Cephalopods Meet Neuroecology: The Role of Chemoreception in Octopus vulgaris Reproductive Behaviour

The aim of this chapter is to fill the gap regarding the potential of cephalopods to affect community structure and function in the sea, giving a neuroecological view of the reproductive behaviour of Octopus vulgaris. Cephalopods are known for their ability to learn, memorize and show sophisticated behaviours in the wild when enacting strategies of predation, defence and reproduction. Furthermore they change colour pattern and texture quickly due to the presence of chromatophores controlled directly by the nervous system. Their boneless bodies, inspired the creation of a soft-bodied robot. They sleep, show a “personality” and the ability to use tools in the wild. Octopuses, in particular, show adaptive behaviours implying the existence of a “consciousness” and appear to perceive the pain; properties that strongly contribute to shaping of their behaviour in the sea. This results in the inclusion of all the species of living cephalopods, in the EU Directive covering the “protection of Animals used for scientific purposes” (1st January, 2013). Attention to the capabilities of these “advanced invertebrates” has been developed, for more than 100 years through behavioural and neurophysiological investigations. The majority of these studies have been conducted on Loligo vulgaris, Sepia officinalis and Octopus vulgaris, which are considered to be good animal models by neuroethologists. The cephalopods live in all oceans of the world with the exception of the Black Sea, spreading from the surface waters down into the deep sea and occupying a wide range of ecological niches. Even though they are the smallest class of the phylum Mollusca, because of their wide distribution they play an important role in the community organization and function of the ecosystems that they inhabit. Much of the language that regulates life of the sea consists of chemical cues. These chemical signals determine feeding, habitat and mating choice. Some cephalopods show social behaviour exclusively during reproduction. The reproductive behaviour of Octopus vulgaris is under the control of a complex set of signal molecules such as sex steroids, neuropeptides and neurotransmitters that guide the behaviour from the level of individuals in evaluating mates, to stimulating or deterring copulation, to sperm-egg chemical signalling that promotes fertilization. These signals are intercepted by the olfactory organs and integrated in the olfactory lobes in the central nervous system. The olfactory organ plays a key role in the development of the switch in behaviour from growth to reproduction. In this context we propose a model in which the olfactory organ of Octopus vulgaris and the olfactory lobe could represent the on-off switch between food intake and reproduction.