Sponges as feeding resource for the white seabream Diplodus sargus (Linnaeus, 1758) from the Mediterranean Sea

Sponges play a significant role in many marine environments. In tropical regions, the relationship between Porifera and spongivorous organisms, including fish, has been extensively studied. In the Mediterranean Sea, the dominant predators of sponges are sea stars, sea urchins and nudibranches, while knowledge of fish feeding on sponges is limited to sporadic events. This study aimed to investigate sponges as part of the diet of the white seabream Diplodus sargus. The results revealed that sponges were abundantly present in seabream stomachs, reaching up to 79.7% of the total biomass ingested by a single individual. Five different species were found in fish stomachs. The presence and organization of the spicular component seemed to affect the biting strategy of fish. Sponges with a prevalent organic component, such as Chondrosia reniformis Nardo, 1847, and Chondrilla nucula Schmidt, 1862, were ingested as fragments, while specimens of the Tethya citrina Sarà & Melone, 1965, characterized by a globular body, were engulfed entirely. Data from this study represent the first effort to investigate the trophic relationship between fish and Porifera in the Mediterranean Sea.