The giant pouched rat (Cricetomys ansorgei) olfactory receptor repertoire

Abstract

For rodents, olfaction is essential for locating food, recognizing mates and competitors, avoiding predators, and navigating their environment. It is thought that rodents may have expanded olfactory receptor repertoires in order to specialize in olfactory behavior. Despite being the largest clade of mammals and depending on olfaction relatively little work has documented olfactory repertoires outside of conventional laboratory species. Here we report the olfactory receptor repertoire of the African giant pouched rat (Cricetomys ansorgei), a Muroid rodent distantly related to mice and rats. The African giant pouched rat is notable for its large cortex and olfactory bulbs relative to its body size compared to other sympatric rodents, which suggests anatomical elaboration of olfactory capabilities. We hypothesized that in addition to anatomical elaboration for olfaction, these pouched rats might also have an expanded olfactory receptor repertoire to enable their olfactory behavior. We examined the composition of the olfactory receptor repertoire to better understand how their sensory capabilities have evolved. We identified 1145 intact olfactory genes, and 260 additional pseudogenes within 301 subfamilies from the African giant pouched rat genome. This repertoire is similar to mice and rats in terms of size, pseudogene percentage and number of subfamilies. Analyses of olfactory receptor gene trees revealed that the pouched rat has 6 expansions in different subfamilies compared to mice, rats and squirrels. We identified 81 orthologous genes conserved among 4 rodent species and an additional 147 conserved genes within the Muroid rodents. The orthologous genes shared within Muroidea suggests that there may be a conserved Muroid-specific olfactory receptor repertoire. We also note that the description of this repertoire can serve as a complement to other studies of rodent olfaction, as the pouched rat is an outgroup within Muroidea. Thus, our data suggest that African giant pouched rats are capable of both natural and trained olfactory behaviors with a typical Muriod olfactory receptor repertoire.

Characterization of oxytocin and vasopressin receptors in the Southern giant pouched rat and comparison to other rodents

“…Whether tuco-tucos rely on AVP signaling in olfactory circuitry instead of OT signaling for social recognition is an open question. Pouched rats are exceptional at olfactory discrimination ( 32 , 35 , 37 , 38 ), which also raises questions about what OT-OTR in the olfactory sensory system does and whether (or how) low levels of OTR in the OB and parts of the PFC impact sensory processing. Potentially, AVP-V1aR signaling in the olfactory regions of the forebrain might impact social recognition in the pouched rat ( 59 ).…”

Gross morpho-biometry, histometry and immunohistochemical investigations of pituitary gland in the juvenile and adult male African giant rats (Cricetomys gambianus)

“…They have a highly developed olfactory system, which enables them to detect and distinguish a wide range of scents (Olude et al, 2014;Freeman et al, 2020). This advantage has been utilized in detecting landmines and tuberculosis in field studies.…”

Isolation ofActinomyces cricetomyissp. nov from orocervicofacial abscesses of African giant pouched rats (Cricetomys ansorgei)

“…are large terrestrial rodents from the family Nesomyidae, native to savannahs and evergreen forests of sub-Saharan Africa. These rodents stand out among other rodents for their relatively large olfactory cortex, bulbs, and ample olfactory receptor repertoire, which provide them with strong olfactory capabilities [1][2][3][4]. Due to their acute sense of smell, they have been successfully trained to diagnose tuberculosis cases in humans [5,6], localize people trapped in collapsed structures [7], and employed in life-saving operations to detect anti-personnel landmines [8].…”