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The purple-spotted bigeye, Priacanthus tayenus, is a marine benthic fish native to the Indian and Pacific Oceans, including the Arabian Gulf in Saudi Arabia. This study identified a myxozoan parasite infecting wild P. tayenus from the Saudi Arabian Gulf. These parasites produced spherical to ovoid-shaped, white plasmodia enclosed within pseudocysts in the fish musculature. The annual infection rate was 5.1%, with the highest prevalence in summer (7.6%), followed by spring (6%), and autumn (2.5%), while no infections were observed in winter. The number of plasmodia per fish ranged from 100 to 150 (135.1 ± 16.2). Their dimensions were 4–4.7 mm (4.3 ± 0.3 mm) in length and 4.5–7 mm (6 ± 1.1 mm) in width. Milky-colored exudates within the plasmodia contained mature spores measuring 8–9 μm (8.6 ± 0.4 μm) x 6–7.5 μm (6.9 ± 0.5 μm). The polar capsules of the spores exhibited dimensions of 2–5 μm (3.5 ± 0.5 μm) x 2.5–4.5 μm (3 ± 0.45 μm). Both morphological and genetic analyses confirmed these plasmodia as a novel Kudoa species. Histopathological examination revealed atrophy in the surrounding muscles without an inflammatory response. This study documents the first occurrence of a novel Kudoa sp. in P. tayenus at the Jubail landing site in Saudi Arabia, emphasizing the need for further surveillance and investigations to elucidate its pathogenesis and implications for wild fish stocks. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the presence of Sarcotaces sp. in Epinephelus epilistictus (the dotted grouper) in Saudi Arabia. So, during our routine clinical examination of fish health conditions at Jubail province in the eastern region of Saudi Arabia (Arabian Gulf), nine grouper fish species were examined for Sarcotaces sp. (Copepoda: Phylichthyidae). Only the dotted grouper (Epinephelus epilistictus) harbored parasitic Sarcotaces spp. with an incidence of 9.06% of 1600 clinically examined fish samples. The collected Sarcotaces sp. was Sarcotaces arcticus (S. arcticus). The copepods were completely encapsulated cysts with a pyriform or pear-like shape, small to large, white-grayish, fluid-filled with thick black ink beneath the skin, or fully embedded in the muscular layer. The cysts present in the lateral aspect of trunk muscles, flank, caudal peduncle, near the anal opening, or pelvic and pectoral fin with an infestation rate (1–6 cysts) per fish. The cyst histopathology reveals the capsular layer of the cyst consisting of fibrous connective with pressure atrophy of the adjacent muscles associated with dilated blood vessels. The absence of infestation in other kinds of grouper fish species from the water of the Arabian Gulf in Jubail province may indicate parasitic host specificity and geographic locality distribution. [ABSTRACT FROM AUTHOR]