A critical period of susceptibility to sound in the sensory cells of cephalopod hatchlings?

Abstract

The cephalopod statocyst and lateral line systems are sensory organs involved in orientation and balance. Lateral lines allow cephalopods to detect particle motion, and are used for locating preys or predators in low light conditions. Here, we show the first analysis of damaged sensory epithelia on three species of cephalopod hatchlings (Sepia officinalis, Loligo vulgaris and Illex coindetii) after sound exposure. Our results indicate lesions in the statocyst sensory epithelia, similarly to what was found in adult specimens. The novelty is that the severity of the lesions worsened faster in hatchling than in adult animals: i.e., a degree of lesion seen in hatchling immediately after noise exposure would develop within 48h in adults. This feature suggests a critical period of increased sensitivity to acoustic trauma in those species as it was described in developing mammalian cochlea and avian basilar papilla. The hair cells in lateral lines of S. officinalis followed the same pattern of damage occurrence while those of L. vulgaris and I. coindetii displayed a decreasing severity of the damage after 24H. These differences could be due to dissimilarities in sizes and live stages between the three species.