Search Results (11)

The Cambrian–Ordovician Plankton Revolution played a crucial role in the Great Ordovician Biodiversification Event (GOBE) or Ordovician Radiation, as a driver of diversification. The emergence of new planktonic species enhanced primary productivity and improved nutrient cycling, fueling diversification across trophic levels. In this context, established plankton consumers like sponges and cnidarians thrived, and animals like euarthropods also radiated in response to these environmental conditions. Here, we hypothesize that Offacolidae, a small group of early chelicerates (the group including sea spiders, spiders, mites, and horseshoe crabs) known from the early Ordovician to the end of the Silurian, were suspension feeders that diversified within this changing ecosystem. Extant chelicerates are primarily predators or parasites, with no known cases of suspension feeding, which is also the case in extinct members. However, anatomical and environmental evidence suggest that Offacolidae may have adopted this feeding strategy. We examine the environmental conditions in which Offacolidae fossils were found, considering both biotic and abiotic factors such as paleolatitude, bathymetry, and the associated plankton community. We also assess the possible biomechanics of their unique appendages to determine their suitability for suspension feeding. Finally, comparisons with extant arthropods, such as the suspension-feeding crustaceans Limnomysis benedeni, Atya gabonensis, Subeucalanus pileatus, and the genus Emerita, provide insights into possible evolutionary analogies in their morphology, which may have served the same function. If confirmed, this hypothesis would make Offacolidae a unique case within chelicerates, illustrating how exceptional early Ordovician conditions fostered novel ecological adaptations and highlighting an interesting case of analogy between different lineages of euarthropods. Full article

Myxozoa is a unique group of obligate endoparasites in the phylum Cnidaria that can cause emerging diseases in wild and cultured fish populations. Recently, we identified a new myxozoan species, Myxobolus bejeranoi, which infects the gills of cultured tilapia while suppressing host immunity. To uncover the molecular mechanisms underlying this successful parasitic strategy, we conducted transcriptomics analysis of M. bejeranoi throughout the infection. Our results show that histones, which are essential for accelerated cell division, are highly expressed even one day after invasion. As the infection progressed, conserved parasitic genes that are known to modulate the host immune reaction in different parasitic taxa were upregulated. These genes included energy-related glycolytic enzymes, as well as calreticulin, proteases, and miRNA biogenesis proteins. Interestingly, myxozoan calreticulin formed a distinct phylogenetic clade apart from other cnidarians, suggesting a possible function in parasite pathogenesis. Sporogenesis was in its final stages 20 days post-exposure, as spore-specific markers were highly expressed. Lastly, we provide the first catalog of transcription factors in a Myxozoa species, which is minimized compared to free-living cnidarians and is dominated by homeodomain types. Overall, these molecular insights into myxozoan infection support the concept that parasitic strategies are a result of convergent evolution. Full article

We used a combination of morphological, molecular and biological data to characterize a novel Henneguya (Myxozoa) species infecting the Amazonian prochilodontid Semaprochilodus insignis or “kissing prochilodus”, a popular food fish and aquarium species in the Brazilian Amazon. Twenty-one S. insignis were caught live from the Tapajós river, Pará State, Brazil, then examined for myxozoan infections. Cysts of a novel Henneguya species were observed in the connective tissue of the fins. Myxospores measured 48 ± 4.9 (39.5–60.8) µm total length, of which caudal appendages were 33 ± 4.5 (26.4–45.2) µm and spore body was 15 ± 1.6 (12.4–20.5) µm. The spore body was 4.0 ± 0.6 (2.7–5.3) µm wide × 3.2 ± 0.4 (2.7–3.6) µm thick, with two unequal polar capsules (nematocysts) 7.2 ±0.8 (5.2–8.3) × 1.5 ± 0.3 (1.0–2.2) µm for the larger capsule and 5 ± 0.7 (4.0–6.3) × 1.4 ± 0.2 (1.0–1.8) µm for the smaller capsule. Polar tubules had 8–13 turns. Generative cells, immature and mature myxospores were observed within plasmodia. Ultrastructure showed plasmodia surrounded by collagen fibers, with the plasmodial membrane having pinocytotic channels. Phylogenetic analysis of small subunit ribosomal DNA sequences showed that the new Henneguya species clustered as a sister taxon to Henneguya tietensis, a parasite of the gills of the prochilodontid fish Prochilodus lineatus, from the geographically distant Paraná–Paraguai River basin. Full article

Myxozoans are a diverse group of parasitic cnidarians of wide distribution. A new species, Myxobolus matogrossoensis n. sp., is herein described infecting wild specimens of tetra mato-grosso Hyphessobrycon eques, caught in the Pantanal biome, the world’s largest tropical wetland area. Cysts were found in 3 of the 30 examined fishes. Mature myxospores were ovoid in shape in frontal and measured 6.6 ± 0.4 µm (6.2–7.0 µm) in length and 3.5 ± 0.2 µm (3.3–3.7 µm) in width. The two polar capsules were elongated in shape, equal in size and occupying almost half of the myxospore body. They measured 3.3 ± 0.2 µm (3.1–3.5 µm) in length and 1.8 ± 0.1 µm (1.7–1.9 µm) in width. The polar tubules presented three to four turns. Phylogenetic analysis placed the new species within a clade containing myxobolid species from South American characiforms fish and appears as a close species of Myxobolus piraputangae and Myxobolus umidus. Nevertheless, the sequences of the new species and P. umidus and P. piraputangae have a large genetic divergence of 12 and 12.2% in their 18S rDNA gene, respectively. To the best of our knowledge, this is the first report of a Myxobolus species parasitizing the tetra fish mato-grosso, thus increasing our knowledge of cnidarian myxosporean diversity from South America. Full article

Myxozoans are a diverse group of microscopic cnidarian parasites and some representatives are associated with important diseases in fish, in both marine and freshwater aquaculture systems. Research on myxozoans has been largely hampered by the inability to isolate myxozoan parasites from their host tissues. In this study, we developed and optimized a method to isolate the myxozoan proliferative stages of different size and cellularity from fish blood, using DEAE-cellulose ion exchange chromatography. We optimized several parameters and obtained 99–100% parasite purity, as well as high survival and infectivity. Using polyclonal pan-carp blood cell-specific antibodies, we further developed a rapid cytometric assay for quantification of the proliferative stages, not only in highly concentrated DEAE-C isolates but also in dilute conditions in full blood. Early developmental stages of myxozoans are key to parasite proliferation, establishment, and pathology in their hosts. The isolation of these stages not only opens new possibilities for in vivo and in vitro studies, but also for obtaining purified DNA and protein extracts for downstream analyses. Hence, we provide a long-desired tool that will advance the functional research into the mechanisms of host exploitation and immune stimulation/evasion in this group, which could contribute greatly to the development of therapeutic strategies against myxozoans. Full article

The evolutionary aspects of cystatins are greatly underexplored in early-emerging metazoans. Thus, we surveyed the gene organization, protein architecture, and phylogeny of cystatin homologues mined from 110 genomes and the transcriptomes of 58 basal metazoan species, encompassing free-living and parasite taxa of Porifera, Placozoa, Cnidaria (including Myxozoa), and Ctenophora. We found that the cystatin gene repertoire significantly differs among phyla, with stefins present in most of the investigated lineages but with type 2 cystatins missing in several basal metazoan groups. Similar to liver and intestinal flukes, myxozoan parasites possess atypical stefins with chimeric structure that combine motifs of classical stefins and type 2 cystatins. Other early metazoan taxa regardless of lifestyle have only the classical representation of cystatins and lack multi-domain ones. Our comprehensive phylogenetic analyses revealed that stefins and type 2 cystatins clustered into taxonomically defined clades with multiple independent paralogous groups, which probably arose due to gene duplications. The stefin clade split between the subclades of classical stefins and the atypical stefins of myxozoans and flukes. Atypical stefins represent key evolutionary innovations of the two parasite groups for which their origin might have been linked with ancestral gene chimerization, obligate parasitism, life cycle complexity, genome reduction, and host immunity. Full article

Myxozoans are a diverse group of cnidarian parasites, including important pathogens in different aquaculture species, without effective legalized treatments for fish destined for human consumption. We tested the effect of natural feed additives on immune parameters of common carp and in the course of a controlled laboratory infection with the myxozoan Sphaerospora molnari. Carp were fed a base diet enriched with 0.5% curcumin or 0.12% of a multi-strain yeast fraction, before intraperitoneal injection with blood stages of S. molnari. We demonstrate the impact of these treatments on respiratory burst, phagocytosis, nitric oxide production, adaptive IgM+ B cell responses, S. molnari-specific antibody titers, and on parasite numbers. Both experimental diets enriched B cell populations prior to infection and postponed initial parasite proliferation in the blood. Curcumin-fed fish showed a decrease in reactive oxygen species, nitric oxide production and B cell density at late-stage infection, likely due to its anti-inflammatory properties, favoring parasite propagation. In contrast, multi-strain yeast fraction (MsYF)-fed fish harbored the highest S. molnari-specific antibody titer, in combination with the overall lowest parasite numbers. The results demonstrate that yeast products can be highly beneficial for the outcome of myxozoan infections and could be used as effective feed additives in aquaculture. Full article

We studied the genetic variability of serine protease inhibitors (serpins) of Myxozoa, microscopic endoparasites of fish. Myxozoans affect the health of both farmed and wild fish populations, causing diseases and mortalities. Despite their global impact, no effective protection exists against these parasites. Serpins were reported as important factors for host invasion and immune evasion, and as promising targets for the development of antiparasitic therapies. For the first time, we identified and aligned serpin sequences from high throughput sequencing datasets of ten myxozoan species, and analyzed 146 serpins from this parasite group together with those of other taxa phylogenetically, to explore their relationship and origins. High intra- and interspecific variability was detected among the examined serpins. The average sequence identity was 25–30% only. The conserved domains (i.e., motif and signature) showed taxon-level differences. Serpins clustered according to taxonomy rather than to serpin types, and myxozoan serpins seemed to be highly divergent from that of other taxa. None of them clustered with their closest relative free-living cnidarians. The genetic distinction of myxozoan serpins further strengthens the idea of an independent origin of Myxozoa, and may indicate novel protein functions potentially related to parasitism in this animal group. Full article

It is assumed that complex life cycles in cnidarian parasites belonging to the Myxozoa result from incorporation of vertebrates into simple life cycles exploiting aquatic invertebrates. However, nothing is known about the driving forces and implementation of this event, though it fostered massive diversification. We performed a comprehensive search for myxozoans in evolutionary ancient fishes (Chondrichthyes), and more than doubled existing 18S rDNA sequence data, discovering seven independent phylogenetic lineages. We performed cophylogenetic and character mapping methods in the largest monophyletic dataset and demonstrate that host and parasite phylogenies are strongly correlated, and that tectonic changes may explain phylogeographic clustering in recent skates and softnose skates, in the Atlantic. The most basal lineages of myxozoans inhabit the bile of chondrichthyans, an immunologically privileged site and protective niche, easily accessible from the gut via the bile duct. We hypothesize that feed-integration is a likely mechanism of host acquisition, an idea supported by feeding habits of chimaeras and ancient sharks and by multiple entries of different parasite lineages from invertebrates into the new host group. We provide exciting first insights into the early evolutionary history of ancient metazoan parasites in a host group that embodies more evolutionary distinctiveness than most other vertebrates. Full article

Motility factors are fundamental for parasite invasion, migration, proliferation and immune evasion and thus can influence parasitic disease pathogenesis and virulence. Salmonid enteronecrosis is caused by a myxozoan (Phylum Cnidarian) parasite, Ceratonova shasta. Three parasite genotypes (0, I, II) occur, with varying degrees of virulence in its host, making it a good model for examining the role of motility in virulence. We compare C. shasta cell motility between genotypes and describe how the cellular protrusions interact with the host. We support these observations with motility gene expression analyses. C. shasta stages can move by single or combined used of filopodia, lamellipodia and blebs, with different behaviors such as static adhesion, crawling or blebbing, some previously unobserved in myxozoans. C. shasta stages showed high flexibility of switching between different morphotypes, suggesting a high capacity to adapt to their microenvironment. Exposure to fibronectin showed that C. shasta stages have extraordinary adhesive affinities to glycoprotein components of the extracellular matrix (ECM). When comparing C. shasta genotypes 0 (low virulence, no mortality) and IIR (high virulence, high mortality) infections in rainbow trout, major differences were observed with regard to their migration to the target organ, gene expression patterns and proliferation rate in the host. IIR is characterized by rapid multiplication and fast amoeboid bleb-based migration to the gut, where adhesion (mediated by integrin-β and talin), ECM disruption and virulent systemic dispersion of the parasite causes massive pathology. Genotype 0 is characterized by low proliferation rates, slow directional and early adhesive migration and localized, non-destructive development in the gut. We conclude that parasite adhesion drives virulence in C. shasta and that effectors, such as integrins, reveal themselves as attractive therapeutic targets in a group of parasites for which no effective treatments are known. Full article

The mucus produced by many marine organisms is a complex mixture of proteins and polysaccharides forming a weak watery gel. It is essential for vital processes including locomotion, navigation, structural support, heterotrophic feeding and defence against a multitude of environmental stresses, predators, parasites, and pathogens. In the present study we focused on mucus produced by a benthic cnidarian, the sea anemone Actinia equina (Linnaeus, 1758) for preventing burial by excess sedimentation and for protection. We investigated some of the physico-chemical properties of this matrix such as viscosity, osmolarity, electrical conductivity, protein, carbohydrate, and total lipid contents. Some biological activities such as hemolytic, cytotoxic, and antibacterial lysozyme-like activities were also studied. The A. equina mucus is mainly composed by water (96.2% ± 0.3%), whereas its dry weight is made of 24.2% ± 1.3% proteins and 7.8% ± 0.2% carbohydrates, with the smallest and largest components referable to lipids (0.9%) and inorganic matter (67.1%). The A. equina mucus matrix exhibited hemolytic activity on rabbit erythrocytes, cytotoxic activity against the tumor cell line K562 (human erythromyeloblastoid leukemia) and antibacterial lysozyme-like activity. The findings from this study improve the available information on the mucus composition in invertebrates and have implications for future investigations related to exploitation of A. equina and other sea anemones’ mucus as a source of bioactive compounds of high pharmaceutical and biotechnological interest. Full article