Immune mechanisms of sea cucumbers (Holothuroidea; Echinodermata) under environmental pressure: an integrative approach

Since Élie Metchnikoff’s Nobel Prize–winning discovery of phagocytosis in sea star larvae, echinoderms have become key models for studying immune mechanisms in invertebrates. Among them, sea cucumbers (holothuroids) remain relatively understudied, particularly regarding the role of their immune cells, the coelomocytes. These animals are also susceptible to Skin Ulceration Syndrome (SUS), a disease that threatens the sustainable aquaculture development of sea cucumbers, which are already under threat in their natural environment due to overfishing for consumption in Asian markets.
This thesis investigates the immune mechanisms of sea cucumbers, with the dual aim of characterising the molecular and cellular actors of their complex immune system and understanding its responses to disease under environmental stress. The research focuses on two species: the European temperate Holothuria forskali and the Indo-Pacific tropical Holothuria scabra. A broad set of cutting-edge approaches—including transcriptomics, single-cell transcriptomics, metabonomics, and spectral flow cytometry—was applied to explore these questions.
The findings provide a molecular framework for redefining coelomocyte diversity and shed light on how environmental changes may favour disease emergence. These results have broad implications, not only for comparative immunology but also for the conservation and sustainable management of sea cucumber populations in a rapidly changing world.