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FIGURE 1. Map of Réunion Island indicating surveyed sites where sea urchin mortalities were observed. Site locations are indicated by pins. Pin colors correspond to habitat type: Pink—outer slope; blue—fringing reef; orange—volcanic tidal pools. Map was created via Google Earth Pro.
FIGURE 2. Sea urchin mortality on Réunion Island. (a) A healthy Echinothrix diadema. (b) Lethargic behavior and initial tissue and spine loss. (c) Moribund individual with weakly moving spines and growing areas of exposed test. (d) Extensive spine loss and tissue necrosis. Apical side showing large areas of exposed test. (e) Bare E. diadema skeleton following mortality and complete tissue loss. (f) Massive stranding of dead sea urchins on Réunion Island's western beaches on August 14, 2023. (g) DaSc‐associated Philaster clade ciliate. (h) Cluster of DaSc‐associated Philaster clade isolated from E. diadema during the early stage of the disease, feeding on coelomic elements, showing vibratile cells from the coelom and red spherule cells. DaSc, Diadema antillarum scuticociliatosis. Photo credit: Jean‐Pascal Quod.
FIGURE 3. Phylogenetic reconstruction of moribund urchin associated ciliates in the Philasteridae. The tree was constructed using MEGAX (Kumar et al., 2018) based on a 313 nt region that was aligned by MUSCLE (Edgar, 2004). Bootstrap support values are based on 1000 iterations. Tree topology was based on Maximum Likelihood following the Tamura 3 parameter model with gamma distributed sites and the nearest neighbor interchange heuristic model. Red colored sequences indicate sequences generated in the present study that fall within the Diadema antillarum scuticociliatosis Philaster clade (Vilanova‐Cuevas et al., 2023). GenBank accession numbers are given after taxon names.
