Sea anemones have developed various strategies for interspecific interaction with other organisms and their own ability to obtain food, due to their coevolutionary history, ranging from mutualistic (e.g. clownfish, crustaceans, etc.) and symbiotic associations (zooxanthellae or zoochlorellae) to depredation (e.g. sea slug). This study aims to record some observations on feeding habits and interspecific interactions of Actinostella flosculifera (Le Sueur, 1817) in the locality of Pedra da Sereia in Vila Velha, Espírito Santo, Brazil, and to describe the hunting strategy of the sea slug Spurilla braziliana MacFarland, 1909 and the escape strategy of A. flosculifera. We found that the habitat of A. flosculifera is characterized by shallow pools ~10 cm deep at low tides, and this functions as a trap for many organisms and some biowaste (e.g. bones or fish drifting in from nearby populations) that fall into the oral disc. This is the first report of S. braziliana predating on A. flosculifera. We also report interspecific relationships between A. flosculifera with four species of crustaceans: Omalacantha bicornuta (Latreille, 1825), Menippe cf. nodifrons Stimpson, 1859, Alpheus cf. angulosus McClure, 2002, and Alpheus cf. carlae Anker, 2012.

We report the first record of the sea anemone Bunodosoma californicum on the Pacific coast of Costa Rica, extending its southern distribution. Four specimens were collected from an artificial breakwater in Mata de Limón, Puntarenas. We present images of the live specimens and analyses of their cnidae composition.

The porcellanid crab, Neopetrolisthes spinatus Osawa & Fujita, 2001, is reported from Rutland Island, south Andaman Islands. The specimen represents the first record of the poorly known species from Indian waters and was collected from a large sea anemone Heteractis crispa (Hemprich & Ehrenberg in Ehrenberg, 1834).

Clownfish and their associated sea anemones are icons of tropical and subtropical coastal ecosystems, but bleaching and collecting for the aquarium trade has reduced their population densities in several Indo-Pacific locations. We surveyed four Entacmaea quadricolor populations and their associated clownfish Amphiprion clarkii in Hong Kong. These assemblages represented a combination of exposed and sheltered, flat bottomed and sloped conditions. Different from tropical areas, where E. quadricolor is usually found in sheltered shallow waters, the four populations in Hong Kong were distributed in 4–10 m depths, being densest on a 40 × 80 m slope of volcanic rocks (34.2–76.6% substrate cover and 48.7–102.1 ind  m−2) at an exposed site. This distribution pattern could be explained by the high turbidities associated with river discharge and sedimentation rates in local waters, which discourage the establishment of E. quadricolor populations in sheltered bays; shallow habitats might not be suitable for E. quadricolor in Hong Kong due to strong wave actions generated by typhoons. Amphiprion clarkii was present at low densities (0.07–0.26 fish m−2) across the sites. Our data provide a baseline for monitoring the changes of these conspicuous members of shallow water communities in Hong Kong.

We report the first record of the sea anemone Anthopleura nigrescens on the Pacific coast of Central America. Five specimens from Mata Limón (Costa Rica) were collected from rocks of a man-made breakwater at sub-tidal level. Images of live specimens are presented. A map with its worldwide distribution is included and we concluded that this actiniarian can be considered widely distributed in the Indo-Pacific.

Little is known about the cleaning behaviour of shrimps in comparison to that of cleaner fish, and only recently have cleaner shrimps been shown to remove parasites effectively from coral reef fish. Here we describe patterns of cleaning interactions between Pederson shrimp Ancylomenes pedersoni and fish clients in St Thomas, US Virgin Islands. Clients observed here were members of at least 16 fish families, including three previously unreported client families. Most cleans lasted <20 seconds; surgeonfish were cleaned most frequently, but lizardfish and groupers received the longest cleans. The shrimp formed social groups of varying sizes on individuals of the host sea anemone Bartholomea annulata, which served as the centres of their cleaning stations. The number and duration of cleans per station increased with the number of resident shrimp, however most anemones hosted small groups of fewer than four individuals, while larger groups of up to nine individuals were relatively rare. Some client fish chased away other fish and competitively excluded them from anemone stations. We conclude that these shrimp clean a wide diversity of clients, vary their clean duration with fish identity, and clean more when in large groups. In addition, clients in part control these patterns of interaction by interfering with access to these stations by other clients.

The occurrence of Nemanthus californicus on the Pacific coast of Costa Rica, the first record outside the type locality in Baja California, is reported. A re-description of its anatomy and notes on its biology are provided. Nemanthus californicus settled on the antipatharian Myriopathes panamensis with the pedal disc surrounding the branch in part or totally, and showed traces of asexual reproduction, an expected adaptation to colonize the black coral. Damage to colonies was significant, causing the death of the black coral. This type of relationship could be parasitism.