Clownfish in hypoxic anemones replenish host O2 at only localised scales

Abstract

The clownfish-anemone association exemplifies a symbiosis where both members benefit from nutrient exchange and protection from predators. Clownfish also perform aeration-like behaviour in their host anemones at night, but it is not yet known whether this is stimulated by the onset of hypoxia, and whether both members benefit from O2 replenishment. Oxygen at 3 distances above the sea anemone Entacmaea quadricolor (0.2, 1.2 and 2.2 cm) therefore was measured under 3 light levels (photon flux density = 0, 55 and 110 µmol m−2 s−1), with and without the anemonefish Amphiprion frenatus. Hypoxia (O2 < 50% air saturation) was recorded in the anemone, but only at 0.2 cm away from the anemone surface under dark conditions when A. frenatus was absent. This localised layer of hypoxia was eliminated by the presence of A. frenatus exhibiting aeration-like behaviour. Respirometry revealed that A. frenatus is extremely hypoxia tolerant (S crit = 14.3% at 25 °C), suggesting that aeration behaviour does not provide a major metabolic advantage to clownfish because they do not breathe water at 0.2 cm and are not metabolically constrained by O2 at distances ≥ 1.2 cm. That the aeration behaviour of A. frenatus facilitates only the metabolism of its O2-conforming host reveals a unique aspect of this symbiotic relationship.

Finding Nemo’s Genes: A chromosome‐scale reference assembly of the genome of the orange clownfishAmphiprion percula

“…Wild adults and juveniles live exclusively in association with a sea anemone, where they gain shelter from predators and benefit from food captured by the anemone (Fautin, ; Fautin & Allen, ; Mebs, ). In return, the sea anemone benefits by gaining protection from predators (Fautin & Allen, ; Holbrook & Schmitt, ), from supplemental nutrition from the clownfish's waste (Holbrook & Schmitt, ) and from increased gas exchange as a result of increased water flow provided by clownfish movement and activity (Herbert, Bröhl, Springer, & Kunzmann, ; Szczebak, Henry, Al‐Horani, & Chadwick, ). The orange clownfish associates with two species of anemone, Stichodactyla gigantea and Heteractis magnifica (Fautin & Allen, ).…”

A methodological evaluation of the determination of critical oxygen threshold in an estuarine teleost

“…While there remains debate in the scientific community regarding the best practices for reaching P crit , there is a growing perception that intermittent flow protocols are preferable (e.g. Snyder et al, 2016; Svendsen et al, 2016; Herbert et al, 2017; Wong et al, 2018). This perception has likely been buoyed, in part, by the fact that intermittent flow is undoubtedly the best method to determine SMR (Steffensen, 1989; Chabot et al, 2016).…”

A chromosome-scale genome assembly of the false clownfish, Amphiprion ocellaris

“…As for all anemonefishes, A. ocellaris is a protandrous hermaphrodite (i.e., male-to-female sex change) that lives in association with sea anemones [5–7]. It is a mutualistic relationship in which the host sea anemone provides food and shelter from predators [6,7], whilst the fish provides supplemental nutrition [8] and increased oxygen uptake by modulating water flow among the anemone’s tentacles [9,10]. The false clownfish is a generalist and can colonize up to four hosts: the magnificent sea anemone ( Heteractis magnifiea ), the leathery sea anemone ( Heteractis crispa ), the giant carpet anemone ( Stichodactyla gigantea ), and Mertens’ carpet sea anemone ( Stichodactyla.…”