Study of histopathology on Arbacia lixula (Arbaciidae: Arbacioida) and Paracentrotus lividus (Parachinidae: Camarodonta) with bald sea urchin disease symptoms in Gran Canaria Island, Spain

Introduction: Sea urchin diseases have been documented in several locations worldwide, with reported occurrences of bacterial, protozoan, fungal, and algal infections. Objective: This study aimed to investigate pathogen agents in populations of Arbacia lixula and Paracentrotus lividus along the coast of Gran Canaria Island (Central-East Atlantic, Spain). Methods: Sampling was conducted at San Cristobal beach, on the Northeast side of the island, where sea urchins were manually collected from depths of 1-3 m during June, July, and October 2022. Swab samples were taken from the external and internal areas of the lesions and cultured on various media plates. Results: Eight different pathogen agents, including bacteria and fungi, were identified, with Vibrio alginolyticus being the most frequently observed bacteria in all diseased sea urchin samples. Additionally, ciliated protozoans were found within the tests, potentially acting as opportunistic parasites. Conclusions: This research provides a unique perspective on bald sea urchin disease by identifying a significant number of associated pathogens, including Candida, previously unreported in diseased organisms. Furthermore, the study highlights the presence of an inflammatory response in tissues with bacterial colonies, offering crucial insights into understanding this sea urchin disease.