Comparative Development of the Ant Chemosensory System

Abstract

Highlights d Ant odorant receptors show unique early expression and localization in pupae d Sensory neuron innervation is necessary for proper antennal lobe development d Sensory neuron ablation reveals latent antennal lobe structure in ants, but not flies d Insects with complex olfactory systems may employ a different developmental logic

Advances in the Study of Olfaction in Eusocial Ants

“…Indeed, the catastrophic changes to the AL during development represent a nontrivial confounding variable. Taken together with more recent efforts [ 104 ], these studies suggest that OR function plays a necessary role in a variety of social behaviors that contribute to the evolutionary success of these insects. That said, it is not possible to distinguish whether the behavioral phenotypes observed in these mutants are the result of the loss of olfactory signaling from the antennae, the large defects in the AL, or any number of potential changes encountered during an altered developmental program.…”

“…In addition to a profound loss of olfactory sensitivity, as well as the alteration of several behavioral phenotypes that were both anticipated, orco mutant ants displayed significant reductions in both OSN populations and the number and volume of AL glomeruli. More recently, AL development in O. biroi has been closely examined during the critical two-week pupation period [ 104 ]. In contrast with Drosophila [ 99 ], OR expression occurs much earlier in ant development, before the formation of glomeruli [ 104 ].…”

“…More recently, AL development in O. biroi has been closely examined during the critical two-week pupation period [ 104 ]. In contrast with Drosophila [ 99 ], OR expression occurs much earlier in ant development, before the formation of glomeruli [ 104 ]. Indeed, Orco expression was high on the first day of pupal development, and almost all of the nearly 500 ant ORs were expressed by day 2 of the pupal stage.…”

“…Taken together, this suggested that orco mutants have impaired AL development due to loss of OSNs, which were necessary for the formation of glomeruli but not their maintenance. Curiously, approximately 90 glomeruli survived both the ablation treatment and in the orco null mutant [ 103 , 104 ]. The authors suggested these remaining glomeruli may be a more basic template upon which the remainder of the more complex AL forms.…”

Olfactory systems across mosquito species

“…This finding suggests a fine-tuned mechanism that regulates expression levels of ORs in Anopheles gambiae and is disrupted by unnaturally high levels of OR2 protein. While in Anopheles gambiae OR2 overexpression or ORCO mutation does not lead to dramatic reduction of the size of the antennal lobe (Maguire et al 2020 ; Sun et al 2020b ), ORCO mutation affects antennal lobe size in clonal and ponerine ants (Trible et al 2017 ; Yan et al 2017 ; Ryba et al 2020 ) and, to a lesser extent, in the moth Manduca sexta (Fandino et al 2019 ) . It therefore appears that there is a continuous spectrum of ORCO – OR function – ORN development interactions amongst insects, despite high conservation of ORCO.…”