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Review article: Review of the Pathological and Histological Effects of Dinoflagellate Infections in Ornamental Fish
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Ali Parchami *   , Hamid Reza Azizi Alavicheh |
| Shahrekord University |
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Abstract: (224 Views) |
| Dinoflagellate parasites are among the most important protozoan pathogens affecting ornamental fish in both freshwater and marine environments. This review summarizes the biological characteristics, pathological manifestations, histological alterations, and diagnostic features associated with infections caused by Amyloodinium ocellatum and Piscinoodinium pillulare. Amyloodinium ocellatum, the etiological agent of marine velvet disease, is a parasitic dinoflagellate with a direct life cycle and a worldwide distribution in tropical and temperate aquatic environments. Transmission occurs through direct exposure to infective dinospores present in the water. The gills are the primary target organ, although severe infections may also involve the skin, fins, and eyes. Histopathological changes commonly include excessive mucus production, gill congestion, epithelial hyperplasia, vacuolar degeneration, epithelial desquamation, fusion of secondary lamellae, and, in advanced cases, tissue necrosis. Piscinoodinium pillulare, the causative agent of freshwater velvet disease, exhibits morphological and developmental characteristics similar to those of A. ocellatum but primarily infects freshwater fish species. Diagnostic approaches commonly rely on microscopic examination and histopathological staining methods, including May–Grünwald–Giemsa and hematoxylin–eosin staining, while iodine staining may assist in detecting amyloid granules. This review highlights the pathological significance of dinoflagellate infections in ornamental fish and emphasizes the importance of accurate histopathological diagnosis for disease management in aquaculture systems. |
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| Keywords: Dinoflagellates, Amyloodinium ocellatum, Piscinoodinium pillulare, Ornamental fish, Histopathology, Velvet disease. |
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Full-Text [PDF 585 kb]
(57 Downloads)
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Type of Study: Applicable |
Subject:
Special
Received: 2026/02/19 | Accepted: 2026/03/30 | Published: 2026/05/30
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