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date: 14 December 2017

Cephalopod Olfaction

Summary and Keywords

Within the Phylum Mollusca, cephalopods encompass a small and complex group of exclusively marine animals that live in all the oceans of the world with the exception of the Black and Caspian seas. They are distributed from shallow waters down into the deep sea, occupying a wide range of ecological niches. They are dominant predators and themselves prey with high visual capability and well-developed vestibular, auditory, and tactile systems. Nevertheless, their perceptions are chemically facilitated, so that water-soluble and volatile odorants are the key mediators of many physiological and behavioral events.

For cephalopods as well as the other aquatic animals, chemical cues convey a remarkable amount of information critical to social interaction, habitat selection, defense, prey localization, courtship and mating, affecting not only individual behavior and population-level processes, but also community organization and ecosystem function. Cephalopods possess chemosensory systems that have anatomical similarities to the olfactory systems of land-based animals, but the molecules perceived from distance are different because their water solubility is of importance. Many insoluble molecules that are detected from distance on land must, in an aquatic system, be perceived by direct contact with the odour source. Most of the studies regarding olfaction in cephalopods have been performed considering only waterborne molecules detected by the “olfactory organs.” However cephalopods are also equipped with “gustatory systems” consisting of receptors distributed on the arm suckers in octopods, buccal lips in decapods, and tentacles in nautiluses.

To date, what is known about the olfactory organ in cephalopods comes from studies on nautiloids and coleoids (decapods and octopods). In the nautiloid’s olfactory system, there is a pair of rhinophores located below each eye and open to the environment with a tiny pore, whereas in coleoids a small pit of ciliated cells is present on either side of the head below the eyes close to the mantle edge.

Keywords: cephalopods, olfaction, chemoreception, olfactory organs, olfactory receptors, taste and smell

Introduction

Cephalopods are a class of mollusks that includes exclusively marine animals occupying a wide range of ecological niches, from the surface waters to the deep sea. They populate all the oceans and seas of the world with the exception of the Black and Caspian seas.

The most common cephalopods are squid, cuttlefish, octopus, and nautilus. In relation to their numbers and distribution, recent work based on fishery data revealed that cephalopod abundance has recently increased, affecting the distribution mainly of benthopelagic and pelagic forms when compared with demersal species (Doubleday et al., 2016). This increasing abundance has been related to ocean warming, which seems to accelerate their already short life cycle (Pecl & Jackson, 2008; Rodhouse et al., 2014). Given these postulated environmental changes, the sensory capabilities of cephalopods provide them with excellent tools to face their changing external milieu.

The external world of cephalopods is perceived via well-developed sense organs, considered the most sophisticated of all those of invertebrates (Packard, 1972; Messenger, 1977; Young, 1977, 1989; Budelmann, 1995, 1996; Anderson et al., 2010). With the exception of Nautilus, they are highly visual animals able to see under a wide range of light conditions (Hanlon & Messenger, 1996; Grable et al., 2002; Yoshida et al., 2015). Cephalopods have remarkable abilities to camouflage themselves on diverse substrates using visual cues alone (Zylinski et al., 2009; Zylinski & Johnsen, 2011) and recently it has been described the mechanism by which cephalopods can achieve color discrimination with only a single photoreceptor (Stubs & Stubs, 2016;). Furthermore, they are equipped with a lateral line (analogous to fishes), low-frequency sensitivity to sound waves, and the ability to detect predators at long distance (Hanlon & Messenger, 1996). Moreover, they have a highly developed vestibular system for directional sensitivity (Budelmann & Williamson, 1994; Williamson & Chrachri, 2007).

Finally, the chemical world of cephalopods also provides an important source of sensory inputs, especially for those that inhabit at light-limited conditions (Nilsson et al., 2012). Chemical cues could work in combination with visual signals, or alone, to inform cephalopods of ecological changes. In cephalopods, the known chemical sensory epithelia are buccal lips and mouth (Emery, 1975), isolated sensory neurons all over the body surface (Baratte & Bonnaud, 2009; Buresi et al., 2014), arm suckers (Graziadei, 1964; Wells et al., 1965; Graziadei & Gagne, 1976), and olfactory organs (von Kölliker, 1844; Von Zernoff, 1869; Watkinson, 1908). In effect, these sensory neurons appear to act as a sophisticated organ (Polese et al., 2016) that plays a crucial role in mate choice (Gilly & Lucero, 1992; Lucero & Gilly, 1995; Lucero et al., 1992, 2000; Piper & Lucero, 1999; Zatynly et al., 2000; Mobley et al., 2007; Cummins et al., 2011; Di Cosmo & Polese, 2014; Polese et al., 2015), predation (Boal et al., 2000), and food odor detection (Boyle, 1983; Basil et al., 2000; Ruth et al., 2002; Anraku et al., 2005).

Cephalopods are able to detect chemical cues through either contact or distant chemoreception (Boyle, 1983, 1986; Chase & Wells, 1986; Lee, 1992; Boal & Golden, 1999; Alves et al., 2007). The behavioral evidence for distant chemoreception shows that the addition of fish juice to the water causes active movements in octopus (Wells, 1963) and cuttlefish (Messenger, 1977). In this context, cephalopods release the ink that they use as a direct deterrent of predators and as an alarm cue for conspecifics (Palumbo et al., 1999; Di Cosmo, 2003, Di Cosmo et al., 2006; Derby, 2014). Boal (1997) argued that female mating choice in cuttlefish was more likely to be based on olfactory cues than on visual cues. Adding dilute extracts of crabs to the water supply increased the ventilation rate of octopus (Boyle, 1983); typical signs of alarm are shown by octopus when exposed to seawater in which a moray eel had been living (Mac Ginitie & Mac Ginitie, 1968). Furthermore, the ability to detect the sex of conspecifics at a distance, in octopuses, could facilitate reproduction as well as problem-solving ability (Boal, 2006; Anderson et al., 2010). Nevertheless, a blinded octopus will move toward a scent that it perceives as a food source (Chase & Wells, 1986).

More recently, Walderon et al. (2011) demonstrated that octopuses respond to chemical signals from conspecifics and detect a wide range of odors as food or nonfood (seaweed). However, as most coleoids are nocturnal or live at depths where little light is present, the ability to track prey, partner, and predator by scent is crucial to their success (Joll, 1977; Budelmann, 1996). This strongly suggests that the coleoid cephalopods, octopods, cuttlefishes, and squids use distance chemoreception, and the ability to integrate chemical signals with the stimuli perceived by their other sense organs allows them to shape their sophisticated behavior in the sea.

Cephalopod Olfaction Research Through the Years

The first description of the olfactory organs in cephalopods was made by Albert von Kölliker in (1844). He was attracted by a pair of dimples found on each side of the head of both squid and octopus. Initially, these structures were thought to be acoustic organs and only later was their chemoreceptive function, similar to the gastropod osphradium, suggested (Hancock, 1852; Chéron, 1866). Von Zernoff (1869) and Watkinson (1908) provided a detailed description of the olfactory organs in several cephalopods, describing the presence of large cells with a big vacuole. Watkinson (1908) compared the morphology of olfactory organs in 23 species of coleoids, suggesting their analogies with nautiloid rhinophores (Barber & Wright, 1969). The morphology of the organs was described as a flattened pad of cells in Sepia, an elongate papilla in Chiroteuthis, and a pit of sensory cells in Octopus.

In 1974, Woodhams and Messenger provided a partial ultrastructural description of the olfactory sensory neurons (OSNs) in O. vulgaris. At about the same time, Emery (1975, 1976) worked on the histology and ultrastructure of the olfactory organ of the squid, Lolliguncula brevis, and of the octopod, Octopus jubini. He provided a detailed description of different types of OSNs in this species and gave an exhaustive comparative analysis of the OSNs previously described in several species of decapods and octopods (Von Zernoff, 1869; Watkinson, 1908). At the end of the 20th century, Wildenburg (1997) described the structure and histology of the “so-called olfactory organ” in the benthic posthatching stage of Eledone moschata and the planktonic paralarva of Octopus vulgaris. He concluded that at the posthatching stage, the organ of the benthic species, E. moschata, is the more developed of the two.

In the 1990s, however, scientific interest in cephalopod olfaction shifted from morphological to physiological approaches. The group that significantly contributed to the physiological aspect of olfaction in cephalopods was led by Mary Lucero and provided many experimental findings demonstrating the chemosensory capabilities of squid OSNs using electrophysiological techniques (Lucero et al., 1992, Lucero & Gilly, 1995; Piper & Lucero, 1999; Mobley et al., 2007, 2008a, 2008b). Based on the morphological typology of OSNs (Emery, 1975), Lucero’s group established the odorant responsiveness of all OSN types and suggested the involvement of the adenylate cyclase pathway in squid olfactory transduction (Mobley et al., 2007, 2008a, 2008b).

Cephalopod OlfactionClick to view larger

Figure 1. Octopus chemical senses from whole animal to organ to cells in the organ. A—whole animal in which are visible the olfactory organ and suckers; B—adult Octopus vulgaris CNS diagram showing a dorsal view of the lobes involved in chemoreception (msf: median superior frontal; mif: median inferior frontal; ol: olfactory lobe; og: optic gland; ped: peduncle lobe; optl: optic lobe; ps: posterior suboesophageal mass; es: esophagus); C—3D reconstruction of the octopus olfactory organ and the different types of OSNs; D—diagram of segment of the arm of Octopus with a sucker and its chemical sensory cell.

Behavioral studies, which started almost contemporaneously with physiological studies, focused mainly on decapods. These studies demonstrated the role played by olfaction in many aspects of the chemosensory ecology of cephalopods (Boyle, 1983, 1986; Chase & Wells, 1986; Lee, 1992; Lucero & Gilly, 1995), such as mate choice, prey detection (Budelmann et al., 1997; Boal & Golden, 1999; Hanlon & Shashar, 2003), and conspecific odor perception (Walderon et al., 2011; Wood et al., 2008). More recently, Polese et al. (2016) described the detailed morphology of young male and female Octopus vulgaris olfactory epithelium. Using a combination of classical morphology and 3D reconstruction techniques, they proposed a new classification for O. vulgaris olfactory sensory neurons (Figure 1A, B, C). Using specific markers such as olfactory marker protein and proliferating cell nuclear antigen, they identified and differentially localized both mature olfactory sensory neurons and olfactory sensory neurons involved in epithelial turnover. This suggests that the O. vulgaris olfactory organ is extremely plastic, capable of changing its shape, and that proliferation of cells continues in older specimens. Furthermore, an integrative view of the role of chemical perception in the life of Octopus vulgaris, at individual, population and ecosystem levels, has been proposed (Di Cosmo & Polese, 2014; Polese et al., 2015, 2016)

Behavioral Evidence for Olfaction in Cephalopods

Spatial orientation in the feeding and reproductive behavior of cephalopods is guided by chemical cues. In nautiloids, the olfactory organ is represented by a pair of rhinophores (Young, 1965; Barber & Wright, 1969; Barber, 1987). These enable animals to follow an “odor” trail to its source in three dimensions. However, if the rhinophores are blocked, either uni- or bilaterally, the 90 thin tentacles can still detect odor, though without providing any spatial information (Basil et al., 2000, 2005).

In tanks, cuttlefishes previously exposed to crab odor perform better on their first attacks on crabs than cuttlefish that were not previously exposed (Boal et al., 2000). This finding suggests that the odors enhance food arousal and improve attention to the odor of the prey of cephalopods, which can then optimize the predatory attack.

Wells (1963) proposed that O. vulgaris can distinguish between objects based on their chemical differences alone. He described the animal’s ability to perceive chemicals using arm suckers as “taste by touch.” He previously proved that the responses of blinded animals to sardine blood were quite unaltered by removal of the olfactory organs (Wells & Wells, 1956). It seems that the O. vulgaris gustatory system consists of receptors distributed on the suckers, where the aquatic equivalent to taste takes place (Wells, 1963; Graziadei & Gagne, 1973; Anraku et al., 2005; Grasso & Basil, 2009) (Figure 1D).

Chemical sensing also plays an important role in cephalopod reproduction. For example, Nautilus pompilius females extend their tentacles fully when tracking male odors (Basil et al., 2002), while sexually mature males are attracted to females by excretions of the rectum (Westermann & Beurlein, 2005). Cuttlefish females choose their mates based on chemical cues (Boal, 1996, 1997), while chemical cues from squid egg capsules stimulate aggressive behavior related to competition for mates in male squids (King et al., 2003). These data demonstrate the importance of chemical perception in cephalopod reproductive behavior. In 2011, Walderon et al. demonstrated the role of olfaction in distance chemoreception of conspecifics in Octopus bimaculoides.

Integrative View of Chemical Perception in Cephalopods

All the sense organs contribute to animal life, but the relative importance of each sense was established during evolution. The apparent difference in the importance of one sense over another is strictly related to the ecological niches that the animals occupy. Cephalopods are described as animals that rely on their visual sense for most of their activities (Hanlon & Messenger, 1996). This prevailing view, together with sophisticated behavior exhibited by cephalopods, almost completely drove the attention of researchers to give chemical perception a secondary role. But even complex and sophisticated animals like cephalopods that occupy many ecological niches of the sea, including the deep sea with low light conditions, must integrate their sensory information appropriately to achieve evolutionary fitness.

Cephalopod OlfactionClick to view larger

Figure 2. Control of reproductive behavior based on chemical cues. The olfactory lobe acts as a switch between growth and reproduction. In addition, the olfactory lobe modulates the olfactory organ to be more sensitive to food or sex odors via the molecular players identified: (in red) FMRFamide, NPY, and Galanin inhibit reproduction and stimulate food intake; (in green) GnRH, APGWamide, ER (estrogen receptor), and NMDA stimulate reproduction inhibiting sensitiveness to food odors.

The integration of multimodal sensory inputs may occur at central and/or peripheral levels, at the output neurons converging to final behavior, or at any intermediate point along the processing path (Di Cosmo & Polese, 2016). It is clear that the localization of the neuronal mechanisms underlying multimodal processing is not an easy task. Recent research (Di Cosmo & Polese, 2014; Polese et al., 2015, 2016) examining the central control, anatomical pathways, and molecules involved in chemical perception via the olfactory organs found that they are often shared with those of other sensory modalities. In fact, the olfactory lobe, which receives nerve fibers coming from the olfactory organ, appears to be at the crossroads of different sensory pathways. This lobe, situated on the optic tract, close to optic gland, is organized in three interconnected lobules (Figure 1B). The olfactory lobe also receives fibers from the dorsal, basal, and optic lobes and sends fibers to the basal and subpedunculate lobes (Messenger, 1967). Based on these neuroanatomical connections, it constitutes a center of convergence and interception of fibers coming from lobes involved in the control of vision, motor programs, and reproduction (Young, 1971; Wells, 1978; Hanlon & Messenger, 1996; Di Cosmo & Di Cristo, 1998; De Lisa et al., 2012a, 2012b; Di Cosmo & Polese, 2013, 2014). The integrative function played by the olfactory lobe has only recently been highlighted by assigning a crucial role to chemical perception in the physiological and behavioral control of cephalopods (Di Cosmo & Polese, 2016; Polese et al., 2015, 2016) (Figure 2). Several experimental findings on chemical perception were presented in the past, but they must now be read in light of this new integrative perspective.

Chemical Cues and How They Are Perceived by Cephalopods

Traditionally, the olfactory system in any animal is the primary sensory system that responds to chemical stimuli emanating from a distant source. The other chemosensory sense is gustation or taste, which generally requires direct contact with the source for detection.

Cephalopods possess sensory systems that have anatomical similarities to the olfactory systems of land-based animals, but the molecules perceived from a distance source are different because their water solubility is of importance.

Consequentially, in the aquatic environment, have been considered ecologically relevant odorants water soluble compounds such as salts, sugars, amino acids, amines, peptides, proteins, and functionalized hydrocarbons.

To perceive this kind of molecule, on the one hand, the relaxed and erect postures of the octopus olfactory organ result in an intrinsic capability of movement that allows the animal to orient itself to detect the spatial gradient of these chemical cues, which help in navigation and trigger spatial memories (Huffard, 2013; Polese et al., 2016).

On the other hand, many insoluble molecules that are detected from distance on land, generally compounds with a molecular weight (MW) smaller than ∼300 Da (Mollo et al., 2017; Mori et al., 2006; Touhara & Vosshall, 2009), must be perceived by touch in aquatic systems if they are not carried by micelles or rafts, but are just held or laid on a substrate. For example, compounds known to contribute to the smell of terrestrial plants have been isolated in marine invertebrates that use them as defensive chemical weapons (Giordano et al., 2017; Mollo et al., 2014), they could be “smelled” by an octopus or any other aquatic animals just when they are touched.

It has been demonstrated that aquatic animals, including crustaceans and fish, have “gustatory systems” (e.g., leg detectors on lobsters and blue crabs, and barbels on catfish) that can detect chemicals dissolved in water without the requirement of physical contact with an object other than the chemicals themselves. These gustatory systems can respond to very low doses of those chemicals and evoke behaviors (Caprio & Derby, 2008; Schmidt & Mellon, 2011). Although it has been shown that both crustacean and fish are able to detect hydrophobic compounds by a tactile form of chemoreception (Giordano et al., 2017); in particular, they show that little shrimp (Palemon elegans) and also fish (Danio rerio) use their chemosensory mouthparts to perceive typical odiferous compounds usually smelled by humans. In the same way, other benthic animals, such as octopus, could follow, or avoid, chemical trails adherent to the substrate by recognizing gradients of concentration.

The debate about the terms taste and olfaction in relation to the various chemosensory systems of marine and aquatic species requires further elaboration, but it is important to avoid making any assumption based solely on organ topology (Mollo et al., 2014, 2017). The traditional view of the chemical senses based on their spatial range is being supplanted by a new vision based on the natural products that are the actual mediators of the chemosensory perceptions.

The majority of the studies regarding the olfaction of cephalopods have considered prevalently waterborne molecules that are detected by the “olfactory organs.” However, cephalopods use “gustatory systems” located on the arm suckers in octopods, the buccal lips in decapods, and the tentacles in nautiloids, which are able to detect molecules by contact. In light of the fact that the majority of volatile odorant molecules are insoluble or have a very low solubility in water, octopuses, as all the other aquatic animals, exhibit a peculiar performance that can be provocatively described as “smell by touch.” This would be supported by the demonstration of the presence of olfactory receptors on their “gustatory systems.”

However, taste and olfaction are part of a multimodal system of information transfer. The synchronous use and integration of different signals using different channels have the advantage of improving recognition, discrimination, and memory of inputs by the environment.

References

Alves, C., Chichery, R., Boal, J. G., & Dickel, L. (2007). Orientation in the cuttlefish Sepia officinalis: Response versus place learning. Animal Cognition, 10, 29–36.Find this resource:

Anderson, R. C., Mather, J. A., & Wood, J. B. (2010). Octopus: The ocean’s intelligent invertebrate. London: Timber.Find this resource:

Anraku, K., Archdale, M. V., Hatanaka, K., & Marui, T. (2005). Chemical stimuli and feeding behavior in octopus, Octopus vulgaris. Phuket Marine Biological Center Bulletin, 66, 221–227.Find this resource:

Baratte, S., & Bonnaud, L. (2009). Evidence of early nervous differentiation and early catecholaminergic sensory system during Sepia officinalis embryogenesis. Journal of Comparative Neurology, 517, 539–549.Find this resource:

Barber, V. C. (1987). The sense organs of Nautilus. In W. B. Saunders and N. H. Landman (Eds.), Nautilus: The biology and paleobiology of a living fossil (pp. 223–230). New York: Plenum Press.Find this resource:

Barber, V. C., & Wright, D. E. (1969) The fine structure of the sense organs of the cephalopod mollusc Nautilus. Zeitschriftfur Zeilforschung und Mikroskopische Anatomie, 102, 293–312.Find this resource:

Basil, J. A., Bahctinova, I., Kuroiwa, K., Lee, N., Mims, D., Preis, M., & Soucier, C. (2005). The function of the rhinophore and the tentacles of Nautilus pompilius L. (Cephalopoda, Nautiloidea) in orientation to odor. Marine and Freshwater Behavior and Physiology, 38, 209–221.Find this resource:

Basil, J. A., Hanlon, R. T., Sheikh, S. I., & Atema, J. (2000). Three-dimensional odor tracking by Nautilus pompilius. Journal of Experimental Biology, 203, 1409–1414.Find this resource:

Basil, J. A., Lazenby, G. B., Nakanuku, L., & Hanlon, R. T. (2002). Female nautilus are attracted to male conspecifics odor. Bulletin of Marine Science, 70, 217–225.Find this resource:

Boal, J. G. (1996). A review of simultaneous visual discrimination as a method of training octopuses. Biology Review, 71, 157–190.Find this resource:

Boal, J. G. 1997. Female choice of males in cuttlefish (Mollusca: Cephalopoda). Behavior, 143, 307–317.Find this resource:

Boal, J. G. (2006). Social recognition: a top down view of cephalopod behaviour. Vie Milieu, 56, 69–79.Find this resource:

Boal, J. G., & Golden, D. K. (1999). Distance chemoreception in the common cuttlefish, Sepia officinalis (Mollusca, Cephalopoda). Journal of Experimental Marine Biology and Ecology, 235, 307–317.Find this resource:

Boal, J. G., Wittenberg, K. M., & Hanlon, R. T. (2000). Observational learning does not explain improvement in predation tactics by cuttlefish (Mollusca: Cephalopoda). Behavioural Processes, 52, 141–153.Find this resource:

Boyle, P. R. (1983). Ventilation rate and arousal in the octopus. Journal of Experimental Marine Biology and Ecology, 69, 129–136.Find this resource:

Boyle, P. R. (1986). Neural control of cephalopod behavior. In A. O. D. Willows (Ed.), The Mollusca (pp. 1–99). Orlando, FL: Academic Press.Find this resource:

Budelmann, B. U. (1995). The cephalopods nervous system: What evolution has made of the molluscan design. In O. Breidbach and W. Kutsuch (Eds.), The nervous system of invertebrates: An evolutionary and comparative approach (pp. 115–138). Basel: Birkhäuser Verlag.Find this resource:

Budelmann, B. U. (1996). Active marine predators: The sensory world of cephalopods. Marine and Freshwater Behaviour and Physiology, 27, 59–75.Find this resource:

Budelmann, B. U., & Williamson, R. (1994). Directional sensitivity of hair cell afferents in the Octopus statocyst. Journal of Exprimental Biology, 187, 245–259.Find this resource:

Budelmann, B. U., Schipp, R., & von Boletzky, S. (1997). Cephalopoda. In F. W. Harrison and A. Kohn (Eds.), Microscopic anatomy of invertebrates (Vol. 6A, Mollusca; pp. 119–414). New York: Wiley-Liss.Find this resource:

Buresi, A., Croll, R. P., Tiozzo, S., Bonnaud, L., & Barratte, S. (2014). Emergence of sensory structures in the developing epidermis in Sepia officinalis and other coleoid cephalopods. Journal of Comparative Neurology, 522, 3004–3019.Find this resource:

Buresi, A., Andouche, A., Navet, S., Bassaglia, Y., Bonnaud-Ponticelli, L., & Baratte, S. (2016). Nervous system development in cephalopods: How egg yolk-richness modifies the topology of the mediolateral patterning system. Developmental Biology, 415, 143–156.Find this resource:

Caprio, J., & Derby, C. D. (2008). Aquatic animal models in the study of chemoreception. In A. I. Basbaum, A. Maneko, G. M. Shepherd, & G. Westheimer (Eds.), The senses A comprehensive reference (Vol. 4; pp. 97–134). San Diego: Academic Press. In: Firestein, S., Beauchamp, G.K. (Eds.), Olfaction and Taste,Find this resource:

Chase, R., & Wells, M. J. (1986). Chemotactic behaviour in Octopus. Journal of Comparative Physiology A, 158, 375–381.Find this resource:

Chéron, J. (1866). Recherches pour servir h l’histoire du système nerveux des Céphalopodes dibranchiaux. Annals of Science (Ser. 5, Zool.), 5, 5–122.Find this resource:

Cummins, S. F., Boal, J. G., Buresch, K. C., Kuanpradit, C., Sobhon, P., Holm, . . . Hanlon, R. T. (2011). Extreme aggression in male squid induced by a β‎-MSP-like pheromone. Current Biology, 21, 322–327.Find this resource:

Darmaillacq, A. S., Chichery, R., & Dickel, L. (2006). Food imprinting, new evidence from the cuttlefish Sepia officinalis. Biology Letters, 2, 345–347.Find this resource:

De Lisa, E., De Maio, A., Moroz, L. L., Moccia, F., Mennella, M. R., & Di Cosmo, A. (2012a). Characterization of novel cytoplasmic PARP in the brain of Octopus vulgaris. Biological Bulletin, 222, 176–181.Find this resource:

De Lisa, E., Paolucci, M., & Di Cosmo, A. (2012b). Conservative nature of oestradiol signalling pathways in the brain lobes of Octopus vulgaris involved in reproduction, learning and motor coordination. Journal of Neuroendocrinology, 24, 275–284.Find this resource:

Derby, C. D. (2014). Cephalopod ink: Production, chemistry, functions and applications. Marine Drugs, 12, 2700–2730.Find this resource:

Di Cosmo, A. (2003). A new model to study the role and biochemical properties of nNOS: The nervous system of cephalopods. In S. G. Pandalai (Ed.), Recent Research Developments in Biochemistry (Vol. 4, pp. 405–421). Kerala: Research Signpost.Find this resource:

Di Cosmo, A., & Di Cristo, C. (1998). Neuropeptidergic control of the optic gland of Octopus vulgaris: FMRF-amide and GnRH immunoreactivity. Journal of Comparative Neurology, 398, 1–12.Find this resource:

Di Cosmo, A., Di Cristo, C., & Messenger, J. B. (2006). L-glutamate and its ionotropic receptors in the nervous system of cephalopods. Current Neuropharmacology, 4, 305–312.Find this resource:

Di Cosmo, A., Paolucci, M., & Di Cristo, C. (2004). N-methyl-D-aspartate receptor-like immunoreactivity in the brain of Sepia and Octopus. Journal of Comparative Neurology, 477, 202–219.Find this resource:

Di Cosmo, A., & Polese, G. (2013). Molluscan bioactive peptide. In A. J. Kastin (Ed.), Handbook of biologically active peptides (pp. 276–286). Amsterdam: Academic Press/Elsevier.Find this resource:

Di Cosmo, A., & Polese, G. (2014). Cephalopods meet neuroecology: The role of chemoreception in Octopus vulgaris reproductive behaviour. In A. Di Cosmo & W. Winlow (Eds.), Neuroecology and neuroethology in molluscs—The interface between behaviour and environment (pp. 117–132). New York: NOVA Science.Find this resource:

Di Cosmo, A., & Polese, G. (2016). Neuroendocrine–immune systems response to environmental stressors in the cephalopod Octopus vulgaris. Frontiers in Physiology, 7, 434.Find this resource:

Doubleday, Z. A., Thomas, A. A. P., Arkhipkin, A., Pierce, G. J., Semmens, J., Steer, M., Leporati, S. C., Lourenço, S., Quetglas, A., Sauer, W., & Gillanders, B. M. (2016). Global proliferation of cephalopods. Current Biology, 26, 387–407.Find this resource:

Emery, D. G. (1975). Ciliated sensory cells and associated neurons in the lip of the squid Lolliguncula brevis Blainville. Cell Tissue Research, 157, 323–329.Find this resource:

Emery, D. G. (1976). Observations on the olfactory organ of adult and juvenile Octopus joubini. Tissue and Cell, 8, 33–46.Find this resource:

Gilly, W. F., & Lucero, M. T. (1992). Behavioral-responses to chemical-stimulation of the olfactory organ in the squid Loligo opalescens. Journal of Experimental Biology, 162, 209–229.Find this resource:

Giordano, G., Carbone, M., Ciavatta, M. L., Silvano, E., Gavagnin, M., Garson, M. J.,. . ., Mollo, E. (2017). Volatile secondary metabolites as aposematic olfactory signals and defensive weapons in aquatic environments. Proceedings of the National Academy of Sciences USA, 114, 3451–3456.Find this resource:

Grable, M. M., Shashar, N., Gilles, N. L., Chiao, C. C., & Hanlon, R. T. (2002). Cuttlefish body patterns as a behavioral assay to determine polarization perception. Biological Bulletin, 203, 232–234.Find this resource:

Grasso, F. W., & Basil, J. A. (2009). The evolution of flexible behavioral repertoires in cephalopod molluscs. Brain, Behavior, and Evolution, 74, 231–245.Find this resource:

Graziadei, P. (1964). Receptors in the sucker of the cuttlefish. Nature, 195, 57–59.Find this resource:

Graziadei, P. (1965). Sensory receptor cells and related neurons in cephalopods. Cold Spring Harbor Symposia on Quantitative Biology, 30, 45–57.Find this resource:

Graziadei, P., & Gagne, H. T. (1973). Neural components in octopus sucker. Journal of Cellular Biology, 59, A21–A121.Find this resource:

Graziadei, P., & Gagne, H. T. (1976). Sensory innervation in the rim of the octopus sucker. Journal of Morphology, 150, 639–680.Find this resource:

Hancock, A. (1852). On the nervous system of Ommastrephes todarus. Annals and Magazines of Natural History, 10, 1–13.Find this resource:

Hanlon, R. T., & Messenger, J. B. (1996). Cephalopod behaviour. Cambridge, U.K.: Cambridge University Press.Find this resource:

Hanlon, R. T., & Shashar, N. (2003). Aspects of the sensory ecology of cephalopods. In S. P. Collin & N. J. Marshall (Eds.), Sensory processing in the aquatic environment (pp. 266–282). New York: Springer-Verlag.Find this resource:

Huffard, C. L. (2013). Cephalopod neurobiology: An introduction for biologists working in other model systems. Invertebrate Neuroscience, 13, 11–18.Find this resource:

Joll, L. M. (1977). The predation of pot-caught western rock lobster (Panulirus lobgipes cygnus) by octopus. Department of Fisheries and Wildlife, Western Australia. Report No. 29, 58 pp.Find this resource:

King, A. J., Adamo, S. A., & Hanlon, R. T. (2003). Squid egg mops provide sensory cues for increased agonistic behaviour between male squid. Animal Behavior, 66, 49–58.Find this resource:

Lee, P. G. (1992). Chemotaxis by Octopus maya: Voss et Solis in a Y-maze. Journal of Experimental Biology and Ecology, 156, 53–67.Find this resource:

Lucero, M. T., & Gilly, W. F. (1995). Physiology of squid olfaction, In N. J. Abbott, R. Williamson, & L. Maddock (Eds.), Cephalopod neurobiology: Neuroscience studies in squid, octopus and cuttlefish (pp. 521–534). London: Oxford University Press.Find this resource:

Lucero, M. T., Horrigan, F. T., & Gilly, W. F. (1992). Electrical responses to chemical stimulation of squid olfactory receptor cells. Journal of Experimental Biology, 162, 231–249.Find this resource:

Lucero, M. T., Huang, W., & Dang, T. (2000). Immunohistochemical evidence for the Na+/Ca2+ exchanger in squid olfactory neurons. Philosophical Transactions of the Royal Scoeiety of London B: Biological Science, 355, 1215–1218.Find this resource:

Mac Ginitie, G. E., & Mac Ginitie, N. (1968). Natural history of marine animals. New York: McGraw-Hill.Find this resource:

Messenger, J. B. (1967). The peduncle lobe: A visuo-motor centre in Octopus. Proceedings of the Royal Society of London B: Biological Science, 167, 225–251.Find this resource:

Messenger, J. B. (1977). Prey-capture and learning in the cuttlefish. Sepia Symposium of the Zoological Society of London, 38, 347–376.Find this resource:

Mobley, A. S., Lucero, M. T., & Michel, W. C. (2008a). Cross-species comparison of metabolite profiles in chemosensory epithelia: An indication of metabolite roles in chemosensory cells. Anatomical Record Advanced in Integrative Anatomy and Evolutionary Biology, 291, 410–432.Find this resource:

Mobley, A. S., Mahendra, G., & Lucero, M. T. (2007). Evidence for multiple signalling pathways in single squid olfactory receptor neurons. Journal of Comparative Neurology, 501, 231–242.Find this resource:

Mobley, A. S., Michel, W. C., & Lucero, M. T. (2008b). Odorant responsiveness of squid olfactory receptor neurons. Advanced in Integrative Anatomy and Evolutionary Biology. 291, 763–774.Find this resource:

Mollo, E., Fontana, A., Roussis, V., Polese, G., Amodeo, P., & Ghiselin, M. T. (2014). Sensing marine biomolecules: Smell, taste, and the evolutionary transition from aquatic to terrestrial life. Froniers in Chemistry, 2, 92.Find this resource:

Mollo, E., Garson, M. J., Polese, G., Amodeoa, P., & Ghiselind, M. T. (2017). Taste and smell in aquatic and terrestrial environments. Natural Product Reports 34, 496–513.Find this resource:

Mori, K., Takahashi, Y. K., Igarashi, K. M., & Yamaguchi, M. (2006). Maps of odorant molecular features in the mammalian olfactory bulb. Physiological Review, 86, 409–433.Find this resource:

Nilsson, D. E., Warrant, E. J., Hanlon, R. T., Shashar, N., & Johnsen, S. (2012). A unique advantage for giant eyes in giant squid. Current Biology, 22, 683–688.Find this resource:

Packard, A. (1972). Cephalopods and fish: The limits of convergence. Biological Review, 47, 241–307.Find this resource:

Palumbo, A., Di Cosmo, A., Poli, A., Di Cristo, C., & d’Ischia, M. (1999). A calcium/calmodulin-dependent nitric oxide synthase, NMDAR2/3 receptor subunits, and glutamate in the CNS of the cuttlefish Sepia officinalis: Localization in specific neural pathways controlling the inking system. Journal of Neurochemistry, 73, 1254–1263.Find this resource:

Partan, S. R., & Marler, P. (2005). Issues in the classification of multimodal communication signals. American Naturalist, 166, 231–245.Find this resource:

Pecl, G. T., & Jackson, G. D. (2008). The potential impacts of climate change on inshore squid: biology, ecology and fisheries. Reviews in Fish Biology and Fisheries, 18, 373–385.Find this resource:

Piper, D. R., & Lucero, M. T. (1999). Calcium signalling in squid olfactory receptor neurons. Biological Signals and Receptors, 8, 329–337.Find this resource:

Polese, G., Bertapelle, C., & Di Cosmo, A. (2015). Role of olfaction in Octopus vulgaris reproduction. General and Comparative Endocrinology, 210, 55–62.Find this resource:

Polese, G., Bertapelle, C., & Di Cosmo, A. (2016). Olfactory organ of Octopus vulgaris: Morphology, plasticity, turnover and sensory characterization. Biology Open 5, 611–619.Find this resource:

Rodhouse, P. G., Pierce, G. J., Nichols, O. C., Sauer, W. H., Arkhipkin, A. I., Laptikhovsky, V. V., . . . Kidokoro, H. (2014). Environmental effects on cephalopod population dynamics: Implications for management of fisheries. Advances in Marine Biology, 67, 99–233.Find this resource:

Ruth, P., Schmidtberg, H., Westermann, B., & Schipp, R. (2002). The sensory epithelium of the tentacles and the rhinophore of Nautilus pompilius L. (Cephalopoda, Nautiloidea). Journal of Morphology, 251, 239–255.Find this resource:

Schmidt, M., & Mellon, De. F. (2011). Neuronal processing of chemical information in crustaceans. In T. Breithaupt & M. Thiel (Eds.), Chemical communication in crustaceans (pp. 123–147). New York: Springer.Find this resource:

Stubs, A. L., & Stubs, C. W. (2016). Spectral discrimination in color blind animals via chromatic aberration and pupil shape. Proceedings of the National Academy of Sciences USA, 113, 8206–8211.Find this resource:

Touhara, K., & Vosshall, L. B. (2009). Sensing odorants and pheromones with chemosensory receptors. Annual Review of Physiology, 71, 307–332.Find this resource:

von Kölliker, R. A. (1844). Entwicklungsgeschichte der Tintenfische [German]. Entwicklungsgeschichte der Cephalopoden. Zurich: Meyer und Zeller.Find this resource:

Von Zernoff, D. (1869). Ueber das Geruchsorgan der cephalopoden. Bulletin de la Société Imperiale des Naturalistes de Moscou, 42, 72–90.Find this resource:

Walderon, M. D., Nolt, K. J., Haas, R. E., Prosser, K. N., Holm, J. B., Holm, J. B., . . .Boal, J. G. (2011). Distance chemoreception and the detection of conspecifics in Octopus bimaculoides. Journal of Molluscan Studies, 77, 309–311.Find this resource:

Watkinson, G. B. (1908). Untersuchungen tüber die sogenannten Geruchsorgane der Cephalopoden. Jenaische Zeitschrift für Naturwissenschaft. 44, 353–414.Find this resource:

Wells, M. J. (1963). Taste by touch: Some experiments with octopus. Journal of Experimental Biology, 40, 187–193.Find this resource:

Wells, M. J. (1978). Octopus. London: Chapman and Hall.Find this resource:

Wells, M. J., Freeman, N. H., & Ashburner, M. (1965). Some experiments on the chemotactile sense of octopuses. Journal of Experimental Biology, 43, 553–563.Find this resource:

Wells, M. J., & Wells, J. (1956). Tactile discrimination and the behaviour of blind Octopus. Pubblicazioni della Stazione zoologica di Napoli, 8, 94–126.Find this resource:

Westermann, B., & Beurlein, K. (2005). Y-maze experiments on the chemotactic behaviour of the tetrabranchiate cephalopod. Nautilus pompilius (Mollusca). Marine Biology, 147, 145–151.Find this resource:

Westermann. B., Schmidtberg, H., & Beuerlein, Knut. (2016). Functional morphology of the mantle of Nautilus pompilius (Mollusca, Cephalopoda) Bettina. Journal of Morphology, 264, 277–285Find this resource:

Wildenburg, G. (1997). Structure of the so-called olfactory organ of octopods after hatching: Evidence for its chemoreceptive function. Vie Milieu, 47, 137–142.Find this resource:

Williamson, R., & Chrachri, A. (2007). A model biological neural network: The cephalopod vestibular system. Philosophical Transactions of the Royal Society of London B: Biological Sciences, 362, 473–481.Find this resource:

Wood J. B., Pennoyer K. E., & Derby, C. D. (2008). Ink is a conspecific alarm cue in the Caribbean reef squid, Sepioteuthis sepioidea. Journal of Experimental Marine Biology and Ecology, 367, 11–16.Find this resource:

Woodhams, P. L., & Messenger, J. B. (1974). A note on the ultrastructure of the Octopus olfactory organ. Cell Tissue Research, 152, 253–258.Find this resource:

Yoshida, M. A., Ogura, A., Ikeo, K., Shigeno, S., Moritaki, T., Winters, G. C., . . . Moroz, L. L. (2015). Molecular evidence for convergence and parallelism in evolution of complex brains of cephalopod molluscs: Insights from visual systems. Integrative and Comparative Biology, 55, 1070–1083.Find this resource:

Young, J. Z. (1965). The central nervous system of Nautilus. Philosophical Transactions of the Royal Sociey of London B, 249, 1–25.Find this resource:

Young, J. Z. (1971). The anatomy of the nervous system of Octopus vulgaris. Oxford: Clarendon.Find this resource:

Young, J. Z. (1977). Brain, behaviour and evolution of cephalopods. Symposium of the Zoological Society of London, 38, 377–434.Find this resource:

Young, J. Z. (1989). The angular acceleration receptor system of diverse cephalopods. Philosophical Transactions of the Royal Society B: Biological Sciences, 325, 189–238.Find this resource:

Zatynly, C., Gagnon, J., Boucaud-Camou, E., & Henry, J. (2000). ILME: A waterborne pheromonal peptide released by the eggs of Sepia officinalis. Biochemical and Biophysical Research Communications, 275, 217–222.Find this resource:

Zylinski, S., & Johnsen, S., (2011). Mesopelagic cephalopods switch between transparency and pigmentation to optimize camouflage in the deep. Current Biology, 21, 1937–1941.Find this resource:

Zylinski, S., Osorio, D., & Shohet, A. J. (2009). Perception of edges and visual texture in the camouflage of the common cuttlefish, Sepia officinalis. Philosophical Transactions of the Royal Society of London B: Biological Sciences, 364, 439–448.Find this resource: