The “Bald Disease” of the Sea Urchin Paracentrotus lividus: Pathogenicity, Molecular Identification of the Causative Agent and Therapeutic Approach

Abstract

In recent decades, various species of Mediterranean sea urchins, including Paracentrotus lividus, have been subject to widespread seasonal episodes of mass mortality whose causative agents are still unclear. In particular, P. lividus is subject to late winter events of mortality, due to a disease manifested by a massive loss of spines and the presence of greenish amorphous material on the tests (i.e., the sea urchin skeleton consisting of spongeous calcite). Documented mortality events show a seasonal epidemic diffusion and might produce economic losses also in aquaculture facilities, besides the environmental constraints to its diffusion. We collected individuals showing conspicuous lesions on the body surface and reared them in recirculated aquaria. Samples of external mucous were collected along with coelomic liquids and cultured to isolate bacterial and fungal strains, further submitted to molecular identification through the amplification of prokaryotic 16S rDNA. In addition, pools of infected sea urchins were reared in recirculated tanks after short baths in a formulated therapeutic compound and their survival rates were compared to non-treated individuals for variable periods. Here, we aimed at a redescription of the etiopathogenetic nature of the parasites and tested the efficacy of a possible treatment, to be proposed for aquaculture purposes.

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

“…Even with all the infectious agents described above, it is important to highlight that these diseases seem to have a multifactorial origin, influenced by physiological and environmental factors (temperature variation, adverse factors, and plankton blooms), and life cycles in trophic networks (Federico et al, 2023). These adverse characteristics in the conditions agree with the season of our study, with the highest temperatures reported in Gran Canaria Island during 2022, and with the reproductive season of the sea urchin species in the area (Núñez-González et al, unpublished data).…”