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HERMAPHRODITISM IN GREY MULLET (MUGIL CEPHALUS) ALONG THE BULGARIAN BLACK SEA COAST: POTENTIAL CONNECTIONS TO ECOLOGICAL FACTORS
Abstract
Hermaphroditism in the flathead grey mullet (Mugil cephalus), manifested as intersex conditions, is linked to various environmental factors and anthropogenic pressures. Key contributors include exposure to endocrine-disrupting compounds (EDCs), heavy metals, and pollutants that disrupt hormonal regulation, leading to sexual development abnormalities. Research indicates that Mugil cephalus is particularly sensitive to EDCs in coastal and brackish ecosystems. Our findings reveal that 19% of male individuals from the Varna-Beloslav Lakes and the brackish waters at the mouths of the Kamchia, Ropotamo, Karaagach and Veleka Rivers exhibited intersex gonads correlated with elevated levels of organochlorine contaminants in their tissues. Laboratory experiments have shown that exposure to 17пїЅ-estradiol (E2) and ethinylestradiol (EE2) during sexual differentiation can induce feminisation and intersex conditions. In addition to EDCs, heavy metals pose significant genotoxic risks. A study in the Varna-Beloslav Lakes demonstrated that mullets exposed to high concentrations of metals such as CuпїЅ?, ZnпїЅ?, and PbпїЅ? exhibited increased frequencies of micronuclei and nuclear anomalies, indicating DNA damage. Climate change further impacts migratory behaviour and reproductive biology, mainly through rising sea surface temperatures. Our study along the Bulgarian Black Sea coast identified warming waters as a significant factor contributing to the decline in Mugil cephalus catches between 2010 and 2024. The combined effects of pollution and climate change synergistically enhance toxicity and increase contaminant sensitivity, amplifying reproductive risks for Mugil cephalus populations along the Bulgarian Black Sea coast.
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