Changes in Kӧlliker’s organs and latent damage following post-capture escape from predation by paralarvae of the East Asian common octopus, Octopus sinensis d'Orbigny, 1841

Post-capture defense is one of the antipredator tactics enabling prey animals to escape from predators after being captured. However, even with a successful escape, it is likely that the prey animal will suffer latent damage, reducing its post-escape survival and growth, due to physical and chemical contact accompanying the predatory attack. Here, following engulfing attacks by fish and subsequent rejection (escape because of post- capture defense), the effects on survival and growth of the paralarvae of Octopus sinensis were evaluated by assessing changes in the micromorphology of the skin surfaces of the paralarvae and the buccal mucosa of the predatory fish. Newly hatched paralarvae sustaining engulfing attacks by Girella punctata 0 − 41 times were reared for 5 d, and 86% of them survived and grew to a dry weight of 0.52 ± 0.15 mg. The number of attacks had no significant effect on paralarval survival and growth. Before experiencing an attack by a fish, the Kӧlliker’s organs (KOs) of the paralarvae were concealed beneath the epidermal layer of mucus, but in response to the fish attacks, they erupted, breaking through the layer of mucus. Among the erupted KOs, 41.7% bore marks of contact with the fish buccal mucosa. The mucus layer lining the fish oral cavity exfoliated from the buccal mucosa with a severity depending on the attack experience, presumably due to being irritated by the KOs. It is concluded that the octopus paralarvae withstood a number of consecutive fish predatory attacks without conspicuous damage, and that the KOs function as part of the post-capture defense repertoire of these paralarvae.