0065-1583 Jagiellonian University in Kraków Ultrastructure of the Plasmodial Development of Myxobolus insignis (Myxozoa), Infecting the Amazonian Fish Semaprochilodus insignis (Prochilodontidae) Azevedo Carlos author De São Clemente Sérgio Carmona author Casal Graça author Matos Patrícia author Oliveira Elsa author Al-Quraishy Saleh author Matos Edilson Rodrigues author King Saud University 02f81g417 Department of Cell Biology, Institute of Biomedical Sciences (ICBAS/UP), and Laboratory of Pathology, Centre for Marine and Environmental Research (CIIMAR/UP), University of Porto, Portugal; Department of Zoology, College of Science, King Saud University, Riyadh, Saudi Arabia; Universidade Federal Fluminense 02rjhbb08 Laboratory of Cell Biology, Institute of Biomedical Sciences (ICBAS/UP), University of Porto, Portugal Department of Cell Biology, Institute of Biomedical Sciences (ICBAS/UP), and Laboratory of Pathology, Centre for Marine and Environmental Research (CIIMAR/UP), University of Porto, Portugal; Departmento de Ciências, Instituto Superior de Ciências da Saúde, Gandra, Portugal; Universidade Federal do Pará 03q9sr818 Zoology Department, College of Science, King Saud University, Riyadh, Saudi Arabia Universidade Federal Rural da Amazônia 02j71c790 Correspondence to: Carlos Azevedo Correspondence to: Sérgio Carmona De São Clemente Correspondence to: Graça Casal Correspondence to: Patrícia Matos Correspondence to: Elsa Oliveira Correspondence to: Saleh Al-Quraishy Correspondence to: Edilson Rodrigues Matos 18 06 2013 Volume 52, Issue 2 2013 91 97 Copyright © 2013 2013 <p>This study used light and electron microscopy to describe a myxosporean, polysporic, histozoic plasmodium infecting the gill filaments of the freshwater teleost, Semaprochilodus insignis, specimens of which were collected from the Trombetas River (Central Amazonian Region, Brazil). Ultrastructural analyses of the fish-infecting spores identified the parasite as Myxobolus insignis, an organism that occurs within whitish unequal-sized plasmodia located in the intralamellar epithelium of the gill. Based on the observed morphological and ultrastructural features of the plasmodia in this study three stages in the plasmodial evolution were distinguished, related to the sporogonic stages of Myxobolus insignis. The plasmodium walls were also found to constitute a number of layers of fibroblasts, surrounded by collagen fibres, which displayed different morphological arrangements according to the different phases of evolution. This represents the first time such ultrastructural features have been described in detail for Myxobolus insignis plasmodia and offers potentially significant points of comparison with plasmodia from other species of myxosporea.<br /> </p>