Highlights
- Exposure to high PCO2/low pH water decreases olfactory sensitivity in sole more markedly in the upper olfactory epithelium (OE).
- Resilience of the lower OE may be linked to exposure to a different environment.
- Regulation of genes related to neuromodulation and neuroplasticity suggests activation of compensatory mechanisms.
- Regulation of immune processes related genes together with histological modifications will likely compromise olfactory sensitivity with behavioural consequences.
- Ocean acidification has effects on the peripheral nervous system at various levels.
Abstract
Increased carbon dioxide (CO2) in the ocean is changing seawater chemistry. Behavioural alterations in CO2 exposed fish have been linked to changes in the central nervous system (CNS). However, we hypothesise that receptor cells in direct contact with the environment are more susceptible to changes in water chemistry than the CNS. Electrophysiology, histology, and transcriptomics were used to explore the effect of exposure to CO2 acidified water on the olfactory epithelium (OE) of the Senegalese sole (Solea senegalensis). The upper and lower OE of this flatfish detect different odorants and are in contact with different environments. Acute exposure to acidified water decreased olfactory sensitivity more in the upper than in the lower OE. After chronic exposure to high CO2 there was no histological changes in the upper OE, however, in the lower OE, there was a massive infiltration of melanomacrophage (MMC) and tissue disorganization. In addition, in the upper OE, differential expressed gene transcripts (DETs) were related to inflammation and innate immune processes whereas in the lower OE, DETs were related to the adaptative immune response. Differential regulation of genes related to neurogenesis and plasticity occurred in both epithelia.
The effects of ocean acidification in sole OE depends on the nostril, however the occurrence of an exacerbated immune response, OE remodelling and reduced sensitivity indicate that ocean acidification is likely to have significant and unpredictable consequences for behaviour.
Costa R. A., Hubbard P., Manchado M., Power D. M. & Velez Z, 2025. Olfactory specialization in the Senegalese sole (Solea senegalensis): CO2 acidified water triggers nostril-specific immune processes. Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology: 111820. doi: 10.1016/j.cbpa.2025.111820. Article.
