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In many vertebrates, the brain’s right hemisphere which is connected to the left visual field specializes in the processing of information about threats while the left hemisphere which is connected to the right visual field specializes in the processing of information about conspecifics. This is referred to as hemispheric lateralization. But individuals that are too predictable in their response to predators could have reduced survival and we may expect selection for somewhat unpredictable responses. We studied hemispheric lateralization in yellow-bellied marmots Marmota flaviventer, a social rodent that falls prey to a variety of terrestrial and aerial predators. We first asked if they have lateralized responses to a predatory threat. We then asked if the eye that they used to assess risk influenced their perceptions of risk. We recorded the direction marmots were initially looking and then walked toward them until they fled. We recorded the distance that they responded to our experimental approach by looking, the eye with which they looked at us, and the distance at which they fled (i.e., flight initiation distance; FID). We found that marmots had no eye preference with which they looked at an approaching threat. Furthermore, the population was not comprised of individuals that responded in consistent ways. However, we found that marmots that looked at the approaching person with their left eye had larger FIDs suggesting that risk assessment was influenced by the eye used to monitor the threat. These findings are consistent with selection to make prey less predictable for their predators, despite underlying lateralization.
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Left-right asymmetry of the visual system in the scallop Nodipecten nodosus (Bivalvia: Pectinidae)
Left–right asymmetries are consistent differences between the left and right sides and represent an intriguing feature of molluscan morphology. Interestingly, external asymmetries, such as inequivalve shells, are often coupled with lateralization in the nervous system, which often includes functional and structural specializa- tions of the left or right sides. In the case of visual asymmetries, lateralized phenotypes frequently include left–right differences in eye position, structure and use. To investigate lateralization and visual asymmetries among bivalves, we examined the visual and nervous systems of the scallop Nodipecten nodosus. We charac- terized different eye morphologies in the species and determined eye-side frequencies. We also studied the anatomy of the nervous system, focusing on the parietovisceral ganglion (PVG). Our results reveal that the visual and nervous systems of the scallop N. nodosus comprise consistent left–right asymmetries: (1) a greater number of eyes on the left side, (2) increased size of the left PVG lateral lobe, (3) larger glomeruli in the left PVG lateral lobe and (4) radial pallial nerves associated with the left lateral lobe spaced more widely than the more compactly arranged pallial nerves associated with the right lateral lobe. In addition, eyes with a distinctive morphology, where the optic vesicle is rotated, are more frequent on the left side. Consid- ering the habit of this species to rest on the right valve, we hypothesize that curved eyes might contribute to expanding the overall visual field. Even though bivalves are not typically considered in the literature on lateralization, accumulating evidence for scallops, as suggested by our results, indicates their potential to reveal novel patterns of visual asymmetry in benthic invertebrates.
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- Award ID(s):
- 1754331
- PAR ID:
- 10438584
- Date Published:
- Journal Name:
- Journal of molluscan studies
- Volume:
- 89
- Issue:
- 2023
- ISSN:
- 1464-3766
- Page Range / eLocation ID:
- eyad007
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/mollus/eyad007
