First Record of the Pathogenic Protist Labyrinthula sp. Infecting the Seagrass Enhalus acoroides (L.f.) Royle
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Abstract
Labyrinthula is a globally distributed pathogen known to cause wasting disease and large-scale die-offs in various seagrass species. However, infection in Enhalus acoroides has not been previously documented. In this study, the marine slime mold Labyrinthula sp., was isolated from a lesion leaf of Enhalus acoroides collected at Pa Khlok Beach, Phuket, Thailand in February 2024. Leaf sections with lesions or suspected affected areas were cut and placed on serum seawater agar for cultivation and examination. The isolate was subsequently inoculated onto axenic E. acoroides plantlets to assess pathogenicity. Within 24–48 hours of incubation, spindle-shaped cells of Labyrinthula sp. formed dense colonies embedded in ectoplasmic networks emerging from leaf edges. By the third week, brown lesions appeared on inoculated plantlets, expanding into band-like patterns by the fourth week. These symptoms confirm the ability of the isolated Labyrinthula sp. to induce lesions and contribute to wasting disease in E. acoroides. However, despite its pathogenic potential, there is not yet conclusive evidence linking this organism to the broader seagrass die-off observed in this region. This study presents the first report of Labyrinthula sp. infecting the seagrass, E. acoroides, and the first documented case of seagrass infection by Labyrinthula in Southeast Asia.
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