Biology of parasitic protozoa X. Myxozoa (Opisthokonta, Animalia) Andrea Bardůnek Valigurová andreav@sci.muni.cz Notice This presentation contains some material available on the web without the permission of the creator or the copyright owner. This presentation is to be used for educational purposes only. Educational purposes are defined as a communicating material for a particular course of instruction or for the administration of such course. Educational purposes do not cover the use of copyright material in PowerPoint for public lectures or other purposes. 5 supergroups = megagroups Myxozoa • organisms previously considered protozoa • recently placed among Metazoa (Opisthokonta) = multicellular organisms (highly derived cnidarians) that are extremely developmentally and structurally altered by parasitic life style • endoparasites mainly of fish and some invertebrates (annelids, polychaetes, bryophytes) • rare findings in mammals and ducks (liver of a shrew, brain of a mole, bile ducts and liver of a duck) • main feature = formation of multicellular spores equipped with polar capsules (= cnidaria) with coiled and ejectable fiber https://www.youtube.com/watch?v=VG_r2KQgljQ Myxozoa • due to evolution into microscopic parasites, they lost many genes responsible for multicellular development, coordination, cell-cell communication, and even aerobic respiration (Henneguya salminicola) • complex life cycle usually involving intermediate host - usually fish and rarely amphibians • envelopment of cells by cells; differentiation of nuclei and cells into the vegetative and generative cells https://doi.org/10.1016/j.pt.2021.01.010 https://www.youtube.com/watch?v=4N_HIkBAez8 https://www.youtube.com/watch?v=sVqExF5-2Ms&t=21s https://phys.org/news/2020-02-henneguya-salminicola-microscopic-parasite-mitochondrial.html https://www.pnas.org/doi/full/10.1073/pnas.1909907117 Three types of spores in Myxozoa myxosporeoan spore actinosporean spore malacosporean spore fish, rarely mammals annelids bryozoans 2 phases of the same organism next phase ??? Myxozoa Myxosporea • myxosporean and actinosporean phases of development + corresponding spores (= developmental stages of the same organism) • annelids (actinosporean phase) and fish (myxosporean phase), annelids are the original hosts where sexual cycle occurs • not all myxozoa have the actinosporean phase Malacosporea • only malacospores known so far • bryozoan parasites • fish as a second host? Myxosporea Myxosporean phase • cavity parasites in fish (bladder, gall pouch, kidney canals, swim bladder) or histozoan parasites (gill epithelium, muscle, cartilage, etc.) • proliferative phase via cell-in-cell system („matryoshka“) - cells forming within other cells Sporogonial phase • formation of sac-shaped plasmodia and multicellular spores • nuclei and cells differentiate into vegetative and generative lines Myxosporea – myxosporean spore Bivalvulida type • freshwater myxozoans • bilateral symmetry • 2 valves • 2 polar capsules Myxosporea – myxosporean spore https://doi.org/10.1186/1471-2148-10-228 Myxosporea – actinosporean spore • 3 valves often with floats, 3 polar capsules, sporoplasm multicellular Life cycle of Myxobolus cerebralis (1984) The complex life cycle of Myxobolus cerebralis involves multiple stages of the parasite and requires two hosts: an aquatic worm Tubifex tubifex, infected by the parasite’s myxospore (A), and a salmonid fish, infected by the triactinomyxon (E). Why belong Myxozoa among Metazoa • multicellular spores • nuclear differentiation • cell differentiation • cell junctions as in Metazoa (tight, adhesive) • similarity of polar capsules with nematocysts of cnidarians • rRNA nucleotide sequence • Cnidaria (Diblastica)? - extreme similarity of polar capsulaes with cnidarian nematocysts • Bilateria (Triblastica)? - presence of HOX genes (determining the antenapodial location of a metazoan cell) • solution???: Buddenbrockia plumatellae is a myxozoon with muscles and body organisation similar to nematodes! • according to phylogenetic analysis B. plumatellae belongs among Cnidaria Myxozoa are: https://doi.org/10.1093/oxfordjournals.molbev.a004155 https://www.youtube.com/watch?v=Pq05yrqsQ4k Buddenbrockia plumatellae Schroeder 1910 Malacospora = 4 soft valves muscles sporoplasm polar capsule up to 3 mm https://folia.paru.cas.cz/pdfs/fol/2002/01/08.pdf Buddenbrockia plumatellae • a "worm" with spores in the cavity of bryzoans = nematode-like cnidarian https://www.science.org/doi/10.1126/science.1142024 https://folia.paru.cas.cz/pdfs/fol/2002/01/08.pdf https://doi.org/10.1016/j.ijpara.2012.06.001 https://doi.org/10.1016/j.ijpara.2012.06.001 Pathological effects of Myxozoa • generally low pathogenicity, but under certain conditions causing serious fish disease • part of the marine fish catch is spoiled by the myxosporidian proliferative stage (having effective proteolytic enzymes) dying in tissues of dead fish becomes gelatinous after cooking consistency • causative agens of inflammatory diseases (PKD - proliferative kidney disease in salmonids) or directly destroying important tissues of the fish ("whirling disease"), infection of gill epithelium Myxobolus cerebralis • agens of Whirling disease in salmonid fish, affecting juvenile fish and causes skeletal deformation and neurological damage A) Unstained mature M. cerebralis myxospores obtained from rainbow trout displaying whirling disease 120 d post-exposure (p.e.). Each infective myxospore displays 2 intact polar capsules. LM. B) Mature myxospore. SEM. C) Unstained mature waterborne triactinomyxon spores released from T. tubifex 120 d p.e. Triactinomyxon spore is larger than the myxospore and contains a minimum of 64 spherical sporoplasm cells (sporozoites) Triactinomyxon spores elicit refractile sporoplasm and transparent processes. LM. D) Mature triactinomyxon penetrating the epidermis of fish host. SEM. E) Histological changes caused by M. cerebralis infection of salmonid cartilage. Giemsa, LM. e https://doi.org/10.3354/dao02856 1-3) Tricapsulate spore of the Triactinomyxon ignotum stage contains several uninucleate sporoplasms (amoebic stage). If these stages are eaten by trout with their hosts (a tubificid worm, e.g., Limnodrilus), they give rise to multinucleate trophozoites within the cartilage (3). 4) Occurrence of uninuclear cytomeres (CY) within the trophozoites. 5-6) One cell (pericytic cell, P) surrounds the other (sporogonic cell, SP). 7-8) Sporogonic cell divides and gives rise to two valvogenic cells, two capsulogenic cells, and 1, 2nucleate sporoplasm. 9) Fully differentiated multicellular spore (Myxobolus stage) which becomes free after death of fish. 10) If a tubificid worm eats such spores, the two valves open in its intestine and the sporoplasm (SP) creeps into the body cavity... Life cycle of Myxobolus cerebralis Whirling disease Clinical signs: whirling behaviour, blackened tail, skeletal deformities of spine and head, mortality https://www.youtube.com/watch?v=SLjgDeX8xGs Whirling disease Representative X-ray image displaying characteristic skeletal deformity. Etiology of whirling disease Aggregation of M. cerebralis (black arrows) accompanied by digestion and destruction of ossification by trophozoites leading to skeletal deformities. Whirling disease Thinly sliced cross sections of infected fish tissues reveal microscopic damage caused by Myxobolus cerebralis to cartilage when compared to healthy fish. A) Cross section through rainbow trout head showing location of cartilage (red circle) in smaller images. B) Cartilage section from an uninfected fish. C) Cartilage section from a heavily infected fish. Myxobolus turbirotundus https://doi.org/10.1111/j.1365-2761.2010.01161.x Gibel carp heavily infected with Myxobolus turpisrotundus. A) Disfigured appearance of fish from infection on body surface. B) Infected intestine with 3 large plasmodia in the foregut (arrow). Thelohanellus hoffmanni https://doi.org/10.3354/dao02870 Histopathology of the caudal fin of goldfish with nodules (plasmodia). HE. A) Plasmodia (P) are filled with different developmental stages of T. hoffmanni. C cyst wall. B) Higher magnification of a nodule from A; D - dermis; E - epidermis; EC - eosinophilic cyst wall. Melanocytes (arrows) are gathering together around the plasmodia. Note that the early developmental stages are in the periphery of the plasmodium (black arrowheads), and the mature spores are in the centre (white arrowheads). Main myxozoan species for which information is available on fish adaptive immune response Pictures in the left column (A, D, G, J, M, P, S) fresh smears of myxospores, except for T. bryosalmonae in which a proliferative stage is shown (S). Middle column refers to clinical signs: note the sunken head syndrome in turbot (arrow in B), the sunken belly and prominent head bones in gilthead sea bream (arrowheads in E), the myoliquefaction in a mackerel (H), the black tail in rainbow trout (K), the swollen and ascitic digestive tract in rainbow trout (N), the pale gills and splenomegaly in common carp (arrows in Q), the swollen kidney and splenomegaly in rainbow trout (arrows in T). The right column depicts histopathological aspects. Catarrhal enteritis in turbot (C, Giemsa); invasion of the paracellular space of the gut (Giemsa, F); hypertrophy of myocytes (I, toluidine blue); invasion of the cartilage of rainbow trout (L, Giemsa); destruction of the intestine with detachment of stages to the lumen (Q, H, E); sporogony in the gill epithelium [R, in situ hybridisation with parasites labelled in by VectorBlue, counterstained with Neutral red; interstitial stages in a kidney imprint (V, Diff-Quick). https://doi.org/10.3389/fimmu.2021.734238 Soricimyxum fegati • parasitising liver of shrews in Czechia https://folia.paru.cas.cz/pdfs/fol/2007/03/01.pdf Thank you for your attention ☺