Polarization vision in terrestrial hermit crabs

Polarization vision is used by a wide range of animals for navigating, orienting, and detecting objects or areas of interest. Shallow marine and semi-terrestrial crustaceans are particularly well known for their abilities to detect predator-like or conspecific-like objects based on their polarization properties. On land, some terrestrial invertebrates use polarization vision for detecting suitable habitats, oviposition sites or conspecifics, but examples of threat detection in the polarization domain are less well known. To test whether this also applies to crustaceans that have evolved to occupy terrestrial habitats, we determined the sensitivity of two species of land and one species of marine hermit crab to predator-like visual stimuli varying in the degree of polarization. All three species showed an ability to detect these cues based on polarization contrasts alone. One terrestrial species, Coenobita rugosus, showed an increased sensitivity to objects with a higher degree of polarization than the background. This is the inverse of most animals studied to date, suggesting that the ecological drivers for polarization vision may be different in the terrestrial environment.

Automated summary

Polarization vision is widely used by animals for navigation, orientation, and detecting objects. While some invertebrates on land use polarization vision for finding habitats or conspecifics, the detection of threats based on polarization is less understood. In this study, researchers tested the sensitivity of land and marine hermit crabs to predator-like visual stimuli with varying degrees of polarization. All three species showed the ability to detect these stimuli based on polarization contrasts alone. The findings suggest that the ecological drivers for polarization vision may differ in terrestrial environments.