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ABSTRACT We observed a novel, nocturnal cleaning interaction between a cleaner shrimp (GenusUrocaridella) and the giant moray eel (Gymnothorax javanicus) on a lagoonal patch reef in Moorea, French Polynesia. Over the course of an 85‐min foraging bout (recorded on video by a snorkeler), we observed three separate, stereotyped cleaning interactions betweenG. javanicusand a cleaner shrimp in the genus Urocaridella (which surveys of Moorea biodiversity previously visually identified asUrocaridella antonbruunii). During these interactions, the shrimp would slowly crawl along one of the eel's flanks towards its head, enter its mouth, emerge on the other side of its head, then crawl back towards the reef along the eel's opposite flank, often causing it to jolt in response. On each of the visits, the moray spent roughly 9–12 min at the cleaning station and was observed being cleaned for a total of 62 s. Although this was a chance observation of only a few instances of cleaning, it may have several important implications for our understanding of the behavioral ecology of cleaning mutualisms, including (1) indicating potential temporal trade‐offs between being cleaned and foraging in eels, (2) suggesting a degree of temporal niche partitioning among sympatric cleaner species and (3) updating our understanding of cleaner‐client communication, given the nocturnal nature of our observations. 

Stony coral tissue loss disease (SCTLD) was first observed in St. Thomas, U.S. Virgin Islands (USVI) in January 2019. This disease affects at least 20 scleractinian coral species; however, it is not well understood how reef diversity affects its spread or its impacts on reef ecosystems. With a large number of susceptible species, SCTLD may not follow the diversity-disease hypothesis, which proposes that high species diversity is negatively correlated with disease prevalence. Instead, SCTLD may have a higher prevalence and a greater impact on reefs with higher coral diversity. To test this, in 2020 we resampled 54 sites around St. Thomas previously surveyed in 2017 or 2019 by the National Oceanic and Atmospheric Administration National Coral Reef Monitoring Program. These sites represented a variety of species diversity values [categorized into poor (<12 spp. rich.) and rich (≥12 spp. rich.)] in multiple disease zones (Endemic: disease present ≥ 9 months; Epidemic: disease present 2–6 months; Control and Emergent: disease present no disease/<2 months). We hypothesized that, contrary to the diversity-disease hypothesis, sites with high species diversity (as measured by species richness or Simpson’s index) would have higher disease prevalence within the epidemic zone, and that high species diversity sites would have a greater impact from disease within the endemic zone. Results indicated a significant positive relationship between disease prevalence and diversity in the epidemic zone, and a similar trend in the endemic zones. Additionally, a negative relationship was seen between pre-outbreak diversity and loss of diversity and coral cover within the endemic zone. This supports the hypothesis that higher diversity predicts greater disease impact and suggests that SCTLD does not follow the diversity-disease hypothesis. Within the epidemic zone, the species with the highest SCTLD prevalence were Dendrogyra cylindrus , Colpophyllia natans , and Meandrina meandrites , while in the endemic zone, Diploria labyrinthiformis , Pseudodiploria strigosa , Montastraea cavernosa , and Siderastrea siderea had the highest SCTLD prevalence. Understanding the relationship between species diversity and SCTLD will help managers predict the most vulnerable reefs, which should be prioritized within the USVI and greater Caribbean region.