Comparative morphology of the peripheral olfactory system of disease vector arthropods

PITTS, RJ; IBARRA BOUZADA, LUCIA; GUERENSTEIN P.G.

Sensory Ecology of Disease Vectors

Wageningen University Press

Año: 2022; p. 29 - 70

Hematophagous arthropod disease vectors heavily rely on their olfactory systems to locate hosts, refuges, oviposition sites and to communicate intraspecifically. Th eperipheral olfactory systems of insects are located on the antennae and certain mouthparts while in other arthropods the first pair of legs are involved. The arthropod olfactory sensory neurons are housed within hair-like cuticular structures called sensilla. There are two morphologically distinct types of olfactory sensilla: those with a single (cuticle) wall and those with a double wall. Interestingly, both types are found throughout virtually all insect orders and in acarines. Morphological subtypes of olfactory sensilla have also been reported, and moreover, subtypes of morphologically similar sensilla have been described based on physiological function. In order to fully characterize a sensillum type a number of studies are required,including scanning electron microscopy (SEM), transmission electron microscopy (TEM) and physiological and/or molecular assays aimed at elucidating the roles of the olfactory sensory neurons (OSNs) housedwithin, specially the chemical ?tuning? of those neurons. Once the olfactory sensillum types and subtypes have been wellcharacterized, comparisons at different taxonomic levels could become very precise, which would lead to a better understanding of thecontributions of specific components (e.g. OSNs, neural circuits) ofthe olfactory system and to propose new hypotheses about the evolution of those components. In this chapter we present information about the peripheral olfactory system of hematophagous arthropods vectors of disease. This includes a description of their peripheral olfactory systems with emphasis on their sensilla types and subtypes,as well as comparisons between different taxa when information wasavailable. Such comparisons are more appropriate when SEM, TEM andsensilla/OSN response studies have been carried out as this facilitates unequivocal functional comparisons. Unfortunately, such comprehensive studies of the peripheral olfactory system of these arthropods are not always found. Despite the fact that robust comparative information is sometimes missing, it has been proposed that blood-feeding arthropods that need to locate a resource at along distance have a more developed peripheral olfactory system thanthose that live very near to, or on, their hosts. In addition, theloss of the blood-feeding habit and reduced mouthparts correlate with reduced numbers of olfactory sensilla. We suggest filling in theexisting gaps in information through more detailed ultrastructural and physiological investigations, especially through collaborative efforts.