COHABITATION OF THREE SPECIES OF ANEMONEFISHES IN THE HOST SEA ANEMONE STICHODACTYLA MERTENSII (CNIDARIA, ACTINIARIA, STICHODACTYLIDAE) AND THE UNIQUE CASE OF SYMBIOSIS OF AMPHIPRION PERIDERION (POMACENTRIDAE, AMPHIPRIONINAE) WITH THIS SEA ANEMONE SPECIES IN NHA TRANG BAY (SOUTHERN CENTRAL VIETNAM)

Abstract

For the first time, three species of anemonefishes – Amphiprion clarkii, A. sandaracinos, and A. perideraion – have been observed cohabiting in the host sea anemone Stichodactyla mertensii. This is also the first description of the symbiosis between A. perideraion and this species of host sea anemone. A. clarkii was represented in the sea anemone by the pair and the subadult, A. sandaracinos was represented by the pair and two juveniles, and A. perideraion was represented only by the juvenile, estimated to be 2.5–3 months old. Observations of this symbiosis were conducted in the northwestern part of Hon Mun Island in Nha Trang Bay. It was shown that the juvenile of A. perideraion occupied the same niche in the host sea anemone as the pair of A. sandaracinos that had previously inhabited the sea anemone. Consequently, the juvenile of A. perideraion was subjected to constant attacks by the pair of A. sandaracinos. For this reason, juvenile of A. perideraion spent only approximately 70% of its time at the edge of the host sea anemone’s oral disc, and 30% of its time on the substrate near the sea anemone. The presence of juvenile of A. perideraion outside the sea anemone for a significant period of time significantly increased their vulnerability to predatory attacks and led to its death. It was shown that symbiosis between three anemonefish species and the sea anemone S. mertensii is possible, but unstable and short-lived. Currents in the area where the S. mertensii was found were analyzed, and the most likely direction of the current that carried the larva of A. perideraion to this sea anemone was determined.