Genes related to senses and their variation across animals?

Question

Animals often have very different numbers of active genes related to any sense. For instance, most fish or even aquatic mammals have very few olfactory receptor genes, whereas this is higher in terrestrial animals. Even among them, there is huge variation; compare dogs and humans, for instance. But this comes at a cost; for instance, dogs are dichromatic, the blind mole is, well, blind. So there is a compensation across the senses which is not merely a plastic change. I was wondering if there is any way to reconcile this with some notion of conservation of the total proportion of active genes involved with sensation.

Answer 1

While there isn’t a strict “conservation” of the total proportion of active genes involved in sensation across species, there is a dynamic balance that reflects each species’ ecological niche and evolutionary pressures (1). For example, dogs have a highly developed sense of smell, with a large number of olfactory receptor genes, but as you stated, they are dichromatic, meaning their color vision is more limited compared to humans (2). This trade-off allows them to excel in their specific environment and roles. Similarly, blind mole rats have lost their vision but have enhanced other senses, such as touch and smell, to adapt to their subterranean lifestyle (3). These adaptations are driven by natural selection, where certain sensory capabilities are favored over others based on the species’ needs and environment (1). The variation in the number of active genes related to different senses reflects the diverse strategies animals have evolved to survive and thrive in their respective habitats (1). In addition to trade-offs in gene function, there are also energetic and neural costs to consider. Sensory systems require significant resources to develop and maintain, and animals tend to prioritize the senses that are most beneficial for their survival. Gene duplication and loss also play key roles, as certain sensory gene families may expand in some lineages (4) (e.g., olfactory genes in dogs) and contract in others (e.g., vision genes in blind species). So, while there isn’t a strict conservation of sensory gene proportions, there is a dynamic allocation of resources and genetic focus that reflects each species’ evolutionary history and ecological demands. This balance highlights the remarkable diversity of strategies animals have evolved to adapt to their environments.  In short: No, because species adapt their sensory capabilities based on their ecological needs and evolutionary pressures, rather than maintaining a "one size fits all" conservation of sensory genes.

   1)Hannah J WilliamsVivek H SridharEdward HurmeGabriella EC GallNatalia BorregoGenevieve E FinertyIain D CouzinC Giovanni GaliziaNathaniel J DominyHannah M RowlandMark E HauberJames P HighamAriana Strandburg-PeshkinAmanda D Melin (2023) Sensory collectives in natural systems eLife 12:e88028.

https://doi.org/10.7554/eLife.88028

  2)https://news.cornell.edu/stories/2022/07/study-finds-new-links-between-dogs-smell-and-vision

3)Rado, R., Bronchti, G., Wollberg, Z., & Terkel, J. (1992). Sensitivity to light of the blind mole rat: behavioral and neuroanatomical study. Israel Journal of Zoology, 38(3-4), 323-331. https://doi.org/10.1080/00212210.1992.10688679

4)Wang Y, Sun Y, Joseph PV (2023) Diverse evolutionary rates and gene duplication patterns among families of functional olfactory receptor genes in humans. PLoS ONE 18(4): e0282575. https://doi.org/10.1371/journal.pone.0282575