Figure 4

Sequence of a resident Ophthalmonoe pettiboneae attacking an intruder; see Supplementary material S6. The intruder is always in the same position on the inner tube wall, except after the attack. (A) Resident in its typical position, host starting to reverse its body. (B) Resident hidden behind host body, host fully reversed. (C) Resident closely approaching the intruder’s anterior end. (D) Resident starting the attack. (E) Resident curling with the intruder during the attack, host slowly retracting its body. (F) Resident still biting the intruder, both curling one over the other, host apparently giving them room to fight. (G) Resident near host’s anterior end, intruder around host’s mid-body. (H) Intruder closely approaching the resident’s posterior end. (I) No reaction from resident, but intruder suddenly reversing its body. (J) No reaction from resident, intruder again closely approaching the resident’s posterior end. (K) Resident slowly moving towards the inhalant siphon, intruder already oriented towards the exhalant siphon. (L) No reaction from resident, intruder almost already outside the tube. White arrows indicate resident’s head; red arrows indicate the intruder’s head. Time course indicated in seconds.