant els paràsits com a components clau de les comunitats planctòniques i bentòniques marines. El fitoplàncton sosté la major part de la producció primària, i de vegades causa proliferacions massives que poden tenir conseqüències negatives per als éssers humans i l’ecosistema. Les proliferacions de dinoflagel·lades sovint tenen lloc en la zona costanera, i col·locorren amb paràsits de tipus zoosporic. En ocasions concretes, les infeccions causades pels paràsits poden ser la causa principal de mortalitat de les dinoflagel·lades, regulant la fi de la proliferació, de manera que s’ha suggerit el seu ús com a agents de control biològic. En la actualitat, hi ha descrits tres grups de paràsits eucariotes de dinoflagel·lades: els Amoebophrya (Sindinial), els Parvilucifera (Perkinsozoa) i els Dinomyces (Chytridiomycota). Ja que aquests paràsits poden controlar l’abundància dels seus hostes, poden afectar la dinàmica del fitoplàncton, l’estructura de la comunitat i la seva diversitat. Tanmateix, se sap molt poc sobre la seva ecologia i diversitat. [...], [EN] Parasitism is a widespread interaction that has evolved practically in all branches of the tree of life. It has historically been neglected in studies of marine microbial systems, limiting our understanding of marine food webs and biogeochemical cycles. Molecular tools have recently revealed many new host-parasite associations, placing parasites as key components of coastal marine planktonic and benthic communities. Phytoplankton sustains most of the marine primary production, sometimes causing massive proliferations or blooms, which may have negative consequences for humans and the ecosystem. Dinoflagellate blooms often occur in coastal areas, sometimes in co-occurrence with zoosporic parasite species. Occasionally, parasitic infections may be the main cause of dinoflagellate mortality, which can modulate bloom termination and consequently, their use has been suggested to biologically control natural blooms. Up to date, three groups of eukaryotic parasites of dinoflagellates have been described: Amoebophrya (Syndiniales), Parvilucifera (Perkinsozoa) and Dinomyces (Chytridiomycota). Such parasites can control the abundance of their hosts populations, and hence they can also affect phytoplankton dynamics, community structure and diversity. However, very little is still known about the ecology and diversity of these parasites, especially Parvilucifera and Dinomyces. [...]

Chytridiomycota, often referred to as chytrids, can be virulent parasites with the potential to inflict mass mortalities on hosts, causing e.g. changes in phytoplankton size distributions and succession, and the delay or suppression of bloom events. Molecular environmental surveys have revealed an unexpectedly large diversity of chytrids across a wide range of aquatic ecosystems worldwide. As a result, scientific interest towards fungal parasites of phytoplankton has been gaining momentum in the past few years. Yet, we still know little about the ecology of chytrids, their life cycles, phylogeny, host specificity and range. Information on the contribution of chytrids to trophic interactions, as well as co-evolutionary feedbacks of fungal parasitism on host populations is also limited. This paper synthesizes ideas stressing the multifaceted biological relevance of phytoplankton chytridiomycosis, resulting from discussions among an international team of chytrid researchers. It presents our view on the most pressing research needs for promoting the integration of chytrid fungi into aquatic ecology

Dinoflagellate blooms are natural phenomena that often occur in coastal areas, which in addition to their large number of nutrient-rich sites are characterized by highly restricted hydrodynamics within bays, marinas, enclosed beaches, and harbors. In these areas, massive proliferations of dinoflagellates have harmful effects on humans and the ecosystem. However, the high cell density reached during blooms make them vulnerable to parasitic infections. Under laboratory conditions parasitoids are able to exterminate an entire host population. In nature, Parvilucifera parasitoids infect the toxic dinoflagellate Alexandrium minutum during bloom conditions but their prevalence and impact remain unexplored. In this study, we evaluated the in situ occurrence, prevalence, and dynamics of Parvilucifera parasitoids during recurrent blooms of A. minutum in a confined site in the NW Mediterranean Sea as well as the contribution of parasitism to bloom termination. Parvilucifera parasitoids were recurrently detected from 2009 to 2013, during seasonal outbreaks of A. minutum. Parasitic infections in surface waters occurred after the abundance of A. minutum reached 104–105 cells L−1, suggesting a density threshold beyond which Parvilucifera transmission is enhanced and the number of infected cells increases. Moreover, host and parasitoid abundances were not in phase. Instead, there was a lag between maximum A. minutum and Parvilucifera densities, indicative of a delayed density-dependent response of the parasitoid to host abundances, similar to the temporal dynamics of predator-prey interactions. The highest parasitoid prevalence was reached after a peak in host abundance and coincided with the decay phase of the bloom, when a maximum of 38% of the A. minutum population was infected. According to our estimates, Parvilucifera infections accounted for 5–18% of the total observed A. minutum mortality, which suggested that the contribution of parasitism to bloom termination is similar t

Parasites are one of the ecologically most relevant groups of marine food webs, but their taxonomic and biological complexity hampers the assessment of their diversity and evolutionary trends. Moreover, the within-host processes that govern parasitoid infection, development and reproduction are often unknown. In this study, we describe a new species of a perkinsozoan endoparasitoid that infects the toxic dinoflagellate Dinophysis sacculus, by including observations of its morphology, ultrastructure, life-cycle development and phylogeny. The SSU rDNA sequence and main morphological features were also obtained for a second parasitoid species infecting the bloom-forming dinoflagellate Levanderina fissa. Phylogenetic analyses including the sequences obtained show that all known Perkinsozoa species infecting dinoflagellates cluster together. However, sequences of Parvilucifera prorocentri and those obtained in this study cluster at the base of the clade, while the rest of Parvilucifera representatives form a separated highly-supported cluster. These results, together with differing morphological characters like the formation of a germ-tube, the presence of trichocysts, or the heterochromatin presence in zoospores nucleus justify the erection of Dinovorax pyriformis gen. nov. et sp. nov., and Snorkelia prorocentri gen. nov. et comb. nov. (=Parvilucifera prorocentri). The morphological features and phylogenetic position of these parasitoids represent ancestral characters for the Perkinsozoa phylum, and also for Dinozoa clade, allowing the inference of the evolutionary framework of these Alveolata members

Recent studies of marine protists have revealed parasites to be key components of marine communities. Here we describe a new species of the parasitoid genus Parvilucifera that was observed infecting the dinoflagellate Durinskia baltica in salt marshes of the Catalan coast (NW Mediterranean). In parallel, the same species was detected after the incubation of seawater from the Canary Islands (Lanzarote, NE Atlantic). The successful isolation of strains from both localities allowed description of the life cycle, ultrastructure, and phylogeny of the species. Its infection mechanism consists of a free-living zoospore that penetrates a dinoflagellate cell. The resulting trophont gradually degrades the dinoflagellate cytoplasm while growing in size. Once the host is consumed, schizogony of the parasitoid yields a sporocyte. After cytokinesis is complete, the newly formed zoospores are released into the environment and are ready to infect new host cells. A distinguishing feature of the species is the radial arrangement of its zoospores around the central area of the sporocyte during their formation. The species shows a close morphological similarity with other species of the genus, including P. infectans, P. sinerae, and P. rostrata