Many pontoniine shrimps are known as symbionts of anthozoans, such as scleractinian corals and sea anemones (Fransen 1989). So far, six shrimp species have been recorded from the solitary, free-living mushroom coral Heliofungia actiniformis (Quoy and Gaimard 1833), a coral resembling a sea anemone with long tentacles (De Grave 1998).

During the Semporna Marine Ecological Expedition (SMEE2010), eastern Sabah (Malaysia), six shrimp species were observed in association with H. actiniformis, including five Pontoniinae: Ancylomenes sarasvati (Okuno, 2002), A. venustus (Bruce, 1990), Cuapetes kororensis (Bruce, 1969), C. tenuipes (Borradaile, 1898), Hamopontonia corallicola (Bruce, 1970), and the hippolytid Thor amboinensis (De Man, 1888). This is a first host record for A. sarasvati. Periclimenes watamuae (Bruce, 1976), recorded by De Grave (1998), was not found in the present survey.

One coral was inhabited by A. sarasvati individuals on and between its tentacles and a pair of C. kororensis deep in between the tentacles. Another coral was occupied by three shrimp species, i.e., individuals of A. venustus on and between the tentacles (Fig. 1a), several T. amboinensis roaming on an adjacent piece of rock, the sandy substrate, and the polyp (Fig. 1b), and a C. tenuipes underneath the coral (Fig. 1c). Another H. actiniformis host was observed with a C. tenuipes in between the tentacles and one more host with a C. tenuipes underneath a small rock in close proximity.

Fig. 1
figure 1

A coral of Heliofungia actiniformis at Bumbun I., eastern Sabah, hosting shrimps: a Ancylomenes venustus, b Thor amboinensis and c Cuapetes tenuipes. Scale bars: 1 cm

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This is the first record of three shrimp species in simultaneous symbiosis with a single mushroom coral host. In previous studies, individuals of just two species were found on a single individual of H. actiniformis (De Grave 1998). Large sea anemones have also been reported with three symbiotic shrimp species, including T. amboinensis (Guo et al. 1996). By occupying different parts of the host or by showing dissimilar behaviour (hiding or moving), multiple shrimp species can co-occur on the same host coral, especially if it offers sufficient hiding places.