DAO 107:19-30 (2013)  -  DOI: https://doi.org/10.3354/dao02661

Ultrastructural and phylogenetic description of Zschokkella auratis sp. nov. (Myxozoa), a parasite of the gilthead seabream Sparus aurata

Sónia Rocha1,2, Graça Casal1,3, Luís Rangel1,4, Ricardo Severino1, Ricardo Castro1, Carlos Azevedo1,2,5, Maria João Santos1,4,*

1Laboratory of Pathology, Interdisciplinary Centre of Marine and Environmental Research (CIIMAR/UP), University of Porto, 4050-123 Porto, Portugal
2Laboratory of Cell Biology, Institute of Biomedical Sciences (ICBAS/UP), University of Porto, 4050-313 Porto, Portugal
3Department of Sciences, High Institute of Health Sciences—North (CESPU), 4585-116 Gandra, Portugal
4Department of Biology, Faculty of Sciences, University of Porto, 4069-007 Porto, Portugal
5Zoology Department, College of Sciences, King Saud University, 11451 Riyadh, Saudi Arabia
*Corresponding author. Email:

ABSTRACT: A new myxosporean, Zschokkella auratis sp. nov., infecting the gall bladder of the gilthead seabream Sparus aurata in a southern Portuguese fish farm, is described using microscopic and molecular procedures. Plasmodia and mature spores were observed floating free in the bile. Plasmodia, containing immature and mature spores, were characterized by the formation of branched glycostyles, apparently due to the release of segregated material contained within numerous cytoplasmic vesicles. Mature spores were ellipsoidal in sutural view and slightly semicircular in valvular view, with rounded ends, measuring 9.5 ± 0.3 SD (8.7–10.3) µm in length and 7.1 ± 0.4 (6.5–8.0) µm in width/thickness. The spore wall was composed of 2 symmetrical valves united along a slightly curved suture line, each displaying 10 to 11 elevated surface ridges. Two equal subspherical polar capsules, 3.7 ± 0.3 (3.0–4.1) µm long and 3.0 ± 0.2 (2.6–3.2) µm wide, were located separately at the spore’s extremities. Each polar capsule contained a polar filament forming 4 to 5 coils. The sporoplasm was binucleate and contained numerous sporoplasmosomes. Morphological data, tissue tropism, and molecular analysis of the small subunit rDNA gene identified this parasite as a new species of Zschokkella. Maximum parsimony, neighbor-joining, and maximum likelihood inferences clustered the parasite in a subclade containing other Zschokkella species parasitizing the gall bladder of brackish and marine fish hosts, located within the coelozoic clade of the major freshwater clade; this supports the existence of a marine subclade within the ‘freshwater’ clade, as well as the existence of a correlation between tissue tropism and myxosporean phylogeny.

KEY WORDS: Zschokkella auratis sp. nov. · Myxosporean · Parasite · Ultrastructure · SSU rDNA gene · Phylogeny · Sparus aurata · Fish farm · Portugal

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Cite this article as: Rocha S, Casal G, Rangel L, Severino R, Castro R, Azevedo C, Santos MJ (2013) Ultrastructural and phylogenetic description of Zschokkella auratis sp. nov. (Myxozoa), a parasite of the gilthead seabream Sparus aurata. Dis Aquat Org 107:19-30. https://doi.org/10.3354/dao02661

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