Exploring visual capabilities of the marbled shore crab (Pachygrapsus marmoratus)

Abstract

The following work aimed at exploring visual capabilities of the marbled shore crab, Pachygrapsus marmoratus, with a special focus on motion detection. Previous work has shown that the species responds to looming stimuli by receding away from the stimulus. Furthermore, individuals are able to detect movement across their entire visual field. There are indications that the crabs carefully monitor speed and direction of an ongoing approach to adjust their reactions accordingly. However, it is yet unclear which aspects of an approaching object trigger an escape response. In an attempt to answer this question, 26 crabs were presented with video clips from different categories. Results from this study showed that P. marmoratus reacted most sensitively towards octopus videos, suggesting that the crabs were perhaps able to recognise octopuses to some extent. Yet, closer investigation did not deliver significant results. The question remains whether P. marmoratus can distinguish between different types of pictorial content and movement, leaving behind a demand for further research.