Visual opsins coupled with Gq‐type G protein have been considered to be responsible for the vision in mollusks. Recent transcriptomic studies, however, revealed the presence of opsin mRNA belonging to different groups of opsin subfamilies in the eyes of mollusks. In the present study, we found that at least three different opsins, Gq‐coupled rhodopsin, opsin5A, and xenopsin, are co‐expressed in the rhabdomeric photoreceptor cell in the eyes of the terrestrial slug Limax valentianus. These opsins were all localized to the microvilli of the rhabdomere. Co‐expression of rhodopsin and opsin5A mRNA was also demonstrated by dual fluorescence in situ hybridization. Co‐expression of multiple opsins in the rhabdomeric photoreceptors cells may explain the previously reported shift in the action spectra of the electroretinogram of eyes of Limax flavus between the light‐ and dark‐adapted states, which was also reproduced in the present study in L. valentianus.

Although the eye is the best-studied photoreceptive organ in animals, the presence of non-ocular photosensing systems has been reported in numerous animal species. However, most of the roles that nonocular photosensory systems play remain elusive. We found that the terrestrial slug Limax valentianus avoids light and escapes into dark areas even if it is blinded by the removal of the bilateral superior tentacle. The escape behaviour was more evident for short-wavelength light. Illumination to the head with blue but not red light elicited avoidance behaviour in the blinded slugs. Illumination to the tail was ineffective. The light-avoidance behaviour of the blinded slugs was not affected by the removal of the penis, which lies on the brain in the head, suggesting that the penis is dispensable for sensing light in the blinded slug. mRNA of Opn5A, xenopsin, retinochrome and, to a lesser extent, rhodopsin was expressed in the brain according to RT-PCR. Lightevoked neural responses were recorded from the left cerebro-pleural connective of the isolated suboesophageal ganglia of the brain, revealing that the brain is sensitive to short wavelengths of light (400-480 nm). This result is largely consistent with the wavelength dependency of the light-avoidance behaviour of the blinded slugs that we observed in the present study. Our results strongly support that the terrestrial slug L. valentianus detects and avoids light by using its brain as a light-sensing organ in the absence of eyes.

The coronavirus disease 2019 (COVID-19) pandemic has led to lifestyle restrictions and might be associated with long-term changes in cognitive function. The aim of the present study was to elucidate the overall effect of the COVID-19 pandemic on the cognitive trajectory of a cohort of patients with cognitive impairment.Methods: We enrolled 160 patients who had been making regular visits to a medical center for dementia. Cognitive function was assessed based on changes in scores on the Mini-Mental State Examination before and during the COVID-19 pandemic throughout a 4-year period. The trajectory of cognitive decline was determined by carrying out a time series analysis using a state-space model.Results: Crude analysis showed that the Mini-Mental State Examination scores decreased from 20.9 AE 4.4 points (mean AE SD) at the time of the initial cognitive assessments to 17.5 AE 5.6 points at the time of the final assessments, and the decline rate was 1.15 AE 1.78 points per year (P < 0.0001). The time series analysis showed an accelerated cognitive trajectory after the COVID-19 outbreak, and the average decline in the Mini-Mental State Examination scores was 0.46 points (95% confidence interval 0.034-0.91) per year before the COVID-19 pandemic, and a steeper decline of 1.87 points (95% confidence interval 1.34-2.67) per year after the outbreak. Conclusions:The COVID-19 pandemic accelerated the rate of cognitive decline in patients with cognitive impairment fourfold in comparison with before the pandemic. Specific strategies designed for cognitively older people in the "new normal" will reconcile both requirements, reducing the risk of infection, and maintaining their physical and psychological well-being.

No abstract