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Anemonefish oxygenate their anemone hosts at night
Joseph T. Szczebak, Raymond P. Henry, Fuad A. Al-Horani, Nanette E. Chadwick


Many stony coral-dwelling fishes exhibit adaptations to deal with hypoxia among the branches of their hosts; however, no information exists on the respiratory ecophysiology of obligate fish associates of non-coral organisms such as sea anemones and sponges. This study investigated metabolic and behavioral interactions between two-band anemonefish (Amphiprion bicinctus) and bulb-tentacle sea anemones (Entacmaea quadricolor) at night. We measured the net dark oxygen uptake (Embedded Image, μmol O2 h−1) of fish–anemone pairs when partners were separate from each other, together as a unit, and together as a unit but separated by a mesh screen that prevented physical contact. We also measured the effects of water current on sea anemone Embedded Image and quantified the nocturnal behaviors of fish in the absence and presence of host anemones in order to discern the impacts of anemone presence on fish behavior. Net Embedded Image of united pairs was significantly higher than that of both separated pairs and united pairs that were separated by a mesh screen. Anemone Embedded Image increased with flow rate from 0.5 to 2.0 cm s−1, after which Embedded Image remained constant up to a water flow rate of 8.0 cm s−1. Furthermore, the percentage time and bout frequency of flow-modulating behaviors by fish increased significantly when anemones were present. We conclude that physical contact between anemonefish and sea anemones elevates the Embedded Image of at least one of the partners at night, and anemonefish behavior at night appears to oxygenate sea anemone hosts and to augment the metabolism of both partners.


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