We have found a new species of Autolytinae (Annelida, Syllidae), Proceraea janetae, feeding on the scleractinian coral Montastrea cavernosa in coral reefs surrounding the Grand Cayman Island (Cayman Islands, British West Indies). The new species has a characteristic combination of transversal brown markings on the segmental margins and diffuse white mid-dorsal transverse bars, together with a diffuse white mid-dorsal longitudinal band. Antennae are brown, tentacular cirri are pale, the first dorsal cirri are white with pale base; the second dorsal cirri are pale, and the remaining dorsal cirri are alternately long, bright yellow-orange with brownish tips and short, entirely brown. The trepan has 18 tricuspid teeth in one ring. There are 9 teeth with all cuspids equally long and 9 with a longer median cuspid, arranged in an alternating pattern. We describe and illustrate the feeding behaviour of the new species, which appears to be closer to parasitism rather than to specialized predation. Proceraea janetae sp. nov. is the second polychaete, and the first syllid, known to feed on scleractinian corals.

High predation by the corallivore gastropod Jenneria pustulata was observed in July 2011 in a high-latitude reef at Bahía de Los Ángeles in the northern Gulf of California. Porites panamensis corals were infested by 15 to 40 sea snails per colony (22 ± 7.25 ind 0.1 m–2 of Porites surface). Coral colonies were 20–30 cm tall and the average size of the sea snails were 1.7 cm (SD ± 0.238, N = 152). These data indicate a change in the daily pattern of movement and feeding of the gastropod in this reef. Despite high density of J. pustulata on the reef, no soft corals were observed as damaged by the sea snail.

Reef-building corals are fundamental to the most diverse marine ecosystems, and the coral–dinoflagellate (zooxanthellae) associations on fine scale remains largely unknown. Spatial variation in the diversity of symbiotic dinoflagellates of two scleractinian coral species was studied in an upwelling region near Qinlan Harbor in eastern Hainan Island, China. Results showed that stress-tolerant Symbiodinium trenchi in individual colonies of Galaxea fascicularis occurred more frequently in shallow back-reef than in deep fore-reef. The higher symbiont diversity was found in colonies of G. fascicularis in shallow and close to the harbour mouth whereas the coral Pocillipora damicornis always harboured Symbiodinium internal transcribed spacer 2 (ITS2) types C1c or C42a. Furthermore, both corals were found to simultaneously contain Symbiodinium ITS2 types belonging to two distinct phylogenetic clades (C and D). This indicates that the distribution of genetically distinct Symbiodinium may correlate with light regime and possibly temperature in some (but not all) colonies at particular locations, which we interpret as holobiont acclimation to the local environmental conditions. Therefore, we conclude that reef-building corals can adapt to the local environment by harbouring genetically distinct symbionts but depend on their respective symbiont transmission modes.