Olfaction sensilla

The sensitivity and selectivity of olfaction and contact chemosensation are due (1) in the brain, to the existence of a neuronal network of neurons tuned to a specific chemical stimulus, and (2) in the periphery, to the existence of olfactory/ chemosensory receptor neurons housed in sensory microorgans called sensilla. The sensilla can best be viewed as simple cuticular porous extrusions that increase the surface that captures airborne odorants or chemicals dissolved in water droplets. They contain the receptive olfactory or chemosensory structures (Schneider, 1969). The olfactory sensilla are most numerous on the antennae and mediate the reception of sex pheromones and plant volatiles, as well as other odorants. Low volatility pheromones may also be detected by contact chemoreceptors on... 

Schmidt M, Gnatzy W (1984) Are the funnel-canal organs the campaniform sensilla of the shore crab, Carcinus maenas (Decapoda, Crustacea) II. Ultrastructure. Cell Tiss Res 237 81-93 Schmitt BC, Ache BA (1979) Olfaction responses of a decapod are enhanced by flicking. Science... 

The matching dichotomy of sensilla construction and neuroanatomical organization of sensory neuropils suggests that in crustaceans chemical information is received and processed in two fundamentally different modes. One mode is Olfaction which we define as chemoreception mediated by the aesthetasc - OL pathway the second mode is Distributed Chemoreception, which we define as chemoreception mediated by bimodal sensilla on all appendages and the associated striated neuropils that serve as local motor centers. Distributed chemoreception not only comprises taste, which we define as contact chemoreception in the context of... 

The aesthetascs are olfactory sensilla and usually all chemoreception mediated by the lateral antennular flagella (or the entire antennules) was attributed to them and hence considered as olfaction. This interpretation is flawed because other chemosensory sensilla are associated with the aesthetascs and likely the activity of dCRNs in these bimodal sensilla was analyzed in most axon recordings from the lateral flagella. 

Mclver, S., Siemicki, R. and Sutcliffe, J, (1980) Bifurcate sensilla on the tarsi of female black flies, Simulium venustum (Diptera Simuliidae) Contact chemosensilla adapted for olfaction. J, Morphol, 165, 1-12. 

---