Olfactory Studies

[DWhatley]

Olfactory-like neurons are present in the forehead of common cuttlefish, Sepia officinalis Linnaeus, 1758 (Cephalopoda: Sepiidae)
Marco A Campinho, Ana R Oliveira Antonio, V Sykes 2017 (full article)

Abstract
According to the literature, the cuttlefish, Sepia officinalis, possesses a specialized olfactory organ and cells, located in olfactory ventral pits. In this study, the location of olfactory receptor neurons (ORNs) at the cellular level was determined using cellular morphology and immunohistochemistry. An antiserum against PBP3 was used as a marker to identify ORN-like cells in cuttlefish after validation for specificity to cephalopod ORN cells in the common octopus, Octopus vulgaris. The results show that ORN-like cells in S. officinalis were not found in the ventral pits, suckers or the mouth lips. Instead, ORN-like cells were found scattered in the forehead, between the eyes. The absence of ORN-like cells in a pit in S. officinalis and the sharing of four similar types of ORN cells with the squid and octopus lineages suggest that this might be a later innovation in olfaction and is probably associated with the specialized lifestyle of these later evolved cephalopods. Together, this evidence suggests a diversification of ORN cell types in Coleoidea, which did not occur in Nautiloidea, which might have preceded the diversification of the Coleoidea.

 

[DWhatley]

An immunohistochemical approach to understanding the organization of the olfactory system in the cuttlefish, Sepia officinalis.
Scaros AT, Croll R, Baratte S. 2018

Abstract
Cephalopods are non-traditional but captivating models of invertebrate neurobiology, particularly in evolutionary comparisons. Cephalopod olfactory systems have striking similarities and fundamental differences with vertebrates, arthropods, and gastropods, raising questions about the ancestral origins of those systems. We describe here the organization and development of the olfactory system of the common cuttlefish, Sepia officinalis, using immunohistochemistry and in situ hybridization. FMRFamide and/or related peptides and histamine are putative neurotransmitters in olfactory sensory neurons. Other neurotransmitters, including serotonin and APGWamide within the olfactory and other brain lobes, suggest efferent control of olfactory input and/or roles in the processing of olfactory information. The distributions of neurotransmitters, along with staining patterns of phalloidin, anti-acetylated α-tubulin, and a synaptotagmin riboprobe help to clarify the structure of the olfactory lobe. We discuss a key difference, the lack of identifiable olfactory glomeruli, in cuttlefish in comparison to other models, and suggest implications for the evolution of olfaction.