Morphological and molecular identification of Marine Fungi associated with Sea Cucumbers (Holothuroidea) on Rocky-Tidal Coasts of Bushehr Province (first report)

Marine ecosystems are home to a diverse range of microbial life, including fungi associated with marine invertebrates such as sea cucumbers (Holothuroidea). This study aimed to identify marine fungi morphologically and molecularly from three species of sea cucumbers: Holothuria leucospilota , Holothuria arenicola , and Holothuria parva , collected from the rocky-tidal coasts of Bushehr Province in the Persian Gulf. This represents the first report of sea cucumber-associated fungi in the Persian Gulf, addressing a critical gap in knowledge about fungal diversity in tropical marine ecosystems and their ecological and biotechnological significance. Specimens were collected from three sites: Heleylah (S1), Owli (S2), and Nakhl-e Taghi (S3). Fungi were isolated from both internal and external body parts, including the skin, intestine, mouth, body wall, cloaca, and coelomic fluid. Through morphological examination and sequencing of the ITS region, 14 fungal strains were identified, representing eight genera: Aspergillus , Byssochlamys , Cladosporium , Fusarium , Penicillium , Paecilomyces , Talaromyces , and Trichoderma . Talaromyces was the most prevalent genus, particularly dominating the skin of H. leucospilota , which exhibited the highest diversity with nine isolates. Fungal distribution varied across both host species and body parts, suggesting possible ecological specialization among fungi associated with different host species and tissues. Moreover, the identification of Penicillium and Aspergillus in this study highlights their ecological adaptability to the harsh conditions of the Persian Gulf and their potential for biotechnological applications. These fungi may function as epiphytes or potential pathogens, influencing the host microbiome and contributing to nutrient cycling. This research significantly enhances our understanding of marine fungal diversity and its ecological roles within the understudied Persian Gulf ecosystem, laying the groundwork for future bioprospecting endeavors. • Sea cucumbers were gathered via SCUBA diving in the Persian Gulf. • Fungi were isolated from different body parts of Holothuria species. • Morphological and molecular techniques were both used for the identification of the fungi. • Isolates were of the Ascomycota phylum and had various Morphological features. • The present study is the first fungal survey of echinoderms in the Persian Gulf.