Involvement of chemical perception in control of reproduction in Octopus vulgaris

Among invertebrates reproductive strategies are much more diversified than vertebrates. Recently we have found in Octopus vulgaris that olfactory sensory neurons (OSNs) express several peptides involved in reproduction and feed intake such as GnRH and NPY (Polese et al., 2015). We suggest at central level, a context-dependent modulation of olfactory epithelial activity by olfactory lobe making the octopus female more sensitive to a sex related stimulus rather than a food one during reproduction. In Octopus vulgaris mainly two lobes, subpedunculate lobe and olfactory lobe (supraoesophageal mass), and a neuroendocrine gland (the optic gland) are the neuroanatomical areas involved in the central control of reproduction. In those, several neuropeptides, NMDA receptors, an oestrogen receptor, oct-ER work in synergy to modulate optic gland activity, in turn involved in the production of a gonadotropin still unknown. The olfactory lobe plays a crucial role in mediating sexual behavior, functioning as an integrative centre in which converges chemosensory information intercepted by olfactory organ via the OSNs. At peripheral level the control of reproduction is mediated by fusiform ganglion that innervates the reproductive tracts in both male and female. Neuropeptides, sex steroid hormones, optic gland hormone and a recently discovered chemoattractant factor octo-SAP are the peripheral physiological players responsible of reproductive behavior. Despite the advanced state of knowledge about the mechanisms that regulate reproduction in Octopus vulgaris and cephalopods in general, many questions remain unanswered.